Saline-alkali-tolerant growth-promoting P.flexus, microbial composition containing P.flexus and application of P.flexus

Abstract

The invention provides a saline-alkaline tolerant and growth-promoting Priestia flexa strain KY87, a microbial composition containing the same and application of the strain KY87, and relates to the technical field of microorganisms and application of the microorganisms. The strain is preserved in the China General Microbiological Culture Collection Center (CGMCC), and the preservation number is CGMCC No.36900. The strain KY87 disclosed by the invention can stably survive under high-salt and strong-alkali conditions and can promote plant growth. The strain is excellent in performance and has wide application prospects in saline-alkali soil improvement and saline-alkali soil crop planting.

Description

Technical Field

[0001] This invention relates to the field of microbiology and its application technology, and in particular to a salt- and alkali-tolerant strain of Curvature Priestella (… Priestia flexa ) strain KY87, microbial compositions containing it and their applications. Background Technology

[0002] Saline-alkali land refers to land with excessive salt and alkali accumulation in the topsoil, which is harmful to crops and represents a barrier to soil degradation. Soil salinization is an increasingly serious global problem, widely distributed worldwide. Soil salinization has become the most significant abiotic limiting factor hindering modern agricultural development, a typical abiotic stress, and a major environmental factor leading to reduced crop yields (Liu et al., 2018). The effects of salt stress on plants are mainly manifested in four aspects: osmotic stress, ion toxicity, nutrient imbalance, and oxidative stress. Regarding osmotic stress, salt stress reduces the osmotic potential of the soil solution, causing water stress (cell dehydration) in plants, leading to the efflux of their own substances (Sairam RK et al., 2004). Regarding ion toxicity, when the concentration of salt ions in the soil is high, Na+ ions are particularly susceptible to ion toxicity. + The leading salt ions inhibit the cell membrane's response to K+ by directly interfering with or competitively inhibiting its activity. + Mg 2+ Ca 2+ The absorption and transport of nutrient ions, especially Na, can lead to serious problems. + Excessive absorption of salts can lead to a corresponding decrease in the absorption of other ions, causing ion imbalances in cells and resulting in ion toxicity (Kalhoro AN et al., 2016). The interaction between salts and mineral nutrients can lead to nutrient imbalances and deficiencies. Salt stress can also cause excessive accumulation of reactive oxygen species in plants, damaging cell structure and leading to cell death, i.e., oxidative stress (Wang Hanxiang et al., 2022). Alkali stress, in addition to this, adds high pH stress, disrupting cellular pH stability and producing a stronger inhibitory effect on plants, severely damaging the structure and function of plant roots (Schumacher K, 2014). Excessive accumulation of salt and alkali components in the surface layer of saline-alkali soils increases soil solution concentration, reduces soil organic matter and nutrient content, and alters soil structure and physical properties, severely affecting plant growth, development, reproductive processes, and physiological metabolic activities, thereby threatening crop yields and seriously damaging farmers' economic benefits (Sun Mingzhen, 2020). Studies by Feng Guoyi et al. have shown that planting cotton in saline-alkali land greatly hinders cotton photosynthesis and reduces cotton yield (2019). Dai Rui studied the effects of salt stress on crop seed germination, growth and development, and gene expression, and the results showed that salt stress has varying degrees of impact on crops throughout their entire developmental period (2019). Therefore, reducing the harm caused by soil salinization is of great significance.

[0003] Developing a comprehensive soil salinization improvement technology system and rationally and efficiently utilizing potential saline-alkali land resources are of significant theoretical value for alleviating land resource shortages, ensuring a balance between population and arable land, and achieving sustainable and healthy regional land development and food security. Currently, the main methods for managing saline-alkali land include physical, chemical, biological, and integrated methods (Xu X, 2023). Physical improvement focuses on improving soil physical structure to regulate the evaporation-to-precipitation ratio in saline-alkali land. This includes traditional methods such as in-situ soil improvement, topsoil improvement, deep plowing and sun-drying, and micro-area soil improvement, as well as new technologies such as biomaterials and ground cover. Chemical improvement methods focus on acid-base neutralization and ion balance to improve soil quality. This is generally achieved by adding different types of materials, such as calcium-based amendments, acid-based amendments, organic amendments, and mineral resource amendments, to accelerate the leaching of salt ions and increase base exchange capacity, thus achieving rapid salinization and alkali improvement (Huang Ting, 2022). Biological improvement methods are further divided into plant-based improvement and microbial improvement (Zhang Yifu et al., 2017). Plant improvement mainly involves introducing, screening, cultivating, and planting salt-tolerant plants, such as Suaeda salsa, alfalfa, and Tamarix chinensis, to improve the physical and chemical properties of soil, enhance soil microbial diversity, and reduce the salt content in saline-alkali soils (Lin Xuezheng et al., 2005; Hou Hui et al., 2023; Li Haiying et al., 2002). Microbial improvement refers to inoculating soil or plants with salt-tolerant microbial agents to improve the rhizosphere environment, soil physical and chemical properties, and soil microclimate, thereby reducing soil moisture evaporation and inhibiting soil salinization, thus achieving the goal of improving saline-alkali land (Furkan O, 2021). Comprehensive improvement methods refer to a combination of two or more of the above improvement measures. Although physical, chemical, and engineering improvement measures are simple and easy to promote on a large scale, they still have problems such as high cost and easy to cause secondary soil salinization. Biological improvement measures, on the other hand, have the advantages of long-lasting desalination, no pollution and good ecological balance, low input cost, simple and feasible operation and management, high efficiency, economic and environmental protection, and no waste of water resources. They are considered to be the most ecologically beneficial measures (Gao Huimin et al., 2020).

[0004] Soil contains abundant microbial resources, some of which are essential "partners" for plant survival (Shen et al., 2015). They participate in plant growth processes, promote plant growth, and drive the material cycle of terrestrial ecosystems. Studies have shown that the application of salt-tolerant growth-promoting bacteria has a good effect on improving crop growth under salt-alkali stress and enhancing crop salt tolerance (Cao et al., 2021; Li et al., 2021). Salt-tolerant growth-promoting bacteria are relatively abundant and play an important role in the development of microbial resources and the utilization of microbial fertilizers, and have now become a hot topic in microecological research. Anam et al. screened a high-salt-alkali tolerant Trichoderma that can not only reduce the EC value and pH value in the soil, but also promote the growth of Sudan grass (2019); Lü et al. isolated a Bacillus amyloliquefaciens PT6-1 with strong salt tolerance from saline-alkali land. After treating giant Napier grass seedlings with a bacterial solution made from this strain, they found that the treatment increased the content of photosynthetic pigments and chlorophyll in giant Napier grass, and enhanced the photosynthetic intensity of giant Napier grass (2023). Plant growth-promoting rhizobacteria (PGPR) can improve the rhizosphere environment, enhance crop resistance to salt and alkali stress, and improve the quality and environmental adaptability of seedlings in saline-alkali land (HeS, 2024). Salt-tolerant growth-promoting bacteria reported in previous studies include those from the genus *Bacillus* (…). Bacillus ), Azospirobacter spp. Azospirillum ), Pseudomonas spp. Pseudomonas Nesterianella ( ) Nesterenkonia ), Enterobacteriaceae ( Enterobacter ), Serratia ( Serratia ), Cochlea spp. Kocuria ) and spp. of Halomonas ( Halomonas Therefore, there is an urgent need to develop new microbial strains suitable for saline-alkali land, safe and efficient functional conditioners for saline-alkali land, and environmentally friendly functional fertilizers, among other green products.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] The purpose of this invention is to address the aforementioned technical problems by providing a salt- and alkali-tolerant strain of *Priscilla curvaturei* (…). Priestia flexa ) strain KY87, microbial compositions containing it and their applications.

[0007] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: In a first aspect, the present invention provides a salt- and alkali-tolerant, growth-promoting strain of *Priscilla curvaturei* (… Priestia flexaThe strain KY87 is deposited at the China General Microbiological Culture Collection Center (CGMCC) with accession number CGMCC No. 36900 and deposit date of December 8, 2025.

[0008] The inventors of this application screened approximately 1500 microbial strains from their own microbial library for strains that could stably grow under high salt / strong alkaline conditions. From these, 12 strains were identified that could stably grow under conditions of 15% NaCl + pH 9. One of these strains, KY87, exhibited high salt and strong alkalinity tolerance, growing up to 18% + pH 9. Subsequent studies also revealed that this strain (or inoculants containing it) had a certain promoting effect on plant growth (e.g., maize) and could alleviate the effects of salt stress on maize seed germination, growth, development, and gene expression. Therefore, it can be used to reduce the harm caused by soil salinization to plant growth.

[0009] In one embodiment, the 16S rDNA sequence of strain KY87 is shown in SEQ ID NO: 1. Results of 16S DNA sequencing of strain KY87 indicate that the base sequence of this strain is similar to... Priestia flexa With a high degree of homology exceeding 99.52%, it was therefore named *Priestella curvilinearis*. Priestia flexa ) strain KY87.

[0010] In a second aspect, the present invention provides a microbial composition containing the aforementioned *Priscilla curvatureii* (…). Priestia flexa ) strain KY87, or containing strains of the aforementioned Curved Priestella ( Priestia flexa Fermentation products obtained from the fermentation of strain KY87.

[0011] In one embodiment, the microbial composition is in liquid or solid form. The microbial composition contains *Priscilla curvatureensis* (…). Priestia flexa The total viable count of strain KY87 is at least 1 × 10⁻⁶. 6 cfu·mL -1 Or 1×10 6 cfu·g -1 .

[0012] In one embodiment, the microbial composition further contains oligosaccharide synergists.

[0013] In one embodiment, the oligosaccharide synergist includes one or more of chitosan oligosaccharides, fucoidan oligosaccharides, chitin oligosaccharides, and amino oligosaccharides, preferably chitosan oligosaccharides.

[0014] In a third aspect, the present invention provides the aforementioned *Priscilla curvatureis* (… Priestia flexa Uses of strain KY87 or the aforementioned microbial composition in the following aspects: (a) Used for the improvement of saline-alkali land; (b) Used to promote plant growth; and (c) Used to improve the salt and alkali tolerance of plants.

[0015] The present invention is based on the curvilinear Priestella ( Priestia flexa Strain KY87 or inoculants or compositions containing it can alleviate the stress on plants caused by high salt (NaCl concentration greater than 15% (w / v), or even 18% (w / v)) and strong alkali (pH greater than 9), improve the salt and alkali tolerance of plants, and help improve and promote the growth of crop organisms in saline-alkali environments.

[0016] In one embodiment, promoting plant growth includes promoting plant growth in saline-alkali or non-saline-alkali environments. Preferably, promoting plant growth includes promoting the growth of plants such as corn, soybeans, and wheat. More preferably, promoting plant growth includes promoting the growth of corn in saline-alkali environments.

[0017] In a fourth aspect, the present invention provides a method for promoting crop growth in a saline-alkali environment, the method comprising using the aforementioned *Priscilla curvatureii* (… Priestia flexa The strain KY87 or the aforementioned microbial composition may be applied to plant seeds, used for root irrigation of plant seedlings, and / or applied to the substrate in which the plant is grown.

[0018] In one embodiment, the saline-alkali environment includes environments of salt stress and / or alkali stress; the plant includes at least one of maize, soybean, and wheat.

[0019] Preservation information: The *Priestella curvaturei* provided in this application ( Priestia flexa The strain, named KY87, is deposited at the China General Microbiological Culture Collection Center (CGMCC), located at No. 3, Courtyard 1, Beichen West Road, Chaoyang District, Beijing, Institute of Microbiology, Chinese Academy of Sciences. The deposit date was December 8, 2025, and the accession number is CGMCC No. 36900. It was confirmed as a viable strain by the collection center on December 8, 2025.

[0020] Beneficial effects: Compared with existing technologies, the present invention isolates and screens *Priscilla curvatureensis* (…). Priestia flexaThe strain KY87 exhibits significantly superior tolerance to high salt and strong alkali conditions, tolerating a maximum concentration of 18% (w / v%) NaCl and a maximum alkali tolerance of pH=12, which is significantly better than related strains reported in the prior art. Furthermore, the strains or inoculants containing these strains can alleviate salt damage symptoms and increase crop biomass under salt stress, thereby promoting crop growth. In particular, when used in combination with oligosaccharide synergists, they can better promote maize growth and mitigate the harmful effects of soil salinization on plant growth and development. The method of this invention for promoting crop growth under environmental stress is beneficial for improving crop growth status, increasing crop yield, improving quality, and reducing the use of chemical fertilizers.

[0021] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0022] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 This is a schematic diagram showing the growth of *Priestella curvature* on culture media with different pH and different NaCl concentrations. Figure 2 The results show the effects of Curvature Priestella on maize plant growth under pure saline-alkali soil conditions. Figure 3 The results show the effects of strain KY87 on maize plant growth under pure saline-alkali soil conditions. Figure 4 The results show the effects of the KY87 strain compound fermentation broth on maize plant growth under saline-alkali mixed nutrient soil conditions. Figure 5 The morphology of strain KY87 under a microscope (10×100). Detailed Implementation

[0023] The present invention will be explained below with reference to embodiments. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0024] The inventors of this application screened approximately 1,500 microbial strains from their own microbial library for strains that could stably grow under high salt / strong alkaline conditions. From these, 12 microbial strains that could stably grow under 15% NaCl + pH 9 conditions were selected. Among them, one target strain, KY87, had high salt and strong alkali tolerance and could grow at a maximum of 18% + pH 9. Subsequent studies also found that this strain (or inoculants containing it) had a certain promoting effect on plant (e.g., corn) growth and could also alleviate the effects of salt stress on corn seed germination, growth and development, and gene expression. It can be used to reduce the harm caused by soil salinization.

[0025] In one aspect, the present invention provides a salt- and alkali-tolerant, growth-promoting strain of *Priscilla curvaturei* (… Priestia flexa The present invention provides strain KY87, which is deposited at the China General Microbiological Culture Collection Center (CGMCC) with accession number CGMCC No. 36900. Compared with the prior art, the present invention provides *Priscilla curvilinearis* (…). Priestia flexa The strain KY87 exhibits remarkable performance, namely, tolerance to high salt and strong alkali.

[0026] Existing strains capable of stable growth under high salt / strong alkaline conditions (15% NaCl + pH 9) are rare. The strain KY87 screened in this application, when cultured on plate medium, still maintains stable growth under these conditions, indicating strong tolerance to 15% NaCl. Furthermore, strain KY87 can still grow under 18% NaCl + pH 9 conditions, although it is somewhat inhibited. Therefore, strain KY87 exhibits a maximum salt tolerance of 18% and a maximum alkali tolerance of pH 12, demonstrating exceptionally high salt and alkali tolerance, a characteristic not previously reported in existing *Priscilla curvatureensis* strains.

[0027] The strain KY87 of this invention not only exhibits excellent salt tolerance on 18% NaCl plates but also demonstrates significant plant growth-promoting effects in saline-alkali soil cultivation. In one specific embodiment, strain KY87 promotes plant (e.g., maize) growth in soil environments with EC values ​​ranging from approximately 6.95 ms / cm to 10.3 ms / cm. In another specific embodiment, strain KY87 also promotes plant growth in severely saline soils, for example, in soil environments with EC values ​​as high as EC ≈ 10.3 ms / cm or higher. Strain KY87 still promotes maize growth and shows significant advantages in maize germination rate, plant height, and vigor, and can be used to alleviate the impact of saline-alkali soil on plant growth and development.

[0028] In the context of this invention, "EC value" refers to Electrical Conductivity, a core indicator for measuring the total amount of soluble salts in soil or water, directly reflecting the degree of salinization and irrigation water quality. Soluble ions (Na+) in soil solution or water... + Cl - Ca² + The higher the concentration of (etc.), the greater the EC value. The EC value of non-saline soil is generally 0-2 ms / cm, the EC value of slightly saline soil is generally 2-4 ms / cm, the EC value of moderately saline soil is generally 4-8 ms / cm, and the EC value of severely saline soil is generally >8 ms / cm.

[0029] In one aspect, the present invention provides a microbial composition containing *Priscilla curvatureii* (… Priestia flexa ) strain KY87, or containing strains of *Priscilla curvature* ( Priestia flexa Fermentation products obtained from the fermentation of strain KY87.

[0030] In one specific implementation, the "fermentation product" refers to the fermentation product obtained after fermentation using the strain. This includes, but is not limited to, fermentation broth, bacterial suspension, and culture metabolites.

[0031] In one specific embodiment, the microbial composition is in liquid or solid form. When the microbial composition is a liquid inoculum, it is obtained by culturing the purified strain KY87. When the microbial composition is a solid inoculum, it is obtained by culturing the purified strain KY87 to obtain a liquid inoculum, and then drying the liquid inoculum to obtain a solid inoculum.

[0032] In one specific embodiment, the liquid microbial agent can be applied by conventional methods in the art, such as root irrigation, seed soaking, and spraying, while the solid microbial agent can be applied by conventional methods in the art, such as root application and hole application. The strains or microbial compositions of this application can be used alone or in combination with other excipients (such as one or more of dispersants, wetting agents, disintegrants, binders, defoamers, antifreeze agents, thickeners, fillers, and solvents).

[0033] In one specific embodiment, the oligosaccharide synergist includes one or more of chitosan oligosaccharides, fucoidan oligosaccharides, chitosan oligosaccharides, and amino oligosaccharides, with chitosan being preferred. Chitosan, also known as chitosan oligosaccharide or chitosan oligomer, is a low-polymerization, water-soluble sugar composed of 2-10 glucosamine molecules linked by β-(1,4)-glycosidic bonds. In a preferred embodiment, commercially available chitosan oligosaccharide powder can be diluted and mixed with KY87 bacterial culture to prepare a microbial composition.

[0034] In one embodiment, the microbial composition can be used as a plant growth promoter, soil conditioner, or plant fertilizer.

[0035] In a third aspect, the present invention provides the aforementioned *Priscilla curvatureis* (… Priestia flexa Uses of strain KY87 or the aforementioned microbial composition in the following aspects: (a) for improving saline-alkali land; (b) for promoting plant growth; and (c) for improving plant salt tolerance.

[0036] In one embodiment, the strains or compositions containing the present invention can be used to alter the soil environment of saline-alkali land, for example, by changing the salt content. In another embodiment, the strains or compositions containing the present invention can promote plant growth in saline-alkali or non-saline-alkali environments, particularly promoting plant growth in soils with varying degrees of salinity. Specifically, promoting plant growth includes promoting plant growth and development, particularly promoting the growth and development of plants in saline-alkali environments. Growth and development refers to the seed germination (germination) and post-emergence development process. In some cases, promoting plant growth and development includes increasing germination rate, stem length, root length, etc. The plants include common crops such as soybeans, corn, mung beans, and wheat; preferably, the plant is corn.

[0037] In a fourth aspect, the present invention provides a method for promoting crop growth in a saline-alkali environment, the method comprising using the aforementioned *Priscilla curvatureii* (… Priestia flexa The strain KY87 or the aforementioned microbial composition may be applied to plant seeds, used for seedling root irrigation, or applied to the substrate in which the plant is grown. In one specific embodiment, the method using strain KY87 of the present invention can improve the seed germination rate of maize, increase the height of maize plants, and promote the growth and development of maize, especially in saline-alkali soil environments.

[0038] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0039] Example 1. Preliminary screening of microbial strains that can grow stably under low to medium salinity / alkalinity conditions. 1.1 Screening of strains in the microbial resource bank Representative soil samples were collected from various provinces across the country, including sandy soil, clay, and black soil. The samples came from different regions such as farmland, pasture, and forest soil. 15-20 grams of sample were collected from each point, and the source (province, county), year and month of collection, and source of the soil (plant, sandy soil, or others) were marked. The samples were stored in a -80℃ freezer. A total of 315 soil samples from various provinces and cities across the country were collected, and a rare microbial resource bank was constructed, containing a total of about 1,500 strains.

[0040] 1.2 Screening for microbial strains that can grow stably under conditions of 5% NaCl + pH 9 1500 strains were streaked on R2A solid medium (0.50 g yeast extract, 0.50 g peptone, 0.50 g trypone, 0.50 g glucose, 0.50 g soluble starch, 0.30 g dipotassium hydrogen phosphate, 0.30 g sodium pyruvate, 0.05 g magnesium sulfate heptahydrate, 15.0 g agar powder, and 1000 mL water) and incubated at 30°C for 24 h. Single colonies were then picked and streaked on R2A solid medium containing 5% NaCl + pH 9 and incubated at 30°C. The growth of the strains was recorded.

[0041] 1.3 Screening for microbial strains that grow stably under conditions of 10% NaCl + pH 9 The microbial strains that can grow stably under 5% NaCl + pH 9 conditions in step 1.2 above were streaked on R2A solid medium containing 10% NaCl + pH 9, and the growth of the strains was recorded.

[0042] 1.4 Duplicate Validation To ensure the growth ability of the strain under different conditions, the microbial strain that grows stably under both 5% NaCl + pH 9 and 10% NaCl + pH 9 conditions can be streaked again on R2A solid medium with different salt concentrations and pH conditions, and then incubated at 30°C to verify whether the microbial strain has the ability to grow under different conditions and to eliminate false positive colonies.

[0043] 1.5 Results From 1,500 microbial strains in the rare microbial strain resource bank, 283 microbial strains that can grow stably under 5% NaCl + pH 9 conditions and 103 microbial strains that can grow stably under both 5% NaCl + pH 9 and 10% NaCl + pH 9 conditions were screened.

[0044] Table 1. Growth of some strains on media with different salt concentrations / pH conditions

[0045] Note: "++" indicates that the strain can grow normally; "+" indicates slight inhibition, but growth is still possible; "-" indicates complete inhibition, and no growth is possible. As shown in Table 1, (1) some strains can grow stably under 5% NaCl + pH 9 and 10% NaCl + pH 9 conditions, such as strains KY40, KY87, and KY207, indicating that they have high tolerance to salt and alkali; (2) some strains can grow stably under 5% NaCl + pH 9 conditions, but their growth is inhibited or they do not grow under 10% NaCl + pH 9 conditions, such as strains KY553, KY1080, KY1123, and KY1165, indicating that they have a certain degree of tolerance to salt and alkali; (3) some strains are slightly inhibited in growth under 5% NaCl + pH 9 conditions, but can grow stably under 10% NaCl + pH 9 conditions, such as strain KY10, indicating that they need the participation of salt and alkali in their growth process and may be a halophilic bacterium; (4) some strains are slightly inhibited in growth under 5% NaCl + pH 9 conditions and do not grow under 10% NaCl + pH 9 conditions, such as strain KY724, indicating that they have weak tolerance to salt and alkali. This shows that different strains have different levels of tolerance to salt and alkali, but there is also a certain degree of growth pattern of tolerance to salt and alkali.

[0046] 2. Advanced screening of microbial strains that can grow stably under high-salt / strong-alkali conditions. 2.1 Screening of microbial strains that can grow stably under 15% NaCl + pH 9 conditions The strains obtained from the rare microbial resource library in step 1, which were streaked on R2A solid medium under conditions of 5% NaCl + pH 9 and 10% NaCl + pH 9, were picked as single colonies and streaked on R2A solid medium of 15% NaCl + pH 9. The commercial strain 92068 (Bacillus subtilis) was used as a control and incubated at 30°C. The growth of the strains was recorded.

[0047] 2.2 Results From the 103 microbial strains that could stably grow under both 5% NaCl + pH 9 and 10% NaCl + pH 9 conditions selected in step 1, 12 microbial strains that could stably grow under 15% NaCl + pH 9 conditions were selected, and the results are as follows.

[0048] Table 2. Growth of some strains on 15% NaCl + pH 9 conditioned medium

[0049] Note: 1. "++" indicates that the strain can grow normally; "+" indicates slight inhibition, but growth is still possible; "-" indicates complete inhibition, and no growth is possible. 2. Priestia flexa(Curvular Priestella) is the most recent name for this genus; previously it was named... Bacillus flexa (Bacillus curvaturei).

[0050] As can be seen from Table 2, (1) some microbial strains that can grow stably under the conditions of 5% NaCl + pH 9 and 10% NaCl + pH 9 do not grow at all under the condition of 15% NaCl + pH 9, indicating that the salt tolerance of these strains is limited to a certain extent, with a salt tolerance of 10%-15%, such as strains KY389, KY433, and KY553; (2) some microbial strains that can grow stably under the conditions of 5% NaCl + pH 9 and 10% NaCl + pH 9 are slightly inhibited in growth under the condition of 15% NaCl + pH 9, indicating that the salt tolerance of these strains is limited to a certain extent, such as strains KY1189 and KY1190; (3) some microbial strains that can grow stably under the conditions of 5% NaCl + pH 9 and 10% NaCl + pH 9 can still grow stably under the condition of 15% NaCl + pH 9, indicating that the salt tolerance of these strains is relatively strong, such as strains KY40, KY87, and KY207.

[0051] In summary, it can be found that the vast majority of the strains that can grow stably under the conditions of 15% NaCl + pH 9 belong to *Priscilla curvilinearis*. Priestia flexa Therefore, this study decided to use this genus ( ). Priestia flexa This study will explore its salt and alkali tolerance characteristics and its effects on alleviating plant toxicity and promoting growth under salt and alkali stress. 3. Determination of the growth of *Priestella curvature* under different high-salt / strong-alkali conditions. 3.1 Determination of the growth of *Priestella curvature* under different high-salt / strong-alkali conditions All *Priestella curvaturei* strains were selected from the rare microbial resource bank and streaked on R2A solid medium. The cultures were incubated at 30°C for 24 hours. Single colonies were then selected and streaked on R2A solid medium containing 15% NaCl+ (pH 12), 16% NaCl+ (pH 9, pH 10, pH 11, pH 12), 17% NaCl+ (pH 9, pH 10, pH 11, pH 12), and 18% NaCl+ (pH 9, pH 10, pH 11, pH 12). *Bacillus subtilis* (92068) was used as a control. All cultures were incubated at 30°C, and the growth of the strains was recorded. 3.2 Results All *Priestella curvature* strains from the microbial resource library were streaked onto culture media with different NaCl concentrations and pH conditions. The results are as follows: Table 3. Growth of the strain on media with different NaCl concentrations and different pH conditions

[0052] Note: "++" indicates that the strain can grow normally; "+" indicates slight inhibition, but growth is still possible; "+-" indicates inhibition and very slow growth; "-" indicates complete inhibition and no growth.

[0053] From Table 3 and Figure 1 It can be seen that, except for strain KY190, the other Curvature Priestella strains can grow stably under the conditions of 15% NaCl + pH 12, indicating that these strains have almost the same tolerance to high salt and strong alkali within their own tolerance range; however, as the salt and alkali concentrations increase and exceed the maximum tolerance of Curvature Priestella, the growth of the same strains begins to differ: (1) Under the conditions of 16% NaCl + pH 10, KY53 and KY151 are inhibited, and when the pH is increased to 12, they hardly grow. Therefore, the maximum salt tolerance concentration for strains KY53 and KY151 is 16% NaCl + pH 10. 16%, and the highest pH tolerance value is pH=11; (2) Under the condition of 17% NaCl + pH9, strains KY40, KY87 and KY207 still showed normal growth, but when the pH was increased, all three were inhibited and did not grow, indicating that when the salt concentration is increased to a certain extent, the tolerance to alkali will be relatively weakened; (3) Under the condition of 18% NaCl + pH9, strain KY40 was inhibited and no single colony appeared, indicating that the highest salt tolerance concentration of this strain is 17%. Strain KY87 can still grow under the condition of 18% NaCl + pH9, but it is also inhibited to a certain extent. In summary, the growth of *Priscilla curvatureis* is not completely the same under different pH + different NaCl concentration conditions.

[0054] 4. Growth-promoting effects of *Priscilla curvature* on plants under different salt and alkali stress conditions Curved Priestella ( Priestia flexa This is the latest name for the genus *Bacillus curvatureus*. Bacillus flexa ), is a species of Bacillus, and is related to Bacillus subtilis ( Bacillus subtilis(They are closely related in terms of phylogenetics). To verify that it can not only grow on high-salt and strong-alkali plates, but also protect / promote plant growth under salt stress, this experiment used the widely used commercial strain 92068 (strain 92068 is a commonly used Bacillus subtilis on the market, mostly used for plant disease prevention and growth promotion) as a control. Curvature Priestella bacteria solution was prepared and mixed with corn seeds, which were then planted in saline-alkali soil. The study compared whether they promoted corn growth under different salt and alkali stress conditions, whether they could alleviate the effects of salt stress on corn seed germination, growth and development, and gene expression, and reduce the harm caused by soil salinization, laying the foundation for subsequent products.

[0055] 4.1 Growth-promoting effects of Bacillus curvatureii on plants under different salt and alkali stress conditions 1) Control strain: Commercial strain 92068 was selected as the control strain; 2) OD 600nm Bacterial suspensions of 92068, KY40, KY87, KY53, KY151, and KY207 with a concentration of 0.05 were inoculated into Erlenmeyer flasks containing 100 mL of R2A liquid medium and incubated at 30°C and 200 rpm for 48 h. The cultures were then analyzed using a visible-ultraviolet spectrophotometer at OD500. 600 After measuring its OD value, OD was prepared. 600nm Prepare 0.1% bacterial culture in a 50 mL centrifuge tube for later use; 3) Distribute equal amounts of pure saline-alkali soil (source of saline-alkali soil: Ordos City, Inner Mongolia, EC value ≈ 10.3 ms / cm) evenly into paper cups, and moisten the saline-alkali soil with water in advance; 4) Take corn seeds of uniform size and full kernels (corn variety: Zhengdan 958) and soak them in centrifuge tubes with prepared bacterial solution. After 30 minutes, plant the corn seeds in paper cups containing saline-alkali soil, with 6 seeds planted in each group. 5) After the corn seedlings emerge, dilute the commercial bacterial strains 92068, KY40, KY87, KY53, KY151, and KY207 (OD207). 600nm =0.1) An equal amount of water was applied to the corn pots, and the growth of the corn was observed and recorded. Watering was done regularly.

[0056] 4.1.1 Results The results of *Priestella curvature* promoting maize plant growth under pure saline-alkali soil conditions (EC value ≈ 10.3 ms / cm) are as follows: Figure 2 As shown. From Figure 2It can be seen that, compared with the control commercial strain 92068, all strains of *Priestella curvaturei* except strain KY53 have a certain effect on promoting maize growth under saline-alkali soil conditions, but there are differences among different strains: (1) The germination rate of maize with *Priestella curvaturei* except strain KY87 is lower than that of commercial strain 92068; (2) Except for strain KY53, the growth of maize plants with *Priestella curvaturei* is stronger than that of commercial strain 92068; (3) Strain KY87 has the best germination rate, maize plant height and growth. In summary, strains with similar salt tolerance characteristics (such as strains KY53 and KY151, strains KY87 and KY40) will show different effects in plant experiments in salt-alkali tolerance plate experiments. Among them, strain KY87 has the most obvious effect on promoting maize growth and alleviating the influence of saline-alkali soil on plant growth and development. Therefore, this study uses strain KY87 as the target strain to carry out subsequent experiments.

[0057] 4.2 Growth-promoting effects of *Priscilla curvatureii* KY87 on plants 1) Control strain: Commercial strain 92068 was selected as the control strain; 2) After streaking 92068 and KY87 onto R2A plates, incubate them at 30℃ for 48 hours. Once the strains have grown, use a disposable inoculation loop to transfer the strains into centrifuge tubes containing sterile water. Shake well to prepare a bacterial suspension. Analyze the suspension using a visible-ultraviolet spectrophotometer at OD500. 600 After measuring its OD value, OD was prepared. 600nm Prepare 0.1% bacterial culture in a 50 mL centrifuge tube for later use; 3) Distribute pure saline-alkali soil (source of saline-alkali soil: Ordos City, Inner Mongolia, EC value ≈ 6.95 ms / cm) evenly into flower pots, and water them in advance to moisten the saline-alkali soil; 4) Take uniformly sized and plump corn seeds (corn variety: Zhengdan 958) and soak them in centrifuge tubes with prepared bacterial solution. After 30 minutes, plant the corn seeds in flower pots filled with saline-alkali soil, with 6 seeds planted in each pot. Set up a blank control with corn seeds soaked in water. 5) After the corn seedlings emerge, dilute the water, commercial strain 92068 bacterial solution, and KY87 bacterial solution (dose of bacterial solution OD). 600nm =0.1) An equal amount of water was applied to the corn pots, and the growth of the corn was observed and recorded. Watering was done regularly.

[0058] 4.2.1 Results The effects of strain KY87 on maize plant growth under pure saline-alkali soil conditions (EC value ≈ 6.95 ms / cm) are as follows: Figure 3 As shown. From Figure 3It can be seen that under pure saline-alkali soil conditions (EC value ≈ 6.95 ms / cm), the germination rate, plant height, and growth vigor of maize seeds treated with *Priscilla curvatureensis* strain KY87 were better than those treated with water and commercial strain 92068 bacterial solution. This indicates that under the same salt stress conditions, strain KY87 has a certain promoting effect on maize growth and can also alleviate the impact of salt stress on maize seed germination, growth, and development, thus reducing the harm caused by soil salinization. Based on this, in order to develop safe and efficient functional conditioners and environmentally friendly functional fertilizers for saline-alkali land, this study plans to compound strain KY87 with existing fermentation broth products to verify whether it can be combined with different products to promote plant growth and reduce the harm caused by soil salinization to plants, laying the foundation for the development of safe and efficient functional conditioners and environmentally friendly functional fertilizers for saline-alkali land.

[0059] 4.3 Growth-promoting effect of KY87 compound fermentation broth on plants 1) After streaking strain KY87 onto an R2A plate, incubate it at 30℃ for 48 hours. Once the strain has grown, use a disposable inoculation loop to transfer the strain into a centrifuge tube containing sterile water. Shake well to prepare a bacterial suspension. Analyze the suspension using a visible-ultraviolet spectrophotometer at OD500. 600 After measuring its OD value, two OD tubes were prepared. 600nm =0.1% KY87 bacterial culture into 50 mL centrifuge tubes for later use, and add chitosan oligosaccharide to one of the tubes according to the ratio; 2) Mix pure saline-alkali soil (source of saline-alkali soil: Ordos City, Inner Mongolia, EC value ≈ 12.82 ms / cm) with nutrient soil in a certain proportion (final EC value ≈ 6.65 ms / cm), then evenly distribute it into flower pots and water them in advance to moisten the saline-alkali soil. 3) Take uniformly sized and plump corn seeds (corn variety: Zhengdan 958) and soak them in centrifuge tubes with prepared bacterial solution. After 30 minutes, plant the corn seeds in flower pots filled with saline-alkali soil, with 6 seeds planted in each pot. Set up corn seed pots with water and water + fermentation liquid in equal proportion as control. 4) After the corn seedlings emerge, dilute the water, water + fermentation liquid, KY87 bacterial solution, and KY87 + fermentation liquid (bacterial solution OD). 600nm =0.1) An equal amount of water was applied to the corn pots, and the growth of the corn was observed and recorded. Watering was done regularly.

[0060] 4.3.1 Results The results of the growth-promoting effect of the KY87 strain compound fermentation broth on maize under saline-alkali mixed nutrient soil conditions (final EC value ≈ 6.65 ms / cm) are as follows: Figure 4 As shown. From Figure 4It can be seen that (1) the growth-promoting effect of strain KY87 on corn under saline-alkali mixed nutrient soil conditions is better than that of corn plants soaked in water or water + fermentation liquid for irrigation, indicating that simply adding fermentation liquid has little effect on alleviating the effects of corn under saline-alkali stress; (2) the germination rate and growth of corn under saline-alkali mixed nutrient soil conditions are promoted by strain KY87 compound fermentation liquid, and the effect is significantly better than that of corn plants soaked in strain KY87 liquid for irrigation, indicating that strain KY87 compound fermentation liquid product has a better effect on promoting corn growth and alleviating the harm caused by soil salinization to plant growth and development, laying the foundation for the development of safe and efficient functional conditioners and environmentally friendly functional fertilizers for saline-alkali land.

[0061] 5. Determination of 16S DNA and analysis of strain morphology 5.1 Determination of 16S DNA of KY87 strain 5.1.1 Extraction of bacterial DNA by CTAB method 1. Inoculate a single colony into 5 mL of R2A and incubate overnight at 30°C; 2. Take 1 mL of seed culture medium and inoculate it into 100 mL of R2A liquid, and incubate at 37℃ and 220 r / min for 16 hours; 3. Centrifuge at 5000 r / min for 10 minutes and discard the supernatant; 4. After centrifugation and washing with 10 mL TE, dissolve the bacterial cells with 10 mL TE, mix well, and store at -20℃ for later use. 5. Take 3.5 mL of bacterial suspension, add 184 μL of 10% SDS, mix well, add 37 μL of 10 mg / mL proteinase K, mix well, and incubate at 37℃ for 1 hour. 6. Add 740 μL of 5 mol / L NaCl, then add 512 μL of LTAB / NaCl, mix well, and incubate at 65℃ for 10 minutes. 7. Add an equal volume of chloroform / isoamyl alcohol, mix well, centrifuge at 10000 r / min for 5 minutes, and retain the supernatant; 8. Add an equal volume of phenol:chloroform:isoamyl alcohol (25:24:1) to the supernatant, mix well, centrifuge at 10000 r / min for 5 minutes, and retain the supernatant; 9. Add 0.6 times the amount of isopropanol, mix well, centrifuge at 10000 r / min for 5 minutes, collect the DNA precipitate, and wash the DNA precipitate with 70% ethanol by centrifugation. 10. Dissolve the DNA in 1 mL TE buffer, add RNase A to a final concentration of 20 μg / mL, and store at 4°C.

[0062] 5.1.2 Amplification and Sequencing PCR amplification of 16S rDNA was performed using universal primers 27f (5'-AGAGTTTGATCCTGGCTCAG-3', SEQ ID NO: 2) and 1492r (5'-GGTTACCTTGTTACGACTT-3', SEQ ID NO: 3). PCR reaction conditions: 94℃ pre-denaturation for 30 s; 94℃ denaturation for 30 s, 52℃ annealing for 30 s, 72℃ extension for 60 s, 30 cycles.

[0063] The PCR products were subjected to 1.5% agarose gel electrophoresis. After agarose gel electrophoresis, the PCR products were recovered, purified, and sequenced. Based on the obtained 16S rDNA sequence, homologous sequences were searched for in GenBank using Blast and homologous sequence analysis was performed. At the same time, the sequence was compared with the 16sRNA database (Chun's lab) recognized by the International Committee for Bacteriology and combined with literature analysis to determine the taxonomic position of strain KY87.

[0064] 5.1.3 16S sequencing results of KY87 strain The 16S rDNA sequence (SEQ ID NO: 1) of strain KY87 is as follows:

[0065] Based on the obtained 16S rDNA sequence (Sequence 1) of KY87, homologous sequences were searched in GenBank and compared with each other. Simultaneously, sequence alignment was performed with the 16S RNA database (Chun's lab) recognized by the International Committee for Bacteriology, and combined with literature analysis to determine the taxonomic position of the target microorganism (Yoon, SH, Ha, SM, Kwon, S., Lim, J., Kim, Y., Seo, H. and Chun, J. (2017). Introducing EzBioCloud: Ataxonomically united database of 16S rRNA and whole genome assemblies. Int JSyst Evol Microbiol. 67:1613-1617). The results showed that the base sequence of this strain was similar to that of strain... Priestia flexa( This is the latest name for this genus; the previous name was... Bacillus flexa With 99.52% high homology, KY87 was identified as... Priestia flexa .

[0066] 5.2 Observation of strain morphology 5.2.1 Methods for observing strain morphology The selected strains were inoculated onto R2A plates and cultured at 30°C for 2 days. The size, shape, color, gloss, viscosity, raised shape, transparency, edge characteristics, and presence or absence of spores of the colonies were observed.

[0067] 5.2.1 Results of Observation of Strains' Morphology After observation of strain KY87 ( Priestia flexa The *Priestella curvaturei* was cultured on R2A medium for 2 days. The colony morphology showed that the colonies were round, short rod-shaped, orange-yellow and opaque, with a smooth and moist surface and regular edges. Microscopic measurements showed that the bacterial diameter was approximately 1-2 μm.

[0068] Summary: This application screened approximately 1500 strains from our proprietary microbial strain library for microbial strains that can stably grow under high salt / strong alkali conditions. One target strain, KY87, exhibited high salt and alkali tolerance, growing at a maximum of 18% + pH 9. 16S DNA sequencing of strain KY87 showed that its base sequence... Priestia flexaIt exhibits high homology. Pot experiments with corn revealed that this strain, compared to the commercial strain Bacillus subtilis 92068, can grow stably under high salinity and strong alkalinity conditions. Furthermore, its effects on promoting corn plant growth and mitigating the harm caused by saline-alkali soil are significantly superior to those of the commercial strain 92068. Therefore, KY87 is a functional microorganism that can stably survive under high salinity and strong alkalinity conditions and promote plant growth.

[0069] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0070] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A strain of a salt-tolerant and alkali-tolerant growth-promoting Prevotella curva (P. curva) strain KY87, characterized by, Priestia flexa ) a 16S rRNA gene sequence as shown in SEQ ID NO: 1, The strain KY87 is preserved in China General Microbiological Culture Collection Center, and the preservation number is CGMCC No. 36900; the preservation time is December 08, 2025.

2. The Prevotella curva (P. curva) strain KY87, having a 16S rDNA sequence set forth in SEQ ID NO: 1, according to claim 1. Priestia flexa ) 3. A microbial composition, characterized in that, The microbial composition contains the Prevotella curva (P. Priestia flexa ) strain KY87 according to claim 1 or 2, or contains a fermentation product obtained by fermentation of the Prevotella curva (P. Priestia flexa ) strain KY87 according to claim 1 or 2.

4. The microbial composition of claim 3, wherein, The total viable count of the strain KY87 of the bacterium Priestia flexa is at least 1 x 10 6 cfu.mL -1 or 1 x 10 6 cfu.g -1 .

5. The microbial composition of claim 3, wherein, The microbial composition also contains an oligosaccharide synergist.

6. The microbial composition of claim 5, wherein, The oligosaccharide synergist includes one or more of chitosan oligosaccharide, fucoidan oligosaccharide, chitooligosaccharide and amino oligosaccharide.

7. The curved-rod-shaped Prevotella (P. curva) strain of claim 1 or claim 2, Priestia flexa ) strain KY87 or the microbial composition of any one of claims 3 to 6 for use in: (a) for saline-alkali soil improvement; (b) for promoting plant growth; and / or (c) for improving plant salt-alkali tolerance.

8. Use according to claim 7, characterized in that, The plant growth promotion includes promoting the growth of corn in a saline-alkali environment.

9. A method of promoting growth of a crop in a saline environment, characterized by, The method comprises applying the strain of Pristolepis fasciata (P. fasciata) of claim 1 or claim 2 or the microbial composition according to any one of claims 3 to 6 to seeds of a plant, to a seedling drench treatment of a plant and / or to a substrate in which the plant is grown. Priestia flexa The method comprises applying the strain of Pristolepis fasciata (P. fasciata) of claim 1 or claim 2 or the microbial composition according to any one of claims 3 to 6 to seeds of a plant, to a seedling drench treatment of a plant and / or to a substrate in which the plant is grown.

10. The method of claim 9, wherein, The saline-alkali environment includes an environment of salt stress and / or alkali stress; and the plant includes at least one of corn, soybean and wheat.

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