Multifunctional phosphorus-solubilizing and potassium-releasing bacteria wzx-pkb-1 and application thereof

Abstract

This application relates to the field of agricultural microbiology technology, and in particular to a multifunctional phosphate-solubilizing and potassium-solubilizing bacterium WZX-PKB-1 and its applications. The multifunctional phosphate-solubilizing and potassium-solubilizing bacterium WZX-PKB-1 is classified and named... Priestia sp. WZX-PKB-1 was deposited at the Guangdong Provincial Center for Microbial Culture Collection on January 28, 2026, with accession number GDMCC NO: 67763. WZX-PKB-1 exhibits significant tolerance to multiple abiotic stresses, including high temperature, salinity, drought, and mixed heavy metals, and demonstrates effective phosphorus and potassium release capacity under these conditions, making it suitable for desert soil improvement and ecological restoration.

Description

Technical Field

[0001] This application relates to the field of agricultural microbiology technology, and in particular to a multifunctional phosphorus-solubilizing and potassium-solubilizing bacterium WZX-PKB-1 and its applications. Background Technology

[0002] Phosphorus and potassium are essential nutrients for plant growth and development, playing a vital role in promoting root growth, enhancing crop resistance, and maintaining ecosystem stability. However, in arid, semi-arid, and desertified regions, due to loose soil structure, low organic matter content, and enrichment of salts and alkaline ions, phosphorus and potassium in the soil mainly exist in the form of insoluble inorganic minerals. Although the total phosphorus / potassium content is high, the available phosphorus / potassium for plant use is severely insufficient.

[0003] Utilizing phosphorus- and potassium-solubilizing microorganisms to convert insoluble phosphorus and potassium in soil into forms that can be absorbed by plants is an important way to improve soil nutrient availability. Existing research shows that phosphorus- and potassium-solubilizing bacteria can promote the release of available phosphorus and potassium through the secretion of organic acids, chelating agents, and extracellular enzymes, showing promising applications in agricultural production and soil improvement. However, most existing phosphorus- and potassium-solubilizing bacteria have been screened and their performance tested under normal temperature, non-saline-alkali, and relatively abundant moisture conditions; their adaptability and functional stability in extreme environments such as saline-alkali, high temperature, and drought remain significantly insufficient.

[0004] In the existing technology, research on stress-tolerant phosphorus-solubilizing and potassium-solubilizing bacteria has mostly focused on screening for tolerance under single stress conditions. The main detection index is the growth of the strain, with less attention paid to the stable maintenance or enhancement of key properties such as phosphorus-solubilizing and potassium-solubilizing under combined stress conditions, thus limiting their application effect in actual desert soils.

[0005] Therefore, there is an urgent need for a phosphorus-solubilizing and potassium-solubilizing microbial resource that can be screened under combined adverse conditions such as salinity, high temperature and drought, so that it can still stably perform or even enhance its biomineralization performance in extreme environments, in order to meet the actual needs of desert soil improvement and ecological restoration. Summary of the Invention

[0006] This application provides a multifunctional phosphorus-solubilizing and potassium-solubilizing bacterium, WZX-PKB-1, and its applications to solve the problems in the prior art.

[0007] Firstly, a multifunctional phosphorus-solubilizing and potassium-solubilizing bacterium, WZX-PKB-1, is provided, and its classification is named as follows: Priestia sp. It was deposited at the Guangdong Provincial Center for Microbial Culture Collection on January 28, 2026, with accession number GDMCC NO: 67763.

[0008] Preferably, its 16S rRNA gene sequence is shown in SEQ ID NO:1.

[0009] Secondly, an application of the multifunctional phosphorus-solubilizing and potassium-solubilizing bacterium WZX-PKB-1 in any of the following aspects is provided: (1) Applications to enhance phosphorus and potassium solubilization capacity under environmental stress; (2) Application in promoting plant growth in desert soils; (3) Application in desert soil improvement, wherein the improvement includes at least one of increasing the organic matter content of desert soil and decreasing the soil pH; The environmental stresses include at least one of high temperature stress, salt stress, alkali stress, drought stress, and mixed heavy metal stress.

[0010] Preferably, the upper limit of the high temperature stress is 45°C.

[0011] Preferably, the NaCl concentration of the salt stress is 5-25%.

[0012] Preferably, the pH range of the alkaline stress is 9.0 to 13.0.

[0013] Preferably, the PEG6000 for drought stress is 6.0~14.0%.

[0014] Preferably, the mixed heavy metals include at least one of lead, cadmium, and chromium (VI).

[0015] The beneficial effects of the technical solution provided in this application include: This application provides a multifunctional phosphorus-solubilizing and potassium-solubilizing bacterium, WZX-PKB-1, and its applications. WZX-PKB-1 exhibits significant tolerance to multiple abiotic stresses, including high temperature, salinity, drought, and mixed heavy metals, and also demonstrates the ability to release effective phosphorus and potassium under these stresses. Desert regions typically experience adverse environmental factors such as salinity, high temperature, and drought, which can restrict the physiological and metabolic activities of microorganisms, thereby significantly reducing their phosphorus-solubilizing and potassium-solubilizing abilities. The multifunctional phosphorus-solubilizing and potassium-solubilizing bacterium WZX-PKB-1 provided in this application induces the construction of a "sugar-acid-phosphorylated sugar adaptive synergistic metabolic regulation response system," which has broad application prospects and economic value in areas such as desert soil improvement. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1SEM image of strain WZX-PKB-1 provided in this application; Figure 2 The colony morphology and lysis zone of strain WZX-PKB-1 provided in this application; Figure 3 The 16S rDNA alignment results for strain WZX-PKB-1 provided in this application; Figure 4 The results of salt tolerance test for strain WZX-PKB-1 provided in this application; Figure 5 The results of alkali resistance test for strain WZX-PKB-1 provided in this application; Figure 6 The results of drought resistance testing for strain WZX-PKB-1 provided in this application; Figure 7 The results of the mixed heavy metal tolerance test for strain WZX-PKB-1 provided in this application; Figure 8 A schematic diagram showing the phosphorus- and potassium-solubilizing properties of strain WZX-PKB-1 provided in this application under different conditions; Figure 9 Statistical results of metabolite classification for strain WZX-PKB-1 provided in this application; Figure 10 A schematic diagram of the colony morphology and lysis zone of strain WZX-PKB-1 provided in this application under initial non-stress conditions; Figure 11 A schematic diagram of the colony morphology and lysis zone of strain WZX-PKB-1 provided in this application under adverse stress conditions; Figure 12 Screening diagram of upregulated differential metabolites for strain WZX-PKB-1 provided in this application; Figure 13 A diagram illustrating the effectiveness of clustering technology for differential metabolite expression levels of strain WZX-PKB-1 provided in this application; Figure 14 A diagram illustrating the effectiveness of clustering techniques for the expression levels of key differentially expressed metabolites of strain WZX-PKB-1 provided in this application; Figure 15 This diagram illustrates the effect of strain WZX-PKB-1 provided in this application on the growth of Caragana korshinskii under different inoculum concentrations. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0019] See Figures 1-15 As shown, this application provides a multifunctional phosphorus-solubilizing and potassium-solubilizing bacterium WZX-PKB-1 and its applications.

[0020] This application provides a multifunctional phosphorus-solubilizing and potassium-solubilizing bacterium, WZX-PKB-1, which is classified and named as follows: Priestia sp. It was deposited on January 28, 2026 at the Guangdong Provincial Center for the Preservation of Microbial Cultures, located at 5th Floor, Building 59, No. 100 Xianlie Middle Road, Guangzhou, with accession number GDMCC NO: 67763.

[0021] The multifunctional phosphorus-solubilizing and potassium-solubilizing bacterium WZX-PKB-1 can tolerate salt stress (NaCl concentration: 5~25%), alkaline stress (pH 9.0~13.0), high temperature 45℃, drought stress (PEG6000: 6.0~14.0%), and mixed heavy metal stress (2.0~5.0 mg / L). Under the above adverse conditions, it not only has the ability to solubilize phosphorus and potassium, but also, under specific combined adverse conditions, the phosphorus-solubilizing and potassium-solubilizing performance of the multifunctional phosphorus-solubilizing and potassium-solubilizing bacterium WZX-PKB-1 is significantly higher than that under the initial culture conditions without adverse stress.

[0022] Both NaCl and PEG6000 are mass concentrations.

[0023] The following examples use some of the following culture media: Liquid culture medium (g / L): yeast extract 5.0, peptone 10.0, glucose 5.0, K2HPO4 1.5, (NH4)2SO4 0.5, MgSO4·7H2O 0.5, deionized water 1000 mL.

[0024] Inorganic phosphorus solid screening medium (g / L): (NH4)2SO4 0.5, MgSO4·7H2O 0.5, NaCl 0.2, Ca3(PO4)2 5, CaCO3 2.5, glucose 5.0, MnSO4 0.02, FeSO4 0.02, agar 20.0, deionized water 1000 mL.

[0025] Organophosphorus solid screening medium (g / L): (NH4)2SO4 0.5, MgSO4·7H2O 0.5, NaCl 0.2, CaCO3 0.5, glucose 5.0, MnSO4 0.02, FeSO4 0.02, lecithin 0.2, agar 20.0, deionized water 1000 mL, pH 7.2.

[0026] Potassium-solubilizing solid screening medium (g / L): sucrose 5.0, (NH4)2SO4 0.5, MgSO4·7H2O 0.5, Na2HPO4 1.5, potassium feldspar powder 5, agar 20.0, deionized water 1000 mL, pH 7.2.

[0027] Example 1: Enhanced strain isolation The strain was derived from rhizosphere soil samples of *Musa coccinea* grown in the Kubuqi Desert. 10 g of rhizosphere soil was weighed and passed through a sieve with approximately 1 mm aperture. It was then added to 100 mL of deionized water containing glass beads and allowed to stand for 20 min. The mixture was then shaken thoroughly for 30 min, heated in an 80℃ water bath for 20 min, and then rapidly cooled to obtain a soil suspension. 1 mL of this soil suspension was then serially diluted to 10⁻⁶ ppm. -1 10 -2 10 -3 10 -4 10 -5 10 -6 10 -7 Soil suspension at dilution.

[0028] Take 10 respectively -3 10 -4 10 -5 10 -6 0.1 mL of gradient soil suspension was evenly spread onto selected solid medium plates (selected solid medium refers to inorganic phosphorus-solubilizing solid screening medium, organic phosphorus-solubilizing solid screening medium, and potassium-solubilizing solid screening medium), and incubated upside down at 45°C for 48 h. Colonies that formed clear transparent zones and showed significant morphological differences were selected as target strains. Subsequently, the target strains were isolated and purified, inoculated onto selected solid medium, and incubated upside down at 45°C for 48 h. Colony morphology was observed and recorded.

[0029] Example 2: Strain Identification WZX-PKB-1 belongs to the Bacillus family, Priestella genus, and is a Gram-positive bacterium. (See also:) Figure 1 As shown, SEM electron microscopy revealed rod-like structures with a length of 4–5 μm and a diameter of 0.5–1 μm; see also... Figure 2 As shown, the colonies on the culture medium are slightly yellow, opaque, viscous, with regular edges and a raised center.

[0030] Physiological and biochemical identification was performed using biochemical identification tubes according to the "Handbook of Systematic Identification of Common Bacteria," and the results are shown in Table 1. The sequencing results were then compared with the 16S rDNA sequence in NCBI using BLAST, and the comparison results are shown below. Figure 3 As shown, this strain is related to ‌ Priestia sp. Bacteria in the genus *Bacteria* show a high degree of similarity, with a similarity of 99%, therefore they can be identified as... Priestia sp. It belongs to the bacteria.

[0031] Table 1. Physiological and biochemical identification results of strain WZX-PKB-1 Note: "+" represents a positive reaction, and "-" represents a negative reaction.

[0032] The 16S rRNA gene sequence of WZX-PKB-1 is shown in SEQ ID NO:1.

[0033] SEQ ID NO:1 .

[0034] Example 3 Salt Tolerance Test Sodium chloride was added to the liquid culture medium to prepare liquid culture media with sodium chloride concentrations of 5%, 10%, 15%, 20%, and 25%, with a volume of 100 mL. OD was inoculated at a rate of 5%. 600 The seed culture with a concentration of 1 was incubated at 45°C and 180 rpm until the stationary phase, and the OD was measured. 600 Values, with salt concentration on the x-axis and OD value on the y-axis. 600 Plot the values ​​on the ordinate.

[0035] WZX-PKB-1's salt resistance is as follows Figure 4As shown, WZX-PKB-1 was incubated at 45℃ and 180rpm for 24h, and the absorbance OD was measured. 600 As an indicator, the tolerance to salt stress (NaCl concentration: 5.0~25.0%).

[0036] Example 4 Alkali resistance test Liquid culture media with pH values ​​of 9, 10, 11, 12, and 13 were prepared, with a volume of 100 mL. OD culture media were inoculated at a rate of 5%. 600 The seed culture with a concentration of 1 was incubated at 45°C and 180 rpm until the stationary phase, and the OD was measured. 600 Values, plotted on pH and OD. 600 Plot the values ​​on the ordinate.

[0037] WZX-PKB-1's alkali resistance is as follows Figure 5 As shown, WZX-PKB-1 was incubated at 45℃ and 180rpm for 24h, and the absorbance OD was measured. 600 As an indicator, the tolerance to alkaline stress (pH: 9.0~13.0).

[0038] Example 5: Determination of drought resistance Add PEG6000 to the liquid culture medium to prepare liquid culture media with PEG6000 concentrations of 6%, 8%, 10%, 12%, and 14%, with a volume of 100 mL. Inoculate OD at a rate of 5%. 600 The seed culture with a concentration of 1 was incubated at 45°C and 180 rpm until the stationary phase, and the OD was measured. 600 Values, with PEG6000 concentration on the x-axis and OD value on the y-axis. 600 Plot the values ​​on the ordinate.

[0039] The drought resistance of WZX-PKB-1 is as follows: Figure 6 As shown, WZX-PKB-1 was incubated at 45℃ and 180rpm for 24h, and the absorbance OD was measured. 600 As an indicator, the drought stress tolerance (PEG6000: 6.0~14.0).

[0040] Example 6: Test of resistance to mixed heavy metals A mixed heavy metal solution (lead, cadmium, and chromium (VI)) with a concentration of 100 mg / L was prepared. The mixed heavy metal solution used Pb(NO3)2, CdCl2, and K2Cr2O7 as solvents. 2+ Cd 2+ Cr 6+The concentrations were all 100 mg / L. Mixed heavy metal solutions with actual concentrations of 2, 3, 4, and 5 mg / L were prepared in liquid culture medium; WZX-PKB-1 seed culture was inoculated at a 5% inoculum and incubated at 45℃ and 180 rpm for 24 h at OD... 600 Measure the absorbance below. For example... Figure 7 As shown: strain WZX-PKB-1 can tolerate mixed heavy metal (lead, cadmium, chromium (VI)) concentrations of 2-5 mg / L, with absorbance OD... 600 The value is 0.2~2.0.

[0041] Example 7: Determination of phosphorus and potassium solubility under non-stress and abiotic stress conditions (1) Method for testing soluble phosphorus content The water-soluble phosphorus content in the culture broth of strain WZX-PKB-1 was determined using the molybdenum antimony colorimetric method. The test strain's seed culture was inoculated at 1% in 50 mL of inorganic / organic phosphorus-free medium, with an uninoculated medium serving as a control. The cultures were incubated at 45℃ and 180 rpm for 120 h. All fermentation broth from each strain was transferred to centrifuge tubes and centrifuged at 4000 rpm for 20 min. The supernatant was then brought to a final volume of 50 mL. This process was repeated twice, with the precipitate discarded, and the supernatant brought to a final volume of 50 mL. The supernatants from both centrifugations were combined and used to determine the water-soluble phosphorus content in the fermentation broth.

[0042] Take 5 mL of the mixed supernatant, add 10 mL of 0.5 mol / L NaHCO3 solution, and dilute to 25 mL with distilled water. Finally, take 5.0 mL of molybdenum antimony colorimetric reagent, mix well, let stand for 30 min, and then perform colorimetric analysis at a wavelength of 720 nm to determine the OD value of the supernatant of the test strain. Then, obtain the soluble phosphorus content in the supernatant of the test strain according to the phosphorus standard curve.

[0043] (2) Method for testing soluble potassium content The sodium tetraphenylborate method was used to determine the water-soluble potassium content in the culture broth of the tested strains. The test strains were inoculated at 1% in 50 mL of potassium-solidifying solid screening medium, with a control group not inoculated. The cultures were incubated at 45℃ and 180 rpm for 120 h. All fermentation broth from each strain was transferred to centrifuge tubes and centrifuged at 4000 rpm for 20 min. The supernatant was then brought to a final volume of 50 mL. A second centrifugation was performed under the same conditions, discarding the precipitate, and the supernatant was brought to a final volume of 50 mL. The supernatants from the two centrifugations were combined and the water-soluble potassium content in the fermentation broth was determined.

[0044] Take 5 mL of the mixed supernatant, add 1 mL of formaldehyde-EDTA masking agent, shake well, and then add 1.0 mL of sodium tetraphenylborate solution to the colorimetric tube. Let it stand at room temperature for 15 min, shake well again, and then dilute to 25 mL with distilled water. Perform colorimetric analysis at a wavelength of 420 nm, and then obtain the soluble potassium content in the supernatant of the test strain according to the potassium standard curve.

[0045] (3) Phosphorus-solubilizing potassium content of the strain under initial non-stress / stress culture conditions The results of phosphorus-solubilizing and potassium-solubilizing performance tests of the strain under initial non-stress conditions and the aforementioned stress conditions, using potassium feldspar, calcium phosphate, and lecithin as inducers, are as follows: Figure 8 As shown in the figure. The initial non-abiotic stress conditions were: 45℃, 180rpm; the abiotic stress conditions were: 45℃, pH=9, NaCl concentration: 5%, PEG6000: 10%, heavy metal concentration: 2mg / L, 180rpm.

[0046] The phosphorus and potassium solubilization performance of WZX-PKB-1 was determined after fermentation at 45℃ and 180 rpm for 72 h under non-adverse stress conditions. When potassium feldspar was used as an inducer, the highest available potassium content was 41.64±0.173 mg / L; when calcium phosphate was used as an inducer, the highest available phosphorus content was 6.46±0.26 mg / L; and when lecithin was used as an inducer, the highest available phosphorus content was 0.78±0.04 mg / L.

[0047] The phosphorus and potassium solubilization performance of WZX-PKB-1 was determined after fermentation for 72 h under the above-mentioned abiotic stress conditions. When potassium feldspar was used as an inducer, the highest available potassium content was 79.78±2.17 mg / L, which was 38.14 mg / L higher than that under the initial conditions. When calcium phosphate was used as an inducer, the highest available phosphorus content was 19.16±1.8 mg / L, which was 12.7 mg / L higher than that under the initial conditions. When lecithin was used as an inducer, the highest available phosphorus content was 29.77±0.9 mg / L, which was 28.99 mg / L higher than that under the initial conditions. WZX-PKB-1 showed significant performance enhancement under abiotic stress conditions, specifically an improved phosphorus and potassium solubilization capacity under environmental stress.

[0048] Based on metabolomics analysis results, such as Figure 9 As shown, strain WZX-PKN-1 can produce a variety of organic metabolites, including 377 organic acid metabolites and 494 amino acids and their derivatives, indicating that this strain has a significant capacity for organic acid synthesis and secretion. These metabolites are rich in active functional groups such as -COOH, -OH, and -NH2, which can be utilized through acidification and chelation of Ca. 2+ Fe3+ Al 3+ Metal cations disrupt the structure of insoluble inorganic phosphorus / potassium minerals, thereby promoting the release of available phosphorus and potassium.

[0049] And, see also Figure 10 and Figure 11 As shown, Figure 10 The colony morphology and lysis zone of WZX-PKB-1 under initial non-stress conditions are shown. Figure 11 The colony morphology and lysis zone of WZX-PKB-1 under abiotic stress conditions are shown. It can be seen that WZX-PKB-1 exhibits a larger lysis zone under abiotic stress conditions, indicating good growth and strong tolerance under adverse conditions. Furthermore, based on the colony morphology... Figure 11 The strains grew more robustly under abiotic stress, indicating that their metabolic activity was not inhibited despite environmental stress.

[0050] It should be noted that, Figure 10 The culture medium used in the initial non-stressful conditions was liquid culture medium. Figure 11 The culture medium used for the test under abiotic stress conditions was a phosphorus-solubilizing and potassium-solubilizing screening medium. The phosphorus-solubilizing and potassium-solubilizing screening medium was based on liquid culture medium, and its components (g / L) were: yeast extract 5.0, peptone 10.0, glucose 5.0, K2HPO4 1.5, (NH4)2SO4 0.5, MgSO4·7H2O 0.5, NaCl: 5%, pH=9, PEG6000=10%, mixed heavy metals: 2mg / L, agar 20g / L, and deionized water 1000 mL.

[0051] Based on the differences in the expression of organic acid metabolites, the results of differential metabolite analysis and the "glucose-acid-phosphorylated sugar synergistic regulatory system" are as follows: Figure 12 As shown, it demonstrates the differential expression of organic acid metabolites. This invention found that under abiotic stress conditions, this strain can induce and significantly upregulate various functional organic acids and their derivatives, and synergistically achieve the complexation, dissolution, sustained release, and redistribution of inorganic phosphorus / potassium. The more significant organic acid metabolites, and those playing a crucial role in phosphorus and potassium solubilization, mainly include 3-amino-4-hydroxybenzoic acid, 4-acetamide butyric acid, D-glucosamine, dihydroferruvic acid, 4-O-β-D-glucuronic acid, 3-hydroxyphenylpropionic acid, D-glucuronic acid-1-phosphate, 2-O-caffeoyl hydroxycitric acid, etc. Figure 12 To illustrate the expression differences among all organic acid metabolites, only some key organic acid metabolites are listed here. These representative organic acids rapidly dissociate into organic acid anions and H+ ions driven by intracellular metabolic flux. +Protons are then actively pumped out of the extracellular matrix via a significantly upregulated ABC transporter system; in a high-salt, alkaline environment, secreted protons mediate the local acidolysis of inorganic phosphorus and potassium minerals; simultaneously, these metabolites are rich in -COOH, -OH, and -PO4. 2- The group, and the organic acid anion (R-COO-) as a powerful chelating agent, binds to the Ca on the surface of inorganic minerals through multi-site complexation. 2+ Fe 3+ And Al 3+ Once the metal cations form stable complexes, they disrupt the mineral lattice, triggering the release of the fixed PO4. 3- and K + .

[0052] The metabolic regulation mechanism revealed in this invention differs from existing technologies that rely solely on organic acid acidification for phosphorus and potassium solubilization. Instead, it exhibits stronger environmental adaptability and sustainability. Therefore, this strain significantly enhances phosphorus and potassium activation efficiency under stress conditions by constructing a "sugar-acid-phosphorylated sugar synergistic regulatory system," promoting the dissolution and release of inorganic phosphorus and potassium. The results indicate that abiotic stress does not inhibit the strain's metabolism but rather induces the activation of an "adaptive metabolic response system."

[0053] like Figure 13 and Figure 14 As shown, the metabolite profiles obtained under adverse stress conditions differed significantly from those of the control group under neutral conditions (initial non-adverse stress conditions). Figure 13 The graph is plotted based on the expression levels of all metabolites under adverse stress and neutral conditions, with red areas indicating significant upregulation. Figure 14 for Figure 13 Heatmap analysis of key metabolites provides a more intuitive view of the significant upregulation changes of these key metabolites under abiotic stress. Differentially expressed metabolites can be stably divided into two main categories, with their expression levels showing a consistent upregulation or downregulation trend under different conditions. The replicate samples showed good clustering under the same conditions, indicating that this metabolic regulation effect has good stability and reproducibility. This change in metabolic pattern is not a random fluctuation of individual metabolites, but rather a holistic adaptive metabolic regulatory network formed by the strain under abiotic stress, providing a stable metabolic basis for the enhanced phosphorus and potassium solubilization functions.

[0054] Example 8 Topsoil (0–30 cm) from the Kubuqi Desert region (N39°52′35″, E108°3′57″) within Ordos City was collected as test soil. After air drying, plant debris and gravel were removed, and the soil was sieved through a 2 mm sieve. The basic physicochemical properties of the soil were determined to be: pH 8.8–9.1, salt content approximately 0.3%, organic matter content approximately 1.06 g / kg, available phosphorus content approximately 3.1 mg / kg, and available potassium content approximately 41.5 mg / kg, classifying it as a typical nutrient-poor desert soil. The treated soil was autoclaved at 121 ℃ for 20 min to reduce interference from other microorganisms.

[0055] Strain strain WZX-PKB-1 was inoculated into liquid culture medium and cultured at 45℃ and 180 rpm for 12 h with shaking to obtain a logarithmic growth phase bacterial suspension. The viable cell count was determined to be 1×10⁻⁶. 8 CFU / mL. The effects of this strain on seed germination and seedling growth of Caragana korshinskii were determined using the dilution plate method and sand pot experiment. Two treatments were set up: a control group (CK) without bacterial inoculation and a treatment group inoculated with strain WZX-PKB-1.

[0056] Dilution plate method: 15 seeds of *Caragana korshinskii* were placed in each plate, and the experiment was repeated three times (experimental group 1, experimental group 2, and experimental group 3). In each experimental group, seven clean plates were selected, each lined with filter paper. 2 mL of bacterial suspension was added at different concentration gradients (0, 0.2, 0.4, 0.8, 1.2, 1.6, and 2.0 μg / mL, with 0 μg / mL serving as a control). 1 mL of distilled water was added every two days to maintain seed viability. The plates were incubated at 30℃ for 7 days, and the number of germinated seeds and germination rate were observed. A pipette was used each time bacterial suspension and distilled water were added, and a sterile pipette tip was used for each dilution to avoid cross-contamination.

[0057] The results of the determination of the number of germinations of Caragana korshinskii seeds are shown in Table 2.

[0058] Table 2. Results of the effect of different bacterial concentrations on the germination number of Caragana korshinskii seeds. Sand cultivation method: Seeds were soaked in bacterial solution for 2 days. Sand was placed in pots, ensuring the sand was fully saturated with water. Each pot contained 24 seeds, evenly divided into three groups of 8 replicates per group. Plastic pots with a diameter of 190×140×60mm were used, and 1 kg of treated desert soil was added to each pot. For the inoculation experimental group, 50 mL of bacterial solution was evenly added to each pot, resulting in a bacterial concentration of approximately 10 in the soil. 7CFU / g soil; the control group received an equal volume of sterile saline. After inoculation, the soil was thoroughly mixed and allowed to stand for 3 days to facilitate bacterial colonization. The pots were then placed on plant racks under continuous light and stored at room temperature; simulating desert cultivation, the plants were irrigated evenly every two days to ensure adequate water absorption, and plant growth was recorded. After 15 days of cultivation, plant growth indicators, including plant height, root length, aboveground fresh weight, and belowground fresh weight, were measured. Simultaneously, soil samples were collected from the pots to determine the available phosphorus and potassium content. Each treatment was performed in triplicate, and data are expressed as mean ± standard deviation.

[0059] See Table 3 for the growth results and growth indicators of Caragana korshinskii. Figure 15 As shown.

[0060] Table 3. Effects of different bacterial concentrations on the growth of Caragana korshinskii. The growth indicators of Caragana korshinskii are shown in Table 4.

[0061] Table 4. Growth Indicators of Caragana korshinskii The effects of desert soil improvement are shown in Table 5.

[0062] Table 5 Desert Soil Improvement Indicators The experimental results showed that, compared with the uninoculated control group, inoculation with strain WZX-PKB-1 significantly promoted the growth of Caragana korshinskii plants. The aboveground plant height of the control group was approximately 0.2 cm, while the inoculated plant height reached 4.7 cm; root length increased from 1.7 cm to 5.6 cm. Aboveground fresh weight increased from 0.005 g to 0.0763 g; underground fresh weight increased from 0.002 g to 0.0096 g; indicating that Caragana korshinskii inoculated with the strain had better growth capacity in desert soil (pH=9.1). See Table 3 for further details. Figure 15 As shown, the experimental group inoculated with strain WZX-PKB-1 promoted the growth of Caragana korshinskii in desert soil. It should be noted that the Caragana korshinskii seeds used in this experiment are natural plant materials, and their germination process is easily affected by individual seed differences and microenvironmental factors. Even under the control conditions without inoculation, there may still be some fluctuation between different replicates, which is a common phenomenon in plant physiology and seed germination experiments. In Table 3, the average number of Caragana korshinskii growths in the control group was 1. Compared with the control group, each experimental group showed a stable and consistent promoting trend at specific bacterial concentrations (0.4~1.2 μg / mL), and the results of multiple replicates showed good consistency, indicating that the effect of the strain was significant and reproducible.

[0063] Meanwhile, the soil nutrient determination results in Table 5 show that after inoculation with strain WZX-PKB-1, the available phosphorus content in the soil increased from 3.1 mg / kg to 45.1 mg / kg, the available potassium content increased from 41.5 mg / kg to 151.7 mg / kg, the organic matter content increased from 1.06 g / kg to 16.7 mg / kg, and the alkaline environment of the desert soil was significantly improved.

[0064] The above results indicate that strain WZX-PKB-1 can significantly increase the content of available phosphorus and potassium in desert soil environments, thereby improving soil nutrient status and promoting root development and aboveground growth, demonstrating good desert soil improvement and plant growth-promoting effects. Therefore, this strain has good application potential in desert soil improvement and agricultural production in arid regions.

[0065] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A multifunctional phosphorus-solubilizing and potassium-solubilizing bacterium, WZX-PKB-1, characterized in that, Its classification is named Priestia sp. It was deposited at the Guangdong Provincial Center for Microbial Culture Collection on January 28, 2026, with accession number GDMCC NO: 67763.

2. The multifunctional phosphorus-solubilizing and potassium-solubilizing bacterium WZX-PKB-1 as described in claim 1, characterized in that, Its 16S rRNA gene sequence is shown in SEQ ID NO:

1.

3. The application of the multifunctional phosphorus-solubilizing and potassium-solubilizing bacterium WZX-PKB-1 as described in any one of claims 1 to 2 in any of the following: (1) Applications to enhance phosphorus and potassium solubilization capacity under environmental stress; (2) Application in promoting plant growth in desert soils; (3) Application in desert soil improvement, wherein the improvement includes at least one of increasing the organic matter content of desert soil and decreasing the soil pH; The environmental stresses include at least one of high temperature stress, salt stress, alkali stress, drought stress, and mixed heavy metal stress.

4. The application as described in claim 3, characterized in that: The upper limit of the high temperature stress is 45°C.

5. The application as described in claim 3, characterized in that: The concentration of NaCl under salt stress is 5-25%.

6. The application as described in claim 3, characterized in that: The pH range of the alkaline stress is 9.0 to 13.

0.

7. The application as described in claim 3, characterized in that: The PEG6000 for drought stress ranges from 6.0% to 14.0%.

8. The application as described in claim 3, characterized in that: The mixed heavy metals include at least one of lead, cadmium, and chromium (VI).

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