Bacillus intergenus MS443 and application thereof

Abstract

The invention discloses bacillus intergenus MS443 and application thereof, and belongs to the technical field of microorganisms. The intergeneric bacillus sp. MS443 is preserved in the China Center for Type Culture Collection, and the preservation number of the intergeneric bacillus sp. MS443 is CCTCC (China Center for Type Culture Collection) NO: M 2025280. The strain has a heterotrophic nitrification function, can effectively convert ammonium nitrogen into nitrate nitrogen, can be applied to soil nitrogen conversion, and converts ammonium nitrogen accumulated in soil into nitrate nitrogen which is more easily absorbed by plants. On the other hand, due to the fact that the utilization efficiency of plants on nitrogen is improved, the yield is improved, and the strain shows a remarkable growth promoting effect on various crops including solanaceae (such as tomatoes and peppers), gramineae (such as corn), malvidae (such as cotton) and cruciferae (such as flowering cabbage) plants and can be applied to agricultural production to improve the nitrogen fertilizer utilization efficiency and the crop yield; the use amount of chemical fertilizer can be reduced.

Description

Technical Field

[0001] This invention relates to the field of microbial technology, specifically to a genus of Bacillus ( ). Mesobacillus (sp.) MS443 and its applications. Background Technology

[0002] Nitrogen is the mineral nutrient element required in the largest quantity by plants, playing a crucial role in crop yield formation and quality regulation. Adequate nitrogen supply can effectively promote lateral branch differentiation and root system architecture, and enhance the translocation and distribution efficiency of assimilates, thereby increasing biomass and economic yield. However, excessive nitrogen fertilizer application can easily lead to numerous problems such as soil nutrient imbalance and soil ecological disorder, further triggering continuous cropping obstacles, ultimately resulting in a significant decrease in crop yield or even crop failure.

[0003] In agricultural production, exogenous nitrogen is mainly applied to the soil in the form of amide nitrogen (such as urea), with only a small amount supplemented in the form of ammonium nitrogen (such as ammonium carbonate and ammonium sulfate). Although some crops have a certain capacity to absorb ammonium nitrogen, their main nitrogen acquisition pathway relies on nitrate nitrogen absorption mediated by nitrate transporters (NRTs). Long-term excessive nitrogen application coupled with the limited assimilation capacity of plants leads to the continuous accumulation of ammonium nitrogen in the soil, causing typical ammonium salt toxicity symptoms, such as chlorosis and yellowing of leaves, stunted growth, and inhibited root elongation, ultimately resulting in a sharp reduction in yield.

[0004] Therefore, how to effectively promote the mineralization and decomposition of organic nitrogen and urea in the soil, and accelerate the nitrification conversion of ammonium nitrogen to nitrate nitrogen, so as to ensure the efficient supply of nitrogen nutrition to crops, has become a core scientific issue for sustainable agricultural production and efficient nitrogen management.

[0005] The rhizosphere microbiome, hailed as the "second genome" of plants, plays a crucial role in regulating crop growth and development, enhancing environmental resilience, and maintaining soil ecosystem health. Studies have shown that rhizosphere microorganisms can directly promote crop growth; for example, Bacillus subtilis (… Bacillus subtilis Berlanga can stimulate embryo development through interaction with seeds and produce a sustained growth-promoting effect on mature plants. et al .,Bacillus subtilis biofilmmatrix components target seed oil bodies to promote growth and anti-fungalresistance in melon. Nat Microbiol 7(2022, 1001-1015.); It can also significantly enhance the crop's adaptability to abiotic stresses. For example, salt-tolerant wild soybean can selectively recruit Pseudomonas bacteria with both salt tolerance and plant growth-promoting functions through root exudates, thereby effectively alleviating physiological damage caused by salt stress (Zheng et al ., Purinesenrich root-associated Pseudomonas and improve wild soybean growth under saltstress. Nat Commun 15 (2024, 3520.). In addition, rhizosphere microorganisms also play an important role in improving nutrient utilization efficiency: nitrogen-fixing microorganisms can convert atmospheric nitrogen into nitrogen forms that plants can utilize; phosphate-solubilizing bacteria and potassium-solubilizing bacteria can activate insoluble phosphorus and potassium elements in the soil, promoting their absorption and utilization by plants.

[0006] Rhizosphere microorganisms play an indispensable role in plant nitrogen metabolism and utilization. Besides converting organic nitrogen and urea into ammonium nitrogen through mineralization and urease, rhizosphere microorganisms also drive the crucial nitrification process, further converting ammonium nitrogen into nitrate nitrogen, which is more easily absorbed by plants. Studies have shown that indica rice, compared to japonica rice, can recruit a higher abundance of nitrogen assimilation and metabolism-related microbial communities, thereby significantly improving nitrogen use efficiency (Zhang...). et al .,NRT1.1B is associated with root microbiota composition and nitrogen use in field-grown rice. Nature Biotechnology , 2019,37(6).).

[0007] However, existing research largely focuses on microbial nitrogen fixation, and a systematic and in-depth understanding of the nitrogen form transformation process mediated by rhizosphere microorganisms and its regulatory mechanisms in interaction with plants is still lacking. Therefore, isolating and identifying plant rhizosphere growth-promoting bacteria with efficient nitrification or nitrogen transformation functions is of great significance for constructing nitrogen-efficient rhizosphere microbial communities, improving crop nitrogen fertilizer use efficiency, and promoting the sustainable development of green agriculture. Summary of the Invention

[0008] The purpose of this invention is to provide a plant rhizosphere growth-promoting bacterium with efficient nitrification or nitrogen conversion functions, which can be applied to improve the utilization efficiency of nitrogen fertilizer by crops.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: This invention isolates a strain of *Bacillus* genus with heterotrophic nitrification function from topsoil. MesobacillusA new strain of *Bacillus mesenchyme* was identified, with the following main biological characteristics: after culturing on TSB plates at 28°C for 2 days, it formed round, white, transparent, smooth, moist, and distinctly raised colonies; the bacterial morphology was coccoid, it could form spores, and it showed Gram-positive or variable staining. The 16S rDNA sequence is shown in SEQ ID NO.1. Phylogenetic tree construction confirmed that this strain belongs to the genus *Bacillus mesenchyme*. Mesobacillus Therefore, this strain was named *Bacillus mesenchyme*. Mesobacillus sp.)MS443.

[0010] This strain was deposited at the China Center for Type Culture Collection (CCTCC) on February 24, 2025, at Wuhan University, Wuhan, China, with accession number CCTCC NO: M 2025280.

[0011] Furthermore, the culture conditions for the strain were as follows: inoculated in TSB medium and cultured at 28-30℃.

[0012] This invention has found that, Mesobacillus sp. MS443 possesses heterotrophic nitrification capabilities, effectively converting ammonium nitrogen into nitrate nitrogen. It is applied to the plant rhizosphere. Mesobacillus sp. MS443 can effectively promote the conversion of ammonium nitrogen to nitrate nitrogen in rhizosphere soil and improve the efficiency of nitrogen utilization by plants.

[0013] Therefore, the present invention provides the aforementioned Mesobacillus Application of sp. MS443 in promoting nitrogen transformation in soil, including the conversion of ammonium nitrogen to nitrate nitrogen. Utilizing the method provided by this invention... Mesobacillus sp. MS443 can accelerate the nitrification conversion of ammonium nitrogen to nitrate nitrogen in the soil. Nitrate nitrogen is more easily absorbed by plants, ensuring an efficient supply of nitrogen nutrition to crops while solving the problem of continuous accumulation of ammonium nitrogen in the soil caused by long-term excessive application of nitrogen fertilizer.

[0014] Furthermore, the application includes: applying [something] to the crop rhizosphere soil. Mesobacillus sp. MS443 bacterial suspension. The bacterial suspension contains... Mesobacillus The concentration of sp. MS443 was 1×10 7 CFU / mL ~ 1×10 8 CFU / mL.

[0015] The present invention also provides the aforementioned Mesobacillus Application of sp. MS443 in promoting plant growth, the application including: applying the aforementioned to the plant growth environment. Mesobacillus sp. MS443. This invention has discovered that... Mesobacillussp. MS443 consistently promotes nitrogen conversion and enhances plant growth in crops of various families and genera. Specifically, plant growth indicators include at least one of the following: plant height, fresh weight, dry weight, and chlorophyll content.

[0016] Furthermore, the application includes: applying a substance containing […] to the plant rhizosphere soil. Mesobacillus ammonium nitrogen nutrient solution of sp. MS443, wherein the nutrient solution contains Mesobacillus The concentration of sp. MS443 was 1×10 7 CFU / mL ~ 1×10 8 CFU / mL.

[0017] Furthermore, the plant can be a plant of the Solanaceae family, Poaceae family, Malvaceae family, or Brassicaceae family, but the present invention is not limited to these.

[0018] Furthermore, the crops include: tomatoes, peppers, corn, cotton, and Chinese cabbage.

[0019] The present invention also provides a plant growth-promoting microbial agent, wherein the microbial agent contains the aforementioned Mesobacillus sp.MS443. The invention provides... Mesobacillus sp. MS443 has been developed into a microbial inoculant and applied to the cultivation of plants, especially vegetable crops.

[0020] Furthermore, the aforementioned Mesobacillus The culture method for sp. MS443 is as follows: *Bacillus mesenchyme* (… Mesobacillus MS443 sp. was inoculated into TSB solid medium and activated at 28-30℃; then a single colony was picked and inoculated into LB liquid medium and cultured with shaking at 28-30℃ and 200-250 r / min for 8-10 h to obtain seed culture; then 1% inoculum was transferred to TSB liquid medium and cultured to the logarithmic phase, and the cells were collected by centrifugation.

[0021] The beneficial effects of this invention are as follows: This invention provides a plant rhizosphere growth-promoting strain Mesobacillussp. MS443, this strain possesses heterotrophic nitrification capabilities, effectively converting ammonium nitrogen into nitrate nitrogen. It can be applied to soil nitrogen transformation, converting accumulated ammonium nitrogen in the soil into nitrate nitrogen, which is more easily absorbed by plants, thus solving the problem of continuous accumulation of ammonium nitrogen in the soil caused by long-term excessive nitrogen fertilizer application. On the other hand, because it improves the efficiency of plant nitrogen use, thereby increasing yield, this strain has shown significant growth-promoting effects on various crops, including Solanaceae (such as tomatoes and peppers), Gramineae (such as corn), Malvaceae (such as cotton), and Brassicaceae (such as Chinese cabbage). It can be applied in agricultural production to improve nitrogen fertilizer utilization efficiency and crop yield, helping to reduce the amount of chemical fertilizers used. Attached Figure Description

[0022] Figure 1 for Mesobacillus Colony morphology of sp. MS443.

[0023] Figure 2 for Mesobacillus Morphological image of sp. MS443.

[0024] Figure 3 This is a phylogenetic tree of MS443 constructed based on the 16S rRNA sequence.

[0025] Figure 4 for Mesobacillus The growth-promoting effect of sp. MS443 on tomatoes is shown in the figure. In the figure, control represents the control group without MS443 inoculation, and MS443 represents the experimental group inoculated with MS443. Different letters in the statistical graph indicate significant differences between the groups. P <0.05.

[0026] Figure 5 for Mesobacillus The growth-promoting effect of sp. MS443 on peppers, with the left figure showing the control group without inoculation with strain MS443 and the right figure showing the experimental group inoculated with strain MS443.

[0027] Figure 6 for Figure 5 The graph shows the statistical values ​​of net photosynthetic rate, dry weight, ammonium nitrogen content in rhizosphere soil, and ammonium nitrogen content in chili pepper plants. Different letters in the graph indicate significant differences between groups. P <0.05.

[0028] Figure 7 for Mesobacillus The growth-promoting effect of sp. MS443 on maize, where the left figure is the control group without inoculation with strain MS443, and the right figure is the experimental group inoculated with strain MS443.

[0029] Figure 8 for Figure 7 The graph shows the statistical values ​​of net photosynthetic rate, dry weight, ammonium nitrogen content in rhizosphere soil, and ammonium nitrogen content in maize plants. Different letters in the graph indicate significant differences between groups. P <0.05.

[0030] Figure 9 for Mesobacillus The growth-promoting effect of sp. MS443 on cotton is shown in the left figure, which is the control group without inoculation with strain MS443, and the right figure is the experimental group inoculated with strain MS443.

[0031] Figure 10 for Figure 9 The graph shows the statistical values ​​of net photosynthetic rate, dry weight, ammonium nitrogen content in rhizosphere soil, and ammonium nitrogen content in cotton plants. Different letters in the graph indicate significant differences between groups. P <0.05.

[0032] Figure 11 for Mesobacillus The growth-promoting effect of sp. MS443 on Chinese cabbage: The upper plants in the figure are the experimental group inoculated with strain MS443, and the lower plants are the control group not inoculated with strain MS443.

[0033] Figure 12 for Figure 11 The chart shows the statistical differences in plant height, fresh weight, and maximum leaf width of Chinese cabbage. Different letters in the chart indicate significant differences between groups. P <0.05. Detailed Implementation

[0034] The present invention will be further described below with reference to specific embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Any modifications or substitutions made to the methods, steps, or conditions of the present invention without departing from the spirit and essence of the invention are within the scope of the invention.

[0035] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; the materials and reagents used are commercially available unless otherwise specified.

[0036] The culture medium, nutrient solution, and reagents used in the following examples have the following compositions: TSB medium: tryptone 17.0 g / L, soybean papain hydrolysate 3.0 g / L, sodium chloride 5.0 g / L, dipotassium hydrogen phosphate 2.5 g / L, glucose 2.5 g / L, pH 7.3±0.2, autoclaved at 21℃ for 15 min. The plate solid medium is prepared by adding 15 g of agar to 1 L of the corresponding liquid medium.

[0037] Heterotrophic nitrification medium: (NH4)2SO4 0.47 g / L, sodium succinate 5.62 g / L, Vickers salt solution 50 mL, pH 7.0.

[0038] Ammonium nitrogen nutrient solution stock solution (10×): K₂SO₄ 3.5 g / L, KH₂PO₄ 0.8 g / L, MgSO₄ 1.2 g / L, MnSO₄ 0.0034 g / L, H₃BO₃ 0.0124 g / L, CuSO₄ 0.005 g / L, ZnSO₄ 0.0056 g / L, (NH₄)₆MO₇O₇ 24 0.00017 g / L, Fe-EDDHA 0.4 g / L, (NH4)2SO4 6.6 g / L, CaCl2 5.3 g / L, pH value 5.8.

[0039] Nessler's reagent: NaOH 160 g / L, HgI 100 g / L, KI 70 g / L.

[0040] Vickers salt solution: K2HPO4 5.00 g / L, MgSO4•7H2O 2.50 g / L, NaCl 2.50 g / L, FeSO4•7H2O 0.05 g / L, MnSO4 0.05 g / L.

[0041] Example 1: Isolation and Identification of Strains 1. Isolation and purification of strains Soil samples used for isolating the bacterial strains were taken from the Agricultural Experiment Station of Huajiachi Campus, Zhejiang University. This plot of land had not been treated with pesticides or fertilizers for a long time. After removing surface weeds and impurities, topsoil from a depth of about 20 cm was collected and transported to the College of Agriculture and Biotechnology, Zijingang Campus, Zhejiang University, where it was air-dried for later use.

[0042] Weigh 1 g of soil sample and add it to 100 mL of sterile water containing glass beads. Shake at 28℃ and 200 rpm for 30 min to prepare a soil suspension. Take 1 mL of the supernatant and perform serial dilutions to obtain 10... -3 10 -4 10 -5 10 -6 10 -7 10 -8Six dilutions were performed. 80 μL of each dilution was streaked three times consecutively onto TSB solid medium and incubated upside down at 28°C for 3 days. Single colonies with distinct morphological differences were picked and inoculated into TSB liquid medium. The culture was then incubated at 28°C with shaking at 200 rpm for 8–12 h, followed by repeated streaking purification until a pure culture was obtained. A portion of the bacterial culture was stored at 4°C for short-term preservation, while the remaining culture was mixed with 50% glycerol at a 1:1 (volume ratio) and stored long-term at -80°C.

[0043] The purified single colonies were inoculated into heterotrophic nitrification medium and incubated upside down at 28°C for 3 days. Nitrite (NO2) was detected using Griess reagent. - (-N), if the solution turns red, it is a positive result. Take a small amount of culture supernatant and add potassium sodium tartrate solution and Nessler's reagent in sequence. The deamination ability of the strain is judged by the intensity of the color development.

[0044] After the above screening, a strain with heterotrophic nitrification function was finally obtained, which was numbered MS443.

[0045] 2. Observation of strain morphology After being cultured on TSB plates at 28°C for 2 days, strain MS443 formed round, white, transparent, smooth, moist, and distinctly raised colonies. Figure 1 ).

[0046] The bacteria are rod-shaped and can form spores; they are Gram-positive or Gram-negative. Figure 2 ).

[0047] It conforms to the genus Bacillus ( Mesobacillus The basic morphological characteristics of ).

[0048] 3. Molecular identification and phylogenetic analysis of the strain The 16S rDNA of strain MS443 was amplified by PCR using primers 799F: 5′-AACMGGATTAGATACCCKG-3′ and 1193R: 5′-ACGTCATCCCCACCTTCC-3′. The amplified product was sent for sequencing, and after strict verification, the DNA fragment sequence shown in SEQ ID NO.1 was obtained.

[0049] Comparison and analysis of the sequencing results with the NCBI database revealed that the sequence was similar to... Mesobacillus Multiple strains within the genus showed similarities exceeding 99.0%. To clarify their phylogenetic positions, a phylogenetic tree was constructed using MEGA 11 software based on the maximum likelihood method. (Evolutionary tree) Figure 3 The results show that strain MS443 is taxonomically classified under the genus *Bacillus*. Mesobacillus ).

[0050] Based on morphological characteristics and molecular systematics evidence, this strain was identified as belonging to the kingdom Bacteria (Bacteria). Bacteria ), Bacillus phylum ( Bacillota ), Bacillus class ( Bacilli ), order Nucleocystales ( Caryophanales ), Bacillus family, genus Bacillus ( Mesobacillus A new member of ), therefore, it is named Mesobacillus sp. MS443.

[0051] The strain was deposited at the China Center for Type Culture Collection (CCTCC) on February 24, 2025, at Wuhan University, Wuhan, Hubei Province, China, with accession number CCTCC NO: M 2025280, and was identified as viable on March 3, 2025.

[0052] Example 2: Mesobacillus Growth-promoting experiment of sp. MS443 on tomatoes Tomato (Ailsa Craig) seeds are sown in seedling trays containing seedling substrate. After the seedlings have emerged and grown steadily for a week, seedlings with uniform growth are selected for use.

[0053] The inoculum preparation for strain MS443 was prepared as follows: First, the preserved strain was inoculated into TSB solid medium and activated at 28℃ for 2 days; a single colony was picked and inoculated into 1 mL LB liquid medium and cultured at 28℃ and 200 r / min for 8-10 h with shaking to obtain the seed culture; then, it was transferred to TSB liquid medium at a 1% inoculum volume and cultured to the logarithmic growth phase. The cells were collected by centrifugation, resuspended in sterile water, and the viable count was adjusted to 1×10⁻⁶. 8 CFU / mL - 1×10 9 CFU / mL was used as the bacterial suspension for treatment.

[0054] The experiment consisted of an experimental group and a control group, with 10 seedlings in each group. In the experimental group, each seedling was treated with an ammonium nitrogen nutrient solution containing MS443 bacterial suspension at a volume ratio of 1:10. The control group received only an equal amount of ammonium nitrogen nutrient solution. Treatment was repeated every 3 days for 30 consecutive days, after which various growth and physiological indicators were measured.

[0055] See relevant results Figure 4The results showed that the tomato plants inoculated with MS443 exhibited significantly higher chlorophyll content and fresh weight, on average, by 34.6% and 53%, respectively, compared to the control group. This synergistic improvement in these two key growth indicators comprehensively reflects a substantial improvement in the plant's nitrogen assimilation capacity and overall nutritional status. Considering the functional characteristics of strain MS443, this significant growth-promoting effect can be reasonably attributed to its ability to optimize nitrogen nutrient supply in plants by promoting the conversion of nitrogen forms to nitrate nitrogen, which is more readily absorbed by tomatoes, after transplanting into the rhizosphere.

[0056] Example 3: Mesobacillus Growth-promoting test of sp. MS443 on pepper Chili pepper (Zhangshugang chili pepper) seeds were sown in seedling trays containing seedling substrate. After germination and stable growth for one week, seedlings with uniform growth were selected and transplanted into individual small pots for later use. The preparation method of the bacterial suspension and the experimental design were the same as in Example 2. After 20 days of treatment, the net photosynthetic rate, ammonium nitrogen content, and plant dry weight were measured.

[0057] Net photosynthetic rate: The net photosynthetic rate was measured using the fourth leaf from the top of the plant as the measurement object, and the LI-6800 portable photosynthetic fluorescence measurement system was used.

[0058] Determination of NH4-N (Nessler's reagent method): Weigh 0.5 g of fresh sample, add 1.4 mL of double-distilled water, grind in an ice bath, extract by shaking at 45℃ for 1 h, then centrifuge at 15000 g for 20 min and collect the supernatant. Take 100 μL of the supernatant and add 100 μL of 40% potassium sodium tartrate and 1 mL of distilled water sequentially. Mix well and let stand for 5 minutes, then add 1 mL of Nessler's reagent for color development. After complete color development, perform colorimetric analysis at 404 nm (or 430 nm) and calculate the content using the ammonium sulfate standard curve.

[0059] Dry weight of plants: Place the above-ground plant samples in kraft paper bags and put them in an oven. First, dry at 100-105℃ for 1-2 hours to kill the greenness, then lower the temperature to 70-80℃ and continue drying until constant weight is reached. After removing and cooling to room temperature, weigh and record as dry weight (DW).

[0060] See relevant results Figure 5 and Figure 6 The results showed that the net photosynthetic rate of pepper plants inoculated with MS443 was significantly higher than that of the control group, and the average dry weight of the plants increased by about 15.9%. Given that ammonia volatilization and soil fixation were negligible under controlled pot cultivation conditions, and considering that the ammonium nitrogen content in the experimental group plants and rhizosphere soil decreased significantly by 30% and 80% respectively during the same period, this synergistic trend (i.e., enhanced growth accompanied by ammonium nitrogen consumption) confirms that the MS443 strain effectively promoted the conversion of ammonium nitrogen to nitrate nitrogen, thereby promoting plant growth.

[0061] Example 4: Mesobacillus Growth-promoting experiment of sp. MS443 on maize The same bacterial suspension preparation method and experimental design as in Example 3 were used to validate the study, with maize (Zhengdan 958) as the test crop. Net photosynthetic rate, ammonium nitrogen content, and plant dry weight were measured 20 days after treatment.

[0062] See relevant results Figure 7 and Figure 8 The results showed that the net photosynthetic rate of maize seedlings inoculated with MS443 increased by an average of about 11% and the dry weight increased by about 20.2% compared with the control group. The ammonium nitrogen content in both the plants and the rhizosphere soil decreased significantly, indicating that strain MS443 can also promote nitrogen form transformation in the rhizosphere of maize and improve nitrogen absorption and growth status of the plants.

[0063] Example 5: Mesobacillus Growth-promoting test of sp. MS443 on cotton The same bacterial suspension preparation method and experimental design as in Example 3 were used, with cotton (Jingmian 94) as the test crop for verification. Net photosynthetic rate, ammonium nitrogen content, and plant dry weight were measured 20 days after treatment.

[0064] See results Figure 9 and Figure 10 The results showed that the net photosynthetic rate of cotton plants inoculated with MS443 increased by an average of about 8% and the dry weight increased by an average of about 6% compared with the control group. At the same time, the ammonium nitrogen content in the plants and rhizosphere soil decreased by about 32.1% and 77.6%, respectively.

[0065] The above results indicate that this strain can stably promote nitrogen conversion and enhance plant growth in crops of different families and genera.

[0066] Example 6: Mesobacillus Growth-promoting experiment of sp. MS443 on Chinese cabbage The preparation method of the bacterial suspension was the same as in Example 3. Seeds of Chinese cabbage (Sijiu Chinese cabbage) were sown in seedling trays filled with seedling substrate. After germination and stable growth for one week, seedlings with uniform growth were selected, and their roots were immersed in a bacterial culture solution diluted 100 times for 15 minutes. They were then transplanted into individual culture pots. The culture conditions were set at 25-30℃ with 14 hours of light per day. After transplanting, the roots were drenched every 3 days with a bacterial culture solution diluted 10 times. The control group was treated simultaneously with the same dilution of uninoculated culture solution. Samples were taken after 10 days of culture, and the fresh weight, plant height, and maximum leaf width of the above-ground parts of the Chinese cabbage were measured. Specific data can be found in [link to relevant documentation]. Figure 11 and Figure 12 .

[0067] The results showed that the experimental group plants had an average plant height increase of 12%, a fresh weight increase of about 74.6%, and a maximum leaf width increase of about 42.4% compared with the control group, indicating that this strain also has a significant growth-promoting effect on Brassica crops.

[0068] The above description is merely a specific embodiment of the present invention, intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly, and should not be construed as limiting the scope of protection of the present invention. All equivalent modifications or substitutions made based on the essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A genus of Bacillus ( Mesobacillus sp.)MS443, characterized in that, The genus *Bacillus* ( Mesobacillus sp.) MS443 is deposited at the China Center for Type Culture Collection, accession number: CCTCC NO: M2025280.

2. The *Bacillus intercalans* as described in claim 1 (… Mesobacillus sp.)MS443, characterized in that, The culture conditions for the strain were: inoculated in TSB medium and cultured at 28-30℃.

3. The *Bacillus intercalans* as described in claim 1 (… Mesobacillus The application of sp.) MS443 in promoting nitrogen transformation in soil is characterized by, The nitrogen conversion includes the conversion of ammonium nitrogen to nitrate nitrogen.

4. The application as described in claim 3, characterized in that, The application includes: applying Bacillus subtilis (B. subtilis) to the rhizosphere soil of crops. Mesobacillus (sp.) MS443 bacterial suspension.

5. The *Bacillus intercalans* as described in claim 1 (… Mesobacillus The application of sp.) MS443 in promoting plant growth is characterized by, The application includes: applying the aforementioned *Bacillus* species to the plant growth environment (…). Mesobacillus sp.)MS443.

6. The application as described in claim 5, characterized in that, The application includes: applying a substance containing Bacillus subtilis (B.) to the plant rhizosphere soil. Mesobacillus (sp.) An ammonium nitrogen nutrient solution containing MS443, wherein the concentration of MS443 in the nutrient solution is 1×10 7 CFU / mL ~ 1×10 8 CFU / mL.

7. The application as described in claim 5, characterized in that, The plants mentioned are plants belonging to the Solanaceae family, Poaceae family, Malvaceae family, or Brassicaceae family.

8. The application as described in claim 7, characterized in that, The plants mentioned include: tomatoes, peppers, corn, cotton, and bok choy.

9. A plant growth-promoting bacterial agent, characterized in that, The bacterial agent contains *Bacillus mesenteriae* as described in claim 1. Mesobacillus sp.)MS443.

10. The plant growth-promoting bacterial agent as described in claim 9, characterized in that, The genus *Bacillus* ( Mesobacillus The culture method for MS443 (sp.) is as follows: Bacillus subtilis (sp.) Mesobacillus MS443 sp. was inoculated into TSB solid medium and activated at 28-30℃; then a single colony was picked and inoculated into LB liquid medium and cultured with shaking at 28-30℃ and 200-250r / min for 8-10 h to obtain a seed culture; then 1% of the inoculum was transferred to TSB liquid medium and cultured to the logarithmic phase, and the cells were collected by centrifugation.

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