Streptomycete X-57 as well as microecological preparation and preparation method thereof

Abstract

The invention relates to a streptomyces X-57, a microecological preparation thereof and a preparation method of the microecological preparation, the streptomyces is preserved in the China Center for Type Culture Collection, the strain preservation number is CCTCC NO: M 20242239, the classification name is streptomyces X-57, and the Latin name is Streptomyces sp.X-57. The invention also discloses a preparation method of the microecological preparation, the streptomyces is preserved in the China Center for Type Culture Collection, and the strain preservation number is CCTCC NO: M 20242239. The microecological preparation is prepared by fermenting streptomycete X-57. The invention also discloses a preparation method of the microecological preparation. A microecological preparation which is prepared from the strain through a corresponding method and is suitable for aquaculture acts on freshwater fishes in a feed additive mode and has broad-spectrum activity of inhibiting fish pathogenic bacteria, and the streptomyces X-57 is used as a feed additive to feed fishes, especially crucian. The growth performance and the immunity of fishes, especially crucian carps, can be improved, and the intestinal flora can be improved. Wherein the effect of resisting infection of aeromonas hydrophila on crucian carps is particularly remarkable, meanwhile, the culture medium can be stably colonized in the crucian carps, the immunocompetence of the crucian carps is effectively improved, and the culture medium has a certain effect of promoting the growth of the crucian carps.

Description

Technical Field

[0001] The invention relates to a microorganism Streptomyces, a microecological preparation thereof and a preparation method thereof, in particular to a strain of Streptomyces X-57, a microecological preparation thereof and a preparation method thereof. Background Art

[0002] With the rapid development of my country's aquaculture industry, while achieving high efficiency and diversification, my country's aquaculture industry is also facing severe challenges. The sustainable development of aquaculture, especially the sustainable development of the environment, has attracted much attention. Without causing damage to the aquatic ecosystem and not exceeding the water's own renewal limit, healthy breeding can be carried out, and the nutrition of farmed aquatic products that are safe and beneficial to the human body can be continuously provided to humans. This is the sustainable development goal of aquaculture that we all pursue. However, due to factors such as water quality deterioration and high-density breeding, the incidence of fish in freshwater aquaculture has risen sharply, seriously affecting the health of fish, causing the breeding cost to continue to increase, thus endangering the sustainable development of my country's aquaculture industry. Aquaculture diseases are characterized by high incidence, diverse types, long onset time, and a wide range of infection. In addition, the number of fish infections during the breeding process has shown an increasing trend year by year. In response to this problem, people use antibiotics as the main means of preventing and controlling fish diseases. Excessive use of antibiotics can lead to increased bacterial resistance, water pollution, and antibiotic residues in fish and aquatic products.

[0003] The aquaculture method of fish has evolved from the traditional extensive aquaculture method with high trophic level richness to the current intensive or semi-intensive aquaculture method with relatively simple trophic levels. Although the scale has been expanded, this development has reduced the self-renewal ability of the aquatic environment of fish, suppressed the immunity of fish, and increased the susceptibility of fish to bacterial diseases. With the in-depth study of bacterial pathogens of fish, people have taken a variety of measures to cope with the challenges of these pathogens, including the use of chemical drugs, Chinese herbal medicines, vaccines, antagonistic microecological preparations and other prevention and control measures. Summary of the invention

[0004] The technical problem to be solved by the present invention is to overcome the above-mentioned defects of the prior art and provide a strain of Streptomyces X-57. The microecological preparation prepared by the new strain of Streptomyces has a good antagonistic effect on a variety of common pathogens of fish and can resist the infection of a variety of bacterial diseases of fish.

[0005] The technical problem to be further solved by the present invention is to provide a Streptomyces microecological preparation suitable for preventing and treating fish diseases in aquaculture.

[0006] A further technical problem to be solved by the present invention is to provide a method for preparing a Streptomyces microecological preparation suitable for preventing and treating fish diseases in aquaculture.

[0007] The technical solution adopted by the present invention to solve its technical problems is as follows: a strain of Streptomyces X-57, which was deposited in the China Center for Type Culture Collection on October 17, 2024, with a strain collection number of CCTCC NO: M20242239; it is classified and named: Streptomyces X-57, with a Latin name of Streptomyces sp. X-57.

[0008] The 16sRNA sequence of Streptomyces X-57 of the present invention is shown in the sequence table SEQ ID No. 1.

[0009] The Streptomyces X-57 of the present invention was screened from soil samples in Linyi, Shandong Province and other areas.

[0010] The technical solution adopted by the present invention to further solve the technical problem is as follows: a Streptomyces microecological preparation suitable for aquaculture is fermented by Streptomyces X-57 with a strain collection number of CCTCC NO: M20242239. The antibacterial active substances in the fermentation liquid of the strain have good acid-base and ultraviolet irradiation stability and are relatively stable in actual production applications; it has a good inhibitory effect on freshwater fish pathogens, can promote fish growth, and improve fish immunity.

[0011] Furthermore, the microecological preparation is a liquid preparation or a solid preparation.

[0012] Furthermore, the aquaculture animals are freshwater fish.

[0013] Furthermore, the freshwater fish is crucian carp, grass carp or carp.

[0014] The present invention further solves the technical problem by adopting the following technical solution: A method for preparing a microecological preparation suitable for aquaculture, comprising the following steps:

[0015] (1) Inoculation and activation: transferring the preserved slant strain of Streptomyces X-57 to an activated slant culture medium for activation to obtain an activated seed solution; the activated slant culture medium is Am6 liquid culture medium (Am6 culture medium is a non-synthetic broth antibiotic culture medium 3);

[0016] The activation culture conditions are as follows: temperature 28-30°C, liquid volume 10-30% of the container volume, and shaking speed 180-200 rpm;

[0017] (2) First expansion culture: The seed liquid activated in step (1) is inoculated into a fermentation tank at an inoculation rate of 1 to 2% for first expansion culture;

[0018] The fermentation medium formula is: soluble starch 14-16g / L, bacteriological peptone 8-12g / L, soybean powder 4-6g / L, glycerol 14-16g / L, CaCO3 1.5-2.5g / L, acid hydrolyzed casein 2-4g / L, pH 7.0-7.4;

[0019] The preferred formula of fermentation medium is: soluble starch 15g / L, bacteriological peptone 10g / L, soybean powder 5g / L, glycerol 15g / L, CaCO 3 2g / L, acid hydrolyzed casein 3g / L, pH 7.2-7.7;

[0020] The culture conditions are as follows: the entire culture process is monitored online, the dissolved oxygen concentration is 35-55%, the temperature is 28-30°C, the culture is 72-96h, and the defoaming agent is added online in real time;

[0021] (3) Second expansion culture: inoculate the seed solution of the first expansion culture in step (2) into a fermentation tank containing a fermentation medium at an inoculum amount of 10-15% for fermentation culture, wherein the fermentation medium formula is the same as the fermentation medium formula in step (2); the culture conditions are: dissolved oxygen concentration of 35-55%, temperature of 28-30° C., culture for 96-168 hours, and real-time online addition of a defoaming agent;

[0022] Furthermore, in step (3), the fermentation tank is preferably filled with a fermentation medium equivalent to 65%-70% of the volume of the fermentation tank, and more preferably a 500L-1000L fermentation tank.

[0023] (4) Concentration and collection: After the culture is completed, the fermentation product is collected in a tank and concentrated to obtain a microecological liquid bacterial agent, or spray-dried to obtain a microecological solid preparation.

[0024] The identification and research methods of Streptomyces X-57 of the present invention are as follows.

[0025] (A) Observation of cell morphological characteristics of strain Streptomyces X-57;

[0026] (ii) identification using 16sRNA gene;

[0027] (III) Physical and chemical properties testing of antibacterial active substances of Streptomyces X-57;

[0028] (iv) Detection of colonization of Streptomyces X-57 in crucian carp;

[0029] (V) Effects of Streptomyces X-57 as a feed additive on the growth and disease resistance of crucian carp.

[0030] The invention has the following beneficial effects: (1) the strain is identified as Streptomyces through 16sRNA gene sequence determination, and has good antibacterial effect on various freshwater fish pathogens such as Aeromonas hydrophila, Aeromonas veronii, Edwardsiella tarda, etc.; (2) Streptomyces X-57 can survive and colonize in fish bodies without causing any harm to fish, which lays a foundation for the strain to play a stable disease prevention and growth promotion role in fish farming; (3) Adding Streptomyces X-57 to feed fish as a feed additive can promote the growth rate and feed efficiency of fish, improve the immunity of fish, and enhance the resistance of fish to pathogens; (4) The method for preparing Streptomyces X-57 into a microecological preparation is relatively simple and has a low production cost. At the same time, it can also effectively reduce the risks of drug residues and pathogenic bacteria resistance caused by the abuse of antibiotics, and has good application prospects.

[0031] The gene of Streptomyces X-57 of the present invention is shown in SEQ ID No. 1:

[0032]

[0033]

[0034] Description of Microbiological Deposit

[0035] The Streptomyces X-57 of the present invention was deposited in the China Center for Type Culture Collection (CCTCC for short, address: Wuhan University, Wuhan, China) on October 17, 2024, and the strain collection number is CCTCC NO: M20242239; the classification name is: Streptomyces X-57; the Latin name is: Streptomyces sp.X-57. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a diagram showing the antibacterial effect of the novel Streptomyces X-57 of the present invention on fish pathogens;

[0037] Figure 2 These are observation diagrams of the morphological characteristics of the novel Streptomyces X-57 of the present invention; a: observation diagram of the plate colony morphology of the strain X-57; b: observation diagram of the strain X-57 under a phase contrast microscope; c: observation diagram of the strain X-57 under Gram staining; d, e: observation diagrams of the strain X-57 under a scanning electron microscope;

[0038] Figure 3 It is a phylogenetic tree diagram constructed from the 16sRNA sequence of the novel Streptomyces X-57 of the present invention;

[0039] Figure 4 The effect of the novel Streptomyces X-57 of the present invention on the tissue structure of crucian carp;

[0040] Figure 5This is a physicochemical property analysis diagram of the novel antibacterial active substance of Streptomyces X-57 of the present invention (*, P < 0.05; **, P < 0.01; ***, P < 0.001);

[0041] Figure 6 This is a diagram of the colonization and protection of a new type of Streptomyces X-57 labeled strain in crucian carp observed by the small animal living imaging system of the present invention;

[0042] Figure 7 This is the analysis result of the effect of the microecological preparation prepared by the novel Streptomyces X-57 of the present invention on the activity of immune-related enzymes in the serum of crucian carp (*, P < 0.05; **, P < 0.01; ***, P < 0.001);

[0043] Figure 8 This is a diagram showing the antagonistic effect of the microecological preparation prepared by the novel Streptomyces X-57 on Aeromonas veronii in crucian carp observed by the small animal living imaging system of the present invention.

[0044] Fig. 9 It is the result of assembling the genome of the novel Streptomyces X-57 of the present invention.

[0045] Fig.10 It is the prediction of the biosynthetic gene cluster of secondary metabolites of the novel Streptomyces X-57 of the present invention. DETAILED DESCRIPTION

[0046] The present invention will be further described below in conjunction with the embodiments and drawings.

[0047] Unless otherwise specified, the chemical reagents used in the embodiments of the present invention were obtained through conventional commercial channels.

[0048] (I) Screening of novel Streptomyces X-57 and determination of antibacterial spectrum

[0049] 115 soil samples from Shandong Province and other regions were fully mixed in sterile water, spread on Goll plates after gradient dilution, and cultured at 30℃ for 5 days. The growth status of the strains was observed and single clones of actinomycetes were picked and inoculated on new culture medium to purify the picked strains. The fish pathogens Aeromonas veronii AvX005, Aeromonas hydrophila, Aeromonas caviae, Aeromonas salmonicida, Aeromonas allosaccharophila, Edwardsiella tarda, Citrobacter freundii, Shewanella xiamenensis, Aeromonas sobria, Plesiomonas shigella shigelloide) was used as the indicator bacteria, and the antibacterial activity of the fermentation supernatant against the above pathogens was detected using the Oxford cup method (the results are shown in Figure 1 ) and found a strain with good antibacterial effect on 10 fish pathogens, named X-57.

[0050] (II) Cell morphological characteristics of the novel Streptomyces X-57

[0051] Strain X-57 was streaked on Gao's solid medium No. 1, and it was observed that the colonies of strain X-57 were small, dry, and had irregular serrated edges. The colonies were in the shape of concentric circles with white edges and light yellow in the middle. Phase contrast microscopy showed that strain X-57 had well-developed mycelium with many branches. Gram staining showed that strain X-57 was a Gram-positive bacterium. Cold-field scanning electron microscopy showed that strain X-57 had many branches and well-developed mycelium, and its spore hyphae were tightly spiraled. Based on the above morphological characteristics, strain X-57 can be preliminarily identified as an actinomycete (see Figure 2 ).

[0052] (III) Identification of the 16sRNA gene of the novel Streptomyces X-57

[0053] The strain X-57 was inoculated into liquid Gould's medium and cultured at 30°C and 120 rpm for 6 days. The bacteria were collected and the genomic DNA of the strain X-57 was extracted using the Ezup column bacterial genomic DNA extraction kit (Shanghai Shenggong Biotechnology Co., Ltd.) and the 16sRNA gene amplification primers were used.

[0054] 16sRNA27F: 5′-AGAGTTTGATCCTGGCTCAG-3′;

[0055] 16sRNA1492R: 5′-CGGTTACCTTGTTACGACTT-3′.

[0056] The 16sRNA gene sequence was amplified using the above primers, and the expected length of the sequence was about 1500 bp.

[0057] PCR reaction system (20 μL):

[0058]

[0059]

[0060] PCR reaction procedure

[0061]

[0062] After the 16sRNA gene PCR product was detected by 1.0% agarose gel electrophoresis, the successfully amplified product was sent to Shanghai Shenggong Biotechnology Co., Ltd. for sequencing.

[0063] The 16sRNA gene sequence of strain X-57 was sequenced and showed to be 1160 bp in length. The amplified sequencing results were compared and analyzed by BLAST on NCBI. The phylogenetic tree of the strain was constructed by the neighbor-joining method using the software MEGAX (see Figure 3 ).

[0064] (IV) Effects of the novel Streptomyces X-57 on the tissue structure of crucian carp

[0065] The conventional feed group (30 days) and the group supplemented with 1×10 9 CFU / mlX-57 feed group (30 days), bacterial strain 1×10 9 Liver, kidney, spleen and intestine immune tissues of the CFU / mlX-57 feeding (30 days) followed by poison challenge (7 days) and the poison challenge (7 days) group.

[0066] The results showed that adding 1×10 9 The tissue status of the group fed with CFU / mlX-57 (30 days) was consistent with that of the group fed with conventional feed (30 days). The cells of liver, kidney, spleen, and intestinal tissues were tightly arranged without pathological symptoms. The intestinal cells of the challenge group injected with Aeromonas hydrophila were continuously destroyed, the intestinal villi were atrophied and the mucosa fell off, the spleen tissue area structure was discrete and necrotic, the kidney tissue lost its original organ cavity structure, and the liver cells were arranged in disorder. 9 The lesions of the experimental group fed with CFU / mlQ15 (30 days) and then challenged with the virus (7 days) were significantly reduced, indicating that strain X-57 is relatively safe for treating infected crucian carp and effectively alleviates the lesions of crucian carp viscera infected with Aeromonas hydrophila.

[0067] (V) Analysis of the physicochemical properties of the novel antibacterial active substances of Streptomyces X-57

[0068] (1) Thermal stability

[0069] The strain X-57 was inoculated into liquid Am6 medium and cultured at 30°C and 120 rpm for 7 days. The fermentation broth was treated at 30°C, 50°C, 70°C, and 90°C for 1 hour. Aeromonas vernix was used as the pathogen indicator bacteria, and the plate well method was used to detect the antibacterial activity of the fermentation supernatant after treatment at different temperatures (see Figure 5 ).

[0070] (2) UV resistance

[0071] The strain X-57 was inoculated into liquid Am6 medium and cultured at 30°C and 120 rpm for 7 days. The fermentation broth was irradiated under ultraviolet light for 10 to 60 minutes. Aeromonas vernix was used as the pathogen indicator bacteria. The antibacterial activity of the fermentation supernatant after different ultraviolet irradiation times was detected by the plate well method (see Figure 5 ).

[0072] (3) Protease resistance

[0073] The strain X-57 was inoculated into liquid Am6d medium and cultured at 30°C and 120 rpm for 7 days. Proteinase K, trypsin and pepsin were used for treatment at 37°C for 1 hour. Aeromonas veronii was used as the pathogen indicator bacteria. The plate well method was used to detect the antibacterial activity of the fermentation supernatant after treatment with different proteases (see Figure 5 ).

[0074] It can be seen that the antibacterial active substances in the fermentation broth of this strain have good medium-high temperature, acid-base, ultraviolet irradiation and protease stability.

[0075] (VI) Preparation of new Streptomyces X-57 microecological preparation

[0076] (1) Inoculation and activation: The novel Streptomyces X-57 preserved slant strain is transferred to an activated slant culture medium for activation to obtain an activated seed solution; the activated slant culture medium is Am6-1 liquid culture medium, and the activation culture conditions are: temperature 28-30° C., liquid volume 10-30% of the container volume, and shaking speed 180-200 rpm;

[0077] (2) First expansion culture: The seed liquid activated in step (1) is inoculated into a fermentation tank at an inoculum amount of 1-2% for the first expansion culture; the fermentation medium formula is: soluble starch 15g / L, bacteriological peptone 10g / L, soybean powder 5g / L, glycerol 15g / L, CaCO3 2g / L, acid hydrolyzed casein 3g / L, pH 7.0-7.4; culture conditions: online monitoring of the entire culture process, dissolved oxygen concentration 35-55%, temperature 28-30°C, culture 72-96h, real-time online addition of defoaming agent;

[0078] (3) Second expansion culture: inoculate the seed solution expanded in step (2) at an inoculum rate of 10-15% into a 500L fermentation tank filled with 65%-70% fermentation medium, the fermentation medium formula is the same as the fermentation medium formula described in step (2); the culture conditions are: dissolved oxygen concentration of 35-55%, temperature of 28-30° C., culture for 96-168 hours, and add defoaming agent online in real time;

[0079] (4) Concentration and collection: After tanking, the fermentation products are collected and concentrated to obtain a microecological liquid bacterial agent, or spray-dried to obtain a microecological solid preparation.

[0080] (VII) Application of the new Streptomyces X-57 in fish farming

[0081] Example 1: Colonization and protective ability of the new Streptomyces X-57 in crucian carp

[0082] The crucian carps of uniform size were randomly divided into two groups, with 30 in each group. The two groups of crucian carps were acclimated for 7 days, and the experiment was carried out when the state of each group of crucian carps was stable. The control group was fed with ordinary feed, and the experimental group was fed with a concentration of 1×10 8 CFU / mL of strain X-57 EGFP The feeding amount was 2% of the crucian carp's body weight. After 15 days of continuous feeding, three crucian carps from the experimental group were randomly selected every 1 day to observe the X-57 strain using a small animal imaging system. EGFP Colonization in crucian carp.

[0083] The results showed that feeding strain X-57 EGFP On the second day, the fluorescence signal could be observed in the small animal imaging system, and the fluorescence signal continued to increase over time. The fluorescence signal first appeared in the gills and the front half of the abdomen of the crucian carp, and then continued to deepen and extend to the back half of the abdomen (see Figure 6 ). This result shows that strain X-57 can stably colonize in crucian carp, laying the foundation for the subsequent study of the effect of strain X-57 on the growth and immune defense ability of crucian carp.

[0084] Example 2: Effects of the new Streptomyces X-57 on the growth and disease resistance of crucian carp

[0085] The crucian carps with uniform body shape were randomly divided into 6 frames, including 3 frames for the experimental group and 3 frames for the control group, with 10 crucian carps in each frame. The experiment was carried out after the crucian carps were domesticated for 7 days and their state was stable. The control group was fed with ordinary feed, and the experimental group was fed with a concentration of 1×108 The strain X-57 with a CFU / mL was fed at a rate of 2% of the crucian carp's body weight for 30 consecutive days, with feed given twice a day at 8:00 and 20:00, and the indoor temperature was controlled at 25±2℃.

[0086] (1) Effects of the novel Streptomyces X-57 on the growth performance of crucian carp

[0087] The weight of crucian carp before grouping was taken as the initial weight (W 0 ), the weight of crucian carp fed for 30 days was the final weight (W t ), feeding time (t), feed intake (g), initial number of crucian carp in the experiment (n 0 ), the final number of crucian carp in the experiment (n 1 ) The following formulas were used to calculate weight growth rate (WGR), specific growth rate (SGR), feed efficiency (FE) and survival rate (SR): WGR = ((W t -W 0 ) / W 0 )×100%, SGR=((lnW t -lnW 0 ) / t)×100%,FE=((W t -W 0 ) / g)×100%,SR=(n 1 / n 0 )×100%(see Table 1).

[0088] Table 1 Crucian carp growth performance parameters

[0089]

[0090] Note: Ⅰ: control group; II: experimental group 1×10 8 CFU / g (*, P<0.05; **, P<0.01; ***, P<0.001)

[0091] It can be seen that the novel Streptomyces X-57 of the present invention has a promoting effect on the growth of crucian carp.

[0092] (2) Effects of the novel Streptomyces X-57 on nonspecific immune parameters in crucian carp serum

[0093] Strain Streptomyces X-57 was added to the feed and fed to crucian carp for 30 days. The activities of alkaline phosphatase (AKP) and acid phosphatase (ACP) in the serum of the X-57-fed group were significantly higher than those of the control group (P < 0.001). Phosphatase is an important regulatory enzyme, among which AKP can increase the amount of inorganic phosphate involved in ATP synthesis, improve the body's metabolic capacity and thus improve the immunity of crucian carp, thereby promoting the healthy growth of crucian carp. There was no significant difference in the enzyme activities of glutathione (GSH) and catalase (CAT) in the X-57-fed group and those in the control group. The activities of total superoxide dismutase (T-SOD) and lysozyme (LZM) in the serum of the X-57-fed group were higher than those in the control group, with a significant difference (P < 0.01). Among them, the increase in T-SOD activity helps the body to scavenge superoxide anion free radicals and protect the body's cells from damage (see Figure 7 ).

[0094] (3) Experiment on the protective effect of the new Streptomyces X-57 on crucian carp

[0095] In order to study the protective effect of strain X-57 on crucian carp infected with Aeromonas vermifuge, the experimental group injected 200 μL of Aeromonas hydrophila into the abdominal cavity of crucian carp fed continuously for 30 days. The control group was injected with the same amount of PBS. The living status of crucian carp after infection was observed for 7 days and the mortality was counted. The study found that the survival rate of crucian carp in the control group fed with basic feed was 10% at 7 days after infection, while the survival rate of crucian carp in the control group fed with 1×10 8 The survival rate of crucian carp in the experimental group with 100 CFU / g was 35%, which was significantly higher than that in the control group (see Table 2).

[0096] Table 2 Experiment on the protective effect of strain X-57 on crucian carp

[0097]

[0098] (VIII) Antagonistic effect of the microecological preparation prepared by the novel Streptomyces X-57 on Aeromonas veroni in crucian carp

[0099] Carassius auratus with uniform body size were randomly divided into 2 groups, 30 in each group. Carassius auratus were acclimated for 7 days and starved for 24 hours. The carassius auratus in the control group and the experimental group were intraperitoneally injected with 100 μL of 1×10 8 CFU / mL of AhX005 mCherry The strain AhX005 was observed every 1 day using a small animal imaging system. mCherry The colonization and distribution of the carp were observed for 7 consecutive days. After the 7th day, the carp in the experimental group were fed with a concentration of 1×10 8 CFU / mL of X-57 was used to observe the distribution and brightness changes of red fluorescence in crucian carp every 1 day using a small animal imaging system for 7 consecutive days.

[0100] The results showed that the fluorescence intensity of Aeromonas verticillata in crucian carp increased over time. On the first day, the fluorescence signal first appeared in the gills and tail, and on the third day, it spread throughout the body, and the signal continued to increase. 8 CFU / mL of strain X-57, the small animal imaging system found that the fluorescence signal of the crucian carp fed with strain X-57 was significantly weakened compared with the control group, indicating that strain X-57 can alleviate the infection of Aeromonas veroni in crucian carp (refer to Figure 8 ).

[0101] (IX) Genome assembly and characteristics of the novel Streptomyces X-57

[0102] After optimizing the genome assembly of the quality-controlled data, the final genome was obtained. The genome consists of 4 contigs with a size of 8,337,383 bp. The assembly results are statistically (refer to Fig. 9 ). The strain X-57 was analyzed online using the online platform antiSMASH to predict its genome secondary metabolite synthesis gene clusters. This analysis was conducted from the nuclear genome tig00001 and plasmid tig00002 of strain X-15. The analysis results are shown in the table. A total of 23 secondary metabolite synthesis gene clusters were obtained (reference Fig.10 ), of which there are 5 gene clusters associated with the synthesis of non-ribosomal polypeptide (NRPS) synthetase, 4 gene clusters related to polyketide synthase (TPKS), 5 gene clusters related to terpenes synthesis, and 1 gene cluster related to lanthipeptides synthesis. It reveals that the new strain of Streptomyces X-57 has diverse biosynthetic potential, indicating that strain X-57 is a new type of Streptomyces with rich secondary metabolites.

Claims

1. A strain of Streptomyces X-57, characterized in that: It is preserved in the China Center for Type Culture Collection, with the strain collection number of CCTCCNO: M20242239; its classification name is Streptomyces X-57, and its Latin name is Streptomyces sp.X-57.

2. A microecological preparation suitable for aquaculture, characterized in that: The product is prepared by fermenting the Streptomyces X-57 strain whose strain preservation number is CCTCC NO: M20242239 as described in claim 1.

3. The microecological preparation suitable for aquaculture according to claim 2, characterized in that: The microecological preparation is a liquid preparation or a solid preparation.

4. The microecological preparation suitable for aquaculture according to claim 2 or 3, characterized in that: The aquaculture animals are freshwater fish.

5. The microecological preparation suitable for aquaculture according to claim 4, characterized in that: The freshwater fish is crucian carp, carp or carp.

6. A method for preparing a microecological preparation suitable for aquaculture as claimed in claim 2 or 3, characterized in that: The following steps are involved: (1) Inoculation and activation: The stored slant strain of Streptomyces X-57 was transferred to the activated slant culture medium for activation to obtain an activated seed solution; (2) First expansion culture: The seed liquid activated in step (1) is inoculated into a fermentation tank at an inoculation rate of 1 to 2% for first expansion culture; (3) Second expansion culture: Inoculate the seed solution of the first expansion culture in step (2) into a fermentation tank containing fermentation medium at an inoculum rate of 10-15%, (4) Concentration and collection: After tanking, the fermentation products are collected and concentrated to obtain a microecological liquid bacterial agent, or spray-dried to obtain a microecological solid preparation.

7. The method for preparing a microecological preparation suitable for aquaculture according to claim 6, characterized in that: In step (1), the shake flask seed activation medium is CSM liquid medium, the formula is: tryptone 15g / L, soy peptone 5g / L, sodium chloride 5g / L, glucose 10g / L, yeast powder 9g / L, MgSO4.7H2O2.2g / L. The activation culture conditions are: temperature 28-30°C, liquid volume 10-30% of the container volume, and shaker speed 150-180rpm.

8. The method for preparing a microecological preparation suitable for aquaculture according to claim 6 or 7, characterized in that: In step (2), the fermentation medium formula is: soluble starch 19-20 g / L, bacteriological peptone 5-7 g / L, glucose 10-12 g / L, CaCO3 4-5 g / L, yeast extract 2-4 g / L, pH 7.2-7.7; The culture conditions are as follows: the entire culture process is monitored online, the dissolved oxygen concentration is 35-55%, the temperature is 28-30°C, the culture is 72-96h, and the defoaming agent is added online in real time.

9. The method for preparing a microecological preparation suitable for aquaculture according to claim 6 or 7, characterized in that: In step (3), the fermentation medium formula is the same as the fermentation medium formula described in step (2); The culture conditions are: dissolved oxygen concentration of 35-55%, temperature of 28-30°C, culture for 96-168 hours, and real-time online addition of defoaming agent.

10. The method for preparing a microecological preparation suitable for aquaculture according to claim 6 or 7, characterized in that: In step (3), the fermentation tank is filled with fermentation medium equivalent to 65-70% of the volume of the fermentation tank.

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