Saline-alkali tolerant Escherichia coli SX-J4 and application thereof

Abstract

The invention belongs to the technical field of microorganisms, and particularly relates to saline-alkaline tolerant Escherichia coli SX-J4 and application thereof. The invention provides Escherichia coli SX-J4, and the preservation number of the Escherichia coli SX-J4 is CGMCC (China General Microbiological Culture Collection Center) NO.31724. The Escherichia coli SX-J4 provided by the invention has relatively strong saline-alkaline resistance, can promote the germination rate of seeds (such as soybean seeds) in a saline-alkaline environment and promote the growth of plants in the saline-alkaline environment, and can effectively reduce the alkalinity of saline-alkaline soil and degrade the concentration of water-soluble sodium ions in the soil when being applied to the saline-alkaline soil. By utilizing the Escherichia coli SX-J4 provided by the invention, large-scale popularization of centralized large-scale photovoltaic area salinization improvement can be realized, the ecological restoration capability of photovoltaic plant area soil is improved, and environmental protection and sustainable utilization of land are promoted.

Description

Technical Field

[0001] The present invention belongs to the technical field of microbiology, and particularly relates to a salt-tolerant and alkali-tolerant Escherichia coli SX-J4 and its application. Background Art

[0002] The centralized photovoltaic power generation area in the soda saline-alkali land with high latitude and low altitude is a clean energy base that China focuses on developing, and is famous for its large-scale photovoltaic power stations and remarkable energy production capacity. However, the saline-alkali land covered by this area faces unique environmental challenges. There are not only the problems of high salinity and alkalinity of traditional saline-alkali soils, but also the influence of the shading effect of photovoltaic panels, soil temperature changes and mechanical compaction. These factors make the saline-alkalization problem of the soil in the photovoltaic power generation area more complex, directly affecting the ecological function of the soil and the long-term stable operation of the photovoltaic power station. Therefore, it is urgent to analyze the microorganisms in the photovoltaic power generation area, isolate and screen functional microorganisms with high efficiency in salt tolerance and alkali tolerance in the photovoltaic power generation area, so as to provide new biotechnology means for large-scale promotion of saline-alkalization improvement in centralized large-scale photovoltaic areas. Summary of the Invention

[0003] The purpose of the present invention is to provide a salt-tolerant and alkali-tolerant Escherichia coli SX-J4 and its application. The Escherichia coli has a significant ability to reduce alkali and dissolve salt, can promote seed germination in saline-alkali environments and plant growth in saline-alkali environments, and provides technical support for saline-alkalization improvement in centralized large-scale photovoltaic areas.

[0004] The present invention provides an Escherichia coli ( Escherichia coil ) SX-J4, with the preservation number of CGMCC NO.31724.

[0005] The present invention also provides a bacterial agent, and the active ingredient of the bacterial agent includes the Escherichia coli SX-J4 described in the above technical solution.

[0006] Preferably, the concentration of Escherichia coli SX-J4 in the bacterial agent is 1×10 6 ~1×10 8 CFU / mL.

[0007] The present invention also provides the application of the Escherichia coli SX-J4 or the bacterial agent described in the above technical solution in one or more of the following: (1) Improvement of saline-alkali soil; (2) Promotion of seed germination in saline-alkali environments; (3) Promotion of plant growth in saline-alkali environments.

[0008] Preferably, the improvement of saline-alkali soil includes one or more of reducing the pH of saline-alkali soil, reducing the electrical conductivity of saline-alkali soil and reducing the content of water-soluble sodium ions in saline-alkali soil.

[0009] Preferably, the basic physical and chemical properties of the saline-alkali soil are as follows: the bulk density is 1.35 - 1.55 g / cm 3 , the average moisture content is 33.2%, the pH value is 9.86 - 10.51, the cation components of the soluble salts include Na + , Fe 2+ , Ca 2+ , Mg 2+ , K + , Mn 2+ , Zn 2+ and Cu 2+ , and the total salt content is 8108.43 μg / g.

[0010] Preferably, promoting the growth of plants in the saline-alkali environment includes increasing one or more of the plant height, chlorophyll content, and biomass of plants in the saline-alkali environment; The seeds include soybean seeds; The plants include soybeans.

[0011] Preferably, the basic physical and chemical properties of the saline-alkali environment are as follows: the bulk density is 1.35 - 1.55 g / cm 3 , the average moisture content is 33.2%, the pH value is 9.86 - 10.51, the cation components of the soluble salts include Na + , Fe 2+ , Ca 2+ , Mg 2+ , K + , Mn 2+ , Zn 2+ and Cu 2+ , and the total salt content is 8108.43 μg / g.

[0012] The present invention also provides a method for improving saline-alkali soil and / or promoting the growth of plants in the saline-alkali environment, including: irrigating the soil with the bacterial agent described in the above technical solution.

[0013] The present invention also provides a method for promoting the germination of seeds in the saline-alkali environment, including: soaking the seeds with the bacterial agent described in the above technical solution and then culturing them in the saline-alkali environment.

[0014] Beneficial effects: The present invention provides an Escherichia coli SX-J4 with a preservation number of CGMCC NO.31724. The Escherichia coli SX-J4 provided by the present invention has strong salt and alkali tolerance, can promote the germination rate of seeds (such as soybean seeds) in saline-alkali environments, promote the growth of plants in saline-alkali environments, and can effectively reduce the alkalinity of saline-alkali soil and degrade the concentration of water-soluble sodium ions in the soil when applied to saline-alkali soil. Using the Escherichia coli SX-J4 provided by the present invention, large-scale promotion of centralized large-scale photovoltaic area salinization improvement can be achieved, the ecological restoration ability of the soil in the photovoltaic plant area can be enhanced, and environmental protection and sustainable land use can be promoted.

[0015] Biological preservation information Escherichia coli SX-J4, taxonomically named Escherichia coli Escherichia coli , was preserved in the General Microbiological Center of the China Committee for Culture Collection of Microorganisms on August 23, 2024, at the address: No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing, with a postal code of 100101 and a preservation number of CGMCC NO.31724. Brief description of the drawings

[0016] 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 embodiments.

[0017] Figure 1 is the colony morphology diagram of SX-J4; Figure 2 is the phylogenetic tree of Escherichia coli SX-J4; Figure 3 is the OD of Escherichia coli SX-J4 under different NaCl concentrations (a) and different pH environments (b) 600 value; Figure 4 is the germination situation of soybean seeds under different experimental treatments; among them, a is the seed germination rate at different culture times; b is the total germination rate; among them, ** represents p <0.01, *** represents p <0.001; Figure 5 is the measurement results of soil pH (a) and conductivity (b) under different experimental treatments; among them, * represents p <0.05, ** represents p <0.01; Figure 6 is the measurement results of soil water-soluble sodium ions under different experimental treatments; among them, ** represents p <0.01; Figure 7Determination results of the effects of Escherichia coli SX-J4 on the growth indicators of soybeans in saline-alkali environments; among them, * indicates p <0.05, ** indicates p <0.01. Detailed implementation mode

[0018] The present invention provides a strain of Escherichia coli ( Escherichia coil ) SX-J4, with the preservation number of CGMCC NO. 31724.

[0019] The Escherichia coli SX-J4 described in the present invention is a strain isolated from the soil between the fixed plates of a centralized large-scale photovoltaic power station area at a high latitude and low altitude. Its colonies growing on LB solid medium are approximately circular, with a smooth, moist, shiny, opaque surface, light yellow in color, slightly convex, and have neat edges and different sizes ( Figure 1 ). The nucleotide sequence of the 16S rRNA of the Escherichia coli SX-J4 described in the present invention is as shown in SEQ ID NO: 1.

[0020] The present invention also provides a bacterial agent, and the active ingredient of the bacterial agent includes the Escherichia coli SX-J4 described in the above technical solution. As an implementation mode, the concentration of Escherichia coli SX-J4 in the bacterial agent of the present invention is 1×10 6 ~1×10 8 CFU / mL; as another implementation mode, the concentration of Escherichia coli SX-J4 in the bacterial agent of the present invention is 5×10 6 ~5×10 7 CFU / mL; as another implementation mode, the concentration of Escherichia coli SX-J4 in the bacterial agent of the present invention is 1×10 7 CFU / mL.

[0021] The present invention also provides the application of the Escherichia coli SX-J4 or the bacterial agent described in the above technical solution in one or more of the following: (1) improving saline-alkali soil; (2) promoting seed germination in saline-alkali environments; (3) promoting plant growth in saline-alkali environments.

[0022] As an implementation mode, the improvement of saline-alkali soil described in the present invention includes one or more of reducing the pH of saline-alkali soil, reducing the electrical conductivity of saline-alkali soil, and reducing the content of water-soluble sodium ions in saline-alkali soil; as another implementation mode, the improvement of saline-alkali soil described in the present invention includes reducing the pH of saline-alkali soil, reducing the electrical conductivity of saline-alkali soil, and reducing the content of water-soluble sodium ions in saline-alkali soil.

[0023] As an implementation manner, the saline-alkali soil described in the present invention includes the saline-alkali soil in a centralized large-scale photovoltaic area. As an implementation manner, the basic physical and chemical properties of the saline-alkali soil described in the present invention are as follows: the bulk density is 1.35-1.55 g / cm 3 , the average moisture content is 33.2%, the pH value is 9.86-10.51, and the cation components of the soluble salts include Na + , Fe 2+ , Ca 2+ , Mg 2+ , K + , Mn 2+ , Zn 2 + and Cu 2+ , and the total salt content is 8108.43 μg / g.

[0024] As an implementation manner, the promotion of plant growth in a saline-alkali environment described in the present invention includes increasing one or more of the plant height, chlorophyll content, and biomass of plants in a saline-alkali environment; as another implementation manner, the promotion of plant growth in a saline-alkali environment described in the present invention includes increasing the plant height, chlorophyll content, and biomass of plants in a saline-alkali environment.

[0025] As an implementation manner, the basic physical and chemical properties of the saline-alkali environment are as follows: the bulk density is 1.35-1.55 g / cm 3 , the average moisture content is 33.2%, the pH value is 9.86-10.51, and the cation components of the soluble salts include Na + , Fe 2+ , Ca 2+ , Mg 2+ , K + , Mn 2+ , Zn 2+ and Cu 2+ , and the total salt content is 8108.43 μg / g.

[0026] As an implementation manner, the seeds described in the present invention include soybean seeds. As an implementation manner, the plants described in the present invention include soybeans. In specific embodiments of the present invention, soybeans are taken as an example for illustration, but it should not be construed as the entire protection scope of the present invention.

[0027] The present invention also provides a method for improving saline-alkali soil, including: irrigating the soil with the microbial agent described in the above technical solution.

[0028] As an implementation method, during irrigation, it is irrigated once every 5 - 10 days, and 100 - 150 mL of water is irrigated per 500 g of soil each time; as another implementation method, during irrigation, it is irrigated once every 7 days, and 100 mL of water is irrigated per 500 g of soil each time. As an implementation method, the number of irrigation times is 3 - 6 times; as another implementation method, the number of irrigation times is 4 times. By irrigating the saline - alkali soil to be improved with the bacterial agent according to the above - mentioned technical solution, the pH value and conductivity of the saline - alkali soil to be improved can be significantly reduced, the salt concentration can be reduced, and the content of soil water - soluble sodium ions in the saline - alkali soil can be significantly reduced; it can also promote the growth of plants in the saline - alkali soil environment.

[0029] The present invention also provides a method for promoting the germination of seeds in a saline - alkali environment, including: soaking the seeds with the bacterial agent according to the above - mentioned technical solution and then culturing them in a saline - alkali environment.

[0030] As an implementation method, the soaking time in the present invention is 2 - 5 h; as another implementation method, the soaking time is 3 h. As another implementation method, the light - dark ratio of the culture in the present invention is 12 / 12 h. As an implementation method, the light intensity of the light - culture in the present invention is 12000 - 20000 LUX; as another implementation method, the light intensity of the light - culture is 15000 LUX. As an implementation method, the relative humidity of the culture in the present invention is 68% - 89%; as another implementation method, the relative humidity of the culture is 80%. As an implementation method, the culture time in the present invention is 6 - 10 d; as another implementation method, the culture time in the present invention is 7 d. By soaking the seeds with the bacterial agent according to the above - mentioned technical solution and then culturing them in a saline - alkali environment, the germination rate of seeds in a saline - alkali environment can be promoted.

[0031] To further illustrate the present invention, the following describes in detail a strain of halotolerant Escherichia coli SX - J4 and its application provided by the present invention with reference to the accompanying drawings and embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0032] Example 1 Isolation and identification of strains 1. Collect the soil from the surface layer of 0 - 20 cm between the fixed plates in a centralized large - scale photovoltaic power station area at high latitude and low altitude. Take 5.0 g of the collected soil, add it to 45 mL of sterilized water, place it on a shaker and shake (180 rpm, 30 min) to make a soil suspension. Then dilute the soil suspension by a 10 - fold gradient to 10 -4Multiply by a factor of, take 0.2 mL of the soil dilution, and spread it onto an LB solid medium with a salinity of 10% and a pH of 12 (5 g / L of yeast extract, 10 g / L of peptone, 100 g / L of NaCl, and 20 g / L of agar powder, pH value 12.0). Incubate it in an inverted position at a constant temperature of 30°C for 4 to 5 days.

[0033] 2. Pick colonies with good morphology, growth vigor, and relatively fast growth rate on the LB solid medium, and use the streak plate method with an inoculation loop to purify them multiple times on a new LB solid medium until pure culture is achieved. A target strain, numbered SX-J4, is screened. The colony morphology is approximately circular, with a smooth, moist, shiny, opaque surface, light yellow in color, slightly raised, and the edges are neat and of different sizes ( Figure 1 ).

[0034]

[0035] 4. Using the NCBI database, BLAST analysis was performed based on the 16S rRNA gene sequence of strain SX-J4, and a phylogenetic tree was constructed. The results showed that strain SX-J4 had a 16S rRNA gene sequence homology of 99.72% with both Escherichia fergusonii ATCC 35469 (accession number NR_074902.1) and Shigella flexneri ATCC 29903 (accession number NR_026331.1), and a 16S rRNA gene sequence homology of 99.57% with Escherichia coli NBRC 102203 (accession number NR_114042.1), Shigella sonnei CECT 4887 (accession number NR_104826.1) and Escherichia fergusonii ATCC 35469 (accession number NR_027549.1), and a 16S rRNA gene sequence homology of 99.29% with Shigella boydii strain P288 (accession number NR_104901.1). Strain SX-J4 had the closest phylogenetic relationship with Escherichia coli ( Escherichia coli ), and based on its cell morphology and colony characteristics, this strain was identified as the genus Escherichia ( Figure 2 ), named Escherichia coli ( Escherichia sp. ) SX-J4, and was deposited for biological preservation. Escherichia coil

[0036] Example 2 Study on the salt and alkali tolerance of Escherichia coli SX-J4 1. Pick Escherichia coli SX-J4 isolated in Example 1 and inoculate it into 10 mL of fermentation medium (10 g / L of Tryptone, 5 g / L of Yeast extract, 10 g / L of NaCl), and culture it at 35 °C with shaking at 180 rpm for 48 h to obtain the SX-J4 seed solution.

[0037] 2. Effect of NaCl concentration on Escherichia coli SX-J4 Inoculate the SX-J4 seed solution into 10 mL of LB liquid medium with different NaCl concentrations (0 wt.%, 2 wt.%, 4 wt.%, 6 wt.%, 8 wt.%, 10 wt.%, 12 wt.%, 14 wt.%, 16 wt.% and 18 wt.%) (5 g / L of yeast powder, 10 g / L of peptone and the corresponding concentration of NaCl, pH value is 7.0) at a volume ratio of 2%, culture it at 35 °C with shaking at 170 rpm for 4 d, and take the bacterial liquid at the end of the culture to measure the OD using a spectrophotometer 600Value determination was initially sorted using Microsoft Excel Office 2016 software, and plotted using R language (R v4.1.2). The results are as Figure 3 shown in a below.

[0038] As can be seen from Figure 3 a below, when adding NaCl at a concentration of 10 wt.% and below in LB liquid medium, the activity of Escherichia coli SX-J4 is good. When further increasing the NaCl concentration, although its activity will decrease, it still has a certain activity. Escherichia coli SX-J4 has strong salt tolerance.

[0039] 3. Effect of pH on Escherichia coli SX-J4 The SX-J4 seed liquid was inoculated into 10 mL of LB liquid medium with different pH values (2.8, 3.4, 4.2, 5.0, 5.8, 6.6, 7.4, 8.2, 9.0, and 10.0) (yeast powder 5 g / L, peptone 10 g / L, and NaCl 100 g / L) at a volume ratio of 2%, and cultured at 35 °C and 170 rpm for 4 d. The bacterial liquid at the end of the culture was taken to measure the OD 600 value. Initial sorting was carried out using Microsoft Excel Office 2016 software, and plotting was carried out using R language (R v4.1.2). The results are as Figure 3 shown in b below.

[0040] As can be seen from Figure 3 b below, the activity of Escherichia coli SX-J4 is good when the pH of LB liquid medium is ≥5.0, and the activity is the best at pH = 7.0 (initial LB medium). When 7.4 ≤ pH ≤ 10.0, as the alkalinity increases, the activity will slightly decrease, but still maintain a relatively high activity intensity. When pH < 5.0, its activity is poor. Escherichia coli SX-J4 has strong alkalinity tolerance and is not suitable for growing in an acidic environment.

[0041] Example 3 Study on the promotion of soybean seed germination by Escherichia coli SX-J4 in an alkaline environment 1. Preparation of Escherichia coli SX-J4 bacterial suspension Escherichia coli SX-J4 isolated in Example 1 was picked and inoculated into 10 mL of LB liquid medium (tryptone 10 g / L, yeast extract 5 g / L, and sodium chloride 10 g / L, pH value 7.0), and cultured at 35 °C and 180 rpm with shaking for 48 h to obtain the SX-J4 seed liquid; the concentration of the SX-J4 seed liquid was adjusted to 1.0×10 8CFU / mL to obtain an Escherichia coli SX-J4 bacterial suspension.

[0042] 2. Select soybeans seeds of uniform size and plumpness, disinfect them with 75% v / v ethanol for 3 min, then wash them 3 times with sterile water to remove residual ethanol. Randomly divide the treated seeds into 4 treatment groups, with 3 replicates in each group, and perform the following treatments: Control group (CK): Soak the treated soybean seeds in sterile water at room temperature for 3 h; Bacterial suspension experimental group (J4): Soak the treated soybean seeds in the Escherichia coli SX-J4 bacterial suspension at room temperature for 3 h; Saline-alkali stress solution experimental group (YJ): Soak the treated soybean seeds in a 10 wt.% NaCl solution with a pH of 10 at room temperature for 3 h; Mixed experimental group of bacterial suspension and saline-alkali stress solution (J4 + YJ): Mix a 10 wt.% NaCl solution with a pH of 10 and the Escherichia coli SX-J4 bacterial suspension in equal volumes to obtain a mixed solution; soak the treated soybean seeds in the mixed solution at room temperature for 3 h.

[0043] After the soaking is completed, select a sterile culture dish for the experiment. Specifically: Place a pre-sterilized filter paper in a 150 mm petri dish, and use a filter paper with good water absorption and water retention as the paper bed. Set the temperature to 30 °C during the day, the light intensity to 15000 LUX for 12 h, and the relative humidity to 80% in the plant incubator; the temperature is set to 25 °C and the relative humidity is 75% for 12 h in the dark, and culture continuously for 7 d. Start counting the germination rate of the seeds from the second day, and take the germination situation of the seeds on the 7th d as the total germination rate. Perform statistical tests according to one-way analysis of variance (ANOVA) in SPSS software to determine whether there are significant differences in the germination rate of soybeans among different experimental groups. After analyzing the data, use R language (R v4.1.2) for plotting, and the results are as Figure 4 shown.

[0044] According to Figure 4 It can be seen that within 7 days, the germination rate of soybean seeds in the control (CK) group is the highest, with an average germination rate of 93.67%; the germination rate of soybean seeds treated with the addition of the SX-J4 bacterial suspension is 87%; while the germination rate of soybean seeds treated with the saline-alkali stress solution is the lowest, with an average germination rate of 19.67%; when treated with the mixture of the SX-J4 bacterial suspension and the saline-alkali stress solution (J4 + YJ), the germination rate of soybean seeds increases by 79.67%. This shows that the addition of the SX-J4 bacterial suspension has a good effect of reducing the stress on soybean seeds inhibited by the saline-alkali solution on their germination rate; when only the SX-J4 bacterial suspension is added, the germination rate of soybean seeds is still very high, indicating that the bacterial suspension does not inhibit the germination rate of soybean seeds ( Figure 4In a). The results of the difference analysis of the total germination rate showed that the soybean germination rates under the CK, J4, and J4+YJ treatments were all higher than those under the YJ treatment group, and there was no significant difference in the soybean germination rate between the CK and SX-J4 bacterial suspension treatments ( Figure 4 In b).

[0045] Example 4 Study on the Alkalinity Reduction and Salt Dissolution of Escherichia coli SX-J4 1. Pick the Escherichia coli SX-J4 isolated in Example 1 and inoculate it into 10 mL of LB liquid fermentation medium (tryptone 10 g / L, yeast extract 5 g / L, and sodium chloride 10 g / L, pH value 7.0). Incubate it at 35 °C with shaking at 180 rpm for 48 h to obtain the SX-J4 seed solution; adjust the concentration of the SX-J4 seed solution to 1.0×10 8 CFU / mL to obtain the Escherichia coli SX-J4 bacterial suspension.

[0046] 2. Soil matrix collection and treatment: On July 19, 2024, in a centralized photovoltaic power generation area at high latitudes and low altitudes, collect natural saline-alkali soil with a soil sampling depth of 0 - 20 cm. After the collected soil is naturally air-dried for about a week and sieved to remove non-soil impurity components and other pretreatment, measure the basic physical and chemical properties, soluble saline-alkali ion components, and total salt content of the soil.

[0047] 3. Mix the sieved soil evenly and put it into 0.4 L flower pots. Randomly divide it into an experimental group (J4) and a control group (CK), with 4 replicates in each group, and carry out the following treatments: Control group (CK): Use NaCl solution (10 g / L) to irrigate 100 mL into the soil matrix every 10 days; Experimental group (J4): Use the Escherichia coli SX-J4 bacterial suspension obtained in step 1 to irrigate 100 mL into the soil matrix every 10 days.

[0048] Place the soil in a plant incubator, set the daytime temperature at 30 °C, light intensity at 15000 LUX for 12 h, relative humidity at 80%; the dark temperature for 12 h, temperature set at 25 °C, relative humidity at 75%, and continuously culture for 40 d, that is, a total of 4 irrigations are carried out.

[0049] 4. After the experiment in Step 3, the soil was taken and air-dried naturally, and then passed through a 2-mm sieve. 10 g of the treated soil was taken into a centrifuge tube, 25 mL of RO water was added, and the mixture was stirred for 30 minutes using a magnetic stirrer or a manual stirrer. The soil pH and conductivity were measured using a pH meter and a conductivity meter respectively. Statistical tests were performed in SPSS software according to the independent samples t-test to determine whether there were significant differences in soil pH and conductivity between different experimental treatment groups. After data analysis, plots were made using R language (R v4.1.2), and the results are as Figure 5 shown.

[0050] According to Figure 5 it can be seen that the soil pH value after culturing with Escherichia coli SX-J4 bacterial suspension for 40 d was significantly lower than that of the soil irrigated with 10 g / L NaCl solution under the control treatment ( p <0.05), indicating that Escherichia coli SX-J4 can reduce the pH value of strongly alkaline soil ( Figure 5 in a)). In addition, the measured soil conductivity value of the control treatment irrigated with 10 g / L NaCl solution was 3.62 Ms / cm, and the soil conductivity value after treatment with Escherichia coli SX-J4 bacterial suspension was 3.31 Ms / cm, which was significantly lower than that of the control group ( p <0.01), indicating that Escherichia coli SX-J4 can reduce the salt concentration ( Figure 5 in b)).

[0051] 5. After the experiment in Step 3, the soil was taken and air-dried naturally, and then passed through a 100-mesh sieve. 10 g of soil was taken and 50 ml of Watson's distilled water was added. It was shaken and cultured at 35 °C and a rotation speed of 180 rpm for 1 h using a shaker to ensure that the water-soluble sodium salts were fully dissolved. The soil sodium salt concentration under the experimental group and the control group was measured using IPC-OES. Statistical tests were performed in SPSS software according to the independent samples t-test to determine whether there were significant differences in soil sodium salt concentration between different experimental treatment groups. After data analysis, plots were made using R language (R v4.1.2), and the results are as Figure 6 shown.

[0052] According to Figure 6 it can be seen that the water-soluble sodium ion concentration in the soil under the control treatment was 3944.37 μg / g, and the water-soluble sodium ion concentration in the soil treated with Escherichia coli SX-J4 was 3459.35 μg / g, which was significantly lower than that of the control group ( p <0.05). It shows that when culturing soil with Escherichia coli SX-J4, the content of water-soluble sodium ions in saline-alkali soil can be significantly reduced.

[0053] Example 5 Study on the Promotion of Soybean Seed Growth in Alkaline Environment by Escherichia coli SX-J4 1. Preparation of Escherichia coli SX-J4 Bacterial Suspension Pick the Escherichia coli SX-J4 isolated in Example 1 and inoculate it into 10 mL of LB liquid medium (10 g / L of tryptone, 5 g / L of yeast extract, and 10 g / L of sodium chloride, pH value 7.0). Incubate it at 35 °C with shaking at 180 rpm for 48 h to obtain the SX-J4 seed liquid; adjust the concentration of the SX-J4 seed liquid to 1.0×10 7 CFU / mL and 1.0×10 8 CFU / mL to obtain Escherichia coli SX-J4 bacterial suspensions with different concentrations.

[0054] 2. Planting Soil Substrate: On July 19, 2024, in a centralized photovoltaic power generation area at high latitude and low altitude, collect natural saline-alkali soil with a soil sampling depth of 0 - 20 cm. After the collected soil is naturally air-dried for about one week and sieved to remove non-soil impurity components and other pretreatment, the sieved soil is obtained and reserved; measure the pH of the sieved soil to be 10.06 and the total salt content to be 8.11 mg / g; Mix nutrient soil (purchased from Stanley), vermiculite, and perlite in a volume ratio of 2:1:1, and stir evenly to obtain nutrient soil.

[0055] 3. Select healthy soybean seeds for surface disinfection (such as treating with 70% v / v ethanol for 1 min, then treating with 1% sodium hypochlorite for 5 min, and finally rinsing several times with sterile water) to obtain treated soybean seeds.

[0056] 4. Fill 4 / 5 of a 0.5 L flower pot according to the mass ratio of the sieved soil to the nutrient substrate of 3:1. First, put the sieved soil into a 0.4 L flower pot, sow the treated soybean seeds on top of the sieved soil, and then cover them with nutrient soil. Plant 4 soybean seeds in each flower pot and place them in a plant incubator. Set the daytime temperature to 30 °C, light intensity to 15000 LUX for 12 h, and relative humidity to 80%; set the dark temperature for 12 h to 25 °C and relative humidity to 80%; during the cultivation period, the following treatments are carried out: Control group (CK): Use NaCl solution (10 g / L) to irrigate 100 mL into the soil substrate every 10 days; Experimental group (J4): Use the Escherichia coli SX-J4 bacterial suspensions with concentrations of 1.0×10 7 CFU / mL and 1.0×10 8 CFU / mL obtained in step 1 to irrigate 100 mL into the soil substrate every 10 days.

[0057] The control group and the experimental group were each set with 4 replicates, and were irrigated a total of four times on the 1st, 11th, 21st, and 31st days after planting. At 35 days of cultivation, the plant height and chlorophyll content of soybeans were measured. At 40 days, the experiment was ended, and the total fresh biomass of soybean plants under different treatments was weighed. The data was statistically analyzed using an independent samples t-test (t-test) in SPSS software to determine whether there were significant differences in the plant height and biomass of soybean plants between different experimental treatment groups. After data analysis, R language (R v4.1.2) was used for plotting, and the results are as Figure 7 shown.

[0058] As can be seen from Figure 7 the above, the average heights of soybeans treated with low-concentration J4 bacteria and high-concentration J4 bacteria were 33.16 cm and 35.89 cm respectively, which were significantly higher than the plant height of 26.26 cm of soybeans treated with a 10 g / L NaCl solution; similarly, the average biomasses of soybeans treated with low-concentration J4 bacteria and high-concentration J4 bacteria were 33.16 g and 35.89 respectively, which were significantly higher than the biomass of 26.26 g of soybeans treated with a 10 g / L NaCl solution. Escherichia coli SX-J4 helps soybean plants grow in saline-alkali soil environments.

[0059] As can be seen from the above, the Escherichia coli SX-J4 provided by the present invention can promote the germination rate of seeds in saline-alkali environments and promote the growth of plants in saline-alkali environments. When applied to saline-alkali soil, it can effectively reduce the alkalinity of saline-alkali soil and degrade the concentration of water-soluble sodium ions in the soil.

[0060] Although the above embodiments have described the present invention in detail, they are only a part of the embodiments of the present invention, rather than all embodiments. People can also obtain other embodiments based on this embodiment without creative efforts, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A strain of Escherichia coli ( Escherichia coil )SX-J4, the deposit number is CGMCC NO.31724.

2. A bacterial agent, characterized in that The active ingredient of the bacterial agent includes the Escherichia coli SX-J4 described in claim 1.

3. The bacterial agent according to claim 2, characterized in that The concentration of Escherichia coli SX-J4 in the bacterial agent is 1×10 6 ~1×10 8 CFU / mL.

4. Use of the Escherichia coli SX-J4 according to claim 1 or the bacterial agent according to claim 2 or 3 in one or more of the following: (1) Improvement of saline-alkali soil; (2) Promote seed germination in saline-alkali environments; (3) Promote the growth of plants in saline-alkali environments.

5. The use according to claim 4, characterized in that: The saline-alkali soil improvement includes one or more of lowering the pH value of the saline-alkali soil, lowering the electrical conductivity of the saline-alkali soil, and lowering the water-soluble sodium ion content of the saline-alkali soil.

6. The use according to claim 4 or 5, characterized in that: The basic physical and chemical properties of the saline-alkali soil are: bulk density is 1.35~1.55g / cm 3 The average water content is 33.2%, the pH value is 9.86~10.51, and the cationic components of soluble salts include Na + , Fe 2+ , Ca 2+ Mg 2+ , K + , Mn 2+ 、Zn 2+ and Cu 2+ , total salt content is 8108.43μg / g.

7. The use according to claim 4, characterized in that: The promoting the growth of plants in saline-alkali environments comprises increasing one or more of the plant height, chlorophyll content and biomass of plants in saline-alkali environments; The seeds include soybean seeds; The plants include soybeans.

8. The use according to claim 4 or 7, characterized in that: The basic physical and chemical properties of the saline-alkali environment are: bulk density is 1.35~1.55g / cm 3 The average water content is 33.2%, the pH value is 9.86~10.51, and the cationic components of soluble salts include Na + , Fe 2+ , Ca 2+ Mg 2+ , K + , Mn 2+ 、Zn 2+ and Cu 2+ , total salt content is 8108.43μg / g.

9. A method for improving saline-alkali soil and / or promoting plant growth in a saline-alkali environment, characterized in that: include: Use the bacterial agent described in claim 2 or 3 to irrigate the soil.

10. A method for promoting seed germination in a saline-alkali environment, characterized in that: include: The seeds are soaked in the bacterial agent described in claim 2 or 3 and then cultured in a saline-alkali environment.

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