Plant growth-promoting rhizobacteria SYR43 and application thereof

Abstract

The invention relates to the technical field of microorganisms, and particularly provides a plant growth-promoting rhizobacteria SYR43 and application thereof. The strain is a new bacillus strain which is separated from a high-yield rubber tree rhizosphere soil environment, and is preserved in Guangdong Microbial Culture Collection Center on June 4, 2025, and the preservation number is GDMCC (China General Microbiological Culture Collection Center) NO: 66467. The strain has the capacity of producing ammonia and protease, and can well grow in the salt concentration of 1% or below and the pH of 5.0-8.0; through morphological, physiological and biochemical and molecular biological identification, the strain is a potential new strain of the novel bacillus. Pot experiment verification shows that the strain can significantly improve the chlorophyll content and photosynthetic ability of arabidopsis thaliana, lettuce and rubber tree seedlings, and promote plant biomass growth and root development. The invention provides a special growth-promoting functional strain resource for plants such as hevea brasiliensis and the like, and has important significance for improving the benefits of natural rubber industry in China.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of microbial technology, and relates to a plant growth-promoting rhizobacteria SYR43 and application thereof. BACKGROUND

[0002] Natural rubber, one of the four major industrial raw materials, is made from the latex flowing out of the rubber tree (Hevea brasiliensis) cut from its bark in the Amazon rainforest region of South America. China is a large consumer of natural rubber, but due to geographical and climatic conditions, rubber tree planting areas are only concentrated in parts of Hainan, Yunnan and other provinces, and the water and heat conditions in the rubber planting areas are poorer than in the Southeast Asian natural rubber producing areas, resulting in generally low yield levels and planting benefits. Therefore, tapping the yield potential and improving the yield of rubber trees is the key to ensuring the security of China's natural rubber supply.

[0003] The development of microbial inoculants using plant growth-promoting rhizobacteria (PGPR) is a green and sustainable agricultural technology for promoting crop growth and increasing yield. Such strains can directly or indirectly promote plant growth through mechanisms such as nitrogen fixation, phosphorus solubilization, and secretion of plant hormones. In theory, PGPR isolated from the rhizosphere of a specific host plant is more likely to colonize and function efficiently when re-inoculated, as it has already adapted to the host root microenvironment, which is known as the "host effect". However, there is still a lack of specialized and efficient PGPR inoculant resources for rubber trees, an important economic forest tree. Existing strains generally have problems such as insufficient adaptation to the rubber tree rhizosphere environment, low colonization efficiency, and unstable growth promotion effect, which greatly limits their industrial application.

[0004] It is worth noting that there are a small number of high-yield single plants in rubber tree production, which can produce 2-3 times the yield of ordinary plants under the same management measures. This suggests that the rhizosphere microenvironment of these ultra-high-yield rubber trees may contain special functional microbial resources related to high-yield traits that have not yet been tapped. Directional isolation and screening of functional strains from the rhizosphere soil of these ultra-high-yield rubber trees and verification of their growth-promoting ability are of great significance for the development of the next generation of efficient and specialized microbial inoculants and the breakthrough of the yield bottleneck of rubber trees.

[0005] In summary, the core problem of the current technology is that there is a lack of specialized PGPR strain resources suitable for rubber trees, and there is a lack of strategies for directional mining from high-yield host sources. The present application aims to address this gap by providing a new strain derived from the rhizosphere of ultra-high-yield rubber trees, which has high growth-promoting ability and good environmental adaptability, to address the shortcomings of existing technology. SUMMARY

[0006] The present application aims at the defect of "few special plant growth-promoting functional bacterial agents suitable for rubber trees" in the prior art, and provides a strain of Neobacillus SYR43 and its application, which is isolated from the rhizosphere soil of super high-yield rubber trees, adapts to the rhizosphere environment of rubber trees, and has a significant growth-promoting effect on Arabidopsis thaliana, lettuce and rubber tree seedlings, thereby filling the resource gap of special growth-promoting bacterial agents for rubber trees.

[0007] In order to achieve the above-mentioned purpose, the technical scheme provided by the present application is as follows:

[0008] In a first aspect, the present application provides a strain of Neobacillus SYR43, which has a preservation number of GDMCC NO: 66467, a preservation date of June 4, 2025, a preservation classification name of Neobacillus, and a preservation unit of Guangdong Microbial Culture Collection Center, located at No. 100, Martyrs' Road, Yuexiu District, Guangzhou, Guangdong, China, on the 5th floor of the Experimental Building, with a postcode of 510075 and a telephone number of 020-37656629.

[0009] After strain identification, the strain has the following characteristics:

[0010] (1) Morphological characteristics: cultured on LB solid medium (10 g of proteose peptone, 5 g of yeast extract, 10 g of NaCl, 15-18 g of agar powder, 1000 mL of distilled water, pH 7.0, 121℃ sterilization for 15 min) at 30℃ for 24-48 h, the colonies are light yellow, round and convex, the surface is smooth and wet, and the diameter is 1.5-3.0 mm; the bacterial body is rod-shaped, about 1.0-1.6 x 2.5-5.5 μm (observed by transmission electron microscope), and gram-positive.

[0011] (2) Physiological and biochemical characteristics: can utilize glucose, maltose, rhamnose, galactose, mannitol, sucrose and fructose, but cannot utilize inulin, lactose, xylose, myo-inositol, sorbitol, melibiose, raffinose, adonitol and arabinose; oxidase negative, peroxidase positive, ornithine positive, lysine negative, urea positive, motility puncture negative, VP test negative, nitrate reduction positive, gelatin liquefaction positive, and citrate positive (see Table 1 for details).

[0012] (3) Environmental adaptability: can grow well in LB medium with a salt concentration of ≤1% (w / v); can grow well in LB medium with a pH of 5.0-8.0, and the OD600 absorbance value is stable at 0.889-0.936.

[0013] (4) Growth-promoting related properties: with ammonia production ability (the reaction of fermentation broth and Nessler's reagent generates yellow-brown precipitate); with protease production ability (transparent hydrolysis circle is formed on protease detection medium, the formula of protease detection medium: yeast extract 5g, proteose peptone 10g, NaCl 5g, skim milk powder 15g, agar 20g, deionized water 1000mL, pH 7.2-7.4, sterilized at 121℃ for 15min).

[0014] (5) Molecular biology properties: containing 1 circular DNA (size 5688996bp, GC content 38.71%) and 1 plasmid (size 114590bp, GC content 36.85%) in whole genome; containing 5589 coding sequences (CDS), 169 tRNAs and 60 rRNAs (20 16S rDNA, 20 23S rDNA and 20 5S rDNA) in total; the full-length of 16S rDNA is 1548bp, the sequence of 16S rDNA is shown as SEQ ID NO: 1, the sequence similarity with close relatives such as Bacillus salipaludis WN066 (NR180481) and Neobacillus drentensis IDA1967 (NR029002) is ≤99.01%, the ANI value of whole genome is ≤84.90%, and it is identified as a potential new species of Neobacillus genus.

[0015] In a second aspect, the present application provides a fermentation broth or a bacterial suspension containing the strain SYR43.

[0016] In a third aspect, the present application provides the use of the strain SYR43 or the bacterial suspension containing the strain SYR43, and the use is any of the following:

[0017] A1) use in promoting the growth of Arabidopsis thaliana, lettuce and rubber tree seedlings;

[0018] The new Bacillus SYR43 is prepared into a bacterial suspension (the concentration is about 1.0×10 8 cfu / mL), and is applied to plants by inoculation (inoculation of Arabidopsis thaliana root tip) or root irrigation (root irrigation of lettuce and rubber tree seedlings) to promote the growth of Arabidopsis thaliana, lettuce and rubber tree seedlings;

[0019] A2) use in preparing a product for promoting the growth of Arabidopsis thaliana, lettuce and rubber tree seedlings.

[0020] In the use, when the plant is Arabidopsis thaliana, the promotion of plant growth includes increasing the fresh weight of whole plant, stem and leaf fresh weight, root fresh weight, root length and chlorophyll content.

[0021] In the application, when the plant is lettuce, the promoting plant growth comprises increasing the whole-plant fresh weight, the above-ground fresh weight, the below-ground fresh weight, the cotyledon number, the leaf soluble sugar content, and the chlorophyll content.

[0022] In the application, when the plant is rubber tree, the promoting plant growth comprises increasing the plant height, the ground diameter, the whole-plant fresh weight, the above-ground fresh weight, the below-ground fresh weight, the above-ground dry weight, the below-ground dry weight, the chlorophyll content, the total root length, the root surface area, the root volume, and the root tip number.

[0023] In a fourth aspect, the application provides a microbial agent for promoting the growth of Arabidopsis, lettuce and rubber tree, wherein the active ingredient of the microbial agent comprises the strain SYR43.

[0024] In a fifth aspect, the application provides a bio-organic fertilizer, wherein the active ingredient of the bio-organic fertilizer comprises the strain SYR43 or the microbial agent.

[0025] Advantages of the application:

[0026] (1) Novel strain resource with independent intellectual property rights:

[0027] The strain SYR43 provided by the application is a potential new species of Bacillus nov. identified by morphology, physiology, biochemistry and molecular biology (16S rDNA sequence similarity and ANI value <95%), and belongs to a brand-new microbial resource.

[0028] (2) Unique source, obvious colonization advantage and strong specificity:

[0029] The strain is directly isolated from the rhizosphere soil of super-high-yield rubber trees, and compared with strains isolated from other environments, it has natural adaptability to the microenvironment of the rhizosphere of rubber trees, is more likely to successfully colonize the rhizosphere of target crops and stably exert the effect, and solves the industry pain point of "acclimatization" of foreign strains.

[0030] (3) Multiple growth-promoting mechanisms, synergistic and efficient:

[0031] Experiments prove that the strain has the ability to produce ammonia and protease. This means that it can not only provide nitrogen sources (ammonia) that can be directly absorbed by plants through metabolic action, but also decompose organic nitrogen (protein) in the soil, activate soil nutrients, and promote plant growth through multiple pathways.

[0032] (4) Significant growth-promoting effect and evidence, and broad-spectrum and specific:

[0033] Excellent effect on target crops (rubber trees): pot experiment shows that the strain can significantly promote the ground diameter growth, biomass accumulation and root development (root length, root surface area and root tip number significantly increased) of rubber tree seedlings, laying a solid foundation for ultimately improving latex yield.

[0034] Broad-spectrum growth promotion potential: the strain also shows strong growth promotion effect on model plant Arabidopsis thaliana and vegetable crop lettuce (such as increasing the fresh weight of Arabidopsis thaliana by more than 200%), indicating that it is not only a rubber tree specific bacteria, but also a high-efficiency broad-spectrum plant growth promoting bacteria with broad market application prospects.

[0035] Improving crop quality: while promoting the growth of lettuce, it can also significantly increase the soluble sugar content (47.87%) of lettuce, improving the quality of agricultural products and increasing the economic value-added. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 Colony morphology of Bacillus nov. SYR43 on LB solid medium;

[0037] Figure 2 Transmission electron microscope morphology of Bacillus nov. SYR43;

[0038] Figure 3 Circular genome map of Bacillus nov. SYR43;

[0039] Figure 4 Plasmid map of Bacillus nov. SYR43;

[0040] Figure 5 16S rDNA phylogenetic tree of Bacillus nov. SYR43;

[0041] Figure 6 ANI heat map of whole genome of Bacillus nov. SYR43 and compared strains;

[0042] Figure 7 Salt concentration tolerance curve of Bacillus nov. SYR43 (horizontal axis: NaCl concentration (w / v), vertical axis: OD600 absorbance value);

[0043] Figure 8 pH tolerance curve of Bacillus nov. SYR43 (horizontal axis: medium pH, vertical axis: OD600 absorbance value);

[0044] Figure 9 Ammonia production ability detection result of Bacillus nov. SYR43 (left: control, right: reaction result of SYR43 bacterial liquid supernatant and Nessler's reagent, brown precipitate can be seen);

[0045] Figure 10The detection result figure of the protease production ability of Bacillus nov. SYR43 (transparent hydrolysis circle around the colony can be seen);

[0046] Figure 11 The comparison figure of the growth promotion effect of Bacillus nov. SYR43 on Arabidopsis (left is the control Arabidopsis, right is the SYR43 treated Arabidopsis, and the size of the plant and the root system difference can be seen);

[0047] Figure 12 The comparison figure of the growth promotion effect of Bacillus nov. SYR43 on lettuce (left is the control lettuce, right is the SYR43 treated lettuce, and the fresh weight of the plant and the leaf difference can be seen);

[0048] Figure 13 The comparison figure of the growth promotion effect of Bacillus nov. SYR43 on rubber tree seedlings (left is the control rubber tree seedling, right is the SYR43 treated rubber tree seedling, and the height of the plant and the root system difference can be seen). DETAILED DESCRIPTION

[0049] The specific embodiments of the present application are described below to facilitate the understanding of the present application for those skilled in the art, but it should be clear that the present application is not limited to the scope of the specific embodiments, and for those skilled in the art, as long as various changes are within the spirit and scope of the present application defined and determined by the appended claims, all the inventions utilizing the concept of the present application are within the scope of protection.

[0050] Example 1 Isolation and screening of Bacillus nov. SYR43

[0051] The rhizosphere soil sample used was collected from the rhizosphere of super-high-yield rubber trees of PR107 strain in 2nd team of Wufenchang of Mengla Farm, Xishuangbanna Dai Autonomous Prefecture, Yunnan Province. The high-yield rubber trees were planted in 1963, tapped in 1970, and the annual dry rubber yield was 107.8 kg in 2005. The rhizosphere soil was obtained by shaking method. 1 g of soil sample was weighed into a 99 mL sterile water flask with glass beads, heated in a 90°C water bath for 30 min to remove other non-heat-resistant bacteria interference, and dispersed at 30°C and 200 rpm for 30 min. This is 10 -2 Gradient soil suspension, 10 -3 , 10 -4 , 10 -5 , 10 -6 Gradient soil suspension was prepared by dilution. 0.1 mL of each gradient suspension was coated on LB solid medium plate, and 3 repeats were set for each gradient. Single colony was selected and subcultured on LB solid medium, and repeated 3 times to obtain pure culture strain.

[0052] The LB solid culture medium formula is as follows: 10 g of proteose peptone, 5 g of yeast extract, 10 g of NaCl, 15-18 g of agar powder, 1000 mL of distilled water, and pH value of about 7.0. Sterilization is performed at 121°C for 15 min.

[0053] Example 2 Identification of new Bacillus sp. SYR43

[0054] In combination with morphological, physiological and molecular biological identification results, the strain SYR43 is identified as a new potential species of Bacillus sp., and the specific identification steps are as follows:

[0055] 1. Morphological identification

[0056] (1) Colony morphological characteristics

[0057] The bacterial liquid is streaked on the LB solid culture medium plate, and after 24-48 hours of culture at 30°C, the colony morphology is observed.

[0058] The colony morphology of SYR43 is shown in Figure 1 , which is light yellow, round and convex, with a smooth and moist surface, and a diameter of 1.5-3.0 mm.

[0059] (2) Bacterial morphology identification

[0060] The single colony is taken by a gun head, placed in 30 μL of sterile deionized water, naturally dispersed, adsorbed and fixed with a 200-mesh copper mesh, stained with 1% phosphotungstic acid sodium staining solution for 2 min, and then dried with filter paper at the edge of the copper mesh. After the staining solution is absorbed, the bacterial morphology is observed using a Hitachi HT7700 transmission electron microscope.

[0061] Under the transmission electron microscope, the SYR43 bacterial body is rod-shaped, with a size of about 1.0-1.6 x 2.5-5.5 μm. The bacterial morphology is shown in Figure 2 .

[0062] 2. Physiological and biochemical identification

[0063] Table 1 Partial physiological characteristics of SYR43

[0064] Test item Results Test item Results Glucose + Inulin - Maltose + Lactose - Rhamnose + Galactose + Xylose - Oxidase - Mannitol + Catalase + Myo-inositol - Ornithine + Sorbitol - Lysine - Melibiose - Urea + Raffinose - Power piercing - Citrate + VP - Plumbagol - Nitrate reduction + Arabinose - Gelatin liquefaction + Sucrose + Gram stain + Fructose +

[0065] 3. Molecular biological identification

[0066] The SYR43 was sequenced by the second generation sequencing platform Illumina and the third generation sequencing platform PacBio. The sequencing results showed that the strain genome contained one circular DNA chain and one plasmid, wherein the genome size was 5 688996 bp, the GC content was 38.71%, the plasmid size was 114 590 bp, and the GC content was 36.85%; the types, positions and sequence information of coding sequences (CDS), tRNA and rRNA in the genome were predicted by using Glimmer (http: / / ccb.jhu.edu / software / glimmer / index.shtml), tRNAscan-SE v2.0 (http: / / trna.ucsc.edu / software / ) and Barrnap (https: / / github.com / tseemann / barrnap) software, and it was predicted that the SYR43 genome and plasmid contained 5589 coding sequences (CDS), among which there were 169 tRNAs and 60 rRNAs; among the rRNAs, there were 20 16s rDNAs, 20 23s rDNAs and 20 5s rDNAs.

[0067] The circular genome structure of SYR43 is shown in Figure 3 The outermost circle of the circle diagram is the identification of the genome size; the second and third circles are the CDS on the positive and negative strands, and different colors represent the functional classification of different COGs of the CDS; the fourth circle is the rRNA and tRNA; the fifth circle is the GC content, the outward red part represents that the GC content of the region is higher than the average GC content of the whole genome, the inward blue part represents that the GC content of the region is lower than the average GC content of the whole genome, and the higher the peak value represents the greater the difference from the average GC content; the innermost circle is the GC-Skew value, and the specific algorithm is G-C / G+C.

[0068] The plasmid contained in SYR43 is shown in Figure 4 The outermost circle of the circle diagram is the identification of the genome size; the second and third circles are the CDS on the positive and negative strands, and different colors represent the functional classification of different COGs of the CDS; the fourth circle is the rRNA and tRNA; the fifth circle is the GC content, the outward red part represents that the GC content of the region is higher than the average GC content of the whole genome, the inward blue part represents that the GC content of the region is lower than the average GC content of the whole genome, and the higher the peak value represents the greater the difference from the average GC content; the innermost circle is the GC-Skew value, and the specific algorithm is G-C / G+C.

[0069] The 16s rDNA sequence of SYR43 was extracted and blast comparison was performed in the NCBI database (https: / / www.ncbi.nlm.nih.gov). The results showed that the 16s rDNA sequence of SYR43 had high sequence similarity with Bacillus salipaludis WN066 (NCBI accession number: NR 180481), Neobacillus drentensis IDA1967 (NCBI accession number: NR029002), Neobacillus niacini IFO15566 (NCBI accession number: NR024695) and Neobacillus bataviensis IDA1115 (NCBI accession number: NR036766), with sequence similarity of 99.01%, 98.75%, 98.69% and 98.40%, respectively.

[0070] The 16s rDNA sequence of SYR43 was extracted and blast comparison was performed in the NCBI database (https: / / www.ncbi.nlm.nih.gov). The results showed that the 16s rDNA sequence of SYR43 had high sequence similarity with Bacillus salipaludis WN066 (NCBI accession number: NR 180481), Neobacillus drentensis IDA1967 (NCBI accession number: NR029002), Neobacillus niacini IFO15566 (NCBI accession number: NR024695) and Neobacillus bataviensis IDA1115 (NCBI accession number: NR036766), with sequence similarity of 99.01%, 98.75%, 98.69% and 98.40%, respectively.

[0071] After selecting and downloading the 16s rDNA sequences with high sequence similarity to the test strain sequence in the NCBI database, the Mega 5.0 software was used to construct a phylogenetic tree by the Neighbor-Joining method, and the Bootstrap value was set to 1000. The 16S rDNA phylogenetic tree of SYR43 is shown in Figure 5 The phylogenetic tree analysis showed that SYR43 was most closely related to Bacillus salipaludis WN066, Neobacillus niacini NBRC15566, Neobacillus drentensis IDA1967 and Neobacillus cucumis AP6, and clustered together.

[0072] The whole genome sequences of Bacillus salipaludis WN066, Neobacillus drentensis IDA1967, Neobacillus niacini IFO15566 and Neobacillus bataviensis IDA1115, etc. with high sequence similarity to the 16s rDNA sequence of SYR43 were downloaded from the NCBI database Figure 6), using the OAT software (version 0.93.1) according to the method of Lee et al. (Lee, I., Kim, Y. O., Park, S. C., & Chun, J. (2015). OrthoANI: An improved algorithm and software for calculating average nucleotide identity. Int J Syst Evol Microbiol. 66: 1100-1103.), the results showed that the average nucleotide identity of SYR43 with Bacillus salipaludis WN066, Neobacillus drentensis IDA1967 and Neobacillus niacini IFO15566 were 84.90%, 75.12% and 73.57%, respectively, and the average nucleotide identity with other reference strains were also below the 95% inter-species classification threshold, combined with the 16s rDNA sequence similarity and phylogenetic tree analysis results, SYR43 was initially identified as a potential new species of Neobacillus genus.

[0073] Example 3 Salt concentration and pH tolerance test of Neobacillus sp. SYR43

[0074] (1) Salt concentration tolerance test

[0075] LB medium was prepared, and the NaCl concentration in the medium was adjusted to a final concentration (w / v) of 1%, 3%, 5%, 7%, and 9%, respectively. The bacterial solution was inoculated into each concentration gradient LB medium at an inoculation amount of 1%, and each gradient treatment was set in triplicate. After 24 h of shaking culture at 30°C and 220 rpm, the OD600 absorbance value was determined to detect the growth status of the strain.

[0076] As shown in Figure 7 , when the NaCl concentration was below 1%, SYR43 could grow well.

[0077] (3) pH tolerance test

[0078] LB medium was prepared by adjusting the pH of the LB medium with 0.1 mol / L sodium hydroxide or 0.1 mol / L hydrochloric acid, and the pH of the LB medium was adjusted to 2.0-10.0 at an interval of 1.0 pH. The medium was sterilized by 0.22 μm sterile filter membrane to avoid pH change caused by high temperature. The activated bacterial solution was inoculated into each pH gradient LB medium at an inoculation amount of 1%, and each gradient was set in triplicate. After 24 h of constant temperature shaking culture at 30°C and 200 rpm, the OD600 absorbance value was determined to detect the growth status of the strain.

[0079] As shown in Figure 8 , the pH was in the range of 5.0-8.0, the strains could grow well, and the OD600 absorbance value was between 0.889-0.936, and the growth concentration was relatively consistent.

[0080] The basic formula of the LB medium is as follows: 10 g of proteose peptone, 5 g of yeast extract, 10 g of NaCl, and about 1000 mL of distilled water. The NaCl concentration and pH value of the medium are adjusted according to the requirements of the test experiment. The pH value of the medium used in the salt concentration and temperature tolerance detection experiment is about 7.0. Except for the pH tolerance medium which is sterilized by filtration, the sterilization conditions of the remaining media are 121°C for 15 minutes.

[0081] Example 4, Identification of the Growth-promoting Properties of Bacillus nov. SYR43

[0082] 1. Ammonia production capacity determination

[0083] The activated strain was inoculated into the LB liquid medium at an inoculation amount of 1%, and cultured at 30°C and 200 rpm for 2 days. After centrifugation of the fermentation broth at 5000 rpm for 3 min, 0.9 mL of supernatant was taken, 0.1 mL of Nessler's reagent was added, and the solution was observed for the generation of yellow-brown precipitate.

[0084] As shown in Figure 9 , the supernatant of the SYR43 fermentation broth can generate yellow-brown precipitate with Nessler's reagent, and no precipitate is generated in the control, indicating that SYR43 has the ability to produce ammonia.

[0085] The formula of the LB liquid medium is as follows: 10 g of proteose peptone, 5 g of yeast extract, 10 g of NaCl, and about 1000 mL of distilled water, with a pH value of about 7.0. The medium is sterilized at 121°C for 15 min.

[0086] The formula of the Nessler's reagent is as follows: 50 g of potassium iodide is dissolved in 50 mL of ice water, saturated mercuric chloride solution (22.0 g of mercuric chloride is added to 350 mL of deionized water) is added until a precipitate is formed, then 200 mL of 5 mol / L NaOH solution is added, diluted to 1 L, and left to stand, and the clear liquid is used.

[0087] 2. Protease production capacity determination

[0088] 0.5 μL of the activated bacterial solution was added to the center of the protease detection medium plate, which was incubated at 30°C for 2 days, and the formation of hydrolysis rings around the colonies was observed.

[0089] As shown in Figure 10 , transparent hydrolysis rings were formed around the colonies of SYR43.

[0090] The culture medium for protease detection is formulated as follows: Culture medium: 5g yeast extract, 10g peptone, 5g NaCl, 15g skim milk powder, 20g agar, 1000ml deionized water, adjust pH to 7.2-7.4. Sterilize at 121℃ for 15min.

[0091] Example 5: Determination of the growth-promoting ability of Bacillus neoplasm SYR43 on Arabidopsis thaliana.

[0092] Inoculate 1% of the culture medium into LB liquid medium and incubate at 30°C and 200 rpm for 1–2 days. Centrifuge the fermentation broth at 5000 rpm for 5 min, discard the supernatant, wash the bacterial pellet twice with sterile water, resuspend, and dilute with sterile water to a bacterial concentration of 1.0 × 10⁻⁶. 8 Approximately CFU / mL.

[0093] Arabidopsis seeds were disinfected with 75% ethanol for 2 min, 10% sodium hypochlorite for 5 min, and rinsed three times with sterile water. They were then spread on 1 / 2 MS medium plates and vernalized in the dark at 4℃ for 3 days. After vernalization, the seeds were transferred to new 1 / 2 MS medium plates with forceps and placed vertically in a light incubator. After one week of culture at 22℃ with a 16h / 8h photoperiod, 5 μL of cell suspension was inoculated into the root tips. After the bacterial suspension was absorbed, the seeds were transferred back to the incubator for vertical culture. The control treatment was inoculated with an equal amount of sterile water. After about two weeks of culture, the fresh weight, stem and leaf fresh weight, root weight, root length, chlorophyll content, and other physiological indicators of Arabidopsis were measured and recorded.

[0094] SYR43 has the effect of promoting photosynthesis in Arabidopsis thaliana, such as... Figure 11 As shown, the chlorophyll content of Arabidopsis leaves treated with SYR43 was significantly increased by 174.84% compared with the control; SYR43 significantly increased plant biomass, with the whole plant fresh weight, stem and leaf fresh weight, and root fresh weight of the treated plant significantly increased by 200.93%, 191.67%, and 234.78% compared with the control, respectively; SYR43 promoted root development, with the root length significantly increased by 58.93% compared with the control.

[0095] Table 2 Effects of bacterial strains on Arabidopsis biomass

[0096]

[0097] Note: Different letters indicate statistically significant differences (P < 0.05).

[0098] Example 6: Determination of the growth-promoting ability of Bacillus neoplasm SYR43 on lettuce.

[0099] Inoculate 1% of the culture medium into LB liquid medium and incubate at 30°C and 200–220 rpm for 1–2 days. Centrifuge the fermentation broth at 5000 rpm for 5 min, discard the supernatant, wash the bacterial pellet twice with sterile water, resuspend, and dilute with sterile water to a bacterial concentration of 1.0 × 10⁻⁶. 8Approximately CFU / mL.

[0100] The lettuce variety used was Italian lettuce, and the potting soil was horticultural potting mix. Lettuce seeds were placed on a 9cm plate lined with moistened filter paper and left to germinate for 2 days in the dark at room temperature. Germinated seeds were then transferred to pots filled with horticultural potting mix and cultured at 22℃ with a 16h / 8h light cycle for 7 days before root drenching. Each plant received 5mL of the nasal solution, while the control group received an equal volume of sterile water for root drenching.

[0101] After culturing at 22℃ for 30 days with a 16h / 8h photoperiod, the number of cotyledons was counted, and the chlorophyll content of the leaves was measured using a SPAD-502Plus chlorophyll meter (Konica Minolta, Inc., Japan). The fresh weight of the whole plant was measured by weighing, and the fresh weight of the aboveground and underground parts of the plant was measured separately by cutting the plant at the rhizome. The soluble sugar content of the leaves was determined by the anthrone colorimetric method.

[0102] SYR43 has the effect of promoting photosynthesis in lettuce, such as Figure 12 As shown, the chlorophyll content of lettuce leaves treated with SYR43 increased by 18.82% compared to the control; SYR43 significantly increased plant biomass, with the whole plant fresh weight, upper part fresh weight, underground part fresh weight, and cotyledon number of the treated plants increasing by 23.08%, 22.26%, 30.95%, and 19.36% respectively compared to the control; SYR43 also improved lettuce quality, with the soluble sugar content of the treated plants significantly increasing by 47.87% compared to the control.

[0103] Table 3 Effects of bacterial strains on lettuce biomass

[0104]

[0105] Note: Different letters indicate statistically significant differences (P < 0.05).

[0106] Example 7: Determination of the growth-promoting ability of Bacillus neoplasm SYR43 on rubber tissue culture seedlings

[0107] The rubber seedlings were tissue culture seedlings prepared using the 7-33-97 hot-process method. The potting soil was a mixture of local Danzhou red soil and peat moss in a 3:1 ratio. The pots had a base diameter, top diameter, and height of 12cm, 18cm, and 32cm, respectively, and were filled with approximately 5L of soil. Healthy, uniformly growing rubber tissue culture seedlings were selected and planted into the pots.

[0108] The strain was inoculated into LB liquid medium at a 1% inoculum rate and cultured at 200 rpm and 30°C for 48 h. The fermentation broth was then centrifuged at 5000 rpm for 5 min, the supernatant was discarded, and the bacterial pellet was washed and resuspended with sterile water. The pellet was then diluted with sterile water to a bacterial concentration of 1.0 × 10⁻⁶. 8 The bacterial suspension used is approximately CFU / mL.

[0109] One week after transplanting, the rubber seedlings were treated with root irrigation. 100 mL of the prepared bacterial solution was applied to the soil around the roots of each seedling. The control group was treated with an equal amount of sterile water. The pot experiment lasted for 90 days.

[0110] The LB liquid culture medium formula is as follows: 10g peptone, 5g yeast extract, 10g NaCl, 1000mL distilled water, pH 7.0. Sterilize at 121℃ for 15min.

[0111] Before and after the experiment, the height and diameter at ground level of the rubber seedlings were measured, and the growth values ​​of plant height and diameter at ground level were calculated. Plant height is the height from the soil surface to the growing point of the main stem, and the growth value of plant height = final plant height - initial plant height; the diameter at ground level is the diameter of the seedling stem at a point approximately 2.0 cm above the soil surface, and the growth value of diameter at ground level = final diameter at ground level - initial diameter at ground level.

[0112] Before the experiment ended, the chlorophyll content of the leaves was measured using a SPAD-502Plus chlorophyll meter (Konica Minolta, Inc., Japan). After the experiment, the rubber seedlings were dug up, washed, and brought back to the laboratory to be weighed. The seedlings were cut at the root collar, and the fresh weight of the above-ground and underground parts was measured separately. The Wanshen LA-S plant root analysis system (Hangzhou Wanshen Testing Technology Co., Ltd., China) was used to scan and analyze data such as root length, root surface area, root volume, and number of root tips. The above-ground and underground parts of the plants were dried in an oven at 80℃ until constant weight, and the dry weight of the above-ground and underground parts was measured. Experimental data were analyzed using Excel and SPSS 25.0 statistical software for analysis of variance and multiple comparisons.

[0113] like Figure 13 As shown in Table 3, the SYR43 treatment significantly increased the biomass of rubber seedlings, exhibiting good effects on increasing plant height, ground diameter, leaf chlorophyll content, total plant fresh weight, and both aboveground and belowground fresh and dry weights. Table 4 shows that the SYR43 treatment increased plant height and ground diameter by 8.72% and 8.30% respectively compared to the control, and the SYR43 treatment increased leaf chlorophyll content by 7.08% compared to the control. Table 4 also shows that the SYR43 treatment increased total plant fresh weight, aboveground fresh weight, belowground fresh weight, aboveground dry weight, and belowground dry weight by 14.71%, 11.31%, 20.24%, 21.13%, and 36.46% respectively compared to the control.

[0114] like Figure 13As shown, SYR43 promotes the root growth of rubber seedlings. Root scanning analysis further confirmed that SYR43 significantly promoted the root growth of rubber seedlings. As shown in Table 5, the root length, root surface area, root volume, and number of root tips of rubber seedlings treated with SYR43 increased by 20.99%, 17.52%, 8.93%, and 16.21%, respectively, compared with the control.

[0115] Table 4. Effects of bacterial strains on rubber seedling growth

[0116]

[0117] Note: Different letters indicate statistically significant differences (P < 0.05).

[0118] Table 5 Effects of bacterial strains on rubber seedling biomass

[0119]

[0120] Note: Different letters indicate statistically significant differences (P < 0.05).

[0121] Table 6 Effects of bacterial strains on root development of rubber seedlings

[0122] Note: Different letters indicate statistically significant differences (P < 0.05).

Claims

1. A Neobacillus strain SYR43, characterized by, The strain SYR43 is classified as Neobacillus sp. SYR43, and the preservation number is GDMCC NO: 66467, which was preserved in Guangdong Microbial Culture Collection Center on June 4, 2025.

2. The strain SYR43 according to claim 1, characterized in that, The sequence of 16S rDNA of the strain SYR43 is shown as SEQ ID NO:

1.

3. A fermentation broth or a bacterial suspension containing the strain SYR43 as claimed in claim 1.

4. Use of the strain SYR43 as claimed in claim 1 or the bacterial suspension as claimed in claim 3, characterized in that, The application is any one of the following: A1) application in promoting plant growth; A2) application in preparing a product for promoting plant growth; The plant includes Arabidopsis thaliana, Lactuca sativa and Hevea brasiliensis.

5. Use according to claim 4, characterized in that, When the plant is Arabidopsis thaliana, the promotion of plant growth includes increasing the fresh weight of the whole plant, the fresh weight of stems and leaves, the fresh weight of roots, root length, and chlorophyll content.

6. Use according to claim 4, characterized in that, When the plant is Lactuca sativa, the promotion of plant growth includes increasing the fresh weight of the whole plant, the fresh weight of the aboveground part, the fresh weight of the underground part, the number of cotyledons, the soluble sugar content of leaves, and the chlorophyll content.

7. Use according to claim 4, characterized in that, When the plant is Hevea brasiliensis, the promotion of plant growth includes increasing the plant height, ground diameter, fresh weight of the whole plant, fresh weight of the aboveground part, fresh weight of the underground part, dry weight of the aboveground part, dry weight of the underground part, chlorophyll content, total root length, root surface area, root volume, and the number of root tips.

8. A microbial inoculum for promoting plant growth, characterized in that, The active ingredient of the microbial agent includes the strain SYR43 as claimed in claim 1; and the plant includes Arabidopsis thaliana, Lactuca sativa and Hevea brasiliensis.

9. A bio-organic fertilizer, characterized by, The active ingredient of the bio-organic fertilizer includes the strain SYR43 as claimed in claim 1 or the microbial agent for promoting plant growth as claimed in claim 8.

10. A method of promoting plant growth, characterized by, The method is to prepare the strain SYR43 as claimed in claim 1 into a bacterial suspension, and apply it to plants by inoculation or root irrigation. The preparation method of the bacterial suspension is as follows: inoculate the strain SYR43 into LB liquid medium at an inoculation amount of 1%, and then culture at 30°C for 48 h at 200 rpm. Centrifuge the fermentation liquid at 5000 rpm for 5 min, discard the supernatant, wash the bacterial pellet with sterile water for 2 times, resuspend, and dilute with sterile water to a bacterial liquid concentration of 1.0×10 8 cfu / mL, which is the bacterial suspension used. The plant includes Arabidopsis thaliana, Lactuca sativa and Hevea brasiliensis, the inoculation is applied to the root tips of Arabidopsis thaliana, and the root irrigation is applied to Lactuca sativa and Hevea brasiliensis seedlings.

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