Paracoccus methylotrophicus as well as composition, product and application thereof

Abstract

The invention belongs to the technical field of microorganisms, and provides paracoccus methylotrophicus as well as a composition, a product and application thereof. The paracoccus methylotrophicus is preserved in the Guangdong Microbial Culture Collection Center on May 15, 2025, the strain preservation number is GDMCC NO: 66343, and the preservation address is the 5th floor, No. 59 building, No. 100 Courtyard, Xianlie Middle Road, Guangzhou. The paracoccus methylotrophicus provided by the invention can effectively inhibit growth and reproduction of fusarium oxysporum, rhizoctonia solani and alternaria ginseng, so that plant wilt such as banana wilt, rice sheath blight disease and panax notoginseng black spot can be effectively prevented and treated, and the problems of environmental pollution and food safety caused by adopting chemical bactericides are solved; and the strain has a siderophore producing function, can reduce the use amount of chemical fertilizers, promote the growth of plants and increase the crop yield, is safe and environment-friendly, and has certain application prospects.

Description

Technical Field

[0001] This application relates to the field of microbial technology, and in particular to a methyl-nutritive paracoccus and its compositions, products and applications. Background Technology

[0002] Currently, controlling soil-borne crop diseases (such as wilt, rice sheath blight, or Panax notoginseng black spot) in agricultural production mainly relies on spraying or irrigating the soil with chemical fungicides, in addition to selecting improved varieties and improving crop cultivation practices. However, most chemical fungicides have varying degrees of toxicity to humans and animals, and their pesticide residues are seriously excessive, leading to a severe decline in crop production quality, serious damage to the farmland system, and hindering sustainable social and economic development. Moreover, these chemical fungicides applied to the soil are absorbed by crop roots and translocated to the edible parts of plants, causing agricultural product safety issues and threatening human health.

[0003] In related technologies, to address the aforementioned problems, biological control techniques, especially those utilizing microorganisms to control crop diseases, are receiving increasing attention. Although there are sporadic reports of strains that can control certain crop diseases, their effectiveness is often unsatisfactory. Microorganisms require a certain biological cycle for reproduction and growth, and they must colonize the soil before they can exert their effects. Compared to chemical methods such as fungicides, microorganisms do not show immediate results. Furthermore, living microbial communities are easily affected by various environmental conditions during reproduction, leading to poor efficacy after application, and also requiring complex extraction processes for active substances. Currently, research on strains that can simultaneously and efficiently control multiple crop diseases faces the problem of insufficient numbers of microorganisms and poor efficacy for crop disease control, limiting the application of biological control technologies.

[0004] Currently, there is a lack of strains that can effectively inhibit the growth and reproduction of pathogens such as Fusarium oxysporum, Rhizoctonia solani, and Alternaria alternata, so as to further prevent and control plant wilt diseases such as banana wilt, rice sheath blight, and Panax notoginseng black spot. Summary of the Invention

[0005] This invention aims to at least partially address one of the problems in the related art. Therefore, the object of this invention is to provide a methyl-nutritive paracoccus, its compositions, products, and applications.

[0006] To achieve the above objectives, this application adopts the following technical solution:

[0007] According to a first aspect of the present invention, a methyl-nutritive paracoccus is provided, named Paracoccus sp. S160, which was deposited on May 15, 2025 at the Guangdong Provincial Microbial Culture Collection Center with the strain accession number GDMCC NO:66343, and the deposit address is 5th Floor, Building 59, No. 100 Xianlie Middle Road, Guangzhou.

[0008] The Paracoccus sp. S160 has the following morphology: on LB agar plates, the colonies are yellow, round, with neat edges, smooth and moist, and have a certain degree of adhesiveness; it is obligate aerobic, the cells are rod-shaped, and it does not produce spores or endospores; it is Gram-negative.

[0009] According to a second aspect of the invention, cultures, live bacteria, freeze-dried bacteria, or inactivated bacteria of methyltrophic paracoccus are provided.

[0010] In some embodiments, the culture comprises a fermentation broth of methyltrophic paracoccus or a concentrated or dried product of the fermentation broth.

[0011] According to a third aspect of the present invention, a composition for improving plant disease resistance is provided, the composition comprising *Paragonimula methyltrophicis*, a culture of *Paragonimula methyltrophicis*, live bacteria, freeze-dried bacteria, or inactivated bacteria; wherein the culture comprises any one of A) to D):

[0012] A) The fermentation broth of the strain;

[0013] B) The supernatant of the fermentation broth of the strain;

[0014] C) The inactivated fermentation broth of the strain;

[0015] D) The concentrated or dried product of any one of A)-C).

[0016] In some embodiments, the composition is any one of a plant growth promoter, a bio-fertilizer, or a bacteriostatic agent.

[0017] According to a fourth aspect of the invention, the use of methyltrophic paracoccus, cultures of methyltrophic paracoccus, live bacteria, freeze-dried bacteria or inactivated bacteria, and compositions for improving plant disease resistance in the preparation of products for improving plant disease resistance is provided.

[0018] In some embodiments, the product for enhancing plant disease resistance is a product that inhibits at least one pathogenic bacterium among Fusarium oxysporum, Rhizoctonia solani, and Alternaria ginseng.

[0019] In some implementations, the product for improving plant disease resistance is a product for preventing or controlling at least one of plant wilt, rice sheath blight, and Panax notoginseng black spot.

[0020] According to a fifth aspect of the present invention, a composition for promoting plant growth is provided; the composition includes a composition for enhancing plant disease resistance, the composition comprising *Paragonimula methyltrophicis*, a culture of *Paragonimula methyltrophicis*, live bacteria, freeze-dried bacteria, or inactivated bacteria; wherein the culture comprises any one of A) to D):

[0021] A) The fermentation broth of the strain;

[0022] B) The supernatant of the fermentation broth of the strain;

[0023] C) The inactivated fermentation broth of the strain;

[0024] D) The concentrated or dried product of any one of A)-C).

[0025] The Paracoccus sp. S160 provided by this invention has the function of producing siderophores, and therefore can be used in the preparation of products that promote plant growth.

[0026] According to a sixth aspect of the invention, the use of methyltrophic paracoccus, a culture of methyltrophic paracoccus, live bacteria, freeze-dried bacteria or inactivated bacteria, and a composition for promoting plant growth in the preparation of a plant growth promoting product is provided.

[0027] The Paracoccus sp. S160 provided by this invention can effectively inhibit the growth and reproduction of Fusarium oxysporum, Rhizoctonia solani, and Alternaria ginseng, thereby effectively preventing and controlling plant wilt diseases such as banana wilt, rice sheath blight, and Panax notoginseng black spot. It solves the environmental pollution and food safety problems caused by the use of chemical fungicides. Moreover, this strain has the function of producing iron carriers, which can reduce the amount of chemical fertilizers used, promote plant growth, increase crop yield, and is safe and environmentally friendly, with broad application prospects.

[0028] The technical solutions provided in this application have the following advantages compared with the prior art:

[0029] (1) The present invention isolated strain S160 from peanut roots and identified it in terms of morphology, physiological and biochemical characteristics and genetics. The 16S rDNA identification results confirmed that it is Paracoccus sp. Through the antagonistic effect experiment on Fusarium oxysporum, Rhizoctonia solani and Alternaria ginseng pathogens, the results showed that the strain can effectively inhibit the growth and reproduction of Fusarium oxysporum, Rhizoctonia solani and Alternaria ginseng, and thus can effectively prevent and control plant wilt diseases such as banana wilt, rice sheath blight and Panax notoginseng black spot. When this strain is used to prepare plant antibacterial agents, it can solve the environmental pollution and food safety problems caused by the use of chemical fungicides.

[0030] (2) The Paracoccus sp. S160 provided in this application has the function of producing iron carriers, which can reduce the amount of chemical fertilizer used, promote plant growth, increase crop yield, and is safe and environmentally friendly, with broad application prospects. Attached Figure Description

[0031] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] In the attached image:

[0034] Figure 1 This is a schematic diagram of the colony morphology of strain S160 provided in Example 1 of this application after being cultured on LB solid medium for 24 hours;

[0035] Figure 2 This is a schematic diagram of the colonies of strain S160 in Example 2 of this application after three days of cultivation on a siderogenic solid medium;

[0036] Figure 3 This is a schematic diagram of the control group in the antagonistic experiment against Fusarium oxysporum in Example 4 of this application;

[0037] Figure 4 This is a schematic diagram of the treatment group in the antagonistic experiment against Fusarium oxysporum in Example 4 of this application;

[0038] Figure 5 This is a schematic diagram of the control group in the antagonistic experiment against Rhizoctonia solani in Example 5 of this application;

[0039] Figure 6 This is a schematic diagram of the treatment group in the antagonistic experiment against Rhizoctonia solani in Example 5 of this application.

[0040] Figure 7 This is a schematic diagram of the control group in the antagonistic experiment against Alternaria ginseng in Example 6 of this application;

[0041] Figure 8 This is a schematic diagram of the treatment group in the antagonistic experiment of Alternaria ginseng in Example 6 of this application. Detailed Implementation

[0042] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0043] Currently, biological control technologies, especially those utilizing microorganisms to control crop diseases, are receiving increasing attention due to their safety, environmental friendliness, and harmlessness. However, the limited number and relatively low effectiveness of microorganisms currently available for crop disease control restricts the application of biological control technologies.

[0044] To address the aforementioned issues, this application provides a Paracoccus sp. strain that can effectively inhibit the growth and reproduction of Fusarium oxysporum, Rhizoctonia solani, and Alternaria ginseng, thereby effectively preventing and controlling plant wilt diseases such as banana wilt, rice sheath blight, and Panax notoginseng black spot. This solves the environmental pollution and food safety problems caused by the use of chemical fungicides. Furthermore, this strain has the function of producing iron carriers, which can reduce the amount of chemical fertilizers used, promote plant growth, increase crop yield, and is safe and environmentally friendly, with broad application prospects.

[0045] The technical solutions of the embodiments of this application are described in detail below with reference to the accompanying drawings.

[0046] The LB solid culture medium used in the following examples (volume 1.0L) includes 10g peptone, 5g yeast extract, 10g sodium chloride (NaCl), 2.0g agar powder, and a pH of 7.0.

[0047] Example 1: Screening of strain S160

[0048] 1. Strains are isolated, purified, and preserved.

[0049] Healthy peanut plants were selected from Qingyuan City, Guangdong Province and brought back to the laboratory. Strains S160 were isolated and purified from the peanuts. The specific isolation and purification steps are as follows:

[0050] The peanuts were pretreated as follows: First, the peanut roots were cut into 1cm sections using sterilized scissors, and then the surface dust was washed off with sterile water to obtain clean peanut roots. The cleaned peanut roots were then soaked in a 2wt% sodium hypochlorite solution for 2 minutes, rinsed once with sterile water, and then soaked in 70% alcohol for 5 minutes. This process was repeated 8 times with sterile water, each time for 5 minutes. 200μL of the sterile water from the final rinse was spread onto LB solid medium for incubation at 37℃ for 24-48 hours. After 24 hours of incubation, the bacterial growth on the LB solid medium (provided by Angel Biotech Co., Ltd.) was observed. If no bacteria grew on the LB solid medium after 24 hours, it indicated that the peanut roots had been thoroughly sterilized, and sterilized peanut roots were obtained.

[0051] Using sterile tweezers, place a 1cm section of naturally dried peanut root stalk into a mortar, add 5mL of sterile water, and grind thoroughly with a grinding stick to obtain a grinding liquid. It is important to note that the grinding operation must be performed in a sterile environment; that is, both the mortar and grinding stick must be sterilized beforehand.

[0052] Take 1 mL of the above-mentioned homogenate and add it to 9 mL of sterile water. Mix thoroughly, and then continue to dilute with sterile water in a 10-fold serial dilution series to obtain concentrations of 10... -4 10 -5 and 10 -6 Dilute the grinding slurry, take 200 μL of each with a concentration of 10 -4 10 -5 and 10 -6 The diluted grinding solution was evenly spread onto LB solid medium that had been sterilized at 121°C for 20 min under high pressure, and incubated at 30°C for 3-5 days to generate single bacteria; wherein, the LB solid medium (1.0L) includes 10g peptone, 5g yeast extract, 10g sodium chloride (NaCl), 2.0g agar powder, and pH value is 7.0.

[0053] Newly generated single bacteria were isolated and purified using the streak plating method. Specifically, newly generated single bacteria were picked and purified on LB solid medium using the streak plating method, and repeatedly subcultured until colonies exhibited the same color, shape, size, texture, and transparency. Subculturing on LB solid medium was performed at a temperature of 37°C and a pH of 7.0. Subculturing on LB liquid medium was performed at a rotation speed of 160 rpm for 24 hours.

[0054] Finally, the colony morphology on LB solid medium was further observed by staining (carbohydrate fuchsin staining), with uniform length, consistent width, and uniform staining as the standard for strain purification. Figure 1The morphology of one of the colonies isolated in Example 1 is shown. The colony is pale yellow, round, with neat edges, smooth and moist, and has a certain degree of adhesiveness. This strain is labeled as strain S160.

[0055] The purified strain S160 was picked up with a sterile inoculation loop, 3-4 loops were placed in the preservation solution (20% glycerol by volume), and stored at -20℃ and -80℃.

[0056] Example 2: Determination of the strain's ability to produce siderophores

[0057] Siderophores are low-molecular-weight substances that can bind ferric ions and supply them to microbial cells. Bacteria compete with plant pathogens for iron ions by secreting siderophores, thereby inhibiting the growth and reproduction of pathogens. The chromate azuril (CAS) assay can be used to detect whether bacteria are capable of producing siderophores.

[0058] The culture medium (solid culture medium for siderogenic capacity) used in the siderogenic capacity determination experiment was:

[0059] MSA-CAS medium (1.0L volume) contains: 5.0g peptone, 4.0g glucose, 0.5g KCl, 0.5g MgSO4·7H2O, 0.015g hexadecyltrimethylammonium bromide, 0.0003g FeCl3, 0.00653g chromate azurite, 0.05g NaH2PO3, 0.2g Na2HPO3, 0.025g NH4Cl, 0.0075g KH2PO4, and 0.02g NaCl. It is used after sterilization at 121℃ for 20 minutes.

[0060] Control group: Incubated for three days in MSA-CAS solid medium without bacterial inoculation at 37°C.

[0061] Treatment group: Strain S160 was inoculated into MSA-CAS solid medium and cultured in an incubator at 37°C for three days.

[0062] Observe the color changes in the control group and the treatment group. The control group, which was not inoculated with the bacterial strain, showed no color change. The treatment group, inoculated with S160, showed the following color changes: Figure 2 As shown, a yellow ring is formed around the colony, indicating that S160 can secrete siderophores.

[0063] Example 3: Physiological and biochemical characteristics and taxonomic identification of the strain

[0064] The strain S160 isolated in Example 1 has the following morphological and physiological and biochemical characteristics:

[0065] a. Cell morphology characteristics (observed using the method described in Example 1): Colonies are pale yellow, round, with neat, smooth, and moist edges, exhibiting a certain degree of adhesiveness; they are obligate aerobic, rod-shaped, and do not produce spores or endospores; they are Gram-negative. The growth temperature range is 20-45℃, and the growth pH is 6.0-10.0.

[0066] b. Biological characteristics: It has the function of producing siderophores.

[0067] The S160 strain was found to produce siderophores using the chromium azurophila (CAS) assay in Example 2. Therefore, this strain S160 can be used in the preparation of bio-fertilizers. Siderophores can dissolve iron compounds, which can then be absorbed and utilized by microorganisms and plants, thereby promoting plant growth. Through chelation, siderophores can inhibit the utilization of iron by pathogens, thus suppressing their growth and metabolic activity, reducing the amount of chemical fertilizer used, promoting crop growth, and increasing crop yield.

[0068] c. Determination of molecular taxonomic status:

[0069] DNA was extracted from strain S160 isolated in Example 1, and the 16S rDNA gene was amplified by PCR (the primers, system and procedure used are shown below), and detected by agarose gel. The PCR amplification product was sent to Hangzhou Youkang Biotechnology Co., Ltd. for sequencing to obtain the 16S rDNA sequence of the strain (as shown in SEQ ID NO.1).

[0070] The primers for amplifying the 16S rDNA gene are:

[0071] 27F: 5'-AGAGTTTGATCCTGGCTCAG-3';

[0072] 1492R: 5'-GGTTACCTTGTTACGACTT-3';

[0073] The system for amplifying the 16S rDNA gene is as follows:

[0074]

[0075] The procedure for amplifying the 16S rDNA gene is shown below.

[0076] PCR amplification conditions: 94℃ pre-denaturation for 2 min; 94℃ denaturation for 30 s, 56℃ annealing for 30 s, 72℃ extension for 2 min, 30 cycles; 72℃ final extension for 10 min.

[0077] The 16S rDNA sequence (as shown in SEQ ID NO.1) was entered into GenBank for BLAST comparison. It was found that the strain S160 in Example 1 of this invention has 99.49% similarity to the Paracoccus sp. type strain SCU-M53. Therefore, the strain S160 in Example 1 of this invention is classified as Paracoccus sp. and named Paracoccus sp. S160.

[0078] e. Biological Preservation Information

[0079] The Paracoccus sp. S160 provided by this invention was deposited on May 15, 2025 at the Guangdong Provincial Center for Microbial Culture Collection, with the strain accession number GDMCC NO:66343, and the deposit address is 5th Floor, Building 59, No. 100 Xianlie Middle Road, Guangzhou.

[0080] Example 4: Antagonistic Experiment of Strains Against Plant Wilt Pathogen

[0081] Fusarium oxysporum is a globally distributed soil-borne pathogen with a wide host range, causing wilt diseases in more than 100 plant species, including cucurbits, solanaceous plants, bananas, cotton, legumes, and flowers. The pathogen used in this experiment was Fusarium oxysporum race 4 (purchased from Wuhan Gray Algae Biotechnology Co., Ltd.).

[0082] The culture medium used for pathogen culture and antagonistic experiments is:

[0083] PDA liquid culture medium (1.0L): Wash and peel the potatoes, weigh 200g of potatoes and cut them into small pieces. Add water and boil for 20-30 minutes until the potatoes are cooked through. Filter with gauze and add 20g of glucose. Add water to make up to 1000mL, stir well, heat thoroughly to dissolve, and then dispense into Erlenmeyer flasks. Sterilize at 121℃ for 20 minutes before use.

[0084] PDA solid medium (1.0L): Wash and peel the potatoes, weigh 200g of potatoes and cut them into small pieces. Add water and boil for 20-30 minutes until the potatoes are cooked through. Filter with gauze and add 20g of glucose and 20g of agar. Add water to make up to 1000mL, stir well, and sterilize at 121℃ for 20 minutes before use.

[0085] LB solid medium (1.0L): 10g peptone, 5g yeast extract, 10g sodium chloride (NaCl), 20g agar powder.

[0086] The antagonistic effect of the strains was observed using the plate confrontation method. Specifically, Fusarium oxysporum was inoculated into PDA liquid medium and cultured at 30°C and 150 r / min for 24 h to obtain the pathogenic bacterial suspension.

[0087] The strain S160 isolated in Example 1 was streaked into LB solid medium and cultured upside down at 37°C for 24 hours to obtain a single colony of S160.

[0088] Control group: 200 μL of pathogenic bacterial suspension was spread on PDA solid medium. After it was fully grown, a circular pathogenic bacterial cake (0.6 cm in diameter) was punched with a sterilized punching ring and placed in the center of the blank PDA solid medium.

[0089] Treatment group: 200 μL of pathogenic bacterial suspension was spread on PDA solid medium. After it was fully grown, a circular pathogenic bacterial cake was punched with a sterile punching ring and placed in the center of a blank PDA solid medium. Then, a single S160 colony was picked up with a sterile bamboo stick and spotted 2 cm away from the center of the pathogenic bacterial cake. Three replicates were set up.

[0090] The petri dishes of the control group and the treatment group were incubated in a 30℃ incubator for one week, and the results were as follows: Figure 3 , Figure 4 As shown: From Figure 3 As can be seen, without the addition of S160 single colonies, the pathogens grew well, almost completely covering the entire PDA solid medium. Figure 4 As can be seen, when S160 single colonies were added 2 cm away from the pathogen, obvious transparent halos appeared around the S160 single colonies, indicating that S160 has an antagonistic effect on the pathogen (i.e., Fusarium oxysporum). This further shows that S160 single colonies have a significant inhibitory effect on the growth of the pathogen (i.e., Fusarium oxysporum), thus effectively preventing and controlling more than 100 kinds of plant wilt diseases such as banana wilt.

[0091] Example 5: Antagonistic Experiment of Strains Against Plant Root Rot Pathogens

[0092] Rice sheath blight is one of the three major diseases of rice. Because it can reproduce through spores, soil, and water, it is a devastating soil-borne disease. Rice is one of my country's four major grain crops, and rice sheath blight significantly impacts the agricultural economic benefits of rice. The pathogen used in this experiment was *Fusarium solani*, purchased from Ningbo Mingzhou Biotechnology Co., Ltd.

[0093] The culture medium used for pathogen culture and antagonistic experiments is:

[0094] PDA liquid culture medium (1.0L): Wash and peel the potatoes, weigh 200g of potatoes and cut them into small pieces. Add water and boil for 20-30 minutes until the potatoes are cooked through. Filter with gauze and add 20g of glucose. Add water to make up to 1000mL, stir well, heat thoroughly to dissolve, and then dispense into Erlenmeyer flasks. Sterilize at 121℃ for 20 minutes before use.

[0095] PDA solid medium (1.0L): Wash and peel the potatoes, weigh 200g of potatoes and cut them into small pieces. Add water and boil for 20-30 minutes until the potatoes are cooked through. Filter with gauze and add 20g of glucose and 20g of agar. Add water to make up to 1000mL, stir well, and sterilize at 121℃ for 20 minutes before use.

[0096] LB solid medium (1.0L): 10g peptone, 5g yeast extract, 10g sodium chloride (NaCl), 20g agar powder.

[0097] The antagonistic effect of the strains was observed using the plate confrontation method. Specifically, Rhizoctonia solani was inoculated into PDA liquid medium and cultured at 30°C with shaking at 150 r / min for 24 h to obtain the pathogenic bacterial suspension.

[0098] The strain S160 isolated in Example 1 was streaked into LB solid medium and cultured upside down at 37°C for 24 hours to obtain a single colony of S160.

[0099] Control group: 200 μL of pathogenic bacterial suspension was spread on PDA solid medium. After it grew to full size, a circular pathogenic bacterial cake was taken out by punching a hole with a sterile punching ring and placed in the center of the blank PDA solid medium.

[0100] Treatment group: 200 μL of pathogenic bacterial suspension was spread on PDA solid medium. After it was fully grown, a circular pathogenic bacterial cake was punched with a sterile punching ring and placed in the center of a blank PDA solid medium. Then, a single S160 colony was picked up with a sterile bamboo stick and spotted 2 cm away from the center of the pathogenic bacterial cake. Three replicates were set up.

[0101] The petri dishes of the control group and the treatment group were incubated in a 30℃ incubator for one week, and the results were as follows: Figure 5 , Figure 6 As shown: From Figure 5 As can be seen, without the addition of S160 single colonies, the pathogens grew well, almost completely covering the entire PDA solid medium. Figure 6The results show that when S160 single colonies were added 2 cm away from the pathogen, a clear halo appeared around each S160 single colony, indicating that S160 single colonies have an antagonistic effect on the pathogen (i.e., Rhizoctonia solani). This further indicates that S160 single colonies have a significant inhibitory effect on the growth of the pathogen (i.e., Rhizoctonia solani), thus effectively controlling rice sheath blight and providing strain resources for the biological control of rice sheath blight occurrence, spread, effective management, and solving continuous cropping obstacles in production.

[0102] Example 6: Antagonistic Experiment of Strains Against the Pathogen of Black Spot Disease in Panax notoginseng

[0103] Black spot disease of Panax notoginseng is a disease caused by Alternaria panax, which affects the stems, leaves, petioles, flower stalks, fruits, fruit stalks, roots, rhizomes, and buds. The pathogen used in this experiment to diagnose black spot disease is Alternaria panax (purchased from Wuhan Gray Algae Biotechnology Co., Ltd.).

[0104] The culture media used for pathogen culture and antagonistic experiments were: PDA liquid medium, PDA solid medium, and LB solid medium; the PDA liquid medium, PDA solid medium, and LB solid medium were prepared according to the method described in Example 4.

[0105] The antagonistic effect of the strains was observed using the plate confrontation method. Specifically, the pathogen of *Streptococcus ginseng* was inoculated into PDA liquid medium and cultured at 30°C and 150 r / min for 24 h to obtain the pathogen suspension.

[0106] The strain S160 isolated in Example 1 was streaked into LB solid medium and cultured upside down at 37°C for 24 hours to obtain a single colony of S160.

[0107] Control group: 200 μL of pathogenic bacterial suspension was spread on PDA solid medium. After it was fully grown, a circular pathogenic bacterial cake (0.6 cm in diameter) was punched with a sterile punching ring and placed in the center of the blank PDA solid medium.

[0108] Treatment group: 200 μL of pathogenic bacterial suspension was spread on PDA solid medium. After it was fully grown, a circular pathogenic bacterial cake was punched with a sterile punching ring and placed in the center of a blank PDA solid medium. Then, a single S160 colony was picked up with a sterile bamboo stick and spotted 2 cm away from the center of the pathogenic bacterial cake. Three replicates were set up.

[0109] The petri dishes of the control group and the treatment group were incubated in a 30℃ incubator for one week, and the results were as follows: Figure 7 , Figure 8 As shown; from Figure 7As can be seen, without the addition of S160 single colonies, the pathogens grew well, almost completely covering the entire PDA solid medium. Figure 4 As can be seen, when S160 single colonies were added 2 cm away from the pathogen, obvious transparent halos appeared around the S160 single colonies, indicating that S160 has an antagonistic effect on the pathogen (i.e., ginseng streptococcus spp.). This further indicates that S160 single colonies have a significant inhibitory effect on the growth of the pathogen (i.e., ginseng streptococcus spp.), thus effectively preventing and controlling Panax notoginseng black spot disease.

[0110] In summary, this invention isolated Paracoccus sp. S160 from peanut roots and identified it morphologically, physiologically, biochemically, and genetically. 16S rRNA identification confirmed its identity as Paracoccus sp. The examples demonstrate the antagonistic effects of this strain on pathogens such as Fusarium oxysporum, Rhizoctonia solani, and Alternaria ginseng. The results show that this strain can effectively inhibit the growth and reproduction of these pathogens, thus effectively controlling plant wilt diseases such as banana wilt, rice sheath blight, and Panax notoginseng black spot, solving the environmental pollution and food safety problems caused by the use of chemical fungicides.

[0111] It is understood that the above embodiments only illustrate preferred embodiments of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can freely combine the above technical features without departing from the concept of the present invention, and can also make several modifications and improvements, all of which fall within the protection scope of the present invention. Therefore, all equivalent transformations and modifications made with respect to the scope of the claims of the present invention should fall within the scope of the claims of the present invention.

Claims

1. A methyl-trophic paracoccus, characterized in that, The strain was named Paracoccus sp. S160 and was deposited on May 15, 2025, at the Guangdong Provincial Center for Microbial Culture Collection, with accession number GDMCC NO:66343. The deposit address is 5th Floor, Building 59, No. 100 Xianlie Middle Road, Guangzhou.

2. The culture, live bacteria, freeze-dried bacteria, or inactivated bacteria of the methyltrophic paracoccus as described in claim 1.

3. The culture, live bacteria, freeze-dried bacteria, or inactivated bacteria of methyltrophic paracoccus according to claim 2, characterized in that, The culture comprises the fermentation broth of methyltrophic paracoccus or the concentrated or dried product of the fermentation broth.

4. A composition for improving plant disease resistance, characterized in that, Includes cultures, live bacteria, freeze-dried bacteria, or inactivated bacteria of the methyltrophic paracoccus as described in claim 1 or any one of claims 2-3; wherein the culture includes any one of A) to D): A) Fermentation broth of the strain; B) The supernatant of the fermentation broth of the strain; C) The inactivated fermentation broth of the strain; D) The concentrated or dried product of any one of A)-C).

5. The composition according to claim 4, characterized in that, The composition is any one of plant growth promoter, bio-fertilizer, and antibacterial agent.

6. The use of the methyl-nutritive paracoccus according to claim 1, the culture, live bacteria, freeze-dried bacteria or inactivated bacteria of the methyl-nutritive paracoccus according to any one of claims 2-3, and the composition for improving plant disease resistance according to any one of claims 4-5 in the preparation of products for improving plant disease resistance.

7. The application according to claim 6, characterized in that, The product that enhances plant disease resistance is one that inhibits at least one pathogenic bacterium among Fusarium oxysporum, Rhizoctonia solani, and Alternaria ginseng.

8. The application according to any one of claims 6-7, characterized in that, The product that enhances plant disease resistance is a product for preventing and treating at least one of the following diseases: plant wilt, rice sheath blight, and Panax notoginseng black spot.

9. A composition for promoting plant growth, characterized in that, Includes cultures, live bacteria, freeze-dried bacteria, or inactivated bacteria of the methyltrophic paracoccus as described in claim 1 or any one of claims 2-3; wherein the culture includes any one of A) to D): A) Fermentation broth of the strain; B) The supernatant of the fermentation broth of the strain; C) The inactivated fermentation broth of the strain; D) The concentrated or dried product of any one of A)-C).

10. The use of the methyl-nutritive paracoccus of claim 1, the culture, live bacteria, freeze-dried bacteria or inactivated bacteria of the methyl-nutritive paracoccus of any one of claims 2-3, and the composition for improving plant disease resistance of claim 9 in the preparation of plant growth promoting products.

Images