A Serratia marcescens XJ108 and its applications

Abstract

The present invention relates to a Serratia marcescens XJ108 and its applications, belonging to the technical field of microorganisms. The Serratia marcescens XJ108 is deposited in the General Microbiology Center of the China Microbial Culture Collection Center, with the deposit number of CGMCC No. 29557, the deposit date of January 10, 2024, and the address of the deposit institution: No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing. The present invention also provides the applications of the Serratia marcescens XJ108 in tolerating acidic environment, alkaline environment, high salinity environment, high chemical fertilizer environment soil and promoting plant growth. The Serratia marcescens XJ108 provided by the present invention has certain biosafety; at the same time, it has the function of promoting plant growth; and it can tolerate a variety of extreme soil environments.

Description

Technical Field

[0001] The present invention relates to the technical field of microorganisms, and specifically relates to a Serratia marcescens XJ108 and its application. Background Art

[0002] Acid soil is the general term for soils with a pH value less than 7. It includes soil types such as laterite, latosol, red soil, yellow soil, and lithosols. In areas with high temperature and abundant rainfall, and hot and humid seasons, the weathering and soil formation processes of the soil are intense, and the leaching of elements in the environment is intense, resulting in a decrease in base saturation, and the pH is generally between 4.5 and 6. Acid soil is mainly distributed in tropical and subtropical regions with abundant rainfall.

[0003] Saline soil refers to a type of soil with a soluble salt content exceeding 0.6% in the surface soil layer, mainly distributed in coastal areas, inland areas with high evaporation, and low-lying basins, plains, and lake basins. The soluble salt base ions in the soil mainly include cations such as sodium ions, potassium ions, calcium ions, and magnesium ions, and anions such as chloride ions, sulfate radicals, carbonate radicals, and bicarbonate radicals. Alkali soil refers to soil in which the exchangeable sodium accounts for more than 15%, generally between 15% and 20%, and the pH is between 8.5 and 11. In alkali soil, soil particles are highly dispersed, with poor structure and poor permeability, and often coexist with saline soil.

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

[0005] Serratia marcescens is a bacterium that can produce bright red pigment, with a shape similar to spherical short bacilli, but with diverse morphologies. Serratia marcescens is widely distributed in nature and is a common resident flora in water bodies and soils. However, a group of Serratia marcescens belongs to conditional pathogens and can cause lung and urinary tract infections and septicemia when the body's immune function is reduced. In addition, Serratia marcescens can only adapt to a single extreme soil environment, such as acid soil, alkali soil, or saline soil. In production practice, a type of strain with high biosafety and the ability to tolerate multiple extreme composite soil environments is needed to efficiently condition 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 multiple extreme soil environments, the present invention provides a Serratia marcescens XJ108 and its application to solve the above problems.

[0007] The technical solution of the present invention is as follows:

[0008] In a first aspect, the present invention provides a strain of Serratia marcescens XJ108. The Serratia marcescens ( Serratia marcescens ) XJ108 is deposited in the General Microbiology Center of the China Committee for Culture Collection of Microorganisms, with the deposit number CGMCC No. 29557, the deposit date being January 10, 2024, and the address of the depositary institution: No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing.

[0009] In a second aspect, the present invention provides an application of Serratia marcescens XJ108 in nitrogen fixation, phosphorus solubilization, potassium solubilization, and siderophore production.

[0010] In a third aspect, the present invention provides an application of Serratia marcescens XJ108 in increasing the pH in an acidic environment.

[0011] In a fourth aspect, the present invention provides an application of Serratia marcescens XJ108 in reducing the environmental alkalinity.

[0012] In a fifth aspect, the present invention provides an application of Serratia marcescens XJ108 in tolerating inorganic salts, where the inorganic salts include at least one of sodium chloride, sodium sulfate, sodium carbonate, or sodium bicarbonate.

[0013] In a sixth aspect, the present invention provides an application of Serratia marcescens XJ108 in tolerating chemical fertilizers, where the chemical fertilizers include at least one of urea, ammonium sulfate, ammonium chloride, potassium chloride, potassium sulfate, monoammonium phosphate, diammonium phosphate, or ammonium nitrate.

[0014] In a seventh aspect, the present invention provides an application of Serratia marcescens XJ108 in promoting plant root growth.

[0015] Further, the plant is sorghum.

[0016] The beneficial effects of the present invention are as follows:

[0017] The Serratia marcescens XJ108 provided by the present invention firstly has a certain biological safety; secondly, in terms of functions, it not only has plant growth-promoting functions, but also can tolerate a variety of extreme environments, including tolerating acidic conditions, alkaline conditions, and various types of high-salt conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0019] Figure 1 It is a colony morphology diagram of Serratia marcescens XJ108 in Example 1 of the present invention.

[0020] Figure 2 It is the phylogenetic tree of Serratia marcescens XJ108 in Example 1 of the present invention.

[0021] Figure 3 It is the result diagram of the hemolysis experiment of Serratia marcescens XJ108 in Example 2 of the present invention.

[0022] Figure 4 It is the result diagram of the acid tolerance experiment of Serratia marcescens XJ108 in Example 3 of the present invention. In the figure, A is the trend diagram of the change of OD600 value of Serratia marcescens XJ108 with time in LB medium with a pH value of 4-7; B is the trend diagram of the change of the pH value of the culture medium of Serratia marcescens XJ108 with time in LB medium with a pH value of 4-7.

[0023] Figure 5 It is the detection result of the alkaline metabolites of Serratia marcescens XJ108 in Example 3 of the present invention.

[0024] Figure 6 It is the result diagram of the alkaline tolerance experiment of Serratia marcescens XJ108 in Example 3 of the present invention. In the figure, A is the trend diagram of the change of OD600 value of Serratia marcescens XJ108 with time in LB medium with a pH value of 7-10; B is the trend diagram of the change of the pH value of the culture medium of Serratia marcescens XJ108 with time in LB medium with a pH value of 7-10.

[0025] Figure 7 It is the result diagram of the inorganic salt tolerance experiment of Serratia marcescens XJ108 in Example 4 of the present invention. In the figure, A is the tolerance trend diagram of Serratia marcescens XJ108 to sodium chloride; B is the tolerance trend diagram of Serratia marcescens XJ108 to sodium sulfate; C is the tolerance trend diagram of Serratia marcescens XJ108 to sodium carbonate; B is the tolerance trend diagram of Serratia marcescens XJ108 to sodium bicarbonate.

[0026] Figure 8 It is the result diagram of the chemical fertilizer tolerance experiment of Serratia marcescens XJ108 in Example 5 of the present invention.

[0027] Figure 9 It is the result diagram of the nitrogen fixation, phosphorus solubilization, potassium solubilization and siderophore production function tests of Serratia marcescens XJ108 in Example 5 of the present invention.

[0028] Figure 10 It is the growth status diagram of sorghum roots in Example 6 of the present invention. Detailed implementation manners

[0029] To enable those skilled in the art to better understand the technical solutions in the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0030] Example 1

[0031] 1. Isolation and identification of Serratia marcescens XJ108

[0032] (1) Sampling: Soil collected from a vegetable greenhouse in Urumqi City, Xinjiang Uygur Autonomous Region in 2023 was placed in a self-sealing bag for storage and standby.

[0033] (2) Isolation:

[0034] Take 5 g of the soil collected in step (1) and add it to a conical flask containing 95 mL of sterilized pure water. Treat it at 28°C and 180 revolutions per minute for half an hour. Using the ten-fold dilution method, obtain samples with different concentration gradients. Take 100 μL of each dilution concentration solution and spread it on an LB plate medium, and incubate it upside down at 37°C. When single colonies grow on the medium, pick the single colonies onto a new LB medium.

[0035] (3) Purification: Streak-purify the strains of each single colony on an LB plate more than 3 times until the colony morphology on the medium is consistent and there are no contaminants, then it is considered that a pure culture is obtained. The colony morphology of the microbial strain of the present invention on the LB medium is as Figure 1 shown. The colonies are round, with neat edges, and the colony surface is moist, smooth, and without wrinkles. After culturing for 48 hours, the colonies turn red.

[0036] (4) Preservation: Pick single colonies, inoculate them into an LB liquid medium, and shake-culture at 37°C and 180 revolutions per minute for 24 hours. Mix with an equal volume of sterile glycerol with a concentration of 50% to prepare a cell mixture with a final glycerol concentration of 25%, and store it at -20°C and -80°C for backup and standby.

[0037] (5) Molecular identification

[0038] The genomic DNA was amplified using the universal primers for bacterial molecular identification 27F (5'-AGAGTTTGATCCTGGCTCAG-3', SEQ ID NO.2) and 1492R (5'-GGTTACCTTGTTACGACTT-3, SEQ ID NO.3) to obtain a 16S rDNA amplification product, and the amplification product was sent to Beijing Tianyi Huiyuan Biotechnology Co., Ltd. for sequencing. The 16S rDNA sequence of this bacterium obtained after forward and reverse splicing and sequencing is shown in SEQ ID NO.1.

[0039] The sequence obtained by sequencing was subjected to homology comparison through the NCBI online Blastn program, and the strain was preliminarily determined to be Serratia marcescens. Serratia marcescens . Further, a phylogenetic tree was constructed by the Neighbor-joining method. The phylogenetic tree of Serratia marcescens XJ108 is as Figure 2 shown. XJ108 and S. marcescens E1-2 clustered on one branch, indicating the closest genetic relationship with S. marcescens E1-2. Combining the morphological characteristics of the strain, the strain XJ108 was named Serratia marcescens ( Serratia marcescens ). XJ108.

[0040] Serratia marcescens ( Serratia marcescens ) XJ108 was deposited in the General Microbiology Center of the China Committee for Culture Collection of Microorganisms, with the deposit number CGMCC No.29557, the deposit date being January 10, 2024, and the address of the deposit institution: No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing.

[0041] Example 2

[0042] Hemolytic experiment of Serratia marcescens XJ108

[0043] Serratia marcescens XJ108 was streaked on the purchased hemolytic medium and cultured at 28°C in the dark for 24 hours. The results are as Figure 3 shown. There was no clear zone or hemolytic ring around Serratia marcescens XJ108, that is, no hemolytic reaction occurred. This indicates that the strain has no hemolytic function and has biological safety.

[0044] Example 3

[0045] Acid and alkali tolerance experiment of Serratia marcescens XJ108

[0046] 1. Acid tolerance experiment of Serratia marcescens XJ108

[0047] Prepare liquid LB medium (5 g yeast extract, 10 g tryptone, 10 g sodium chloride, 1 L distilled water), adjust the pH value to 4 (measured value 4.09), 5 (measured value 5.10), 6 (measured value 6.06), and 7 (measured value 6.81) with HCl respectively, filter and sterilize with a sterile filter membrane to obtain sterile liquid LB medium with different pH values, and pipette 195 μL into each well of a 96-well plate.

[0048] Pick a single colony of Serratia marcescens XJ108 and streak it onto a new LB plate (5 g yeast extract, 10 g tryptone, 10 g sodium chloride, 15 - 20 g agar powder, 1 L distilled water), and culture at 28 °C until single colonies grow. Pick a single colony on the plate into 500 μL of sterile water, vortex and mix well to obtain a bacterial cell suspension. Pipette 5 μL of the cell suspension onto a 96-well plate containing 195 μL of liquid LB medium with different pH values, culture upright at 28 °C, start reading the OD600 absorbance value of each well with a microplate reader from 0 hour, and test once every half day (12 hours) for a total of 5.5 days.

[0049] The results of the adaptation of Serratia marcescens XJ108 to acidic environment are as Figure 4 shown. Serratia marcescens XJ108 can grow in LB medium with a pH value of 4 - 7, and its OD600 value can reach 1.73 - 1.80 after one day of culture ( Figure 4 A in it).

[0050] In an acidic environment, Serratia marcescens XJ108 can rapidly increase the pH of the solution ( Figure 4 B in it). When the initial pH is 4.09, Serratia marcescens XJ108 can increase the pH to 7.27 within 12 hours and to 8.05 at 24 hours. When the initial pH is 5.10, Serratia marcescens XJ108 can increase the pH to 7.53 at 12 hours and to 8.15 at 24 hours. When the initial pH is 6.06, Serratia marcescens XJ108 can increase the pH to 7.62 within 12 hours and to 8.26 at 24 hours. When the initial pH is 6.81, Serratia marcescens XJ108 can increase the pH to 7.62 within 12 hours and to 8.26 at 24 hours; after 48 hours of culture, the pH reaches and remains at 8.55.

[0051] The above results indicate that Serratia marcescens XJ108 can quickly adapt and proliferate rapidly 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 the improvement of acidic soil, and has certain potential for improving the vast acidic soil in the south and acidified vegetable fields everywhere.

[0052] In an acidic environment, microorganisms can also balance the intracellular pH by consuming hydrogen ions. This process is mediated by decarboxylase. Lysine decarboxylase CadA and ornithine decarboxylase SpeE have been reported to exist in Escherichia coli. During the decarboxylation of amino acids, one hydrogen ion is consumed and one CO 2 is released, thus maintaining the intracellular pH homeostasis. Through gene alignment, it was found that the cad related genes of Serratia marcescens XJ108 include cadA and cadB genes, spe and the speF related genes include speF gene. Under acidic stress, these genes in Serratia marcescens XJ108 are highly expressed and rapidly consume intracellular hydrogen ions to maintain intracellular pH homeostasis and assist XJ108 in quickly adapting to the acidic environment.

[0053] Producing alkaline substances is also one of the strategies to maintain intracellular pH homeostasis in cells to counteract 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 deiminases, and it has been reported in the literature that the deiminases of Escherichia coli are involved in the production of ammonia and combine with hydrogen ions in the cell to form NH 4 + ), and the glsB gene (encoding glutaminase, which can catalyze the release of ammonia from L-glutamine in Escherichia coli to improve the acid tolerance of cells) have the lowest gene expression levels at 6 hours, and the expression levels gradually increase at 12 hours and 24 hours, reaching the highest at 24 hours. Further through metabolomics testing technology, it was found that in an acidic solution, with the extension of time, various alkaline metabolites accumulate in the solution of Serratia marcescens XJ108. As Figure 5 shown, four amine substances (loperamide, morpholine ethylamine, N-(5-aminopentyl)acetamide, and 1,3-propanediamine) were detected in the solution at 6 hours, and the contents of these four substances at 6 hours were counted as 1-fold amount. 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. This result indicates that Serratia marcescens XJ108 can increase the extracellular environmental pH by producing alkaline substances and alleviate the stress of the acidic environment on cells.

[0054] 2. Alkaline tolerance experiment of Serratia marcescens XJ108

[0055] Prepare liquid LB 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) respectively. Filter and sterilize them with a sterile filter membrane to obtain sterile liquid LB media with different pH values. Pipette 195 μL of sterile LB medium into a 96-well plate.

[0056] Pick a single colony of Serratia marcescens XJ108 and streak it onto a new LB plate, and culture it at 28 °C until single colonies grow. Pick a single colony from the plate and transfer it to 500 μL of sterile water, then vortex to mix evenly to obtain a cell suspension of the bacteria. Pipette 5 μL of the cell suspension into a 96-well plate containing 195 μL of liquid LB with different pH values, and culture it upright at 28 °C. Observe the colony growth within 132 hours.

[0057] The results of the adaptation of Serratia marcescens XJ108 to the alkaline environment are as Figure 6 shown. Serratia marcescens XJ108 can grow in liquid LB media with pH values ranging from 7 to 9, and its OD600 can reach 1.59 - 1.75 after 24 hours of culture ( Figure 6 A in it). Under the condition of pH = 10, Serratia marcescens XJ108 can tolerate for 3 days, and grows rapidly on the 4th day, and its OD600 can reach 1.27 on the 5.5th day ( Figure 6 A in it).

[0058] In the 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 lower the pH to 7.92 - 7.94 within 12 - 24 hours, and then raise the pH to about 8.40 - 8.53 within 36 - 48 hours; when the initial pH is 9.07, Serratia marcescens XJ108 can lower the pH to 8.03 within 12 hours, adjust it to 8.29 at 24 hours, and then raise and maintain it at about 8.54 at 48 hours; when the initial pH is 9.92, Serratia marcescens XJ108 can slowly lower the pH to 8.90 within 5 days (i.e., within 120 hours) and maintain it between 8.8 and 8.9.

[0059] The above results show that Serratia marcescens XJ108 can quickly adapt and proliferate in the alkaline environment with pH = 8 - 9, and at the same time change the alkaline environment to reduce the damage of alkaline conditions to cells; in the extremely alkaline environment with pH = 10, this strain can tolerate the extreme environment and grow when the conditions are appropriate. The results indicate that this strain may have application prospects in improving alkaline soil and has the potential to be used as a microbial fertilizer or biological organic fertilizer for alkaline soil improvement.

[0060] Example 4

[0061] Inorganic Salt Tolerance Experiment of Serratia marcescens XJ108

[0062] Soil water-soluble salts are an important indicator to characterize soil salt content and salinity, including cations and anions. Among them, the cation that has the greatest negative impact on plant growth is sodium ion, and the anions are mainly chloride ion, sulfate ion, and carbonate ion. The anion compositions in saline-alkali soils in different regions of China are not the same. Therefore, in this example, 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.

[0063] Soil salt content represents the total amount of soluble salts in the soil. When describing the soil salt status, the electrical conductivity of soil leachate is often used to reflect the soil salt status, which is an important reference basis for evaluating the soil salt status. According to the summary in "Soil Agricultural Chemistry Analysis" (China Agriculture Press, 2000), when the electrical conductivity is 0-2 dS / m, it is a non-saline soil; when the electrical conductivity is 2-4 dS / m, it is a saline soil; when the electrical conductivity is 4-8 dS / m, it is a moderately saline soil; when the electrical conductivity is 8-16 dS / m, it is a severely saline soil; when the electrical conductivity is >16 dS / m, it is an extremely severely saline soil.

[0064] In this example, while testing the tolerance of Serratia marcescens XJ108 to different concentrations of inorganic salts, the electrical conductivity values of different concentrations of inorganic salts were also synchronously tested to comprehensively reflect the ability of Serratia marcescens XJ108 to tolerate different salt concentrations and electrical conductivities, providing multi-index options for the evaluation of saline-alkali land improvement with multiple indicators in production practice.

[0065] Pick a single colony of Serratia marcescens XJ108 and streak it onto a new LB plate, and culture it at 28 °C until single colonies grow. Pick a single colony on the plate into 500 μL of sterile water and vortex to mix evenly to obtain a cell suspension of bacteria. Pipette 5 μL and inoculate it into a 96-well plate containing 195 μL of LB liquid medium with different salt ion concentrations, and culture it upright at 28 °C. The CK group is a sterilized conventional LB liquid medium (containing 1% NaCl), and 5 μL of sterile water is inoculated. Observe the growth of the bacterial solution after 48 hours, and the results are as Figure 7 shown.

[0066] Tolerance of Serratia marcescens XJ108 to sodium chloride ( Figure 7A): XJ108 can grow in LB liquid medium with a sodium chloride concentration of 1% - 5%; its growth is inhibited at a sodium chloride concentration of 10% - 11%, and its growth amount is only about 17% of that at a sodium chloride concentration of 1%. At the same time, as the sodium chloride concentration increases, the conductivity of the solution also increases. The conductivities of 1%, 5%, and 10% sodium chloride solutions are 17.58 mS / cm, 69.88 mS / cm, and 121 mS / cm respectively. Referring to the standard for evaluating soil salinization by soil conductivity in the above-mentioned "Soil Agricultural Chemistry Analysis", the conductivity values of sodium chloride solutions at various concentrations in the present invention far exceed the conductivity of extremely severely salinized soil, indicating that the Serratia marcescens XJ108 of the present invention can tolerate an extremely high salinized environment mainly composed of sodium chloride.

[0067] Tolerance of Serratia marcescens XJ108 to sodium sulfate ( Figure 7 B): Serratia marcescens XJ108 can grow on liquid LB medium with a sodium sulfate concentration of 1% - 10%, and its growth is inhibited at a sodium sulfate concentration of 15% - 16%. As the sodium sulfate concentration increases, the conductivity of the solution also increases. The conductivities of 1%, 5%, 10%, 15%, and 16% sodium sulfate solutions are 12.85 mS / cm, 42.47 mS / cm, 69.77 mS / cm, 89.83 mS / cm, and 92.09 mS / cm respectively. Referring to the standard for evaluating soil salinization by soil conductivity in the above-mentioned "Soil Agricultural Chemistry Analysis", the conductivity values of sodium sulfate solutions at various concentrations in the present invention far exceed the conductivity of extremely severely salinized soil, indicating that the Serratia marcescens XJ108 of the present invention can tolerate an extremely high salinized environment mainly composed of sodium sulfate.

[0068] Tolerance of Serratia marcescens XJ108 to sodium carbonate ( Figure 7 C): Serratia marcescens XJ108 can grow on liquid medium with a sodium carbonate concentration of 1% - 5%, but when the sodium carbonate concentration is 2% - 5%, the cell growth amount is only half of that at a sodium carbonate concentration of 1%. As the sodium carbonate concentration increases, the conductivity of the solution also increases. The conductivities of 1%, 2%, and 5% sodium carbonate solutions are 13.02 mS / cm, 23.36 mS / cm, and 45.02 mS / cm respectively. Referring to the standard for evaluating soil salinization by soil conductivity in the above-mentioned "Soil Agricultural Chemistry Analysis", the conductivity values of sodium carbonate solutions at various concentrations in the present invention far exceed the conductivity of extremely severely salinized soil, indicating that the Serratia marcescens XJ108 of the present invention can tolerate an extremely high salinized environment mainly composed of sodium carbonate.

[0069] Tolerance of Serratia marcescens XJ108 to sodium bicarbonate ( Figure 7D): Serratia marcescens XJ108 can grow on liquid media with sodium bicarbonate concentrations ranging from 1% to 5%. However, when the sodium bicarbonate concentration is 3%, its growth amount 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 conductivities of 1% and 5% sodium bicarbonate solutions are 10.53 mS / cm and 34.05 mS / cm respectively. Referring to the standard for evaluating soil salinization by soil conductivity in the above-mentioned "Soil Agricultural Chemistry Analysis", the conductivity values of sodium bicarbonate solutions at various concentrations in the present invention far exceed the conductivity of extremely severely salinized soil, indicating that the Serratia marcescens XJ108 of the present invention can tolerate an extremely high sodium bicarbonate-dominated salinized environment.

[0070] From the above experimental results, it can be seen that Serratia marcescens XJ108 can tolerate sodium salts composed of various anions. This indicates that this strain has a certain survival potential in saline soils with different anion compositions.

[0071] Example 5

[0072] Fertilizer tolerance experiment of Serratia marcescens XJ108

[0073] To test whether Serratia marcescens XJ108 can be used in combination with chemical fertilizers, common chemical fertilizers on the market were selected for testing in the present invention. Urea, ammonium sulfate, and ammonium chloride were selected as nitrogen fertilizers, potassium chloride and potassium sulfate were selected as potassium fertilizers, and monoammonium phosphate, potassium dihydrogen phosphate, and potassium nitrate were selected as compound fertilizers. The operation method was the same as that in Example 4.

[0074] Pick a single colony of Serratia marcescens XJ108 and streak it onto a new LB plate, and culture it at 28 °C until single colonies grow. Pick a single colony on the plate and transfer it to 500 μL of sterile water, and vortex to mix evenly to obtain a bacterial cell suspension. Pipette 5 μL and inoculate it into a 96-well plate containing 195 μL of different nitrogen fertilizer concentrations (weigh different masses of nitrogen fertilizers and dissolve them in conventional LB solution). The CK group is the LB solution with a nitrogen fertilizer concentration of 1%, and 5 μL of sterile water is inoculated. Incubate at 28 °C upright, and observe the growth of the bacterial solution after 48 hours. The results are as Figure 8 shown in the nitrogen fertilizer part.

[0075] Pick a single colony of Serratia marcescens XJ108 and streak it onto a new LB plate, and culture it at 28 °C until single colonies grow. Pick a single colony on the plate and transfer it to 500 μL of sterile water, and vortex to mix evenly to obtain a bacterial cell suspension. Pipette 5 μL and inoculate it into a 96-well plate containing 195 μL of different potassium fertilizer concentrations (weigh different masses of potassium fertilizers and dissolve them in conventional LB solution). The CK group is the LB solution with a potassium fertilizer concentration of 1%, and 5 μL of sterile water is inoculated. Incubate at 28 °C upright, and observe the growth of the bacterial solution after 48 hours. The results are as Figure 8 shown in the potassium fertilizer part.

[0076] Pick a single colony of Serratia marcescens XJ108 and streak it onto a new LB plate. Incubate at 28 °C until single colonies grow. Pick a single colony from the plate and transfer it to 500 μL of sterile water. Vortex to mix well to obtain a cell suspension of the bacteria. Pipette 5 μL and inoculate it into a 96-well plate containing 195 μL of different compound fertilizer concentrations (weigh different masses of compound fertilizer and dissolve it in conventional LB solution). The CK group is the LB solution with a compound fertilizer concentration of 1%, and 5 μL of sterile water is inoculated. Incubate upright at 28 °C. After 48 hours, observe the growth of the bacterial solution. The results are as Figure 8 shown in the composite part.

[0077] Figure 8 shown, 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 in combination with a variety of chemical fertilizers within a certain concentration range.

[0078] Example 6

[0079] Experiment on the plant growth-promoting ability of Serratia marcescens XJ108

[0080] 1. Tests on the nitrogen fixation, phosphorus solubilization, potassium solubilization, and siderophore production functions of Serratia marcescens XJ108. The components of the culture media used are as follows:

[0081] Potassium medium: 5 g of sucrose, 2 g of disodium hydrogen phosphate, 0.5 g of magnesium sulfate heptahydrate, 0.005 g of ferric chloride, 0.1 g of calcium carbonate, 1 g of potassium feldspar, 18 g of agar, 1 L of distilled water, pH adjusted to 7 - 7.5.

[0082] Meng Jinna organic phosphorus medium: 10 g of glucose, 0.5 g of ammonium sulfate, 0.3 g of potassium chloride, 0.3 g of sodium chloride, 0.03 g of ferrous sulfate heptahydrate, 0.3 g of magnesium sulfate heptahydrate, 0.03 g of manganese sulfate tetrahydrate, 5 g of calcium carbonate, 0.2 g of lecithin, 15 - 18 g of agar powder, 1 L of distilled water, pH adjusted to 7 - 7.5.

[0083] Ashby (nitrogen fixation) medium: 10 g of mannitol, 0.2 g of potassium dihydrogen phosphate, 0.2 g of magnesium sulfate heptahydrate, 40 g of sodium chloride, 0.2 g of calcium sulfate dihydrate, 5 g of calcium carbonate, 15 g of agar, 1 L of distilled water.

[0084] The CAS detection medium is an externally purchased medium, purchased from Beijing Coolaber Technology Co., Ltd., product number PM0821 - 1L.

[0085] Pick a single colony of Serratia marcescens XJ108 and streak it onto a new LB plate. Incubate at 28°C until single colonies grow. Pick a single colony from the plate and transfer it to 500 μL of sterile water. Mix well on a shaker to prepare a cell suspension of Serratia marcescens XJ108. Pipette 5 μL of the cell suspension onto Ashby (nitrogen-fixing) medium, Meng Jina organic phosphorus medium, potassium medium, and CAS detection medium. Incubate upright at 28°C and observe the colony growth and the formation of clear zones after 3 - 5 days.

[0086] The experimental results are as Figure 9 shown. Serratia marcescens XJ108 can not only grow well on the above four media, but also produce obvious clear zones. Especially on the organic phosphorus medium (for organic phosphorus decomposition), potassium medium (for potassium decomposition), and CAS detection medium (for siderophore production), the clear zones are very obvious, and their diameters are larger than the colony diameters, indicating that this strain has the abilities of nitrogen fixation, organic phosphorus decomposition, potassium decomposition, and siderophore production. The above results show that this 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.

[0087] 2. Use seed germination bags to test the effect of Serratia marcescens XJ108 on the root growth of sorghum

[0088] Design two treatments, namely the blank control group (CK) and the treatment group added with Serratia marcescens XJ108 (XJ108). The specific operation is as follows: After surface sterilization of sorghum seeds, conduct germination treatment. First, moisten the sterile seed germination bags with sterile water, and then place the germinated seeds into the seed germination bags. Place eight germinated sorghum seeds in each bag. Add 1 mL of the water suspension of Serratia marcescens XJ108 to the XJ108 group, and add an equal volume of sterile water to the CK group. Incubate at 25°C. Observe the growth status of sorghum roots after 4 days. The results are as Figure 10 shown.

[0089] Only 6 out of 8 seeds in the CK group germinated and grew, while all 8 seeds in the Serratia marcescens XJ108 treatment group germinated and grew. Secondly, the average root length of sorghum in the CK group was 5.9 cm, and the average root length in the XJ108 group was 11.98 cm, which was significantly better than that of the CK group. This indicates that Serratia marcescens XJ108 has a significant promoting effect on the root growth of sorghum.

[0090] Although the present invention has been described in detail by reference to the accompanying drawings and in conjunction with the preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and essence of the present invention, those of ordinary skill in the art can make various equivalent modifications or substitutions to the embodiments of the present invention, and all such modifications or substitutions should be within the scope of the present invention / Any person skilled in the art within the technical scope disclosed by the present invention can easily conceive of changes or substitutions, which should all be covered within the protection scope 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 is 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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