Streptomyces virginiae S-45, and microecological preparation and preparation method thereof

Abstract

The invention relates to Streptomyces virginiae S-45, a microecological preparation thereof and a preparation method of the microecological preparation, the Streptomyces virginiae S-45 is preserved in China Center for Type Culture Collection, the strain preservation number is CCTCC NO: M 20242238, the Streptomyces virginiae S-45 is classified and named as Streptomyces virginiae S-45, and the Latin literature name is Streptomyces virginiae S-45. The microecological preparation is prepared by fermenting streptomycete S-45. The invention also discloses a preparation method of the microecological preparation. The application of the streptomyces sp. S-45 in a microecological preparation shows remarkable biological activity and stability. The streptomyces sp. S-45 disclosed by the invention has an excellent antibacterial effect on various freshwater fish pathogenic bacteria, such as aeromonas veronii, aeromonas salmonicida and aeromonas amylophila. The feed can survive and colonize in freshwater fishes such as crucian and the like, and is safe and harmless to the freshwater fishes such as crucian and the like. The streptomyces virginiae S-45 microecological preparation is used as a feed additive, can remarkably improve the immune system function of freshwater fishes such as crucian carps and the like, and enhances the defense capability of the freshwater fishes on fish pathogenic bacteria.

Description

Technical Field

[0001] The invention relates to a strain of Streptomyces, a microecological preparation thereof and a preparation method thereof, in particular to a strain of Streptomyces virginica, a microecological preparation suitable for aquaculture prepared by fermenting the strain, and a preparation method of the microecological preparation. Background Art

[0002] Aquaculture is considered to be one of the fastest growing primary industries to meet the protein needs of the global population. With the rapid development of aquaculture, while it has brought huge economic benefits, many problems have also emerged. The gradual expansion of the scale of farming and the increase in the degree of high-density intensiveness, the accumulation of organic and inorganic wastes, and various microbial infections have led to the continuous deterioration of the farming environment. The outbreak of bacterial diseases has caused huge economic losses to the aquaculture industry and has become the main constraint on fish farming. Various chemical and biological agents are routinely used in aquaculture to solve this crisis. However, the long-term and frequent use of antibiotics and chemical drugs will lead to their deposition in the aquatic environment, thereby increasing multiple antibiotic resistance. These residual antibiotics will eventually enter the food supply chain and be consumed by humans, posing a potential risk to human health.

[0003] Microecological preparations developed based on high technologies such as microbial technology and biotechnology are currently non-toxic green products with good applications in improving aquaculture water quality, replacing antibiotics to prevent and treat diseases, promoting the growth of aquatic animals and improving nutrient utilization. Streptomyces is a type of microorganism with wide application potential. In aquaculture, Streptomyces has been widely studied and applied in the development of microecological preparations. The antibacterial substances and bioactive substances produced by them can effectively control pathogens in water bodies and improve the health level of aquatic animals.

[0004] However, there are still some problems in the application of microecological preparations, such as poor stability of bacterial activity and a small number of bacterial species. Therefore, it is necessary to conduct deeper and more comprehensive research on microbial strains and microecological preparations, and to increase the number of microbial strains and microecological preparations as much as possible, so as to provide more biological means for the prevention and treatment of bacterial diseases in aquaculture fish. Summary of the invention

[0005] The technical problem to be solved by the present invention is to overcome the above-mentioned defects of the prior art and provide a novel strain of Streptomyces virginica S-45 which has good antagonistic effect on a variety of fish pathogens.

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

[0007] A further technical problem to be solved by the present invention is to provide a method for preparing the microecological preparation which is easy to operate.

[0008] The technical solution adopted by the present invention to solve the technical problem is as follows: a strain of Streptomyces virginiae S-45, deposited in the China Center for Type Culture Collection on October 17, 2024, with a strain deposit number of CCTCC NO: M 20242238; classified and named: Streptomyces virginiae S-45. Hereinafter, it is sometimes referred to as strain S-45.

[0009] The 16S rRNA sequence of the Streptomyces virginica S-45 of the present invention is shown in the sequence listing SEQ ID No. 1.

[0010] The Virginia Streptomyces S-45 of the present invention was screened from 60 soil samples in Yunnan Province and other regions.

[0011] The technical solution adopted by the present invention to further solve its technical problems is as follows: a Streptomyces microecological preparation suitable for aquaculture, which is fermented by Streptomyces virginiana S-45 with a strain collection number of CCTCC NO: M 20242238. Studies have shown that the Streptomyces virginiana S-45 microecological preparation of the present invention can inhibit the growth of various fish pathogens such as Aeromonas vernix, Aeromonas salmonicida and Aeromonas abnormal saccharophilus. The antibacterial active substances in the fermentation broth of this strain have good medium and high temperature, ultraviolet irradiation and protease stability, and are relatively stable in actual production applications; they have a good inhibitory effect on freshwater fish pathogens, can promote fish growth, and improve fish immunity. Through the microecological preparation, Streptomyces virginiana S-45 can be simply and conveniently added to the environment where it is needed, such as mixing the Streptomyces virginiana S-45 microecological preparation into feed or adding it to the water environment.

[0012] Furthermore, the microecological preparation is a liquid preparation or a solid preparation.

[0013] Furthermore, the aquaculture animals are freshwater fish.

[0014] Furthermore, the freshwater fish is crucian carp, grass carp or carp.

[0015] 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:

[0016] (1) Inoculation and activation: transferring the slant strain of Streptomyces virginica S-45 to a shake flask seed activation medium for activation, thereby obtaining a seed solution; the activated slant medium is Am6 liquid medium;

[0017] 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 / min;

[0018] (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 to obtain the seed liquid after the first expansion culture;

[0019] The fermentation medium formula is: soluble starch 19-21g / L, glucose 9-11g / L, bacteriological peptone 4-6g / L, yeast extract 4-6g / L, calcium carbonate 4-6g / L, pH 7.0-7.4;

[0020] The preferred formula of the fermentation medium is: soluble starch 20g / L, glucose 10g / L, bacteriological peptone 5g / L, yeast extract 5g / L, calcium carbonate 5g / L, pH 7.0-7.4;

[0021] The culture conditions are as follows: the entire culture process is monitored online, the dissolved oxygen content is 35-55%, the temperature is 28-30°C, the culture is carried out for 72-96 hours, and a fermentation defoamer is used during the culture process to avoid foaming;

[0022] (3) Second expansion culture: inoculate the seed liquid 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 content of 35-55%, temperature of 28-30° C., culture for 96-168 hours, and use a fermentation defoamer to avoid foaming during the culture process;

[0023] Furthermore, in step (3), the fermentation tank is preferably filled with fermentation medium equivalent to 65%-70% of the volume of the fermentation tank.

[0024] Furthermore, in step (3), a fermentation tank with a volume of 500L-1000L is preferred.

[0025] (4) Concentration and collection: After tanking, collect the fermentation products of the second expanded culture and concentrate them to obtain a microecological liquid bacterial agent, or spray dry them to obtain a microecological solid preparation.

[0026] The identification and research methods of the Streptomyces virginica S-45 of the present invention are as follows.

[0027] (A) Observation of cell morphological characteristics of strain Streptomyces S-45;

[0028] (ii) Identification using the 16S rRNA gene;

[0029] (III) Physical and chemical properties of antibacterial active substances of Streptomyces virginica S-45;

[0030] (iv) Detection of colonization of Streptomyces virginica S-45 in crucian carp;

[0031] (V) Effects of Streptomyces virginica S-45 as a feed additive on the growth and disease resistance of crucian carp.

[0032] The beneficial effects of the present invention are as follows: (1) The strain was identified as Streptomyces virginiae (strain collection number: CCTCC NO: M 20242238; classification name: Streptomyces virginiae S-45, Latin name: Streptomycesvirginiae) by 16S rRNA gene sequencing. (1) The microecological preparation prepared by fermenting the Virginia Streptomyces S-45 of the present invention is suitable for aquaculture, especially freshwater fish farming, and has no toxic effect on the liver cells of grass carp and the body of crucian carp, laying a foundation for the strain to play a stable disease prevention and growth promotion role in fish farming; (2) The microecological preparation of Virginia Streptomyces S-45 is suitable for aquaculture, especially freshwater fish farming, and has no toxic effect on the liver cells of grass carp and the body of crucian carp, laying a foundation for the strain to play a stable disease prevention and growth promotion role in fish farming; (3) Feeding fish with the microecological preparation of Virginia Streptomyces S-45 as a feed additive can improve the growth rate and feed efficiency of fish, enhance the immunity of fish, and thus significantly improve the resistance of freshwater fish such as crucian carp to fish pathogens; (4) The method for preparing Virginia Streptomyces S-45 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.

[0033] SEQ ID №1:

[0034]

[0035]

[0036] Description of Microbiological Deposit

[0037] The Virginia Streptomyces S-45 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 deposit number is CCTCC NO: M 20242238; the classification name is: Virginia Streptomyces S-45, Latin name: Streptomyces virginiae S-45. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a diagram showing the antibacterial effect of Streptomyces virginica S-45 on fish pathogens;

[0039] Figure 2 Observation diagrams of morphological characteristics of Streptomyces virginica S-45 of the present invention; a: observation diagram of plate colony morphology of strain S-45; b: observation diagram of strain S-45 under phase contrast microscope; c: observation diagram of Gram staining of strain S-45; d, e: observation diagrams of strain S-45 under scanning electron microscope;

[0040] Figure 3 is a phylogenetic tree diagram constructed from the 16S rRNA sequence of Streptomyces virginica S-45 of the present invention;

[0041] Figure 4 is a circle diagram of the whole genome of Streptomyces virginica S-45 of the present invention;

[0042] Figure 5 This is a diagram of the physical and chemical properties of the antibacterial active substance of Streptomyces virginica S-45 of the present invention (*, P < 0.05; **, P < 0.01; ***, P < 0.001, ****, P ≤ 0.0001);

[0043] Figure 6 This is a diagram of the colonization and protection of Streptomyces virginicae S-45 labeled strain in crucian carp observed by the small animal living imaging system of the present invention;

[0044] Figure 7 This is a graph showing the effect of the microecological preparation prepared by Streptomyces virginiae S-45 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, ****, P ≤ 0.0001);

[0045] Figure 8 This is a diagram showing the antagonistic effect of the microecological preparation prepared by Streptomyces virginia S-45 on Aeromonas veronii in crucian carp observed by the small animal living imaging system 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 Streptomyces virginica S-45 and determination of antibacterial spectrum

[0049] 60 soil samples from Yunnan Province and other regions were thoroughly mixed in sterile water, and then diluted by 10-fold gradient dilution method. -4 , 10 -5 , 10 -6 0.1 ml of the three dilutions were applied to the solution containing potassium dichromate (concentration 30×10-6 The culture medium was plated on Gao's Ⅰ plate (200 μg / mL) at 30℃ for 4 days. According to the difference in colony shape and color on the plate, 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 and Plesiomonas shigelloide were used as indicator bacteria, and the antibacterial activity of the fermentation supernatant against the above pathogens was detected by the Oxford cup method (see Figure 1 ) and discovered a new strain with good antibacterial effect on 5 fish pathogens, named Virginia Streptomyces S-45.

[0050] (II) Cell morphological characteristics of Streptomyces virginica S-45

[0051] Strain S-45 was streaked on Gao's solid medium No. 1. After culturing at 30°C for 4 days, it was observed that the colonies were small and compact, with abundant spores, protruding in the middle, dry and irregularly serrated edges. Phase contrast microscopy showed that the mycelium of strain S-45 was well developed and had many branches. Gram staining showed that strain S-45 was a Gram-positive bacterium. Cold-field scanning electron microscopy showed that the aerial hyphae of strain S-45 had many branches and well-developed mycelium. Based on the above morphological characteristics, strain S-45 was preliminarily identified as an actinomycete (see Figure 2 ).

[0052] (III) Identification of the 16S rRNA gene of Streptomyces virginica S-45

[0053] The spores of strain S-45 were inoculated into Am6 liquid medium (30°C, 120 rpm) and cultured for 4 days by shaking. Then, fresh bacterial liquid was collected by centrifugation in an EP tube. The genomic DNA of strain S-45 was extracted using the Ezup column bacterial genomic DNA extraction kit (Shanghai Shenggong Biotechnology Co., Ltd.). The 16S rRNA gene was amplified using the following primer sequence:

[0054] 27F: 5′-AGAGTTTGATCCTGGCTCAG-3′;

[0055] 1492R: 5′-CGGTTACCTTGTTACGACTT-3′.

[0056] The gene sequences corresponding to the strains were amplified using the above primers, and the expected lengths of the sequences were about 1500 bp.

[0057] PCR reaction system (20 μL): sterile double distilled water, 5.2 μL; 2×Buffer, 10 μL; dNTP, 1.6 μL; 1492-R (10 μM), 1 μL; 27-F (10 μM), 1 μL; genomic template, 1 μL; PrimerSTAR DNA Polymerase (Takara), 0.2 μL;

[0058] PCR reaction program: pre-denaturation at 95°C for 5 min; 30 cycles: 95°C, 30 sec; 58°C, 30 sec; 72°C, 1.5 min; 72°C, 10 min.

[0059] After the 16S rRNA gene PCR products were detected by 1.0% agarose gel electrophoresis, the successfully amplified products were sent to Wuhan Sangon Biotechnology Co., Ltd. for sequencing.

[0060] The 16S rRNA gene sequence of strain S-45 was sequenced and showed to be 1425 bp in length. The amplified sequencing results were analyzed by BLAST comparison on NCBI, and the phylogenetic tree of the strain was constructed by the neighbor-joining method in MEGA X software (see Figure 3 ).

[0061] (IV) Identification of the GTDBTK strain of Streptomyces virginiana S-45 with the whole genome

[0062] After the whole genome of strain S-45 was sequenced, the whole genome sequence of strain S-45 and its closest relative strain were compared online using the GTDBTK database, and a circle diagram was drawn (see Figure 4 ), the similarity between strain S-45 and them is about 97.25%. Combining the morphological characteristics and molecular biological identification of strain S-45, the strain was further identified as a new species of Streptomyces and named Streptomyces virginiae S-45 (Latin name: Streptomyces virginiae S-45).

[0063] (V) Analysis of the physicochemical properties of antibacterial active substances of Streptomyces virginica S-45

[0064] (1) Thermal stability

[0065] The strain S-45 was inoculated into Am6 liquid culture medium, cultured at 30°C, 120 rpm for 3 days, and centrifuged at 12000 rpm / min for 5 minutes. The obtained supernatant was divided into 4 groups, and 1 ml of each group was placed in a water bath at 30°C, 50°C, 70°C, and 90°C for 1 hour and returned to room temperature. A control group (fermentation supernatant was not treated) was set up, and Aeromonas vernix was used as a pathogen indicator bacteria. The antibacterial activity of the fermentation supernatant after treatment at different temperatures was detected by the plate well method (see Figure 5 ).

[0066] (2) UV resistance

[0067] The strain S-45 was inoculated into liquid Am6 medium and cultured at 30°C and 120 rpm for 3 days. The fermentation liquid was irradiated under ultraviolet light for 10 to 60 minutes. Aeromonas vernix was used as a pathogen indicator bacteria and cultured upright at 30°C for 24 hours to observe the antibacterial changes of each group (see Figure 5 ).

[0068] (3) Protease resistance

[0069] The strain S-45 was inoculated into liquid Am6 medium and cultured at 30°C and 120 rpm for 3 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 ).

[0070] The results showed that the antibacterial active substances in the fermentation broth of this strain had good medium-high temperature, ultraviolet irradiation and protease stability.

[0071] (VI) Preparation of Streptomyces virginica S-45 probiotic preparation

[0072] (1) Inoculation and activation: The Streptomyces S-45 slant strain was transferred to a shake flask seed activation medium for activation, thereby obtaining a seed solution; the activation medium was Am6 liquid medium; the activation culture conditions were: temperature 29±0.5°C, liquid volume 20% of the container volume, and shaker speed 190 rpm / min;

[0073] (2) First expansion culture: The seed liquid activated in step (1) is inoculated into a fermentation tank at an inoculation rate of 1-2% for first expansion culture, to obtain seed liquid after first expansion culture; the fermentation medium formula is: soluble starch 20 g / L, glucose 10 g / L, bacteriological peptone 5 g / L, yeast extract 5 g / L, calcium carbonate 5 g / L, pH 7.2;

[0074] The culture conditions were as follows: the entire culture process was monitored online, the dissolved oxygen content was 45%, the temperature was 29±0.5°C, the culture time was 85h, and fermentation defoamers were used during the culture process to avoid foaming;

[0075] (3) Second expansion culture: inoculate the seed liquid 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, and the fermentation medium formula is the same as the fermentation medium formula in step (2); the culture conditions are: dissolved oxygen content 45%, temperature 29±0.5°C, culture for 132 hours, and use a fermentation defoamer to avoid foaming during the culture process;

[0076] (4) Concentration and collection: After tanking, collect the fermentation products of the second expanded culture and concentrate them to obtain a microecological liquid bacterial agent, or spray dry them to obtain a microecological solid preparation.

[0077] (VII) Application of Streptomyces virginica S-45 in fish farming

[0078] Example 1: Colonization and protective ability of the new Streptomyces S-45 in crucian carp

[0079] Healthy crucian carps of the same size were selected and randomly divided into a control group and an experimental group, with 30 fish 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 crucian carps in the control group were fed with a basic feed, and the experimental groups were fed with a concentration of 1.5×10 7 CFU / mL of strain S-45 EGFP The feeding amount was 1% 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 strain S-45 using a small animal imaging system. EGFP Colonization in crucian carp.

[0080] The results showed that feeding strain S-45 EGFP Fluorescence signals can be observed in the small animal imaging system on the second day, and the fluorescence signals increase over time (see Figure 6 ). This result shows that strain S-45 can stably colonize in crucian carp, laying the foundation for the subsequent study of the effects of strain S-45 on the growth and immune defense ability of crucian carp.

[0081] Example 2: Effects of Streptomyces virginica S-45 on growth and disease resistance of crucian carp

[0082] The crucian carps with uniform body size were randomly divided into 3 frames, including two experimental groups and one control group, with 30 crucian carps in each frame. The experiment was carried out after the crucian carps were domesticated for 7 days and the state of the crucian carps was stable. The control group was fed with ordinary feed, and the experimental group was fed with a concentration of 1.5×10 7 CFU / mL and 1.5×10 8The strain S-45 with a CFU / m was fed at a feeding amount of 1% 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℃.

[0083] (1) Effects of Streptomyces virginica S-45 on the growth performance of crucian carp

[0084] The weight of crucian carp before grouping was taken as the initial weight (W0), and the weight of crucian carp fed for 30 days was taken as the final weight (W t ), feeding time (t), feed intake (g), the initial number of crucian carp in the experiment (n0), and the final number of crucian carp in the experiment (n1) were used to calculate the weight growth rate (WGR), specific growth rate (SGR), feed efficiency (FE), and survival rate (SR): WGR = ((W t -W0) / W0)×100%, SGR=((lnW t -lnW0) / t)×100%FE=((W t -W0) / g)×100%, SR=(n1 / n0)×100% (see Table 1).

[0085] Table 1 Crucian carp growth performance parameters

[0086]

[0087] It can be seen that the Virginia Streptomyces S-45 of the present invention has a promoting effect on the growth of crucian carp.

[0088] (2) Effects of Streptomyces virginica S-45 on nonspecific immune parameters in crucian carp serum

[0089] The strain Streptomyces S-45 was added to the feed and fed to crucian carp for 30 days. The fish were starved for 24 hours. In each group, crucian carp were randomly taken for blood sampling from the tail vein. The serum was collected statically and the activities of six non-specific factors in the serum, including alkaline protease (AKP), acid phosphatase (ACP), reduced glutathione (GSH), catalase (CAT), superoxide dismutase (T-SOD), and lysozyme (LZM), were measured using kits. Phosphatase is an important regulatory enzyme, among which alkaline protease 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; the increase in superoxide dismutase activity helps the body to scavenge superoxide anion free radicals and protect the body's cells from damage. The results showed that feeding strain S-45 can improve the non-specific immune indicators of crucian carp and enhance the disease resistance of crucian carp (see Figure 7).

[0090] (3) Experiment on the protective effect of Streptomyces virginicae S-45 on crucian carp

[0091] In order to study the protective effect of strain S-45 on crucian carp infected with Aeromonas veroni, 100 μL of Aeromonas veroni was injected intraperitoneally into crucian carp fed continuously for 30 days. The living status and survival rate of crucian carp in the control group and the strain S-45 feeding group after infection were observed for 7 days. The survival rate of crucian carp in the strain S-45 feeding group was 43.33%, which was significantly higher than that of the control group (see Table 2).

[0092] Table 2 Experiment on the protective effect of strain S-45 on crucian carp

[0093]

[0094]

[0095] (VIII) Antagonistic effect of the probiotic preparation prepared by Streptomyces virginiana S-45 against Aeromonas vermifuge in crucian carp

[0096] 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 1.5×10 7 CFU / mL of AvX005 mCherry The strain AvX005 was observed every 1 day using a small animal imaging system. mCherry The colonization and distribution of the crucian carp were observed for 7 consecutive days. After the 7th day, the crucian carp in the experimental group were fed with a concentration of 1.5×10 7 The distribution and brightness changes of red fluorescence in crucian carp were observed using a small animal imaging system every 1 day for 7 consecutive days.

[0097] The results showed that the fluorescence intensity of Aeromonas vermifuge in crucian carp increased over time. 7 CFU / mL of strain S-45. The small animal imaging system found that the fluorescence signal of crucian carp fed with strain S-45 was significantly weakened compared with the control group, indicating that strain S-45 can alleviate the infection of Aeromonas veronis in crucian carp (see Figure 8 ).

Claims

1. A strain of Streptomyces virginica S-45, characterized in that: It is deposited in China Center for Type Culture Collection with the strain collection number of CCTCC NO: M 20242238; its classification name is Streptomyces virginiae S-45, and its Latin name is Streptomyces virginiae S-45.

2. A microecological preparation suitable for aquaculture, characterized in that: The product is prepared by fermenting the Streptomyces virginica S-45 as claimed 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, grass 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 Streptomyces S-45 slant strain was transferred to the shake flask seed activation medium for activation, thereby obtaining seed liquid; (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, thereby obtaining a seed liquid after the first expansion culture; (3) Second expansion culture: inoculating 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%, and expanding the culture again to obtain a fermentation product of the second expansion culture; (4) Concentration and collection: After tanking, collect the fermentation products of the second expanded culture and concentrate them to obtain a microecological liquid bacterial agent, or spray dry them 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 culture medium is Am6 liquid culture medium, and the activation culture conditions are: temperature 28-30°C, liquid volume 10-30% of the container volume, and shaker speed 180-200 rpm / min.

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 19-21g / L, glucose 9-11g / L, bacteriological peptone 4-6g / L, yeast extract 4-6g / L, calcium carbonate 4-6g / L, pH 7.0-7.4; The culture conditions are as follows: the entire culture process is monitored online, the dissolved oxygen content is 35-55%, the temperature is 28-30° C., the culture time is 72-96 hours, and a fermentation defoamer is used during the culture process to avoid foaming.

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 content 35-55%, temperature 28-30°C, culture 96-168h, and fermentation defoamer is used during the culture process to avoid foaming.

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; the volume of the fermentation tank is 500L-1000L.

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