Acid-tolerant phosphorus solubilizing bacteria and application thereof

Abstract

The present application belongs to the field of microbial technology. More specifically, it relates to an acid-tolerant phosphorus-solubilizing bacterium and its application. The present application provides Trinickia diaoshuihuensis A PSM strain and a microbial inoculum formed by the PSM strain in combination with biochar. Pot experiment shows that application of the microbial inoculum of the present application can significantly increase the pH value of the soil in the counter-acid field, relieve acid damage, increase the content of soil organic carbon and total nitrogen, relieve the problem of phosphorus deficiency in the soil, improve the rhizosphere environment of the plant and significantly promote the growth of the plant. The microbial inoculum of the present application not only overcomes the bottleneck of difficult colonization and weak function of the existing microbial inoculum in the counter-acid field, but also realizes the resource utilization of rice straw, provides a green solution for the ecological restoration in the acid sulphate soil distribution area, and has good application prospect and value.

Description

Technical Field

[0001] This invention belongs to the field of microbial technology. More specifically, it relates to an acid-resistant phosphate-solubilizing bacterium and its applications. Background Technology

[0002] Soil acidification is one of the core limiting factors in agricultural production, with acid sulfate soil (ASS) being a typical example. In current agricultural applications, ASS can further evolve into acid-reverse soils, widely distributed in the coastal areas of South my country. These soils are characterized by strong acidity (pH below 4.0), high exchangeable aluminum, low phosphorus, and poor organic matter content, severely inhibiting crop root development and nutrient absorption, resulting in low yields or even crop failure for major crops such as rice. Currently, remediation measures for ASS mainly include applying alkaline substances such as lime to neutralize acidity, or adding organic materials to improve soil structure. However, while lime can raise soil pH in the short term, it easily leads to the formation of insoluble precipitates of phosphorus and various trace elements, reducing their availability, and cannot address the fundamental problem of low soil microbial activity; while single organic fertilizers decompose slowly under strong acidic conditions, limiting nutrient release, and their remediation effect is often insignificant.

[0003] Phosphate-solubilizing microorganisms (PSMs) are a group of functional microorganisms that can convert insoluble phosphorus in the soil into available phosphorus that plants can absorb and utilize. They participate in the nutrient cycling and transformation in the soil, increasing the content of soil organic carbon, nitrogen, and other nutrients, improving the structure of the soil microbial community, and enhancing soil fertility and quality. However, the growth and activity of PSMs are usually limited by environmental factors, resulting in a significant reduction in remediation effects. Furthermore, existing PSMs still face two major bottlenecks in ASS (Alternative Soil Assay) applications: firstly, most strains struggle to survive and colonize in extremely acidic environments with a pH < 4.0; secondly, even with successful inoculation, their phosphate-solubilizing and growth-promoting functions are often difficult to express stably in real soil due to intense competition for ecological niches with native microbial communities, thus limiting their actual growth-promoting effects.

[0004] Most microbial agents currently on the market suffer from low colonization rates, unstable functional performance, and insignificant growth-promoting effects in acidic soils, failing to meet the actual needs of agricultural production for efficient and long-lasting soil improvement technologies. Therefore, there is an urgent need to screen functional strains with both strong acid tolerance and efficient phosphorus solubilization capabilities, and to construct novel microbial agents capable of stable colonization and sustained growth-promoting effects under extremely acidic conditions, in order to promote the green and sustainable remediation of acid sulfate soils (ASS). Summary of the Invention

[0005] This invention aims to overcome the shortcomings of existing microbial agents in acid-reactive fields, such as low colonization rate, unstable function, and insignificant growth-promoting effect, and to provide a strain that combines strong acid resistance with high phosphorus solubilization ability. Trinickia diaoshuihuensis PSM strain, and microbial agents constructed from the biochar of this strain.

[0006] The first objective of this invention is to provide a plant Trinickia diaoshuihuensis PSM strain.

[0007] The second objective of this invention is to provide a microbial inoculant.

[0008] A third objective of this invention is to provide the application of the aforementioned PSM strain or the aforementioned microbial agent.

[0009] The fourth objective of this invention is to provide a method for improving acidic soil.

[0010] The above-mentioned objective of this invention is achieved through the following technical solution:

[0011] This invention provides a plant Trinickia diaoshuihuensis The PSM strain was deposited at the Guangdong Provincial Center for Microbial Culture Collection on December 9, 2025, with accession number GDMCC No: 67443.

[0012] The present invention provides a microbial inoculant containing the above-mentioned PSM strain or its fermentation broth.

[0013] Preferably, the above-mentioned microbial inoculant also contains an agriculturally acceptable carrier.

[0014] More preferably, the agriculturally acceptable carrier is biochar.

[0015] Preferably, the raw material for the biochar is rice straw.

[0016] Preferably, the biochar is prepared by crushing rice straw and then treating it at 400-600℃ for 2-4 hours under anaerobic conditions to obtain rice straw biochar.

[0017] Optionally, rice straw biochar can be ground and passed through an 80-120 mesh sieve.

[0018] Preferably, the biochar has a pH value of 9.0-11.0 and a specific surface area of ​​20-50 m². 2 / g.

[0019] Preferably, the above-mentioned microbial inoculant is prepared by mixing the fermentation broth of PSM strain with biochar and culturing it to obtain the microbial inoculant.

[0020] Specifically, the culture is carried out at 28~32℃ and 160~200r / min for 48~96 h.

[0021] As an alternative implementation, the microbial agent is prepared by adding biochar to a liquid culture medium at a mass-to-volume ratio of 5-15%, sterilizing it, and then inoculating it into the fermentation broth of the above-mentioned PSM strain at a volume ratio of 2-8% to obtain the microbial agent.

[0022] Optionally, the liquid culture medium is NBRIP liquid culture.

[0023] The microbial inoculant of this invention can significantly increase the pH value of acidified soil, alleviating acid damage; simultaneously, it increases the content of soil organic carbon and total nitrogen, alleviating phosphorus deficiency, and significantly promoting plant growth. Therefore, this invention claims protection for the following applications: Application of the above-mentioned PSM strains or the above-mentioned microbial agents in promoting plant growth.

[0024] Application of the above-mentioned PSM strains or microbial agents in the preparation of products that promote plant growth.

[0025] Application of the above-mentioned PSM strains or the above-mentioned microbial agents in phosphorus solubilization.

[0026] The application of the above-mentioned PSM strains or the above-mentioned microbial agents in the preparation of products with phosphorus solubilization capabilities.

[0027] The application of the above-mentioned PSM strain or the above-mentioned microbial agent in promoting plant growth under environmental stress, wherein the environmental stress is at least one of low phosphorus stress, aluminum stress, and acid stress.

[0028] The application of the above-mentioned PSM strain or the above-mentioned microbial agent in the preparation of products that promote plant growth under environmental stress, wherein the environmental stress is at least one of low phosphorus stress, aluminum stress, and acid stress.

[0029] The acid-base stress includes acid stress with a pH value of 3.8 to 4.2.

[0030] Application of the above-mentioned PSM strains or microbial agents in improving acidic soils.

[0031] Application of the above-mentioned PSM strains or microbial agents in the preparation of acidic soil conditioners or conditioning agents.

[0032] A method for improving acidic soil involves treating the soil using the aforementioned PSM strain or the aforementioned microbial agent.

[0033] The present invention has the following beneficial effects: This invention provides Trinickia diaoshuihuensisThe PSM strain and its microbial inoculant, formulated with rice straw biochar, demonstrated significant comprehensive benefits in improving acidic sulfate soils (acidic soils). This strain exhibits excellent growth and efficient inorganic phosphorus dissolution in a strongly acidic environment (pH 4.0); its phosphorus-dissolving capacity is further enhanced after loading onto rice straw biochar. Scanning electron microscopy confirmed that PSM cells effectively attach to and colonize the porous structure of biochar. Biochar loading significantly promotes strain growth, enabling it to enter the exponential growth phase more quickly, increasing its maximum biomass and prolonging the stationary phase, thus laying the foundation for its colonization and functional expression in real soil. In pot experiments, application of the microbial inoculant of this invention rapidly increased the pH of acidic sulfate soil (initial pH approximately 3.7) to 5.85-5.97 within 0-28 days, effectively mitigating the direct damage of strong acid to crop roots. Simultaneously, the microbial inoculant treatment significantly increased the total and available phosphorus content of the soil, solving the phosphorus deficiency problem in acidic soils. This microbial agent showed significant growth-promoting effects on both Xiangya Xiangzhan and Huanghuazhan rice varieties, resulting in robust plant growth and demonstrating good potential for agronomic application.

[0034] In summary, this invention organically combines acid-resistant, highly efficient phosphorus-solubilizing bacteria with agricultural waste-derived biochar to construct a green soil improvement system that integrates "acidity adjustment, aluminum reduction, phosphorus solubilization, fertilization, and growth promotion." This system not only overcomes the bottlenecks of existing microbial agents in acidic soils, such as difficulty in colonization and weak functionality, but also realizes the resource utilization of rice straw. It has advantages such as low cost, environmental friendliness, and strong sustainability, providing a practical and feasible technical path for the ecological restoration of acidic sulfate soils, and has good application prospects and value. Attached Figure Description

[0035] Figure 1 for Trinickia diaoshuihuensis Plate colony morphology of PSM strain.

[0036] Figure 2 for Trinickia diaoshuihuensis Gram staining results of PSM strain.

[0037] Figure 3 for Trinickia diaoshuihuensis Phylogenetic tree of PSM strains.

[0038] Figure 4 for Trinickia diaoshuihuensis Scanning electron microscope image of PSM strain loaded with biochar.

[0039] Figure 5 for Trinickia diaoshuihuensis The results of phosphorus solubility and pH test of PSM bacterial solution and its inoculant (Figure A) Trinickia diaoshuihuensis PSM bacterial culture; Figure B shows biochar loading. Trinickia diaoshuihuensis(The bacterial agent prepared from the PSM strain).

[0040] Figure 6 for Trinickia diaoshuihuensis A comparison of the growth curves of PSM strains and their growth after being loaded with biochar.

[0041] Figure 7 To compare the growth of two types of rice plants under different treatments.

[0042] Figure 8 The results of phenotypic index measurements of two rice plants under different treatments are shown in Figure A (leaf area); Figure B (plant height); and Figure C (SPAD value of leaves).

[0043] Figure 9 The effects of different treatments on soil carbon, nitrogen, phosphorus, and available phosphorus content are shown in Figure A (total organic carbon content, total nitrogen content, total phosphorus content, and available phosphorus content).

[0044] Figure 10 The results show the determination of exchangeable aluminum content in soil under different treatments. Detailed Implementation

[0045] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in this technical field.

[0046] Unless otherwise specified, all reagents and materials used in the following examples are commercially available.

[0047] The sequence of primer 27F is (5'-3'): AGRGTTYGATYMTGGCTCAG (SEQ ID NO.1); The sequence of primer 1492R is (5'-3'): RGYTACCTTGTTACGACTT (SEQ ID NO.2).

[0048] NBRIP liquid culture medium formula: Per liter of deionized water, there are 10g glucose, 5g tricalcium phosphate, 0.3g sodium chloride, 0.5g ammonium sulfate, 0.3g magnesium sulfate, 0.3g potassium chloride, 0.03g ferrous sulfate, and 0.03g magnesium sulfate. After preparation, adjust the pH to 4.0-4.2 with HCl or NaOH, and autoclave at 121°C for 30 minutes.

[0049] Example 1: Screening and purification of highly efficient phosphate-solubilizing bacteria I. Soil Sampling Soil samples were collected from Taishan City, Guangdong Province. Immediately after collection, the soil samples were placed in sterile bags, stored at 4℃, and transported back to the laboratory. 10g of soil sample was weighed and added to 100mL of sterile water. The mixture was shaken at 180 rpm for 30 minutes and allowed to stand for 10 minutes to obtain a concentration of 10%. -1 Soil suspension at g / mL.

[0050] Subsequently, continuous enrichment culture was performed: 10 mL of 10 -1 The supernatant of a soil suspension at a concentration of g / mL was inoculated into 100 mL of NBRIP liquid medium at pH 4.0 and incubated at 28–30 °C for 3 days. This process was repeated three times. Each transfer was equivalent to a 10-fold dilution of the original soil suspension, thus forming 10 g / mL of NBRIP liquid medium. -1 (original solution), 10 -2 and 10 -3 10 -4 Enrichment culture systems with four concentration gradients.

[0051] II. Isolation, Purification and Preservation of Strains The plating method was used to isolate bacterial strains from culture systems with different dilutions. In a clean bench, each gradient dilution was evenly spread onto sterile solid NBRIP agar plates, with three replicates per treatment, and incubated upside down at 28–30°C for 72 h. Single colonies with clear edges, good growth, and obvious phosphate-solubilizing zones were selected for secondary screening.

[0052] The secondary screening was performed using the streak plating method: dominant colonies obtained from the initial screening were picked up with an inoculation loop and streaked onto fresh, sterile solid NBRIP medium, and incubated upside down at 30°C for 72 hours. Finally, a single colony with the largest transparent lysing zone and uniform morphology was selected and named the PSM strain.

[0053] The strain was preserved as follows: The purified strain was inoculated into sterile NBRIP liquid medium and cultured at 30℃ with shaking at 180 rpm for 72 h. The OD of the bacterial culture was then measured. 600 When the value reaches approximately 0.6, mix with a 40% (v / v) glycerol solution at a 1:1 volume ratio, dispense, and store at -80°C for long-term storage.

[0054] Example 2: Strain Identification I. Identification of bacterial strain morphology The PSM strain purified in Example 1 was inoculated onto inorganic phosphorus solid medium and incubated upside down at 30°C for 3 days. The colony morphology of the PSM strain is as follows: Figure 1 As shown, the colonies were observed to be yellow, round, with a smooth, raised surface. The colonies were moist with clear edges, and wrinkles appeared on the surface during the later stages of growth. Gram staining results for the PSM strain are shown below. Figure 2 As shown, the strain appears as a pink rod, indicating that it is a Gram-negative bacterium.

[0055] II. Physiological and Biochemical Identification of Strains Physiological and biochemical identification of the PSM strain was performed. The results are shown in Table 1. Table 1 shows that this strain can utilize D-sorbitol, L-proline, and D-arabinose to hydrolyze lactose; it produces hydrogen sulfide, catalase, urease, and amylase; it is positive for nitrate reduction, oxidase, gelatin liquefaction, and methyl red reaction; while it is negative for cellulose hydrolysis, VP test, and lactose fermentation.

[0056] Table 1. Results of Physiological and Biochemical Characteristic Identification

[0057] Note: In the table, "+" indicates a positive result or that the product can be used; "-" indicates a negative result or that the product cannot be used.

[0058] III. Molecular biological identification of strains Species identification of PSM strains was performed using 16S rRNA gene sequence analysis. PCR amplification was conducted using universal bacterial primers 27F and 1492R. The products were sequenced and BLASTed in NCBI to determine the strain species. Simultaneously, gene sequences of other strains with high homology were downloaded, and a phylogenetic tree was constructed using MEGA X software. A maximum likelihood tree based on the 16S rRNA gene sequence was also used.

[0059] The 16S rRNA gene sequence of the strain is shown in SEQ ID NO.3. SEQ ID NO.3:

[0060] Phylogenetic tree of PSM strains as follows Figure 3 As shown, the results indicate that the PSM strain and the NEAU-SY24T strain ( Trinickia diaoshuihuensis The 16S rRNA gene sequence similarity of this strain was 99.488%, therefore the strain was identified as... Trinickia diaoshuihuensis .

[0061] Trinickia diaoshuihuensis The PSM strain was deposited at the Guangdong Provincial Center for Microbial Culture Collection on December 9, 2025, with accession number GDMCC No: 67443.

[0062] Example 3 Biochar Preparation Rice straw was used as raw material. The rice straw was crushed and then placed in a muffle furnace for anaerobic pyrolysis carbonization at 500℃ for 3 hours to obtain rice straw biochar. The biochar was then ground and passed through a 100-mesh sieve for later use. The physicochemical properties of rice straw biochar are shown in Table 2.

[0063] Table 2 Physicochemical properties of rice straw biochar

[0064] Example 4: Functional identification of strain PSM and its biochar-supported system I. Preparation of Trinickia inoculant The PSM strain was inoculated into sterile NBRIP liquid medium at pH 4.0 at a 5% (v / v) inoculation rate and cultured at 30°C and 180 rpm for 72 hours until 0D. 600 =0.6, PSM bacterial solution was obtained. Rice straw biochar prepared in Example 3 was added to NBRIP liquid medium at 10% (w / v) and autoclaved at 121℃ for 30 min. After cooling, it was inoculated into the PSM bacterial solution at 5% (v / v) and placed at 30℃, shaken at 180 r / min for 72 hours to obtain Trinickia bacterial agent.

[0065] Scanning electron microscopy was performed on the Trinickia inoculant, and the results are as follows: Figure 4 As shown, the results indicate that the bacteria can effectively attach to the porous structure of biochar and grow well.

[0066] II. Phosphorus Solubility Determination Sample preparation: 1. Test samples treated with PSM bacterial solution (PSM): PSM strain was inoculated into sterile NBRIP liquid medium at an inoculation rate of 5% (v / v) and cultured at 30℃ and 180r / min for 24, 48, 72, 96, 120, 148, 172 and 196 h. 5 mL of the sample at each time point was taken and sonicated for 20 min. Then, 3 mL of the supernatant was collected by centrifugation at 12000r / min and diluted with water to 20 mL to obtain the test samples treated with PSM bacterial solution.

[0067] 2. Test samples treated with Trinickia bacterial agent (PSM+B): The biochar prepared in Example 3 was added to NBRIP liquid medium at 10% (w / v) and autoclaved at 121℃ for 30 min. After cooling, it was mixed with PSM bacterial solution at a ratio of 5% (v / v) and cultured at 30℃ and 180 r / min on a shaker for 24, 48, 72, 96, 120, 148, 172 and 196 h. 5 mL of the sample was taken at each time point, sonicated for 20 min, and then centrifuged at 12000 r / min to obtain 3 mL of supernatant. The supernatant was diluted with water to 20 mL to obtain the test samples treated with Trinickia bacterial agent.

[0068] Preparation of phosphorus standard solution: Weigh 43.94 g KH2PO4 and dissolve it in 100 mL of ultrapure water. Add 5 mL of concentrated sulfuric acid and dilute to 1 L to obtain a 100 mg / L phosphorus standard solution stock solution (which can be stored for a long time). Take 10 mL of the stock solution and dilute it with ultrapure water to 200 mL to obtain a 5 mg / L working solution (which should be stored in a brown bottle protected from light).

[0069] Standard curve preparation: Take 0, 2, 4, 6, 8, and 10 mL of 5 mg / L working solution into 50 mL colorimetric tubes, respectively. Simultaneously add an equal volume of blank solution to the sample solution. Dilute the sample to 20 mL with ultrapure water. Add 6 drops of dinitrophenol indicator to each volumetric flask, neutralize with 2 mol / L NaOH until slightly yellow, add 5 mL of molybdenum antimony reagent, react at room temperature for 30 min, and then bring the volume to 50 mL. Measure the absorbance at 700 nm. Plot a standard curve with phosphorus concentration on the ordinate and absorbance on the abscissa.

[0070] Determination of phosphorus content in the sample: Add 6 drops of dinitrophenol indicator to the sample diluted to 20 ml, neutralize with 2 mol / L NaOH until slightly yellow, add 5 mL of molybdenum antimony colorimetric reagent, react at room temperature for 30 min, and then bring the volume to 50 mL. Measure the absorbance at 700 nm and calculate the phosphorus content of the sample by substituting it into the standard curve.

[0071] Phosphorus solubility test results are as follows Figure 5As shown, the results indicate that the highest phosphorus solubility of the free strain was 88.7 μg / mL, while the highest phosphorus solubility of the biochar-loaded strain reached 104.5 μg / mL, significantly improving the phosphorus solubility efficiency (P<0.05).

[0072] III. Growth curves of PSM strains and biochar-loaded strains PSM strain and Trinickia inoculum were inoculated into NBRIP liquid medium and cultured at 30℃ and 180 r / min with shaking. OD was measured every 24 h. 600 The treatment continued until the values ​​decreased. Uninoculated culture medium was used as a control, and each treatment was repeated three times.

[0073] Growth curve measurement results are as follows Figure 6 As shown, the results indicate that biochar loading treatment can significantly promote cell growth, enabling the strain to rapidly enter the exponential growth phase and increase the growth rate, indicating that biochar has a growth-promoting effect on strain PSM.

[0074] Example 5: Effect of biochar-supported Trinickia microbial agent on the improvement of acidic sulfate soil. I. Effects of Trinickia inoculant on the improvement of acidic sulfate soil and the promotion of rice growth The tested soil was collected from the top 20 cm of acidic sulfate soil farmland in Taishan, Guangdong. Its basic physicochemical properties are shown in Table 3. After natural air drying, sieving, and mixing, the soil was placed into plastic flower pots (3 kg per pot), and soil conditioner was added according to different treatments and mixed thoroughly.

[0075] The preparation method of Trinickia bacterial agent is as follows: 60g of biochar is added to 600ml of culture medium and sterilized at 121℃ for 20min. After cooling, 3mL of PSM bacterial solution is added and cultured at 30℃ and 180r / min for 3d to obtain Trinickia bacterial agent.

[0076] Configure the following process: CK group: blank control (no modifier added); Group B: Add 2% (w / w) of the biochar prepared in Example 3 (20g of biochar per kilogram of soil); BPSM group: Add Trinickia inoculant (200 mL Trinickia inoculant per kilogram of soil).

[0077] Two rice varieties, "Xiangya Xiangzhan" and "Huanghuazhan", were selected and transplanted at the two-leaf-one-heart stage. The soil was kept submerged and the soil pH was measured every 7 days for 6 weeks.

[0078] Table 3 Basic Physicochemical Properties of Soil

[0079] II. Effects of different treatments on soil pH The pH regulation capabilities of different conditioners on soil are shown in Table 4. The results showed that compared with biochar alone (Group B), the BPSM treatment increased the soil pH by 1-2. The soil of Xiangya Xiangzhan rice reached its highest pH (5.89) on day 21, while Huanghuazhan reached its peak (5.85) on day 35, indicating that Trinickia inoculant has a sustained and efficient ability to improve acidic soils.

[0080] Table 4 pH regulation capacity under different treatments

[0081] III. Impact on rice growth When the rice plants have grown for 60 days, the height of each rice plant from the surface of the soil in the pot is measured using a ruler. The measurements are repeated in parallel, and the average value is calculated as the plant height. The relative chlorophyll content of the rice leaves is measured using a SPAD chlorophyll meter. The rice leaves are measured using a portable leaf area meter. When measuring, the leaves should be gently flattened with your fingers, and the base of the leaf sheath should be placed into the instrument first and then pulled towards the leaf tip at a uniform speed.

[0082] The growth of rice plants under different treatments is as follows: Figure 7 As shown in the figure, the phenotypic indicators of rice plants under different treatments were measured as follows: Figure 8 As shown, the results indicate that, compared with the blank control and biochar treatment alone, the addition of Trinickia inoculant significantly increased the leaf area, plant height, and chlorophyll content of rice.

[0083] IV. Impact on soil carbon, nitrogen, phosphorus and available phosphorus content Soil samples were collected 60 days after rice planting to determine the contents of organic carbon, total nitrogen, total phosphorus, and available phosphorus. The results are as follows: Figure 9 As shown, the results indicated that compared with the control (CK), both treatments B and BPSM significantly increased soil organic carbon and total nitrogen content (P<0.05), with BPSM showing a better effect, indicating that the PSM strain participated in soil carbon and nitrogen cycling. Notably, compared with the blank control and biochar addition (B) treatment, the BPSM treatment significantly increased soil available phosphorus content, while treatment B had no significant effect on total phosphorus and available phosphorus, suggesting that the strain's phosphorus-solubilizing function was effectively utilized in the soil.

[0084] V. Impact on Soil Exchangeable Aluminum Content The exchangeable aluminum content in the soil of each treatment was determined, and the results are as follows: Figure 10 As shown, the results indicate that BPSM treatment significantly reduced the exchangeable aluminum content in the soil, suggesting that BPSM treatment can alleviate the aluminum toxicity of crops by acidic sulfate soil to some extent.

[0085] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A plant Trinickia diaoshuihuensis PSM strain, characterized in that, The bacteria was deposited at the Guangdong Provincial Center for Microbial Culture Collection on December 9, 2025, with accession number GDMCC No: 67443.

2. A microbial inoculant, characterized in that, Contains the PSM strain of claim 1 or its fermentation broth.

3. The microbial agent according to claim 2, characterized in that, It also contains an agriculturally acceptable carrier; preferably, the agriculturally acceptable carrier is biochar.

4. The microbial agent according to claim 3, characterized in that, The biochar has a pH value of 9.0–11.0 and a specific surface area of ​​20–50 m². 2 / g.

5. The microbial agent according to claim 3, characterized in that, The preparation method is as follows: the fermentation broth of PSM strain is mixed with biochar and cultured to obtain microbial inoculum.

6. The use of the PSM strain of claim 1 or any of the microbial agents of claims 2 to 5 in promoting plant growth, or in the preparation of products that promote plant growth.

7. The application of the PSM strain of claim 1 or any of the microbial agents of claims 2 to 5 in phosphorus solubilization, or in the preparation of products with phosphorus solubilization capabilities.

8. The application of the PSM strain of claim 1 or any of the microbial agents of claims 2 to 5 in promoting plant growth under environmental stress, or in the preparation of products with the ability to promote plant growth under environmental stress, wherein the environmental stress is at least one of low phosphorus stress, aluminum stress, and acid stress.

9. The application of the PSM strain of claim 1 or any of the microbial agents of claims 2 to 5 in improving acidic soil, or in the preparation of acidic soil conditioners or conditioning agents.

10. A method for improving acidic soil, characterized in that, Soil is treated using the PSM strain of claim 1 or any of the microbial agents of claims 2 to 5.

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