Serratia marcescens XJ108 and application thereof

Abstract

The invention relates to serratia marcescens XJ108 and application thereof, and belongs to the technical field of microorganisms. The serratia marcescens XJ108 is preserved in the China General Microbiological Culture Collection Center (CGMCC), the preservation number is CGMCC No.29557, the preservation date is January 10, 2024, and the address of the preservation institution is No.3, Yard 1, Beichen West Road, Chaoyang District, Beijing. The invention also provides application of the serratia marcescens XJ108 in acid environment, alkaline environment, high salinity environment and high chemical fertilizer environment soil tolerance and plant growth promotion. The serratia marcescens XJ108 provided by the invention has certain biological safety; meanwhile, the plant growth promoting function is achieved; and various extreme soil environments can be tolerated.

Description

Technical Field

[0001] The invention relates to the technical field of microorganisms, and in particular to a strain of Serratia marcescens XJ108 and application thereof. Background Art

[0002] Acidic soil is a general term for soil with a pH value less than 7. It includes brick red soil, red soil, red soil, yellow soil and dry red soil. In areas with high temperature and heavy rain, and hot and humid seasons, the weathering and soil formation of the soil are strong, and the leaching of elements in the environment is strong, resulting in a decrease in base saturation, and the pH is generally between 4.5 and 6. Acidic soil is mainly distributed in tropical and subtropical areas with abundant rainfall.

[0003] Saline soil refers to a type of soil in which the topsoil contains more than 0.6% soluble salts. It is mainly distributed in coastal areas, inland areas with high evaporation, and low-lying basins, plains, and lake basin depressions. The soluble basic ions in the soil mainly include cations such as sodium ions, potassium ions, calcium ions, magnesium ions, and anions such as chloride ions, sulfate ions, carbonate ions, and bicarbonate ions. Alkaline soil refers to soil in which the exchangeable sodium content in the soil is >15%, generally between 15% and 20%, and the pH is between 8.5 and 11. The soil particles in alkaline soil are highly dispersed, with poor structure and permeability, and are often associated with saline soil.

[0004] Soil conditioners containing microorganisms can comprehensively regulate the physical, chemical and biological properties of the soil caused by acidic soil, saline soil, alkaline soil and excessive application of chemical fertilizers, improve soil structure and regulate the occurrence and circulation of elements in the soil, thereby improving soil quality and soil health index.

[0005] Serratia marcescens is a bacterium that can produce bright red pigment. It is shaped like a spherical short rod, but has various forms. Serratia marcescens is widely distributed in nature and is a common flora in water and soil. However, there is a group of Serratia marcescens that is a conditional pathogen, which can cause lung and urinary tract infections and sepsis when the body's immune function is reduced. In addition, Serratia marcescens can only adapt to a single extreme soil environment, such as acidic soil, alkaline soil or saline soil. In production practice, a type of bacteria with high biosafety and the ability to tolerate a variety of extreme complex soil environments is needed to efficiently regulate the soil environment and provide a healthy environment for plant growth. Summary of the invention

[0006] Aiming at the problem that the existing Serratia marcescens has poor utilization effect in various extreme soil environments, the present invention provides a strain of Serratia marcescens XJ108 and application thereof to solve the above problem.

[0007] The technical solution of the present invention is as follows: In a first aspect, the present invention provides a strain of Serratia marcescens XJ108, Serratia marcescens (Serratia marcescens ) XJ108 is deposited in the General Microbiology Center of China Microorganism Culture Collection Administration, with the deposit number CGMCC No.29557 and the deposit date January 10, 2024. The address of the deposit institution is No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing.

[0008] In a second aspect, the present invention provides a use of Serratia marcescens XJ108 in nitrogen fixation, phosphorus solubilization, potassium solubilization and iron carrier production.

[0009] In a third aspect, the present invention provides a use of Serratia marcescens XJ108 for increasing pH in an acidic environment.

[0010] In a fourth aspect, the present invention provides a use of Serratia marcescens XJ108 in reducing environmental alkalinity.

[0011] In a fifth aspect, the present invention provides a use of Serratia marcescens XJ108 in tolerating inorganic salts, wherein the inorganic salt comprises at least one of sodium chloride, sodium sulfate, sodium carbonate or sodium bicarbonate.

[0012] In a sixth aspect, the present invention provides an application of Serratia marcescens XJ108 in tolerant fertilizers, wherein the fertilizer includes at least one of urea, ammonium sulfate, ammonium chloride, potassium chloride, potassium sulfate, monoammonium hydrogen phosphate, diammonium phosphate or ammonium nitrate.

[0013] In a seventh aspect, the present invention provides a use of Serratia marcescens XJ108 in promoting the growth of plant roots.

[0014] Furthermore, the plant is sorghum.

[0015] The beneficial effects of the present invention are: The Serratia marcescens XJ108 provided by the present invention firstly has certain biological safety; secondly, in terms of function, it not only has the function of promoting plant growth, but also can tolerate a variety of extreme environments, including tolerance to acidic conditions, tolerance to alkaline conditions and tolerance to various types of high-salt conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0017] Figure 1 It is a colony morphology diagram of Serratia marcescens XJ108 in Example 1 of the present invention.

[0018] Figure 2This is the phylogenetic tree of Serratia marcescens XJ108 in Example 1 of the present invention.

[0019] Figure 3 This is a graph showing the results of the hemolytic activity test of Serratia marcescens XJ108 in Example 2 of the present invention.

[0020] Figure 4 It is a graph showing the results of the acid tolerance experiment of Serratia marcescens XJ108 in Example 3 of the present invention. In the figure, A is a graph showing the change trend of the OD600 value of Serratia marcescens XJ108 in an LB medium with a pH value of 4 to 7 over time; B is a graph showing the change trend of the pH value of the medium of Serratia marcescens XJ108 in an LB medium with a pH value of 4 to 7 over time.

[0021] Figure 5 This is the detection result of the alkaline metabolites of Serratia marcescens XJ108 in Example 3 of the present invention.

[0022] Figure 6 It is a graph showing the results of the alkaline tolerance experiment of Serratia marcescens XJ108 in Example 3 of the present invention. In the figure, A is a graph showing the change trend of the OD600 value of Serratia marcescens XJ108 in an LB medium with a pH value of 7 to 10 over time; B is a graph showing the change trend of the pH value of the medium of Serratia marcescens XJ108 in an LB medium with a pH value of 7 to 10 over time.

[0023] Figure 7 1 is a graph showing the results of the inorganic salt tolerance experiment of Serratia marcescens XJ108 in Example 4 of the present invention. In the graph, A is a trend graph showing the tolerance of Serratia marcescens XJ108 to sodium chloride; B is a trend graph showing the tolerance of Serratia marcescens XJ108 to sodium sulfate; C is a trend graph showing the tolerance of Serratia marcescens XJ108 to sodium carbonate; and B is a trend graph showing the tolerance of Serratia marcescens XJ108 to sodium bicarbonate.

[0024] Figure 8 This is a graph showing the results of a fertilizer tolerance experiment on Serratia marcescens XJ108 in Example 5 of the present invention.

[0025] Fig. 9 This is a graph showing the test results of the nitrogen fixation, phosphate solubilization, potassium solubilization and siderophore production functions of Serratia marcescens XJ108 in Example 5 of the present invention.

[0026] Fig.10 This is a diagram showing the growth status of the sorghum root system in Example 6 of the present invention. DETAILED DESCRIPTION

[0027] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0028] Example 1 1. Isolation and identification of Serratia marcescens XJ108 (1) Sampling: Soil was collected from vegetable greenhouses in Urumqi City, Xinjiang Uygur Autonomous Region in 2023 and stored in ziplock bags for future use.

[0029] (2) Separation: Take 5 g of soil collected in step (1) and add it to a conical flask containing 95 mL of sterile pure water, and treat it at 28°C and 180 rpm for half an hour; use the ten-fold dilution method to obtain samples with different concentration gradients, take 100 μL of each diluted concentration solution, spread it on the LB plate culture medium, and invert and culture it at 37°C. When a single colony grows on the culture medium, pick the single colony and place it on a new LB culture medium.

[0030] (3) Purification: Each single colony of the strain is purified by streaking on the LB plate for more than 3 times until the colony morphology on the culture medium is consistent and there are no foreign bacteria. This is considered to be a pure culture. The colony morphology of the microbial strain of the present invention on the LB medium is as follows: Figure 1 As shown, the colonies are round, with neat edges, moist, smooth and wrinkle-free surfaces. After 48 hours of culture, the colonies turn red.

[0031] (4) Preservation: Pick a single colony and inoculate it into LB liquid culture medium, shake it at 37℃, 180 rpm for 24 hours. Mix it with an equal volume of sterile 50% glycerol to prepare a bacterial mixture with a final glycerol concentration of 25%, and store it at -20℃ and -80℃ for later use.

[0032] (5) Molecular identification The genomic DNA was amplified using the universal primers 27F (5'-AGAGTTTGATCCTGGCTCAG-3', SEQ ID NO.2) and 1492R (5'-GGTTACCTTGTTACGACTT-3, SEQ ID NO.3) for bacterial molecular identification to obtain the 16S rDNA amplification product, which was sent to Beijing Tianyi Huiyuan Biotechnology Co., Ltd. for sequencing. The 16S rDNA sequence of the bacterium obtained by forward and reverse splicing and sequencing is shown in SEQ ID NO.1.

[0033] The sequence obtained was compared with the NCBI online Blastn program for homology, and the strain was preliminarily determined to be Serratia marcescens. Serratia marcescens The phylogenetic tree was further drawn by the neighbor-joining method. The phylogenetic tree of Serratia marcescens XJ108 is shown in Figure 2 As shown, XJ108 and S. marcescens E1-2 clustered on one branch, indicating S. marcescens E1-2 is the closest relative. Based on the morphological characteristics of the strain, strain XJ108 was named Serratia marcescens ( Serratia marcescens )XJ108.

[0034] Serratia marcescens ( Serratia marcescens ) XJ108 is deposited in the General Microbiology Center of China Microorganism Culture Collection Administration, with the deposit number CGMCC No.29557 and the deposit date January 10, 2024. The address of the deposit institution is No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing.

[0035] Example 2 Hemolytic test of Serratia marcescens XJ108 Serratia marcescens XJ108 was streaked onto the purchased hemolytic medium and cultured at 28°C in the dark for 24 hours. Figure 3 As shown, there is no transparent ring or hemolytic ring around Serratia marcescens XJ108, that is, no hemolytic reaction occurs, indicating that the strain has no hemolytic function and is biosafe.

[0036] Example 3 Acid-base tolerance test of Serratia marcescens XJ108 1. Acid tolerance test of Serratia marcescens XJ108 Liquid LB culture medium (5 g yeast extract, 10 g tryptone, 10 g sodium chloride, 1 L distilled water) was prepared, and the pH values ​​were adjusted to 4 (measured value 4.09), 5 (measured value 5.10), 6 (measured value 6.06), and 7 (measured value 6.81) with HCl, and sterilized by filtering with a sterile filter membrane to obtain sterile liquid LB culture medium with different pH values, and 195 μL was pipetted into each well of a 96-well plate.

[0037] Pick a single colony of Serratia marcescens XJ108 and streak it onto a new LB plate (5g yeast extract, 10g tryptone, 10g sodium chloride, 15-20g agar powder, 1L distilled water), and culture at 28°C until a single colony grows. Pick a single colony on the plate and add it to 500μL sterile water, vortex and mix well to obtain a bacterial cell suspension. Pipette 5μL of the cell suspension and add it to a 96-well plate containing 195μL of liquid LB culture medium with different pH values, culture it upright at 28°C, and read the OD600 absorption value of each well with an ELISA reader from 0 hours, test it every half day (12 hours), and record it for a total of 5.5 days.

[0038] The results of Serratia marcescens XJ108 adapting to acidic environment are as follows Figure 4 As shown in the figure, Serratia marcescens XJ108 can grow in LB medium with a pH value of 4 to 7, and its OD600 value can reach 1.73 to 1.80 after one day of cultivation ( Figure 4 Middle A).

[0039] In an acidic environment, Serratia marcescens XJ108 can rapidly increase the pH of the solution ( Figure 4 (B). When the initial pH was 4.09, Serratia marcescens XJ108 was able to increase the pH to 7.27 within 12 hours and to 8.05 within 24 hours. When the initial pH was 5.10, Serratia marcescens XJ108 was able to increase the pH to 7.53 within 12 hours and to 8.15 within 24 hours. When the initial pH was 6.06, Serratia marcescens XJ108 was able to increase the pH to 7.62 within 12 hours and to 8.26 within 24 hours. When the initial pH was 6.81, Serratia marcescens XJ108 was able to increase the pH to 7.62 within 12 hours and to 8.26 within 24 hours; after 48 hours of culture, the pH reached and remained at 8.55.

[0040] The above results indicate that Serratia marcescens XJ108 can quickly adapt and proliferate in an acidic environment by consuming hydrogen ions in the acidic solution or by secreting alkaline metabolites to change the acidic environment. This result indicates that the strain may have application prospects in acidic soil improvement and has certain potential for improving the vast acidic soil in the south and acidified vegetable fields in various places.

[0041] In an acidic environment, microorganisms can also balance intracellular pH by consuming hydrogen ions. This process is mediated by decarboxylases. Currently reported in Escherichia coli are lysine decarboxylase CadA and ornithine decarboxylase SpeE, which consume a hydrogen ion and release a CO2 in the process of catalyzing amino acid decarboxylation, thereby maintaining intracellular pH homeostasis. Through gene comparison, it was found that the cad Related genes include cadA and cadB Gene, spe Related genes include f Under acidic stress, these genes are highly expressed in Serratia marcescens XJ108 and rapidly consume intracellular hydrogen ions to maintain intracellular pH homeostasis, helping XJ108 to quickly adapt to the acidic environment.

[0042] Producing alkaline substances is also one of the strategies to maintain intracellular pH homeostasis to resist acidic stress. Through transcriptome sequencing technology, it was found that the QBD88_12430 gene and QBD88_10470 gene of Serratia marcescens XJ108 (these two genes encode deiminase. Literature reports that the deiminase of Escherichia coli is involved in the production of ammonia and combines with hydrogen ions in the cell to form NH4 + )and gsB The gene (encoding glutaminase, which can catalyze L-glutamine to release ammonia in Escherichia coli to improve the acid resistance of cells) was expressed at the lowest level at 6 hours, and gradually increased at 12 hours and 24 hours, reaching the highest level at 24 hours. Further metabolomics testing technology found that when Serratia marcescens XJ108 was in an acidic solution, a variety of alkaline metabolites accumulated in the solution as time went on. Figure 5 As shown, four amine substances (loperamide, morphine ethylamine, N-(5-aminopentyl) acetamide and 1,3-propylenediamine) were detected in the solution at 6 hours, and the contents of these four species at 6 hours were counted as 1 times. At 12 hours, the contents of these four substances were 1.26, 1.22, 1.15 and 1.10 times that of 6 hours, respectively, and at 24 hours, the contents were 1.41, 1.40, 1.28 and 1.23 times that of 6 hours, respectively. The results show that Serratia marcescens XJ108 can increase the pH of the extracellular environment and reduce the stress of the acidic environment on cells by producing alkaline substances.

[0043] 2. Alkaline tolerance test of Serratia marcescens XJ108 Liquid LB culture media with pH values ​​of 7 (measured value 7.02), 8 (measured value 8.14), 9 (measured value 9.07), and 10 (measured value 9.92) were prepared, and sterilized by filtering with a sterile filter membrane to obtain sterile liquid LB culture media with different pH values. 195 μL of sterile LB culture media was pipetted into a 96-well plate.

[0044] Pick a single colony of Serratia marcescens XJ108 and streak it onto a new LB plate. Cultivate at 28°C until a single colony grows. Pick a single colony on the plate and add it to 500μL of sterile water. Vortex and mix to obtain a bacterial cell suspension. Pipette 5μL of the cell suspension into a 96-well plate containing 195μL of liquid LB with different pH values. Cultivate it upright at 28°C and observe the growth of the colony within 132 hours.

[0045] The results of Serratia marcescens XJ108 adapting to alkaline environment are as follows Figure 6 As shown, Serratia marcescens XJ108 can grow in liquid LB medium with a pH value of 7 to 9, and its OD600 can reach 1.59-1.75 after 24 hours of cultivation ( Figure 6 At a pH of 10, Serratia marcescens XJ108 could tolerate the condition for 3 days and grew rapidly on the 4th day, with the OD600 reaching 1.27 on the 5.5th day ( Figure 6 Middle A).

[0046] In an alkaline environment, Serratia marcescens XJ108 can quickly adjust the pH of the solution. When the initial pH is 8.14, Serratia marcescens XJ108 can first reduce the pH to 7.92-7.94 within 12-24 hours, and then increase the pH to about 8.40-8.53 within 36-48 hours; when the initial pH is 9.07, Serratia marcescens XJ108 can reduce the pH to 8.03 within 12 hours, adjust it to 8.29 within 24 hours, and then increase it to about 8.54 within 48 hours; when the initial test pH is 9.92, Serratia marcescens XJ108 can slowly reduce the pH to 8.90 within 5 days (i.e., 120 hours), and maintain it between 8.8 and 8.9.

[0047] The above results show that Serratia marcescens XJ108 can quickly adapt and proliferate in an alkaline environment of pH=8-9, and change the alkaline environment to reduce the damage to cells caused by alkaline conditions; in an extremely alkaline environment of pH=10, the strain can tolerate the extreme environment and grow when conditions are suitable. The results show that the strain may have application prospects in improving alkaline soils and has the potential to be used as a microbial fertilizer or bio-organic fertilizer in alkaline soil improvement.

[0048] Example 4 Inorganic salt tolerance test of Serratia marcescens XJ108 Soil water-soluble salt is an important indicator to characterize soil salt content and salinity, including cations and anions. Among them, the cation with the greatest negative impact on plant growth is sodium ion, and the anions are mainly chloride ions, sulfate ions and carbonate ions. The anion composition in saline-alkali soils in different regions of China is different. Therefore, in this embodiment, sodium chloride, sodium sulfate, sodium carbonate and sodium bicarbonate are used to evaluate the tolerance of Serratia marcescens XJ108 to salt concentrations in representative saline-alkali soils.

[0049] Soil salt content indicates the total amount of soluble salt in the soil. When describing the soil salinity, the conductivity of soil leachate is often used to reflect the soil salinity, which is an important reference for evaluating the soil salinity. According to the summary of Soil Agrochemical Analysis (China Agriculture Press, 2000), when the conductivity is 0~2dS / m, it is non-salinized soil; when the conductivity is 2~4dS / m, it is salinized soil; when the conductivity is 4~8dS / m, it is moderately salinized soil; when the conductivity is 8~16dS / m, it is heavily salinized soil; when the conductivity is >16dS / m, it is extremely heavily salinized soil.

[0050] While testing the tolerance of Serratia marcescens XJ108 to inorganic salts of different concentrations, this example also simultaneously tests the conductivity values ​​of inorganic salts of different concentrations to comprehensively reflect the ability of Serratia marcescens XJ108 to tolerate different salt concentrations and conductivity, and provides a multi-index selection for the multi-index saline-alkali land improvement evaluation in production practice.

[0051] Pick a single colony of Serratia marcescens XJ108 and streak it onto a new LB plate. Culture it at 28°C until a single colony grows. Pick a single colony on the plate and add it to 500μL of sterile water. Vortex and mix well to obtain a bacterial cell suspension. Pipette 5μL and inoculate it into a 96-well plate containing 195μL of LB liquid culture medium with different salt ion concentrations. Culture it upright at 28°C. The CK group is a sterilized conventional LB liquid culture medium (containing 1% NaCl) inoculated with 5μL of sterile water. Observe the growth of the bacterial liquid after 48 hours. The results are as follows: Figure 7 shown.

[0052] Tolerance of Serratia marcescens XJ108 to sodium chloride ( Figure 7 A): XJ108 can grow in LB liquid culture medium with a sodium chloride concentration of 1% to 5%; its growth is inhibited at a sodium chloride concentration of 10% to 11%, and its growth amount is only about 17% of that when the sodium chloride concentration is 1%. At the same time, as the sodium chloride concentration increases, the conductivity of the solution also increases. The conductivity of 1%, 5%, and 10% sodium chloride solutions are 17.58mS / cm, 69.88mS / cm, and 121mS / cm, respectively. Referring to the standard for evaluating salinization of soil conductivity in the above-mentioned "Soil Agrochemical Analysis", the conductivity values ​​of sodium chloride solutions of various concentrations in the present invention far exceed the conductivity of extremely severely salinized soils, indicating that the Serratia marcescens XJ108 of the present invention can tolerate extremely high salinization environments dominated by sodium chloride.

[0053] Tolerance of Serratia marcescens XJ108 to sodium sulfate ( Figure 7Middle B): Serratia marcescens XJ108 can grow on liquid LB medium with a sodium sulfate concentration of 1% to 10%, and its growth is inhibited at a sodium sulfate concentration of 15% to 16%. As the sodium sulfate concentration increases, the conductivity of the solution also increases. The conductivity of 1%, 5%, 10%, 15% and 16% sodium sulfate solutions are 12.85mS / cm, 42.47mS / cm, 69.77mS / cm, 89.83mS / cm and 92.09mS / cm, respectively. Referring to the standard for evaluating salinization of soil conductivity in the above-mentioned "Soil Agrochemical Analysis", the conductivity values ​​of sodium sulfate solutions of various concentrations in the present invention far exceed the conductivity of extremely severely salinized soils, indicating that Serratia marcescens XJ108 of the present invention can tolerate extremely high salinization environments dominated by sodium sulfate.

[0054] Tolerance of Serratia marcescens XJ108 to sodium carbonate ( Figure 7 C): Serratia marcescens XJ108 can grow on liquid culture media with sodium carbonate concentrations of 1% to 5%, but the cell growth rate at 2% to 5% sodium carbonate concentration is only half of that at 1% sodium carbonate concentration. As the sodium carbonate concentration increases, the conductivity of the solution also increases. The conductivity of 1%, 2%, and 5% sodium carbonate solutions are 13.02mS / cm, 23.36mS / cm, and 45.02mS / cm, respectively. Referring to the standard for evaluating salinization of soil conductivity in the above-mentioned "Soil Agrochemical Analysis", the conductivity values ​​of sodium carbonate solutions of various concentrations in the present invention far exceed the conductivity of extremely severely salinized soils, indicating that the Serratia marcescens XJ108 of the present invention can tolerate extremely high salinization environments dominated by sodium carbonate.

[0055] Tolerance of Serratia marcescens XJ108 to sodium bicarbonate ( Figure 7 D): Serratia marcescens XJ108 can grow on liquid culture media with sodium bicarbonate concentrations of 1% to 5%, but when the sodium bicarbonate concentration is 3%, its growth is only one-third of that when the sodium bicarbonate concentration is 1%. As the sodium bicarbonate concentration increases, the conductivity of the solution also increases. The conductivity of 1% and 5% sodium bicarbonate solutions are 10.53mS / cm and 34.05mS / cm, respectively. Referring to the standard for evaluating salinization of soil conductivity in the above-mentioned "Soil Agrochemical Analysis", the conductivity values ​​of sodium bicarbonate solutions of various concentrations in the present invention far exceed the conductivity of extremely severely salinized soils, indicating that the Serratia marcescens XJ108 of the present invention can tolerate extremely high salinization environments dominated by sodium bicarbonate.

[0056] From the above experimental results, it can be seen that Serratia marcescens XJ108 can tolerate sodium salts composed of various anions, indicating that the strain has a certain survival potential in saline soils with different anion compositions.

[0057] Example 5 Experiment on the tolerance of Serratia marcescens XJ108 to chemical fertilizers In order to test whether Serratia marcescens XJ108 can be used in combination with chemical fertilizers, the present invention selects common chemical fertilizers circulated in the market for testing. Urea, ammonium sulfate and ammonium chloride are selected as nitrogen fertilizers, potassium chloride and potassium sulfate are selected as potash fertilizers, and monoammonium phosphate, potassium dihydrogen phosphate and potassium nitrate are selected as compound fertilizers. The operation method is the same as that of Example 4.

[0058] Pick a single colony of Serratia marcescens XJ108 and streak it onto a new LB plate. Culture it at 28°C until a single colony grows. Pick a single colony on the plate and add it to 500μL of sterile water. Vortex and mix well to obtain a bacterial cell suspension. Pipette 5μL and inoculate it into a 96-well plate containing 195μL of different nitrogen fertilizer concentrations (weigh different masses of nitrogen fertilizer and dissolve them in regular LB solution). The CK group is an LB solution with a nitrogen fertilizer concentration of 1%, inoculated with 5μL of sterile water. Culture it upright at 28°C and observe the growth of the bacterial solution after 48 hours. The results are as follows: Figure 8 As shown in the nitrogen fertilizer section.

[0059] Pick a single colony of Serratia marcescens XJ108 and streak it onto a new LB plate. Culture it at 28°C until a single colony grows. Pick a single colony on the plate and add it to 500μL of sterile water. Vortex and mix well to obtain a bacterial cell suspension. Pipette 5μL and inoculate it into a 96-well plate containing 195μL of different potassium fertilizer concentrations (different masses of potassium fertilizer are weighed and dissolved in regular LB solution). The CK group is an LB solution with a potassium fertilizer concentration of 1%, inoculated with 5μL of sterile water. Culture it upright at 28°C and observe the growth of the bacterial solution after 48 hours. The results are as follows: Figure 8 As shown in the potash fertilizer section.

[0060] Pick a single colony of Serratia marcescens XJ108 and streak it onto a new LB plate. Culture it at 28°C until a single colony grows. Pick a single colony on the plate and add it to 500μL of sterile water. Vortex and mix well to obtain a bacterial cell suspension. Pipette 5μL and inoculate it into a 96-well plate containing 195μL of different compound fertilizer concentrations (compound fertilizers of different masses are weighed and dissolved in regular LB solution). The CK group is an LB solution with a compound fertilizer concentration of 1%, inoculated with 5μL of sterile water. ), culture it upright at 28°C, and observe the growth of the bacterial solution after 48 hours. The results are as follows: Figure 8 As shown in the composite part.

[0061] Figure 8 As shown in the figure, Serratia marcescens XJ108 can tolerate 5% urea, 25% ammonium sulfate, 6.25% ammonium chloride, 6.25% potassium chloride, 6% potassium sulfate, 12.5% ​​monoammonium phosphate, 12% potassium dihydrogen phosphate and 12.5% ​​potassium nitrate, and grow well. Therefore, Serratia marcescens XJ108 can be used together with a variety of fertilizers within a certain concentration range.

[0062] Example 6 Experiment on the ability of Serratia marcescens XJ108 to promote plant growth 1. The culture medium components used for the nitrogen fixation, phosphate solubilization, potassium solubilization and siderophore production test of Serratia marcescens XJ108 are as follows: Potassium culture medium: sucrose 5g, disodium hydrogen phosphate 2g, magnesium sulfate heptahydrate 0.5g, ferric chloride 0.005g, calcium carbonate 0.1g, potassium feldspar 1g, agar 18g, distilled water 1L, pH adjusted to 7-7.5.

[0063] Montgina organophosphorus medium: 10g glucose, 0.5g ammonium sulfate, 0.3g potassium chloride, 0.3g sodium chloride, 0.03g ferrous sulfate heptahydrate, 0.3g magnesium sulfate heptahydrate, 0.03g manganese sulfate tetrahydrate, 5g calcium carbonate, 0.2g lecithin, 15-18g agar powder, 1L distilled water, pH adjusted to 7-7.5.

[0064] Ashby (nitrogen-fixing) medium: 10 g mannitol, 0.2 g potassium dihydrogen phosphate, 0.2 g magnesium sulfate heptahydrate, 40 g sodium chloride, 0.2 g calcium sulfate dihydrate, 5 g calcium carbonate, 15 g agar, and 1 L distilled water.

[0065] CAS detection medium was purchased from Beijing Coolbo Technology Co., Ltd., with the catalog number PM0821-1L.

[0066] Pick a single colony of Serratia marcescens XJ108 and streak it onto a new LB plate, and culture it at 28°C until a single colony grows. Pick a single colony on the plate and add it to 500μL of sterile water, mix it with an oscillator, and prepare a cell suspension of Serratia marcescens XJ108. Pipette 5μL of the cell suspension and spot it onto Ashby (nitrogen-fixing) medium, Montgena organophosphate medium, potassium medium, and CAS detection medium, and culture it upright at 28°C. After 3 to 5 days, observe the growth of the colonies and the formation of transparent circles.

[0067] The experimental results are as follows Fig. 9 As shown, Serratia marcescens XJ108 can not only achieve good growth on the above four culture media, but also produce obvious transparent zones, especially on the organophosphate medium (organic phosphorus decomposition part), potassium medium (potassium decomposition part) and CAS detection medium (siderophore production part). The transparent zone is very obvious and its diameter is larger than the colony diameter, indicating that the strain has the ability to fix nitrogen, decompose organic phosphorus, decompose potassium and produce siderophores. The above results show that the strain can promote the supply and release of inorganic nitrogen, inorganic phosphorus and inorganic potassium in the soil, and chelate iron ions through siderophores to promote plant growth.

[0068] 2. Testing the Effect of Serratia marcescens XJ108 on Root Growth of Sorghum Using Seed Germination Bags Two treatments were designed, namely the blank control group (CK) and the treatment group (XJ108) with the addition of Serratia marcescens XJ108. The specific operation was as follows: after the surface of the sorghum seeds were disinfected, they were germinated. First, the sterile seed germination bag was soaked with sterile water, and then the white seeds were placed in the seed germination bag. Eight white sorghum seeds were placed in each bag. 1 mL of an aqueous suspension of Serratia marcescens XJ108 was added to the XJ108 group, and an equal volume of sterile water was added to the CK group. Culture was carried out at 25°C. The growth of the sorghum root system was observed after 4 days. The results are as follows. Fig.10 shown.

[0069] Only 6 out of 8 seeds in the CK group germinated and grew, while all 8 seeds in the group treated with Serratia marcescens XJ108 germinated and grew. Secondly, the average root length of sorghum in the CK group was 5.9 cm, while the average root length of the XJ108 group was 11.98 cm, which was significantly better than the CK group. This shows that Serratia marcescens XJ108 has a significant promoting effect on the growth of sorghum roots.

[0070] Although the present invention has been described in detail with reference to the accompanying drawings and in combination with the preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and essence of the present invention, a person of ordinary skill in the art may make various equivalent modifications or substitutions to the embodiments of the present invention, and these modifications or substitutions shall be within the scope of the present invention. Any person of ordinary skill in the art may easily think of changes or substitutions within the technical scope disclosed by the present invention, and these shall be within the scope of protection of the present invention.

Claims

1. A strain of Serratia marcescens XJ108, characterized in that: Serratia marcescens ( Serratia marcescens ) XJ108 is deposited in the General Microbiology Center of China Microorganism Culture Collection Administration, with the deposit number CGMCC No.29557 and the deposit date January 10, 2024. The address of the deposit institution is No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing.

2. The Serratia marcescens XJ108 according to claim 1, characterized in that The 16SrDNA sequence of Serratia marcescens XJ108 is shown in SEQ ID NO.

1.

3. Use of the Serratia marcescens XJ108 as claimed in claim 1 in nitrogen fixation, phosphorus solubilization, potassium solubilization and siderophore production.

4. A use of the Serratia marcescens XJ108 as claimed in claim 1 to increase pH in an acidic environment.

5. Use of the Serratia marcescens XJ108 as claimed in claim 1 in reducing environmental alkalinity.

6. Use of the Serratia marcescens XJ108 according to claim 1 in tolerating inorganic salts, characterized in that: The inorganic salt includes at least one of sodium chloride, sodium sulfate, sodium carbonate or sodium bicarbonate.

7. A use of the Serratia marcescens XJ108 according to claim 1 in fertilizer tolerance, characterized in that: The fertilizer includes at least one of urea, ammonium sulfate, ammonium chloride, potassium chloride, potassium sulfate, monoammonium hydrogen phosphate, diammonium phosphate or ammonium nitrate.

8. Use of the Serratia marcescens XJ108 as claimed in claim 1 in promoting the growth of plant roots.

9. The use according to claim 8, characterized in that The plant is sorghum.

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