Acinetobacter solani BP2 and related application thereof

Abstract

The invention belongs to the technical field of microorganisms, and in particular relates to an Acinetobacter solani BP2 strain and a related application of the Acinetobacter solani BP2 strain. The strain is preserved in China General Microbiological Culture Collection Center (CGMCC) on December 4, 2025, the address is Institute of Microbiology, Chinese Academy of Sciences, No.3, No.1 Yard, West Beichen Road, Chaoyang District, Beijing, and the preservation number is CGMCC No.36892. The acinetobacter soilis BP2 is found to have multiple growth promoting functions of efficiently secreting indoleacetic acid, dissolving insoluble organic phosphorus and inorganic phosphorus, fixing nitrogen and producing siderophores at the same time; when applied to the plant growth process, the seed germination and growth of crops can be remarkably promoted. According to the invention, excellent strain resources are provided for soil nutrient activation and plant growth promotion, and a foundation is laid for development of efficient microbial agents.

Description

Technical Field

[0001] This invention belongs to the field of microbial technology, specifically relating to a strain of Acinetobacter BP2 in soil and its related applications. Background Technology

[0002] In agricultural production, long-term irrational farming and land use have led to a decline in soil quality, with widespread problems such as low nutrient content and severe structural obstacles. This seriously affects crop growth and development, becoming a key factor restricting crop yield increases. While traditional fertilizers can quickly replenish nutrients in the short term, they suffer from excessive input, severe nutrient fixation, and low utilization rates, and can also cause a series of derivative problems such as environmental pollution and ecological imbalance. Therefore, developing a green and efficient method to effectively improve the nutrient levels of obstacle soils and promote crop growth has become an important task urgently needing to be addressed in promoting sustainable agricultural development.

[0003] In recent years, plant growth-promoting bacteria have attracted widespread attention due to their multiple functions in promoting crop growth. These microorganisms can effectively improve the rhizosphere microenvironment and enhance crop nutrient absorption and utilization efficiency through direct or indirect mechanisms such as activating soil nutrients (e.g., nitrogen fixation, phosphorus solubilization, potassium solubilization) and secreting plant hormones (e.g., auxins, gibberellins). Specifically, growth-promoting bacteria regulate crop physiological processes by secreting indoleacetic acid (IAA), promoting cell growth, division, and differentiation, thereby stimulating root development and stem elongation. They can also convert insoluble phosphorus and potassium into plant-available forms by secreting organic acids, phosphatases, and phytases, thereby increasing the available phosphorus and potassium content in the soil and enhancing plant absorption and utilization of these nutrients. Furthermore, some growth-promoting bacteria produce siderophores that can specifically chelate iron in the soil, increasing the available iron content and promoting iron absorption by plants. Therefore, plant growth-promoting bacteria can serve as a high-quality strain resource for developing microbial fertilizers, increasing crop yields while reducing reliance on chemical fertilizers.

[0004] Currently, patents have reported various strains with growth-promoting functions, involving multiple genera such as Bacillus and Pseudomonas. Among Acinetobacter strains, Acinetobacter calcoaceticus and Acinetobacter junii have been reported to have certain growth-promoting potential. However, there are no publicly available reports on Acinetobacter soli possessing multiple growth-promoting functions, including efficient secretion of indoleacetic acid, dissolution of organic and inorganic phosphorus, nitrogen fixation, and synthesis of siderophores. Summary of the Invention

[0005] In view of this, the present invention screened and obtained a strain of *Acinetobacter soli* BP2 from albic soil in the Sanjiang Plain. This bacterium possesses the functions of efficiently secreting IAA, dissolving insoluble organic and inorganic phosphorus, fixing nitrogen, promoting growth by producing iron carriers, and effectively promoting maize seed germination and growth. Therefore, this strain has broad application prospects in the development of microbial fertilizers and plant growth promotion.

[0006] To achieve the above objectives, the present invention is implemented through the following solution:

[0007] This invention provides a strain of Acinetobacter soli BP2 isolated from albic soil, which is deposited at the China General Microbiological Culture Collection Center, with accession number CGMCC No. 36892.

[0008] The 16S rRNA sequence of Acinetobacter BP2 is shown in SEQ ID NO: 1:

[0009]

[0010] The *Acinetobacter BP2* strain provided by this invention is a Gram-negative bacterium. After growing on LB solid medium for 48 h, the colonies are pale yellow, round, slightly convex, with a smooth surface and neat, transparent edges.

[0011] The present invention also provides a microbial preparation comprising the above-mentioned Acinetobacter BP2 and / or its culture;

[0012] The concentration of *Acinetobacter spp.* BP2 and / or its culture in the microbial preparation is 2.1 × 10⁻⁶. 8 CFU / mL;

[0013] In this invention, the culture is a substance obtained by culturing Acinetobacter BP2 in a bacterial culture medium, including the strain itself and its fermentation metabolites;

[0014] The method for preparing the microbial agent includes: culturing *Acinetobacter spp.* BP2 in a liquid culture medium, and obtaining the microbial agent after centrifugation and solvent resuspension of the culture.

[0015] The preferred culture temperature is 30℃, the preferred culture time is 48 h, the preferred liquid culture medium is LB liquid culture medium, and the solvent is PBS buffer.

[0016] The microbial preparations provided by this invention also have some or all of the following functions: efficient secretion of IAA, dissolution of insoluble organic and inorganic phosphorus, nitrogen fixation, secretion of siderophores, promotion of plant seed germination (such as increasing germination potential and / or germination rate), and promotion of plant growth (such as increasing plant root length and shoot length).

[0017] This invention provides the application of the above-mentioned Acinetobacter BP2 in soil or the above-mentioned microbial preparation in promoting plant growth and / or germination;

[0018] The soil Acinetobacter BP2 or microbial preparations containing soil Acinetobacter BP2 and soil Acinetobacter BP2 culture provided by the present invention promote plant growth and / or germination by secreting IAA, dissolving different types of insoluble phosphorus, fixing nitrogen and secreting siderophores.

[0019] In practical applications of this invention, the plant includes corn;

[0020] The promotion of plant germination includes, in particular, promoting the growth of corn seed roots and shoots.

[0021] This invention provides the application of the above-mentioned Acinetobacter BP2 or the above-mentioned microbial preparation in the preparation of indoleacetic acid.

[0022] This invention provides the application of the above-mentioned Acinetobacter BP2 or the above-mentioned microbial preparation in the preparation of phosphate-solubilizing agents, characterized in that the substances dissolved by the phosphate-solubilizing agent include organic phosphorus and inorganic phosphorus;

[0023] In practical applications of this invention, the organic phosphorus and inorganic phosphorus specifically refer to insoluble organic phosphorus and inorganic phosphorus, and are further limited to calcium phosphate, lecithin and calcium phytate.

[0024] This invention provides the application of the above-mentioned Acinetobacter BP2 in soil or the above-mentioned microbial preparation in nitrogen fixation.

[0025] This invention provides the application of the above-mentioned Acinetobacter BP2 in soil or the above-mentioned microbial preparation in secreting siderophores.

[0026] Compared with existing technologies, the present invention has the following advantages:

[0027] 1. The soil Acinetobacter BP2 provided by this invention was isolated from albic soil, a typical obstacle soil in Northeast China. It has a natural adaptability and colonization advantage to compacted and barren soil environments, and has great application potential.

[0028] 2. The *Acinetobacter BP2* strain provided by this invention has multiple growth-promoting functions, including efficient secretion of indoleacetic acid, dissolution of insoluble organic and inorganic phosphorus, nitrogen fixation, and iron production. These multiple growth-promoting mechanisms work synergistically, resulting in a more significant and stable growth-promoting effect on plants.

[0029] 3. This invention provides a novel strain / inoculant that can effectively promote the germination of corn seeds and the growth and development of buds, taproots, and lateral roots, and has direct application value in improving crop yield and quality.

[0030] Biological Preservation Instructions

[0031] Acinetobacter soli BP2 was deposited on December 4, 2025, at the China General Microbiological Culture Collection Center (CGMCC), Institute of Microbiology, Chinese Academy of Sciences, No. 3, No. 1 Beichen West Road, Chaoyang District, Beijing, with accession number CGMCC No. 36892. Attached Figure Description

[0032] Figure 1 This is a colony morphology diagram of Acinetobacter BP2 on LB medium.

[0033] Figure 2 Gram staining image of Acinetobacter BP2 in soil;

[0034] Figure 3 Phylogenetic tree diagram of Acinetobacter BP2 in soil;

[0035] Figure 4 A schematic diagram showing the results of the ability of Acinetobacter BP2 in soil to secrete indoleacetic acid.

[0036] Figure 5 This is a schematic diagram showing the formation of phosphorus-solubilizing zones by *Acinetobacter BP2* on *Monkina* inorganic phosphorus solid medium, *Monkina* organic phosphorus solid medium, and calcium phytate organic phosphorus solid medium, all with calcium phosphate, lecithin, and calcium phytate as phosphorus sources.

[0037] Figure 6 Quantitative determination of the phosphorus-solubilizing ability of Acinetobacter BP2 in soil;

[0038] Figure 7 The growth status of Acinetobacter BP2 on Ashby nitrogen-free solid medium;

[0039] Figure 8 A schematic diagram showing the formation of iron chelate rings by *Acinetobacter BP2* on CAS detection medium;

[0040] Figure 9 The germination status of maize seeds treated with Acinetobacter BP2 in soil after 7 days of culture;

[0041] Figure 10 Germination potential, germination rate, root length, and shoot length of maize seeds treated with Acinetobacter BP2. Detailed Implementation

[0042] This invention aims to provide a strain of *Acinetobacter spp.* BP2 and its related applications. The invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The following embodiments are merely a few specific examples of this invention, not all examples, and are not intended to limit the scope of the claimed invention. Unless otherwise specified, the instruments and equipment involved in the following embodiments are conventional instruments and equipment; the biochemical reagents and raw materials involved are commercially available products; and the experimental methods involved are conventional methods.

[0043] The culture medium used in the following examples:

[0044] Monkina Inorganic Phosphorus Culture Medium:

[0045] Ingredients: 10 g glucose, 0.5 g yeast extract, 5 g Ca3(PO4)2, 0.5 g (NH4)2SO4, 0.3 g NaCl, 0.3 g MgSO4·7H2O, 0.3 g KCl, 0.03 g MnSO4·H2O, 0.03 g FeSO4·7H2O, 1000 mL distilled water, pH 7.0; if using a solid culture medium, add 15 g agar.

[0046] Monkina Organic Phosphorus Medium:

[0047] Ingredients: 10 g glucose, 0.5 g (NH4)2SO4, 0.3 g NaCl, 0.3 g MgSO4·7H2O, 0.3 g KCl, 0.03 g MnSO4·H2O, 0.03 g FeSO4·7H2O, 5 g CaCO3, 2 g lecithin, 1000 mL distilled water, pH 7.0; if using a solid culture medium, add 15 g agar.

[0048] Calcium phytate organic phosphorus culture medium:

[0049] Ingredients: 10 g glucose, 0.5 g (NH4)2SO4, 0.3 g NaCl, 0.3 g KCl, 0.03 g FeSO4·7H2O, 0.03 g MnSO4·4H2O, 0.3 g MgSO4·7H2O, 0.4 g yeast extract, 2 g calcium phytate, pH 7.0; if using a solid culture medium, add 15 g agar.

[0050] Ashby nitrogen-free solid culture medium:

[0051] Mannitol 10 g, KH2PO4 0.2 g, MgSO4 0.2 g, NaCl 0.2 g, CaSO4 0.1 g, CaCO3 5 g, distilled water 1000 mL, pH 7.0.

[0052] Chromium Azure S (CAS) detection medium:

[0053] CAS 0.0605 g, hexadecyltrimethylammonium bromide (HDTMA) 0.0729 g, FeCl3·6H2O 0.002645 g, NaH2PO4·2H2O 0.29525 g, Na2HPO4·12H2O 1.2135 g, NH4Cl 0.125 g, KH2PO4 0.0375 g, NaCl 0.0625 g, agar 9 g, distilled water 1000 mL, pH 6.8±0.2.

[0054] MKB liquid culture medium:

[0055] Casein amino acids 5 g, K2HPO4 2.5 g, MgSO4·7H2O 2.5 g, glycerol 15 mL, distilled water 1000 mL, pH 7.0~7.2.

[0056] LB medium:

[0057] 10 g tryptone, 5 g yeast extract, 10 g sodium chloride, 1000 mL distilled water, pH 7.0~7.2.

[0058] Example 1

[0059] Screening, isolation, and purification of Acinetobacter BP2 in soil

[0060] Topsoil samples (0-20 cm) were collected from albic soil distribution areas in the Sanjiang Plain where maize has been continuously cropped. The samples were placed in sterile bags, brought back to the laboratory, and stored at 4°C. 10 g of the albic soil sample was weighed and placed in a 250 mL Erlenmeyer flask containing 90 mL of sterile water (containing glass beads). The flask was shaken at 30°C and 200 rpm for 30 min, then allowed to stand to obtain a soil suspension. 1 mL of the soil suspension was added to 9 mL of sterile water and mixed thoroughly to prepare 10... -2 Concentration dilution solution, obtained by this method, 10 -3 10 -4 10 -5 10 -6 10 -7 10 -8 The soil dilution solution was applied using a dilution-coating method, with 10 samples taken from each sample. -4 ~10 -8 Gradual dilutions of 100 μL were spread onto Monkina inorganic phosphorus solid medium and incubated at 30°C for 2 days. Colonies with good growth and clear phosphate-solubilizing zones were selected and repeatedly streaked onto Monkina inorganic phosphorus solid medium for purification. Finally, a strain that stably dissolved insoluble inorganic phosphorus was obtained and designated as BP2 for subsequent studies.

[0061] Example 2

[0062] Identification and preservation of Acinetobacter BP2 in soil

[0063] 1. Morphological identification of strains

[0064] The strain BP2 isolated and purified in Example 1 was inoculated onto LB solid medium and cultured at 30°C for 48 h. BP2 colonies were observed to be pale yellow, round, slightly convex, with a smooth surface and neat, transparent edges. Figure 1 Simultaneously, Gram staining of strain BP2 was performed using a Gram staining kit, indicating that the strain was a Gram-negative bacterium. Figure 2 ).

[0065] 2. Molecular identification of strains

[0066] One loopful of BP2 slant bacteria was inoculated into LB liquid medium and cultured at 30°C and 180 rpm with shaking until the logarithmic growth phase (OD=1.0). The bacterial cells were then collected by centrifugation, and total DNA was extracted using a DNA extraction kit.

[0067] PCR products were obtained by PCR amplification using the universal bacterial primers 27F (5'-AGAGTTTGATCCTGGCTCAG-3', SEQ ID NO: 2) and 1492R (5'-TACCTTGTTACGACTT-3', SEQ ID NO: 3).

[0068] PCR amplification system: PCR Mix 21 µL, Primer F (5 pmol / µL) 1 µL, Primer R (5 pmol / µL) 1 µL, DNA template 2 µL.

[0069] The PCR amplification conditions were as follows: 96 °C pre-denaturation for 5 min; 96 °C denaturation for 30 s, 56 °C annealing for 30 s, 72 °C extension for 1 min, 35 cycles; 72 °C extension for 5 min.

[0070] Three µL of PCR product was collected and validated by 2% agarose gel electrophoresis. The amplified product was then sent to BGI Genomics for 16S rDNA sequencing analysis. Based on the sequencing results, homology comparison was performed using the NCBI database to obtain related strains with high similarity. Finally, a phylogenetic tree was constructed using MEGA 11.

[0071] The results are as follows Figure 3 As shown, the strain BP2 screened in this invention belongs to the genus Acinetobacter and is most closely related to Acinetobacter soli, with a homology of over 99%. Based on morphological observation and Gram staining results, BP2 was identified as Acinetobacter soli and named Acinetobacter soli BP2 (i.e., soil Acinetobacter BP2).

[0072] The 16S rDNA sequence of Acinetobacter BP2 is shown in SEQ ID NO: 1:

[0073]

[0074] 3. Preservation of bacterial strains

[0075] Acinetobacter soli BP2 was deposited on December 4, 2025, at the China General Microbiological Culture Collection Center (CGMCC) with accession number CGMCC No. 36892.

[0076] Example 3

[0077] Detection of the ability of Acinetobacter BP2 in soil to secrete indoleacetic acid

[0078] The Salkowski colorimetric method was used, based on color reaction and OD (Oxygen Demand). 530 The value was used to analyze the ability of strain BP2 to secrete IAA. In short, the activated (OD) 600 Strain BP2 (L-tryptophan concentration = 1.0) was inoculated at a 1% inoculum into LB liquid medium containing 100 mg / L L-tryptophan and cultured at 30 °C with shaking at 180 r / min for 6 days. On days 1, 2, 4, and 6, bacterial culture was collected, centrifuged at 10000 rpm for 5 min, and 2 mL of the supernatant was taken. An equal volume of Salkowski colorimetric solution was added, mixed well, and allowed to stand in the dark for 30 min. The color change was then observed. A red color indicated a positive result, suggesting the strain had the ability to secrete indoleacetic acid; otherwise, it did not. Simultaneously, the OD value at a wavelength of 530 nm was measured (OD0.0). 530 The amount of IAA produced by the strain was calculated by plotting a standard curve using IAA standard solution.

[0079] Qualitative analysis showed that strain BP2 could elicit a red reaction and had the ability to secrete IAA; quantitative results indicated that the maximum IAA production of the strain was 74.92 mg / L, and that the IAA production showed a trend of "first increasing and then decreasing" with increasing culture time, reaching a peak on day 4. This may be related to the physiological characteristics and metabolic regulation mechanism of the strain. Figure 4 Strain BP2 is a highly efficient IAA-producing strain with strong potential to promote crop growth, providing an important theoretical basis for its application as a plant growth-promoting bacterium.

[0080] Example 4

[0081] Detection of the growth-promoting ability of Acinetobacter BP2 in soil

[0082] 1. Determination of the ability of *Acinetobacter BP2* to dissolve insoluble inorganic and organic phosphorus.

[0083] The phosphorus-solubilizing ability of the strain was qualitatively assessed using the phosphate-solubilizing zone method. Activated (OD) samples were collected. 600=1.0) 10 μL of strain BP2 was inoculated onto Monkina inorganic phosphorus solid medium, Monkina organic phosphorus solid medium, and calcium phytate organic phosphorus solid medium, respectively, using calcium phosphate, lecithin, and calcium phytate as phosphorus sources. After incubation at 30 ℃ for 7 days, the diameter of the clear zone (D) and the colony diameter (d) were measured, and the D / d value was used as the phosphorus solubility index of the strain to preliminarily assess the phosphorus solubility of the strain.

[0084] The phosphate-solubilizing ability of the strain was quantitatively assessed using a liquid culture method. The activated (OD) 600 =1.0) strain BP2 was inoculated at a 1% inoculum into sterilized Monkina inorganic phosphorus liquid medium and calcium phytate organic phosphorus liquid medium, and cultured at 30 ℃ with shaking at 180 rpm for 6 days. Simultaneously, uninoculated inorganic phosphorus and calcium phytate organic phosphorus media were used as blank controls, and each treatment was performed in triplicate. On days 1, 2, 4, and 6 of culture, bacterial suspensions were collected, centrifuged at 10000 rpm for 5 min, and the supernatant was used to determine pH and soluble phosphorus content.

[0085] The results showed that strain BP2 exhibited a broad-spectrum and highly efficient phosphorus-solubilizing ability for both poorly soluble inorganic and organic phosphorus. It formed distinct clear zones on all three culture media using calcium phosphate, lecithin, and calcium phytate as the sole phosphorus source, with phosphorus solubility indices of 2.58±0.133, 2.23±0.019, and 3.06±0.134, respectively. Figure 5 This indicates that the strain has a good dissolving effect on different types of insoluble phosphorus.

[0086] Further analysis revealed that strain BP2 had a maximum solubility of 337.32 mg / L for insoluble calcium phosphate. The amount of phosphorus solubilized showed a trend of "increasing first and then decreasing" with increasing culture time, and was negatively correlated with pH changes. This indicates that the strain secretes organic acids during cultivation, thereby driving the dissolution of insoluble phosphorus. Furthermore, strain BP2 had a maximum solubility of 230.62 mg / L for insoluble calcium phytate, and the amount of phosphorus solubilized showed little change with prolonged culture time. In summary, strain BP2 possesses a strong ability to dissolve insoluble phosphorus and has great potential for improving phosphorus availability in albic soils.

[0087] 2. Determination of nitrogen fixation capacity of Acinetobacter BP2 in soil

[0088] Take activated (OD) 600 =1.0) 10 μL of strain BP2 was inoculated onto Ashby nitrogen-free solid medium and incubated at 30 ℃ for 4 days. Then it was subcultured into fresh medium, and this subculture operation was repeated 4 times. The nitrogen fixation characteristics of the strain were determined by observing the colony growth.

[0089] like Figure 7As shown, after four subcultures, strain BP2 grew well on Ashby nitrogen-free solid medium and formed large colonies, indicating that the strain has a stable nitrogen-fixing ability.

[0090] 3. Determination of the siderophore-producing capacity of *Acinetobacter BP2* in soil

[0091] Take activated (OD) 600 =1.0) 10 μL of strain BP2 was spot-inoculated onto CAS detection medium and incubated in a 30 ℃ constant temperature incubator for 7 days. Observe whether orange iron chelate rings are produced on the plate. If so, it indicates that the strain has the ability to secrete vectors.

[0092] Activated (OD) 600 =1.0) Strain BP2 was inoculated at a 1% inoculum into sterilized MKB liquid medium and cultured at 30℃ and 180 rpm for 6 days with shaking. After centrifugation at 10000 rpm for 5 min, 2 mL of the supernatant was taken and thoroughly mixed with an equal volume of CAS detection solution, and allowed to stand in the dark for 30 min. The absorbance (As) of the mixture at 630 nm was measured using a spectrophotometer, with the absorbance measured on uninoculated MKB liquid medium as a control (Ar). The ability of the strain to secrete siderophores was assessed by the relative content of siderophores and the As / Ar ratio. Generally, it is considered that for every 0.2 decrease in As / Ar, a "+" sign is added, and the smaller the As / Ar ratio, the stronger the ability of the strain to produce siderophores. The formula for the relative content of siderophores is as follows:

[0093]

[0094] The results showed that strain BP2 could produce iron chelation zones on CAS detection plates. Figure 8 Quantitative analysis showed that the relative content of its secreted siderophores was 22.11%±0.032, and the As / Ar value was 0.779±0.031. Therefore, the siderophore production capacity of strain BP2 was determined to be "+", indicating that the strain has the ability to secrete siderophores.

[0095] Example 5

[0096] The effect of Acinetobacter BP2 on maize seed germination

[0097] Preparation of bacterial suspension: The purified strain BP2 was inoculated into LB liquid medium and cultured overnight at 30 ℃ and 180 r / min. After the culture was completed, the culture was centrifuged at 8000 rpm for 5 min, the bacterial cells were collected, washed twice with sterile water and resuspended, and the OD of the bacterial suspension was adjusted. 600 Approximately 1.0, for backup.

[0098] Disinfection and germination of corn seeds: Select plump, healthy and uniform-sized "Zhengdan 958" corn seeds, disinfect them with 75% ethanol for 5 minutes, soak them in 1% sodium hypochlorite solution for 5 minutes, and finally rinse them several times with sterile water.

[0099] Corn seed germination test: Surface-sterilized corn seeds were immersed in sterile water and germinated at 30 ℃ for 4 h. Using sterile forceps, the germinated corn seeds were transferred to germination boxes pre-lined with moistened filter paper (containing 8 mL of bacterial suspension), with 15 seeds placed in each dish. Another sheet of sterile filter paper was then placed on top, and 8 mL of bacterial suspension was added to the filter paper to completely moisten it. Corn seeds not treated with the bacterial suspension were immersed in sterile water as a control. The germination boxes were placed in a constant temperature incubator at 25 ℃ for 7 days. On the second day of incubation, the top filter paper was removed, and a suitable amount of sterile water was added periodically to maintain humidity. The number of germinated corn seeds was observed on the third and seventh days of germination, and the root length and shoot length were measured on the seventh day. The germination potential and germination rate of the corn seeds were calculated using the following formulas.

[0100]

[0101]

[0102] The results showed that *Acinetobacter BP2* significantly promoted the germination and growth of maize seeds. Figure 9 and Figure 10 Maize seeds treated with *Acinetobacter BP2* showed germination potential and germination rate of 62.22% and 84.44%, respectively, significantly higher than the control (CK) by 8.89% and 17.78% (p < 0.05), indicating that *Acinetobacter BP2* can significantly promote maize seed germination. Furthermore, the taproot length and shoot length of maize seeds also increased significantly under *Acinetobacter BP2* treatment (p < 0.05), reaching 23.63 cm and 13.16 cm, respectively. Simultaneously, the length and number of lateral roots also increased significantly, further demonstrating that the application of *Acinetobacter BP2* helps promote the growth of maize seed roots and shoots.

[0103] In conclusion, *Acinetobactersoli* BP2, screened from albic soils where maize has been grown monoculture for a long time, is a superior growth-promoting bacterium with multiple functions. This strain not only efficiently produces IAA (inorganic phosphorus) and dissolves inorganic and organic phosphorus, but also possesses nitrogen fixation and siderophore production capabilities, significantly promoting maize seed germination and growth. This strain shows promising application prospects and widespread value in the biological improvement of obstacle soils, and can play an important role in improving soil fertility and crop yield.

[0104] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description and ideas, and it is neither necessary nor possible to exhaustively describe all implementation methods here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A strain of *Acinetobacter spp.* isolated from albic soil ( Acinetobacter soli BP2, characterized in that, The *Acinetobacter BP2* strain is deposited at the China General Microbiological Culture Collection Center (CGMCC), with accession number CGMCC No. 36892.

2. The *Acinetobacter BP2* of soil according to claim 1, characterized in that, The 16S rRNA sequence of Acinetobacter BP2 is shown in SEQ ID NO:

1.

3. A microbial preparation, characterized in that, The microbial preparation includes the *Acinetobacter BP2* of claim 1 and / or its culture; The concentration of *Acinetobacter spp.* BP2 and / or its culture in the microbial preparation is 2.1 × 10⁻⁶. 8 CFU / mL.

4. The use of the *Acinetobacter BP2* of claim 1 or the microbial preparation of claim 3 in promoting plant growth and / or germination.

5. The application according to claim 4, characterized in that, The plant mentioned includes corn.

6. The use of the *Acinetobacter BP2* of claim 1 or the microbial preparation of claim 3 in the preparation of indoleacetic acid.

7. The application of the *Acinetobacter BP2* of claim 1 or the microbial preparation of claim 3 in the preparation of phosphate-solubilizing agents, characterized in that, The phosphorus-soluble preparation dissolves substances including organic phosphorus and inorganic phosphorus.

8. The application of the *Acinetobacter BP2* of claim 1 or the microbial preparation of claim 3 in nitrogen fixation.

9. The use of the *Acinetobacter BP2* of claim 1 or the microbial preparation of claim 3 in secreting siderophores.

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