Modulation of global regulatory mechanisms and biosynthetic gene clusters for simplified production of natural products

Abstract

The present invention relates to a method for finding global regulators in order to induce or increase production of target secondary metabolites. The method comprises providing a bacterium indicator strain producing two fluorescent reporter signals under the same control of two different biosynthetic gene clusters (BGC), preferably highly expressed BGC, performing random mutagenesis in said bacterium indicator strain, and selecting mutant bacteria not producing said reporter signals. The invention also relates to a method to activate the production of target secondary metabolites, and to a CRISPR / Cas based single plasmid to delete or inactivate a global regulator and / or activate a BGC. Finally, the inventive method can be performed in high-throughput format allowing to speed-up the procedure.

Description

[0001] Modulation of global regulatory mechanisms and biosynthetic gene clusters for simplified production of natural products Specification The present invention relates to a method for finding global regulators in order to induce or increase production of target secondary metabolites. The method comprises providing a bacterium indicator strain producing two fluorescent reporter signals under the same control of two different biosynthetic gene clusters (BGC), preferably highly expressed BGC, performing random mutagenesis in said bacterium indicator strain, and selecting mutant bacteria not producing said reporter signals. The invention also relates to a method to activate the production of target secondary metabolites, and to a CRISPR / Cas based single plasmid to delete or inactivate a global regulator and / or to activate a BGC. Finally, the inventive method can be performed in high-throughput format allowing to speed-up the procedure. Background of the invention Numerous medicines are directly originated or are inspired from bacterial natural products and their secondary metabolites. These secondary metabolites are known to be produced by bacteria in response to environmental stress or interaction with host, providing competitive advantages. Proteins essential for the production of the bioactive compound are usually encoded by large cryptic gene clusters that remain silent under normal laboratory conditions, which hinders the discovery of new secondary metabolites. The corresponding biosynthetic gene cluster (BGC) can be identified biometric and act as an indicator or marker of bacterial capacity for the production of secondary metabolites. In general, cryptic BGCs are essentially present 5 - 10 times more than expressed BGCs, so that all bacterial genomes contain many more BGCs than there are secondary metabolites known from that particular strain. Understanding the modality of expression of these BGCs will not only allow discovery of new beneficial compounds but also revealing pathogenic mechanisms. The recognition of the global regulators controlling silent biosynthetic gene clusters can help to achieve these goals. In contrast to pathway-specific regulators which control the transcription of a small number of genes, global regulators control hundreds of genes.

[0002] GAR-P04397WO09 Application (final)2.docx Activation / inactivation of global regulators is related to significant changes in the production of secondary metabolites and to the induction of corresponding biosynthetic gene clusters. For example, global regulatory mechanisms dramatically affect the production of almost all secondary metabolites (SM, also called natural products (NPs)), in bacteria such as those of the genera Photorhabdus and Xenorhabdus. Several BGCs are silent under the conditions used in laboratories for growing bacterial or fungi strain, or the secondary metabolites are only produced in very minute amounts. Since these secondary metabolites might have interesting biological activities acting as antibiotics, anti-cancer or immune suppressive drugs with applications in medicine, biotechnology and agriculture, it would be desirable to speed-up access to these secondary metabolites. International patent application WO 2019192281 refers to a method for mining secondary metabolism strong promoter based on Streptomyces transcriptome, and application thereof. Taking the strong promoter ermE*p as a reference, using the egfp reporter gene to characterize the activity of the ultimate promoters, and confirm the relatively high activity of the promoter in secondary metabolism. Using high-expression Streptomyces natamycin pathway specific positive regulation factors of the promoters obtained by screening increases the natamycin yield. U.S. patent application US 2016348097 discloses compositions and methods for activating a silent gene or gene cluster with a bacteriophage and / or Streptomyces Antibiotic Regulatory Protein (SARP) transcription factor. Park Jimin et al. (ACS Synthetic Biology, 2021, 10 (8), pp. 1859-73) report on a high-throughput transcriptional characterization of regulatory sequences from bacterial biosynthetic gene clusters (BGCs). In the publication a cell-free expression platform for rapid characterization of regulatory sequence activities in S. albidoflavus is described. Xiang et al. (Communications Biology, 2022, 5 (1), p.901) report on a visualization reporter system for characterizing antibiotic biosynthetic gene clusters expression with high-sensitivity. A visualization reporter system based on Gram-negative bacterial acyl-homoserine lactone quorum-sensing (VRS-bAHL) is also disclosed. The authors showed that VRS-bAHL can be

[0003] GAR-P04397WO09 Application (final)2.docx widely used for characterizing gene expression in Streptomyces. With the guidance of VRS-bAHL, a novel oxazolomycin derivatives is discovered. Jingjing et al. (Journal of Biological Chemistry, 2017, 292 (48), pp. 19708- 20) report on a double-reporter-guided targeted activation of the oxytetracycline silent gene cluster in Streptomyces rimosus M527. In Streptomyces rimosus M527, the oxytetracycline (OTC) biosynthetic gene cluster is not expressed under laboratory conditions. The authors used a reported-guided mutant selection (RGMS) procedure to activate the cluster and to obtain a working mutant M527-pAGT-R7. The authors could show that OTC gene cluster was successfully activated using the RGMS method. At the present a robust and efficient method to find global regulators in bacteria such as bacteria and fungi, and for producing secondary metabolites at high levels is missing. This is particular relevant for the bacteria Photorhabdus and Xenorhabdus. It is the objective of the present invention to provide a method for screening for global regulator genes that can be manipulated to activate biosynthetic gene clusters (BGC) for producing target secondary metabolites at high level and / or inhibit background production of other not relevant metabolites. Thus, the present invention further comprises a method to elicit production of a secondary metabolite from a BGC based on deleting a global regulator and / or activating a BGC or based on activating a BGC and / or deleting a global regulator. Importantly, the present invention provides a recombination single plasmid for CRISPR / Cas based gene editing that allows efficient gene deletion and replacement. The objective of the present invention is solved by the teaching of the independent claims. Further advantageous features, aspects and details of the invention are evident from the dependent claims, the description, the figures, and the examples of the present application. Brief description of the invention The present invention relates to a method for finding global regulators in order to induce or increase production of target secondary metabolites. The method comprises providing a bacterium indicator strain producing two fluorescent reporter signals under the same control of two different biosynthetic gene clusters (BGC), preferably highly expressed BGC; performing random mutagenesis in said

[0004] GAR-P04397WO09 Application (final)2.docx bacterium indicator strain, and selecting mutant bacteria not producing said reporter signals. The invention also relates to a method to activate the production of target secondary metabolites, and to a CRISPR / Cas based single plasmid for gene editing to delete or inactivate a global regulator, to activate one or more BGC, to substitute a BGC with a fluorescent reporter, or for refactoring. Finally, the method can be performed in high-throughput format allowing to speed-up the procedure. Therefore, the present invention provides a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first BGC and of the second BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein the replacing of step a) and b) is in frame; wherein said GR gene regulates production of a target secondary metabolite. In a preferred embodiment, the method for screening for a global regulator (GR) gene in a bacterium, the method comprises: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene;

[0005] GAR-P04397WO09 Application (final)2.docx b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite. In a preferred embodiment, the method for screening for a global regulator (GR) gene in a bacterium, the method comprises: a) replacing a gene sequence of a first highly expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second highly expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d);

[0006] GAR-P04397WO09 Application (final)2.docx h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first highly expressed BGC and of the second highly expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite. Reworded, the inventice method for screening for a global regulator (GR) gene in a bacterium, the method comprises: a) replacing a gene sequence of a first biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first BGC and of the second BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, and wherein the first BGC and the second BGC are no cryptic BGCs. In a preferred embodiment of the above inventive method, the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging.

[0007] GAR-P04397WO09 Application (final)2.docx In a more preferred embodiment of the invention, the method further comprises after step h), the following step i): i) screening for production of secondary metabolites by HPLC / mass spectrometry analysis. In a more preferred embodiment of the invention, the method further comprises after step h), the following step i): i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis. In a further preferred embodiment of the above inventive method, performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis. In a further more preferred embodiment of the above inventive method, said BGC of step a) and / or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non- ribosomal peptide synthetase, terpene synthase / cyclase, polyketide synthase, ribosomally produced peptide (RiPP). In a still more preferred embodiment of the above inventive method, the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug, and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives. In a preferred embodiment of the above inventive method, the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces. In a preferred embodiment of the above inventive method, the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus. In a preferred embodiment of the above inventive method, the bacterium is not Streptomyces. In a preferred embodiment of the above inventive method, the steps a) and b) are performed introducing in said bacterium a Cas gene and a first and second BGC

[0008] GAR-P04397WO09 Application (final)2.docx specific crRNA array, a first and second fluorescent reporter gene, a first and second pair of BGC specific homology regions left and right. In a preferred embodiment of the above inventive method, steps a) to e) are performed culturing and handling the bacteria in microtiter plates. In a preferred embodiment of the above inventive method, steps a) to e) are performed using an automated liquid handling robotics, and wherein said robotics enables high-throughput manipulation of liquid added to or removed from cultures comprising the bacteria. The invention also relates to a method to elicit production of a secondary metabolite from a BGC in a bacterium, wherein the method comprises the following steps: i) deleting a GR gene in said bacterium, and ii) optionally activating a BGC in said bacterium; or wherein the method comprises the following steps: i') essentially activating a BGC in said bacterium, and ii') optionally deleting a GR gene in said bacterium; and the method further comprises: iii) expressing in said bacterium at least one positive selectable marker gene and at least one negative selectable marker gene; wherein deleting a GR gene of steps i) or ii’) comprises introducing in said bacterium at least one GR specific siRNA, or a group of sequences comprising a Cas gene, at least one GR specific crRNA array, a pair of GR specific homology regions left and right; and / or wherein activating a BGC of steps ii) or i') comprises introducing in said bacterium a group of sequences comprising a Cas gene, at least one BGC specific crRNA array, a pair of BGC specific homology regions left and right, a promoter system, and optionally an enhancer sequence. In other words, the invention also relates to a method to elicit production of a secondary metabolite by a bacterium, wherein the method comprises the following steps: i) deleting a global regulator (GR) gene in said bacterium, and ii) optionally activating a biosynthetic gene cluster (BGC) involved in production of said secondary metabolite in said bacterium; or wherein the method comprises the following steps: i') essentially activating a biosynthetic gene cluster (BGC) involved in production of said secondary metabolite in said bacterium, and

[0009] GAR-P04397WO09 Application (final)2.docx ii') optionally deleting a GR gene in said bacterium; and the method further comprises: iii) expressing in said bacterium at least one positive selectable marker gene and at least one negative selectable marker gene; wherein deleting a GR gene of steps i) or ii') comprises introducing in said bacterium at least one GR specific siRNA, or a group of sequences comprising a Cas gene, at least one GR specific crRNA array, a pair of GR specific homology regions left and right; and / or wherein activating a BGC of steps ii) or i') comprises introducing in said bacterium a group of sequences comprising a Cas gene, at least one BGC specific crRNA array, a pair of BGC specific homology regions left and right, a promoter system, and optionally an enhancer sequence. In a preferred embodiment of the the above method to elicit production of a secondary metabolite from a BGC in a bacterium, the GR gene is cyaA gene. In a further preferred embodiment of the the above method to elicit production of a secondary metabolite from a BGC in a bacterium, the BGC is xenoamicin. In a preferred embodiment of the above method to elicit production of a secondary metabolite from a BGC in a bacterium, deleting a GR gene of steps i) or ii’) comprises introducing in said bacterium at least one group of sequences comprising a Cas gene, at least one GR specific crRNA array, a pair of GR specific homology regions left and right. In a further preferred embodiment of the method to elicit production of a secondary metabolite from a BGC in a bacterium, the Cas is selected from the group comprising Cas9, Cas12 and Cas13. In a more preferred embodiment of the method to elicit production of a secondary metabolite from a BGC in a bacterium, step ii) or step i') comprises activating at least 2 BGCs in said bacterium. In a still more preferred embodiment of the method to elicit production of a secondary metabolite from a BGC in a bacterium, said BGC is selected from the group comprising puromycin, madumycin II, xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives.

[0010] GAR-P04397WO09 Application (final)2.docx In other words, in a still more preferred embodiment of the method to elicit production of a secondary metabolite from a BGC in a bacterium, said secondary metabolite is selected from the group comprising puromycin, madumycin II, xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives. In a preferred embodiment, the method further comprises culturing and handling the bacteria in microtiter plates. In a further preferred embodiment, the step i) - iii) are performed using an automated liquid handling robotics, and wherein said robotics enables high-throughput manipulation of liquid added to or removed from cultures comprising the bacteria. Finally, the present invention provides a recombination single-plasmid to activate or silence a BGC in a bacterium by CRISPR / Cas-mediated homology-directed repair, the plasmid comprising: an origin of transfer sequence (oriT), a cas gene under control of a first inducible promoter, genes for a suitable recombinase system under control of a second inducible promoter, at least one positive selectable marker gene, at least one negative selectable marker gene, a crRNA system selected from the group consisting of: I) a crRNA system to activate a BGC comprising: at least one crRNA framework, at least one target spacer specific for a genome sequence positioned upstream to a BGC gene, homology region left complementary to a genome sequence positioned upstream to said BGC gene, homology region right complementary to a genome sequence positioned inside said BGC gene, and a promoter system positioned between said homology region left and said homology region right, and optionally an enhancer sequence; II) a crRNA system to silence a BGC or to delete or inactivate a GR comprising: at least one crRNA framework, at least one target spacer specific for a genome sequence positioned inside a BGC gene or inside said GR, GAR-P04397WO09 Application (final)2.docx homology region left complementary to a genome sequence positioned upstream said BGC gene or said GR, homology region right complementary to a genome sequence positioned downstream said BGC gene or said GR, and optionally a fluorescent reporter gene positioned between said homology region left and said homology region right. In a particular embodiment of the recombinant plasmid, the Cas is selected from the group comprising Cas9, Cas12, Cas13, dCas9. Description of the invention The inventors have here developed a method to finding global regulators to increase secondary metabolite production. The method is based on replacement of at least two constitutively expressed biosynthetic gene clusters by two different fluorescent reporters, followed by random mutagenesis and analysis for loss of fluorescence for both reporters (Figure 1). BGC expression can be analysed by using fluorescence microscopy or FACS. Thus, the disclosed method comprises random mutagenesis, e.g. transposon mutagenesis, screening for loss of fluorescence and mass spectrometry analysis to detect all secondary metabolites. The disclosed method can also be performed in high-throughput in 96-well format or higher (Figure 16A-C), allowing replacement of up to 96 BGCs or more in parallel. The disclosed method allows direct bioactivity testing from crude extracts or simplified isolation of the secondary metabolites. The inventors have also developed a single and easy to assemble vector to apply CRISPR / Cas (Figures 1B, 3A-B, 6A-C) to generate bacterial indicator strains that express a fluorescent protein, for example mNeonGreen, in replacement for a biosynthetic gene cluster (Figure 17A-B) under the same control of said BGC. When global regulatory mechanisms are modified to shut-off global SM production, and then a biosynthetic gene clusters (BGC) for the production of a desired SM is selectively activated, only a single SM class is produced at high level, as showed by the activation of rupshomicin BGC in mutants with deletion of the hfq gene encoding a global regulator (strains V-IX in Figure 12). This is of GAR-P04397WO09 Application (final)2.docx particular advantage to elicit or increase production of a SM from a silent or lowly- expressed BGC. The developed CRISPR / Cas single-plasmid can also be used to delete or inactivate a global regulator or part of it (Figures 1D, 3B) , or to activate BGC expression by promoter exchange (Figures1C, 1D, 3B, 6A-C, 7, 8, 9). Genome editing can be checked by PCR on isolated colonies (Figure 5). Therefore, the present invention also provides a method to elicit production of a secondary metabolite from a BGC based on deleting a global regulator and / or activating a BGC or based on activating a BGC and / or deleting a global regulator, by using the described CRISPR / Cas single-plasmid (Figure 3A-B). Refactoring of mxn BGC (Example 5) led to a substantial increase in the production titer of madumycin to approximately 250 mg / l (Figure 8 B, C and D, Figure 9). Refactoring of xsc BGC (Example 6, Figure 10) allowed reaching safracin B production titers above 150 mg / l. Remarkably, the safracin B amount of the Xenorhadus sp. TS4 strain harboring a single-plasmid for xsc BGC activation was 14 times higher than that of E. coli strain LZ84 harboring the xsc Cluster encoded on three expression plasmids (Figure 11 B). Importantly, the inventive method for refactoring allowed discovering a novel BGC named rpmA-O, producing the compounds 19 - 26, wherein 26 is the primary product named rupshomycin. Compounds 19 - 26 (Figures 12, 13, 14) are not described in the prior art. Therefore, the inventive method has the advantage over the prior art to speed-up access to SM normally produced in very minute amounts, and / or from silent BCG, which is particularly relevant for SMs acting as antibiotics, anti-cancer or immune suppressive drugs. Moreover, the inventive method allows production of several secondary metabolites by a single bacterial multi-producer strain wherein at least 2 BGC are activated by promoter exchange and / or refactoring (Example 13). Such multi- producer strains (or extracts derived thereof) have the advantage of being easier GAR-P04397WO09 Application (final)2.docx to handle compared to culture of several mono-producing strains or handling of many extracts of individual compounds to be combined. The inventive method also allows direct bioactivity testing from crude extracts or simplified isolation of SMs that can also be achieved in high-throughput in 96-well format or higher. Deletion of crucial global regulators allows a much “cleaner” production of desired SM due to the lack of production of interfering SMs. The inventive CRISPR / Cas single plasmid allows multiple rounds of gene cluster optimization, that is especially important for multiple transcriptional units, such as for mxn (Figures 8, 9), xsc (Figure 10) or rpm (Figure 12, 13) BGCs. The inventive CRISPR / Cas single plasmid also allows direct conjugation of the plasmid from E. coli to the recipient strain without any integration of the plasmid or its parts into the genome. Importantly, the developed inventive CRISPR / Cpf1 single plasmid allows transformation of Photorhabdus and Xenorhabdus, wherein Photorhabdus had poor transformation efficiency and Xenorhabdus was not transformable at all with the prior art methods (Example 3). Global regulators and global regulatory mechanisms that affect natural product biosynthesis can be transcription factors (TF), chaperones, metabolic switches, signalling compounds binding to TFs. Exemplary global regulator are Hfq, which is a RNA chaperone mediating interaction of mRNA and sRNA (Example 7) ; ArcZ, a sRNA partner; DNA methyltransferase Dam1; the cAMP synthase CyaA (Example 12). Exemplary global regulators are transcription factors that bind to the regulatory element of DNA of a BGC and help to coordinate the responses of several genes to direct the production of biosynthesis of secondary metabolites. Only non-essential regulators can be addressed with the methodology disclosed herein, as individual clones need to be grown in production cultures to test and verify the effect on natural product production. On the other side, most regulators involved in natural product biosynthesis are non-essential even if they are quite global since the natural products are often not essential. Here might be a slight GAR-P04397WO09 Application (final)2.docx "Bacterial indicator strain" refers to a strain wherein a first BGC of interest is replaced by a first fluorescent reporter and the second BGC of interest is replaced by a second fluorescent reporter. "Bacterial indicator strain" is used interchangeably with "bacterial reporter strain". Thus, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite. The screening of fluorescent reporter strains is preferably performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging. Table 11 reports some fluorescent proteins that can be inserted in a BGC according to the disclosed method. Therefore, the present invention also relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: GAR-P04397WO09 Application (final)2.docx a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging. An embodiment of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, GAR-P04397WO09 Application (final)2.docx g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite. A particular embodiment of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, GAR-P04397WO09 Application (final)2.docx wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging. Random mutagenesis can be performed by a method selected from chemical random mutagenesis, UV mediated random mutagenesis, transposon mutagenesis, or error prone PCR. Transposon mutagenesis allows isolating mutants easily with antibiotic resistance caused by transposon insertion successfully. Accordingly, a particular embodiment of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis. GAR-P04397WO09 Application (final)2.docx A still more particular embodiment of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging, wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis. A further more particular embodiment of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; GAR-P04397WO09 Application (final)2.docx d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis. A still more particular embodiment of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); GAR-P04397WO09 Application (final)2.docx h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis. "Biosynthetic gene cluster" A "biosynthetic gene cluster" (BGC) can be defined as a physically clustered group of two or more genes in a particular genome that together encode a biosynthetic pathway for the production of a specialized metabolite. A "silent BCG" refers to silent or cryptic BGC under standard laboratory growth conditions, so the SM for which are responsible are not produced. Selective activation of a BGC refers to the selective stimulation of the expression of a particular BGC in order to obtain production of the SM for which is responsible at high level. Examples of BGC that can be modulated with the present invention: - encoding enzymes responsible for production of secondary metabolytes, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase / cyclase, polyketide synthase, ribosomally produced peptide (RiPP). - producing secondary metabolites selected from the group comprising an antibiotic, or an anti-cancer drug, or an immune suppressive drug. - producing a secondary metabolite selected from the group comprising Puromycin, Madumycin II, Xenoamicin, Rupshomycin, safracin. Non-ribosomal peptides (NRP) are not directly encoded in the genome like typical proteins or peptides but are produced by metabolic pathways encoded by BGCs. NRPs are a large family of structurally diverse and pharmacologically GAR-P04397WO09 Application (final)2.docx useful natural products with broad biological activities. Prominent examples are the antibiotic daptomycin or the immunosuppressant cyclosporine A2. They are assembled by multifunctional enzyme complexes called non-ribosomal peptide synthetases (NRPSs) that are organized in a modular fashion. Each module activates and modifies a specific amino acid (aa) that is then subsequently elongated with an aa activated and modified by the next module thereby generating peptides with their length depending on the number of modules used Therefore, a particular embodiment of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein said BGC of step a) and / or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase / cyclase, polyketide synthase, ribosomally produced peptide (RiPP). An alternative embodiment of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: GAR-P04397WO09 Application (final)2.docx a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein said BGC of step a) and / or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase / cyclase, polyketide synthase, ribosomally produced peptide (RiPP). A preferred alternative embodiment of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; GAR-P04397WO09 Application (final)2.docx d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein said BGC of step a) and / or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase / cyclase, polyketide synthase, ribosomally produced peptide (RiPP). A further preferred alternative embodiment of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); GAR-P04397WO09 Application (final)2.docx h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein said BGC of step a) and / or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase / cyclase, polyketide synthase, ribosomally produced peptide (RiPP). A further more preferred alternative embodiment of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; GAR-P04397WO09 Application (final)2.docx wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; wherein said BGC of step a) and / or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase / cyclase, polyketide synthase, ribosomally produced peptide (RiPP). An aspect of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging, wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; GAR-P04397WO09 Application (final)2.docx wherein said BGC of step a) and / or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase / cyclase, polyketide synthase, ribosomally produced peptide (RiPP). A further aspect of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; wherein said BGC of step a) and / or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase / cyclase, polyketide synthase, ribosomally produced peptide (RiPP). GAR-P04397WO09 Application (final)2.docx Another aspect of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; wherein said BGC of step a) and / or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase / cyclase, polyketide synthase, ribosomally produced peptide (RiPP). Secondary metabolites (natural products) Secondary metabolites (SM) are natural products (NP) synthesized mainly by bacteria, fungi and plants. They are molecules of low molecular weight with GAR-P04397WO09 Application (final)2.docx diverse chemical structures and biological activities. Exemplary SMs are pigments, antibiotics, anti-cancer or immune suppressive drugs with applications in medicine, biotechnology and agriculture. Secondary metabolites play important roles in cellular growth and signaling, nutrient acquisition, intra- and interspecies communication, and virulence. A subset of natural products is produced by nonribosomal peptide synthetases (NRPSs). Exemplary SMs are: Safracin compounds, comprising Safracin B that can be used for the semisynthesis of the two chemoterapeutics Ecteinascidin 743 and (–)- Jorumycin (Figures 10, 11), rupshomycin and derivatives produced from rpm BGC (Figure 12-14), Madumycin II (Figure 8, 9), Xenoamicine (Figure 22), Puromycin, Stilbenes (Figure 2, 4), GameXPeptides (gxpS, Figure 7A, Table 10), glidobactin (glbA, Figure 7A), Xenocoumacins (xcnA, Figure 7B, Table 10), Rhabdopeptides (rxpA, Figure 7B), Indigoidine, (indC, Figure 6, Table 10). Genetic loci involved in the biosynthesis of indigoidine have been found in E. chrysanthemi (indA∼indC), V. indigofera (igiA∼igiE) (GenBank™ accession number AF088856), and Photorhabdus luminescens (plu2182, plu2186, and plu2187). indC, igiD, and plu2186 genes in these loci seem to encode NRPS. The glidobactin-like natural products (GLNPs) glidobactin A and cepafungin I have been reported to be potent proteasome inhibitors and are regarded as promising candidates for anticancer drug development. Their biosynthetic gene cluster (BGC) plu1881–1877 is present in entomopathogenic Photorhabdus laumondii but silent under standard laboratory conditions. The plu1881 has the same function as the homologue glbB, i.e. catalysis of the 4-hydroxylation reaction of L-lysine. The biosynthesis of xenortides A-D consists of two NRPS coded by genes XndA and XndB. The XndA consists of a condensation, adenylation, methylation, and thiolation domain, and has been implicated for the loading of N-methylleucine (xenortides A-B) or N-methylvaline (xenortides C-D). The XndB consists of a condensation, adenylation, methylation, thiolation, and terminal condensation domains. XndB has been implicated in elongation with N-methylphenylalanine, as well as the final condensation of the enzyme-bound peptide with either decarboxylated phenylalanine (phenylethylamine in xenortides A and C) or decarboxylated tryptophan (tryptamine in xenortides B and D), ending the biosynthesis. GAR-P04397WO09 Application (final)2.docx In Xenorhabdus and Photorhabdus (XP), GxpS, an NRPS with five modules, is responsible for the biosynthesis of GameXPeptides (Table 10), which are a class of cyclic pentapeptides composed of valine, leucine, and phenylalanine. RXP are rhabdopeptide / xenortide-like peptides (Table 10). Other natural products produced by XP: silathride, xenoautoxin, phenylethylamide, tryptamide, rhabdopeptide, and PAX. Thus, a preferred aspect of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives. GAR-P04397WO09 Application (final)2.docx A more preferred aspect of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging. A still more preferred aspect of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; GAR-P04397WO09 Application (final)2.docx e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives. A further preferred aspect of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; GAR-P04397WO09 Application (final)2.docx i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging. A further more preferred aspect of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising GAR-P04397WO09 Application (final)2.docx Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis. A further still more preferred aspect of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging, wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis. GAR-P04397WO09 Application (final)2.docx The present invention also relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis. The present invention further relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; GAR-P04397WO09 Application (final)2.docx b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis. The present invention alternatively relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; GAR-P04397WO09 Application (final)2.docx c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein said BGC of step a) and / or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase / cyclase, polyketide synthase, ribosomally produced peptide (RiPP). The present invention preferably relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, GAR-P04397WO09 Application (final)2.docx f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein said BGC of step a) and / or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase / cyclase, polyketide synthase, ribosomally produced peptide (RiPP); wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging. An embodiment of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); GAR-P04397WO09 Application (final)2.docx h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein said BGC of step a) and / or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase / cyclase, polyketide synthase, ribosomally produced peptide (RiPP). A particular embodiment of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; GAR-P04397WO09 Application (final)2.docx i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein said BGC of step a) and / or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase / cyclase, polyketide synthase, ribosomally produced peptide (RiPP); wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging. A more particular embodiment of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; GAR-P04397WO09 Application (final)2.docx wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein said BGC of step a) and / or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase / cyclase, polyketide synthase, ribosomally produced peptide (RiPP); wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis. A still more particular embodiment of the the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, GAR-P04397WO09 Application (final)2.docx wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein said BGC of step a) and / or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase / cyclase, polyketide synthase, ribosomally produced peptide (RiPP); wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis. A further more particular embodiment of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; GAR-P04397WO09 Application (final)2.docx wherein said GR gene regulates production of a target secondary metabolite; wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein said BGC of step a) and / or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase / cyclase, polyketide synthase, ribosomally produced peptide (RiPP); wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis. A further still more particular embodiment of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; GAR-P04397WO09 Application (final)2.docx wherein said GR gene regulates production of a target secondary metabolite, wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein said BGC of step a) and / or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase / cyclase, polyketide synthase, ribosomally produced peptide (RiPP); wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis. Contemplated Bacteria: Preferred bacteria for the present invention are Gram negative bacteria (Pseudomonas, Xenorhabdus, Photorhabdus, Serratia, Vibrio etc.) and other strains that produce natural products, such as myxobacteria, cyanobacteria, Pseudomonades, Bacillus, Paenibacillus or Streptomyces. Therefore, an aspect of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); GAR-P04397WO09 Application (final)2.docx h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces. A further aspect of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, and Paenibacillus. GAR-P04397WO09 Application (final)2.docx A further aspect of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein the bacterium is not Streptomyces. A further aspect of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, GAR-P04397WO09 Application (final)2.docx f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces. Preferably, the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, and Paenibacillus. A particular aspect of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; GAR-P04397WO09 Application (final)2.docx i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces. Preferably, the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, and Paenibacillus. A preferable aspect of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, GAR-P04397WO09 Application (final)2.docx wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces. Preferably, the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, and Paenibacillus. An alternative aspect of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; GAR-P04397WO09 Application (final)2.docx wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces. Preferably, the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, and Paenibacillus. A preferred aspect of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging, wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces. GAR-P04397WO09 Application (final)2.docx Preferably, the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, and Paenibacillus. A further preferred aspect of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces. Preferably, the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, and Paenibacillus. GAR-P04397WO09 Application (final)2.docx A more preferred aspect the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces. Preferably, the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, and Paenibacillus. GAR-P04397WO09 Application (final)2.docx A still more preferred aspect the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein said BGC of step a) and / or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase / cyclase, polyketide synthase, ribosomally produced peptide (RiPP); and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces. Preferably, the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, and Paenibacillus. A particular aspect of present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; GAR-P04397WO09 Application (final)2.docx b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein said BGC of step a) and / or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase / cyclase, polyketide synthase, ribosomally produced peptide (RiPP); and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces. Preferably, the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, and Paenibacillus. A more particular aspect of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; GAR-P04397WO09 Application (final)2.docx b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein said BGC of step a) and / or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase / cyclase, polyketide synthase, ribosomally produced peptide (RiPP); and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces. Preferably, the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, and Paenibacillus. A still more particular aspect of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; GAR-P04397WO09 Application (final)2.docx b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein said BGC of step a) and / or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase / cyclase, polyketide synthase, ribosomally produced peptide (RiPP). A further more particular aspect of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; GAR-P04397WO09 Application (final)2.docx d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; wherein said BGC of step a) and / or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase / cyclase, polyketide synthase, ribosomally produced peptide (RiPP); and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces. Preferably, the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, and Paenibacillus. An alternative embodiment of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; GAR-P04397WO09 Application (final)2.docx d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging, wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; wherein said BGC of step a) and / or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase / cyclase, polyketide synthase, ribosomally produced peptide (RiPP); and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces. Preferably, the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, and Paenibacillus. A preferred embodiment of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; GAR-P04397WO09 Application (final)2.docx c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; wherein said BGC of step a) and / or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase / cyclase, polyketide synthase, ribosomally produced peptide (RiPP); and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces. Preferably, the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, and Paenibacillus. A more preferred embodiment of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; GAR-P04397WO09 Application (final)2.docx b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; wherein said BGC of step a) and / or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase / cyclase, polyketide synthase, ribosomally produced peptide (RiPP); and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces. Preferably, the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, and Paenibacillus. GAR-P04397WO09 Application (final)2.docx A still more preferred embodiment of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives, and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces. Preferably, the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, and Paenibacillus. A further more preferred embodiment of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; GAR-P04397WO09 Application (final)2.docx b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging, and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces. Preferably, the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, and Paenibacillus. In particular, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; GAR-P04397WO09 Application (final)2.docx d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives, and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces. Preferably, the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, and Paenibacillus. More in particular, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; GAR-P04397WO09 Application (final)2.docx e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces. Preferably, the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, and Paenibacillus. Also more in particular, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; GAR-P04397WO09 Application (final)2.docx e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces. Preferably, the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, and Paenibacillus. Still more in particular, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; GAR-P04397WO09 Application (final)2.docx e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging, wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces. Preferably, the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, and Paenibacillus. A particular embodiment of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; GAR-P04397WO09 Application (final)2.docx d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces. Preferably, the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, and Paenibacillus. A more particular embodiment of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; GAR-P04397WO09 Application (final)2.docx c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces. Preferably, the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, and Paenibacillus. A further more particular embodiment of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; GAR-P04397WO09 Application (final)2.docx b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein said BGC of step a) and / or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase / cyclase, polyketide synthase, ribosomally produced peptide (RiPP); and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces. Preferably, the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, and Paenibacillus. A further still more particular embodiment of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: GAR-P04397WO09 Application (final)2.docx a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein said BGC of step a) and / or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase / cyclase, polyketide synthase, ribosomally produced peptide (RiPP); wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces. Preferably, the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, and Paenibacillus. GAR-P04397WO09 Application (final)2.docx Preferably, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein said BGC of step a) and / or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase / cyclase, polyketide synthase, ribosomally produced peptide (RiPP); and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces. GAR-P04397WO09 Application (final)2.docx Preferably, the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, and Paenibacillus. More preferably, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein said BGC of step a) and / or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase / cyclase, polyketide synthase, ribosomally produced peptide (RiPP); GAR-P04397WO09 Application (final)2.docx wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces. Preferably, the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, and Paenibacillus. Further preferably, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein said BGC of step a) and / or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group GAR-P04397WO09 Application (final)2.docx comprising non-ribosomal peptide synthetase, terpene synthase / cyclase, polyketide synthase, ribosomally produced peptide (RiPP); wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces. Preferably, the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, and Paenibacillus. Further more preferably, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising GAR-P04397WO09 Application (final)2.docx Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein said BGC of step a) and / or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase / cyclase, polyketide synthase, ribosomally produced peptide (RiPP); wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces. Preferably, the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, and Paenibacillus. The present invention also relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; GAR-P04397WO09 Application (final)2.docx i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein said BGC of step a) and / or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase / cyclase, polyketide synthase, ribosomally produced peptide (RiPP); wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces. Preferably, the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, and Paenibacillus. The present invention particularly relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, GAR-P04397WO09 Application (final)2.docx g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein said BGC of step a) and / or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase / cyclase, polyketide synthase, ribosomally produced peptide (RiPP); wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis, and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces. Preferably, the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, and Paenibacillus. CRISPR / Cas based gene editing CRISPR-Cas systems are native to bacteria and Archaea and provide adaptive immunity against viruses and plasmids. The CRISPR-Cas endonuclease system is utilized in genomic engineering as follows: the gRNA complex (either a crRNA:tracrRNA complex or an sgRNA) binds to Cas9, inducing a conformational change that activates Cas9 and opens the DNA binding cleft, the protospacer domain of the crRNA (or sgRNA) aligns with the complementary target DNA and GAR-P04397WO09 Application (final)2.docx Cas9 binds the PAM sequence, initiating unwinding of the target DNA followed by annealing of the protospacer domain to the target, after which cleavage of the target DNA occurs. The Cas9 contains two domains, homologous to endonucleases HNH and RuvC respectively, wherein the HNH domain cleaves the DNA strand complementary to the crRNA and the RuvC-like domain cleaves the non-complementary strand. This results in a double-stranded break in the genomic DNA. When repaired by non-homologous end joining (NHEJ) the break is typically repaired in an imprecise fashion, resulting in the DNA sequence being shifted by 1 or more bases, leading to disruption of the natural DNA sequence and, in many cases, leading to a frameshift mutation if the event occurs in a coding exon of a protein-encoding gene. The break may also be repaired by homology directed recombination (HDR), which permits insertion of new genetic material based upon exogenous DNA introduced into the cell with the Cas9 / gRNA complex, which is introduced into the cut site created by Cas9 cleavage A second class 2 CRISPR system, assigned to type V, has been identified. This type V CRISPR-associated system contains Cpf1, which is a ˜1300 amino acid protein—slightly smaller than Cas9 from S. pyogenes. The PAM recognition sequence of Cpf1 is TTTN, in contrast to the NGG PAM recognition domain of S. pyogenes Cas9. Having the ability to target AT-rich areas of the genome will be greatly beneficial to manipulate and study gene targets in regions that are lacking GG dinucleotide motifs. The Cpf1 system is also remarkably simple in that it does not utilize a separate tracrRNA, and only requires a single short crRNA of 40-45 base length that both specifies target DNA sequence and directs binding of the RNA to the Cpf1 nuclease. In contrast to Cas9 which produces blunt-ended cleavage products, Cpf1 facilitates double stranded breaks with 4-5 nucleotide overhangs. The advantage of this is that it may ensure proper orientation as well as providing microhomology during non-homologous end joining (NHEJ). This could also be advantageous in non-dividing cell types that tend to be resistant to homology-directed repair (HDR). Furthermore, when Cpf1 cleaves, it does so further away from PAM than Cas9, which is also further away from the target site. As a result, the protospacer, and especially the seed sequence of the protospacer, are less likely to be edited, thereby leaving open the potential for a second round of cleavage if the desired repair event doesn't happen the first time. The Cpf1 protein forms a complex with a single stranded RNA oligonucleotide to mediate targeted DNA cleavage. The single strand guide RNA oligonucleotide consists of a constant region of 20 nt and a target region of 21-24 nt for an overall length of 41-44 nt. GAR-P04397WO09 Application (final)2.docx A further suitable Cas for the present invention is Cas13. The term "crRNA framework" (crRNA FW) refers to a nucleotide sequence comprising a constitutive or inducible promoter, a crRNA leader, direct repeat, a spacer dummy (comprising a BsaI or BsmbI or any other type II restriction sites for insertion of target spacers A and B), direct repeat, a terminator. Suitable crRNA frameworks for the present invention are shown in Figure 19. The term "crRNA array" refers to a group of nucleotide sequences comprising: - a crRNA framework; - "target" specific target spacers A and / or B inserted inside said crRNA framework; - optionally further elements such as promoter system as defined herein, translational enhancer, fluorescent reporter gene. Thus, a crRNA array is target specific. The target specific crRNA array is formed in the plasmid for gene editing from the elements of the homology arms left and right. The "target" can be for example a gene of a BGC for BGC activation, or a gene of a BGC for silencing or replacement with a FR gene, or a GR for GR deletion. The term "crRNA system" refers to a group of dsDNA fragments (dsDNA nucleotide sequences) comprising: at least one crRNA framework, at least one target spacer A or B, target specific homology region left, target specific homology region right, and optionally a fluorescent reporter gene, or a promoter system or enhancer sequence positioned between said homology region left and said homology region right. A "crRNA leader" sequence can be an AT-rich sequence, but can also be part of the UTR of the promoter, so it is not necessary as an independent component. A "direct repeat" refers to a 36 bp long direct repeat that is an essential part of the crRNA framework and must be encoded upstream of any target specific spacer to be recognized by the Cas protein, such as Cpf1. A repeat after the spacer is not necessary if the spacer has already been shortened to the mature length of 23 bp. GAR-P04397WO09 Application (final)2.docx The term "target spacer" refers to a nucleic acid sequence having the function of "target specific crRNA". A "target spacer" is selected from the genome of the target organism and is located distally after a PAM sequence (in the best-case TTTV). Best editing results can be achieved selecting one spacer for each leading and lagging strand, i.e. target spacer A and target spacer B. It should be avoided to have three or more “T” in the sequence. A GC content of 50% should be aimed at. moreover, a "target spacer" has a nucleic acid sequence with a length between 23 and 31 bp depending on whether there is a direct repeat after the target spacer. A "spacer dummy" refers to a polynucleotide sequence which should not have homology to the target host; and must be accessible for any kind of cloning (Gibson, Golden Gate, Gateway, Restriction cloning). A "spacer dummy" can comprise a reporter gene (e.g. mCherry) or a toxin (e.g. ccdB) to allow identification of the cloning success; A "terminator" or "transcriptional terminator" refers to a target host adapted terminator or standard terminator from the iGEM library (http: / / parts.igem.org / Terminators / Catalog). The term "homology arm left" (HA-L) refers to a synthetic dsDNA fragment comprising the following elements in this order: spacer with restriction site (e.g. BsaI site), target spacer A or B (TS-A or TS-B), direct repeat (DR), optionally a terminator, homology region left (HR-L), spacer with restriction site (e.g. BsaI site). The target spacer A or B and DR form the "target specific crRNA array" in the assembled single plasmid, e.g. pAR20 in the Examples of this invention. The term "homology arm right" (HA-R) refers to a synthetic dsDNA fragment comprising the following elements in this order: spacer with restriction site (e.g. BsaI site), homology region right (HR-R), a constitutive promoter (e.g. J23119), direct repeat (DR), target spacer A or B (TS-A or TS-B), spacer with restriction site (e.g. BsaI site). The constitutive promoter, crRNA leader, DR, and target spacer form the "target specific crRNA array" in the assembled single plasmid, e.g. pAR20 in the Examples of this invention. GAR-P04397WO09 Application (final)2.docx The term "homology region" left or right refers to a nucleic acid sequence which is contained in the single plasmid for CRISPR / Cas gene editing and is complementary to the target BGC or global regulatory gene. It is used for repair after CRISPR induced double strand break. A nucleic acid sequence for "homology region" left or right depends on the recombination genes and the used strains. A nucleic acid sequence for "homology region" left or right can comprise at least 50, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000 bp (basepair). A nucleic acid sequence for "homology region" left or right can comprise at most 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1200, 1400, 1600, 1700, 1800, 1900, 2000 bp. A nucleic acid sequence for "homology region" left or right preferably comprises between 100 and 500 bp, 100 and 600 bp, 100 and 700 bp, 100 and 800 bp, 100 and 900 bp, 100 and 1000 bp, 100 and 1100 bp, 100 and 1200 bp, 100 and 1300 bp, 100 and 1400 bp, 100 and 1500 bp, 100 and 1600 bp, 100 and 1700 bp, 100 and 1800 bp, 100 and 1900 bp, 100 and 2000 bp, 50 and 500 bp, 50 and 600 bp, 50 and 700 bp, 50 and 800 bp, 50 and 900 bp, 50 and 1000 bp, 50 and 1100 bp, 50 and 1200 bp, 50 and 1300 bp, 50 and 1400 bp, 50 and 1500 bp, 50 and 1600 bp, 50 and 1700 bp, 50 and 1800 bp, 50 and 1900 bp, 50 and 2000 bp, The present invention alternatively relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; GAR-P04397WO09 Application (final)2.docx wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. More in particular, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. GAR-P04397WO09 Application (final)2.docx In other embodiments, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. In particular embodiments, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; GAR-P04397WO09 Application (final)2.docx c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. In particular embodiments, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, GAR-P04397WO09 Application (final)2.docx f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. In preferred embodiments, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; GAR-P04397WO09 Application (final)2.docx wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging, wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis, wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. In more preferred embodiments, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; GAR-P04397WO09 Application (final)2.docx wherein said GR gene regulates production of a target secondary metabolite; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. In alternative embodiments, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; GAR-P04397WO09 Application (final)2.docx wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. In further embodiments, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein said BGC of step a) and / or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase / cyclase, polyketide synthase, ribosomally produced peptide (RiPP); wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and GAR-P04397WO09 Application (final)2.docx second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. More in particular, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein said BGC of step a) and / or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase / cyclase, polyketide synthase, ribosomally produced peptide (RiPP); wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. GAR-P04397WO09 Application (final)2.docx The present invention further relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein said BGC of step a) and / or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase / cyclase, polyketide synthase, ribosomally produced peptide (RiPP); wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. The present invention also relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; GAR-P04397WO09 Application (final)2.docx b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein said BGC of step a) and / or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase / cyclase, polyketide synthase, ribosomally produced peptide (RiPP); wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. The present invention is also directed to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; GAR-P04397WO09 Application (final)2.docx b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; wherein said BGC of step a) and / or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase / cyclase, polyketide synthase, ribosomally produced peptide (RiPP); wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. More in particular, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; GAR-P04397WO09 Application (final)2.docx c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging, wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; wherein said BGC of step a) and / or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase / cyclase, polyketide synthase, ribosomally produced peptide (RiPP); wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. The present invention preferably relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; GAR-P04397WO09 Application (final)2.docx c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; wherein said BGC of step a) and / or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase / cyclase, polyketide synthase, ribosomally produced peptide (RiPP); wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. The present invention more preferably relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; GAR-P04397WO09 Application (final)2.docx c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; wherein said BGC of step a) and / or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase / cyclase, polyketide synthase, ribosomally produced peptide (RiPP); wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. The present invention still more preferably relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; GAR-P04397WO09 Application (final)2.docx b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. The present invention further more preferably relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; GAR-P04397WO09 Application (final)2.docx d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. The present invention also preferentially relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); GAR-P04397WO09 Application (final)2.docx h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. The present invention more preferentially relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; GAR-P04397WO09 Application (final)2.docx i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. The present invention more preferentially relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; GAR-P04397WO09 Application (final)2.docx wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. The present invention still more preferentially relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, GAR-P04397WO09 Application (final)2.docx wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging, wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. Thus, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; GAR-P04397WO09 Application (final)2.docx wherein said GR gene regulates production of a target secondary metabolite; wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. In a particular aspect, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, GAR-P04397WO09 Application (final)2.docx wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. Thus, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; GAR-P04397WO09 Application (final)2.docx wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein said BGC of step a) and / or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase / cyclase, polyketide synthase, ribosomally produced peptide (RiPP); wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. More in particular, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising GAR-P04397WO09 Application (final)2.docx Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein said BGC of step a) and / or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase / cyclase, polyketide synthase, ribosomally produced peptide (RiPP); wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. Thus, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; GAR-P04397WO09 Application (final)2.docx wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein said BGC of step a) and / or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase / cyclase, polyketide synthase, ribosomally produced peptide (RiPP); wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. More in particular, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, GAR-P04397WO09 Application (final)2.docx wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein said BGC of step a) and / or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase / cyclase, polyketide synthase, ribosomally produced peptide (RiPP); wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. In an aspect, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; GAR-P04397WO09 Application (final)2.docx wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein said BGC of step a) and / or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase / cyclase, polyketide synthase, ribosomally produced peptide (RiPP); wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. More in particular, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; GAR-P04397WO09 Application (final)2.docx wherein said GR gene regulates production of a target secondary metabolite, wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein said BGC of step a) and / or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase / cyclase, polyketide synthase, ribosomally produced peptide (RiPP); wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. Moreover, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; GAR-P04397WO09 Application (final)2.docx i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein said BGC of step a) and / or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase / cyclase, polyketide synthase, ribosomally produced peptide (RiPP); wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. More in particular, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); GAR-P04397WO09 Application (final)2.docx h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein said BGC of step a) and / or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase / cyclase, polyketide synthase, ribosomally produced peptide (RiPP); wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. Thus, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; GAR-P04397WO09 Application (final)2.docx e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. More in particular, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); GAR-P04397WO09 Application (final)2.docx h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. Thus, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; GAR-P04397WO09 Application (final)2.docx wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. More in particular, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, GAR-P04397WO09 Application (final)2.docx wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. Thus, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; GAR-P04397WO09 Application (final)2.docx wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. More in particular, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging, wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; GAR-P04397WO09 Application (final)2.docx wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. In a further more particular embodiment, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; GAR-P04397WO09 Application (final)2.docx and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. In a still more particular embodiment, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; GAR-P04397WO09 Application (final)2.docx and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. In a more particular embodiment, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein said BGC of step a) and / or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase / cyclase, polyketide synthase, ribosomally produced peptide (RiPP); and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces; GAR-P04397WO09 Application (final)2.docx wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. In a more particular embodiment,the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein said BGC of step a) and / or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase / cyclase, polyketide synthase, ribosomally produced peptide (RiPP); and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces; GAR-P04397WO09 Application (final)2.docx wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. In a particular embodiment, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein said BGC of step a) and / or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase / cyclase, polyketide synthase, ribosomally produced peptide (RiPP); and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces; GAR-P04397WO09 Application (final)2.docx wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. In a particular aspect, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein said BGC of step a) and / or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase / cyclase, polyketide synthase, ribosomally produced peptide (RiPP); wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and GAR-P04397WO09 Application (final)2.docx second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. Morevoer, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; wherein said BGC of step a) and / or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase / cyclase, polyketide synthase, ribosomally produced peptide (RiPP); and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and GAR-P04397WO09 Application (final)2.docx second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. In other particular embodiments, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging, wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; wherein said BGC of step a) and / or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase / cyclase, polyketide synthase, ribosomally produced peptide (RiPP); and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces; GAR-P04397WO09 Application (final)2.docx wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. In other alternative embodiments, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; wherein said BGC of step a) and / or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase / cyclase, polyketide synthase, ribosomally produced peptide (RiPP); GAR-P04397WO09 Application (final)2.docx and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. In other particular embodiments, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; GAR-P04397WO09 Application (final)2.docx wherein said BGC of step a) and / or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase / cyclase, polyketide synthase, ribosomally produced peptide (RiPP); and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. In other preferred embodiments, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising GAR-P04397WO09 Application (final)2.docx Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives, and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. In other embodiments, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging, and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces; GAR-P04397WO09 Application (final)2.docx wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. A further aspect of present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives, and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces; GAR-P04397WO09 Application (final)2.docx wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. A still more particular aspect of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mut...

Claims

Claims 1. A method to elicit production of a secondary metabolite by a bacterium, wherein the method comprises the following steps: i) deleting a global regulator (GR) gene in said bacterium, and ii) optionally activating a biosynthetic gene cluster (BGC) involved in production of said secondary metabolite in said bacterium; or wherein the method comprises the following steps: i') essentially activating a biosynthetic gene cluster (BGC) involved in production of said secondary metabolite in said bacterium, and ii') optionally deleting a GR gene in said bacterium; and the method further comprises: iii) expressing in said bacterium at least one positive selectable marker gene and at least one negative selectable marker gene; wherein deleting a GR gene of steps i) or ii') comprises introducing in said bacterium at least one GR specific siRNA, or a group of sequences comprising a Cas gene, at least one GR specific crRNA array, a pair of GR specific homology regions left and right; and / or wherein activating a BGC of steps ii) or i') comprises introducing in said bacterium a group of sequences comprising a Cas gene, at least one BGC specific crRNA array, a pair of BGC specific homology regions left and right, a promoter system, and optionally an enhancer sequence.

2. The method according to claim 1, wherein step ii) or step i') comprises activating at least 2 BGCs in said bacterium.

3. The method according to claim 1 or 2, wherein the GR gene is cyaA gene.

4. The method according to any one of the claims 1 – 3, wherein said BGC is selected from the group comprising puromycin, madumycin II, xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives.

5. The method according to any one of the claims 1 – 4, wherein the GR gene is cyaA gene and said BGC is xenoamicin.

6. The method of any one of the claims 1 – 5, wherein the step i) - iii) are performed using an automated liquid handling robotics, and wherein said GAR-P04397WO09 Application (final)2.docxrobotics enables high-throughput manipulation of liquid added to or removed from cultures comprising the bacteria.

7. A method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in step a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite.

8. The method of claim 7, wherein step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging.

9. The method of claim 7 or 8, further comprising after step h), the following step i): i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis.

10. The method of any one of the claims 7 – 9, wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV- GAR-P04397WO09 Application (final)2.docxmediated random mutagenesis, or error-prone PCR or transposon mutagenesis.

11. The method of any one of the claims 7 – 10, wherein said BGC of step a) and / or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non- ribosomal peptide synthetase, terpene synthase / cyclase, polyketide synthase, ribosomally produced peptide (RiPP).

12. The method of any one of the claims 7 – 11, wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives.

13. The method of any one of the claims 7 – 12, wherein the bacterium is not Streptomyces.

14. The method of any one of the claims 7 – 13, wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, and Paenibacillus.

15. The method of any one of the claims 7 – 14, wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA arrays, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right.

16. A compound of general formula (I)wherein Y represents –CH=CH2 or ; GAR-P04397WO09 Application (final)2.docxR1, R2, R3, R4, and R5are independently of each other selected from –H, –NH2, –NHR6, –F, –OH, –OCH3, –OCH2CH3, and –OCH2CH2CH3; or R2and R3or R3and R4together with the carbon atom to which they are bound to form one of the following rings:with the proviso that when Y represents –CH=CH2, R1, R2, R4, and R5cannot be –H, and R3cannot be –OH simultaneously.

17. The compound according to claim 16 having the following structurewherein Y, and R1– R5have the meanings as defined in claim 16.

18. The compound according to claim 16 having the following structurewherein Y, and R1– as in claim 16. GAR-P04397WO09 Application (final)2.docx19. The compound according to claim 16 selected from the group consisting of:GAR-P04397WO09 Application (final)2.docx20. The compound according to claim 19, wherein the compound is a (2E)- thiazolidine isomer.

21. The compound according to claim 19, wherein the compound is a (2Z)- thiazolidine isomer. GAR-P04397WO09 Application (final)2.docx

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