Plant lactobacillus T-7a and application thereof

Abstract

The invention relates to a plant lactobacillus T-7a and application thereof, and belongs to the technical field of microorganisms, the preservation number of the plant lactobacillus T-7a is CGMCC (China General Microbiological Culture Collection Center) No.36806, and the plant lactobacillus T-7a can tolerate 6% of salt environment at most, can remarkably promote wheat seed germination and wheat seedling growth in the salt environment, and can improve the photosynthetic capacity and the antioxidant capacity of wheat leaves, so that the plant lactobacillus T-7a has the advantages of high yield, high yield and the like. The method is of great significance in improving the yield and quality of wheat in saline-alkali soil.

Description

Technical Field

[0001] This invention relates to the field of microbial technology, specifically to a strain of Lactobacillus plantarum T-7a and its applications. Background Technology

[0002] Saline-alkali land refers to soil with excessively high soluble salt content and a pH value deviating from neutral. This type of soil leads to slow crop growth and low yields, severely hindering crop development. Globally, a large amount of land is affected by salinization, especially in arid and semi-arid regions where soil salinization is severe. Wheat, as one of the world's most important food crops, is severely impacted by saline-alkali land. The high salinity and alkalinity inhibit wheat seed germination, affect seedling growth and development, and ultimately lead to a decline in wheat yield and quality.

[0003] Currently, technologies for mitigating salt stress damage in wheat mainly include soil improvement (such as applying organic fertilizers), chemical regulation (such as spraying plant growth regulators), and microbial regulation (such as utilizing beneficial microorganisms). Among these, microbial regulation technology has become a research hotspot in recent years due to its advantages such as low cost, environmental friendliness, and strong sustainability. Lactic acid bacteria, as a type of safe and beneficial bacteria, have been widely used in food fermentation and crop disease control. Currently, there is limited research on isolating lactic acid bacteria from halophytes, and related strains and their application scenarios still need to be developed. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a strain of *Lactobacillus plantarum* T-7a and its applications.

[0005] The technical solution of this invention is as follows: A strain of *Lactobacillus plantarum* T-7a, the *Lactobacillus plantarum* ( Lactiplantibacillus plantarum T-7a was deposited on November 28, 2025, at the China General Microbiological Culture Collection Center, located at No. 3, Courtyard 1, Beichen West Road, Chaoyang District, Beijing, with accession number CGMCC No. 36806.

[0006] The 16S rRNA sequence of *Lactobacillus plantarum* T-7a is shown in SEQ ID NO.1.

[0007] The method for culturing *Lactobacillus plantarum* T-7a includes the following steps: (1) Plant Lactobacillus plantarum T-7a was inoculated onto MRS solid medium and activated at 37±2℃ to obtain activated strain; (2) Inoculate the activated strain from step (1) into MRS liquid culture medium and culture it with shaking at 180~200 rpm and 37±2℃ to obtain activated bacterial solution; (3) Inoculate the activated bacterial solution from step (2) into MRS liquid culture medium at an inoculation amount of 2-4% by volume, and culture with shaking at 180-200 rpm and 37±2℃ to obtain plant lactobacillus T-7a bacterial solution.

[0008] The application of *Lactobacillus plantarum* T-7a in promoting wheat seed germination under salt conditions.

[0009] The application of *Lactobacillus plantarum* T-7a in promoting wheat growth under saline conditions.

[0010] The application of *Lactobacillus plantarum* T-7a in increasing chlorophyll content in wheat leaves under saline conditions.

[0011] The application of *Lactobacillus plantarum* T-7a in enhancing the antioxidant capacity of wheat leaves under salt conditions.

[0012] A live bacterial preparation with *Lactobacillus plantarum* T-7a as the active ingredient.

[0013] The beneficial effects of this invention are: The *Lactobacillus plantarum* T-7a provided by this invention can tolerate a salt environment of up to 6% (60 g / L). It can significantly promote wheat seed germination, wheat seedling growth, and improve the photosynthetic capacity (increase the chlorophyll content of wheat leaves) and antioxidant capacity of wheat leaves under saline conditions. It is of great significance for improving the yield and quality of wheat in saline-alkali land. Attached Figure Description

[0014] Figure 1 The results show the salt tolerance test results for strains T-7a, NO.A331014, and NO.A333630. Figure 2 The effects of strains T-7a, NO.A331014, and NO.A333630 on wheat seed germination rate under salt stress were investigated. Figure 3 The effects of strains T-7a, NO.A331014, and NO.A333630 on wheat seedling height under salt stress were investigated. Figure 4 The effects of strains T-7a, NO.A331014, and NO.A333630 on root length of wheat seedlings under salt stress were investigated. Figure 5 The effects of strains T-7a, NO.A331014, and NO.A333630 on the fresh weight of wheat seedlings under salt stress were investigated. Figure 6 The effects of strains T-7a, NO.A331014, and NO.A333630 on chlorophyll content in wheat leaves under salt stress were investigated. Figure 7 The effects of strains T-7a, NO.A331014, and NO.A333630 on MDA content in wheat leaves under salt stress were investigated. Figure 8 The effects of strains T-7a, NO.A331014, and NO.A333630 on SOD activity in wheat leaves under salt stress were investigated. Figure 9 The effects of strains T-7a, NO.A331014, and NO.A333630 on POD activity in wheat leaves under salt stress were investigated. Detailed Implementation

[0015] The following description is based on specific embodiments: Explanation of the source of experimental materials: Lactobacillus plantarum ( Lactobacillus plantarum NO.A331014, Lactobacillus plantarum ( Lactobacillus plantarum NO. A333630: All were purchased from Sangon Biotech (Shanghai) Co., Ltd. The aforementioned *Lactobacillus plantarum* is an older name for *Lactobacillus plantarum*; both are different names for the same bacterium.

[0016] MRS liquid culture medium: peptone 10.0 g / L, beef extract 8.0 g / L, yeast extract 4.0 g / L, glucose 20.0 g / L, dipotassium hydrogen phosphate 2.0 g / L, diammonium hydrogen citrate 2.0 g / L, sodium acetate 5.0 g / L, magnesium sulfate 0.2 g / L, manganese sulfate 0.04 g / L, Tween 80 1.0 g / L.

[0017] MRS solid medium: Add 15 g / L agar to the MRS liquid medium.

[0018] Example 1: Isolation, screening and identification of Lactobacillus plantarum T-7a Leaves of *Suaeda salsa* were collected from saline lands in Shandong Province and Dongying City, China, and subjected to the following pretreatment: First, the leaves were repeatedly rinsed with tap water to thoroughly remove mud, sand, and impurities adhering to the leaf surface. Then, the leaves were dried with sterile filter paper. One gram of the pretreated leaves was weighed for double surface disinfection: first, it was immersed in a 5% sodium hypochlorite solution for 1 minute, then transferred to a 75% ethanol solution for 1 minute. After disinfection, the leaves were rinsed three times with sterile water to ensure the removal of residual disinfectant. Finally, the leaves were dried with sterile filter paper. The last sterile water rinse solution was evenly spread on MRS solid medium and incubated under suitable conditions. The thoroughness of leaf surface disinfection was determined by observing whether colonies grew on the medium (no colony growth indicates thorough disinfection). After successful disinfection verification, the leaves were cut into small pieces with sterile scissors and transferred to MRS liquid medium, and incubated at 37°C for 24 hours. After incubation, the culture medium was diluted with sterile water in six gradients (10-10). -1 10 -2 10 -3 10 -4 10 -5 10 -6 Take 100 μL of each of the three dilution gradients (10... -4 10 -5 10 -6 The culture medium of each colony was spread onto MRS solid medium and cultured until single colonies appeared. Based on the differences in colony morphology, single colonies of different morphologies were picked and purified multiple times on MRS solid plates using the streak plate method until a single colony was obtained and named "T-7a".

[0019] Molecular biological identification of strain T-7a: The whole-genome DNA of the strain was extracted and used as a template to amplify the 16S rRNA gene sequence. The amplified product was sequenced, and the sequencing results are shown in SEQ ID NO.1. The obtained 16S rRNA sequence was compared with existing gene sequences in the NCBI database. The results showed that strain T-7a had a similarity of over 99% with *Lactobacillus plantarum*. Based on the physiological characteristics of the strain, it was identified as *Lactobacillus plantarum*. Lactiplantibacillus plantarum ).

[0020] The above-mentioned Lactobacillus plantarum ( Lactiplantibacillus plantarum T-7a was deposited on November 28, 2025, at the China General Microbiological Culture Collection Center (CGMCC), located at No. 3, Courtyard 1, Beichen West Road, Chaoyang District, Beijing, with accession number CGMCC No. 36806.

[0021] Example 2: Culture of Lactobacillus plantarum T-7a The specific method is as follows: (1) Plant Lactobacillus plantarum T-7a was inoculated onto MRS solid medium and activated at 37±2℃ for 24h to obtain activated strain; (2) The activated strain from step (1) was inoculated into MRS liquid culture medium and cultured with shaking at 180 rpm and 37±2℃ for 24 h to obtain activated bacterial solution; (3) The activated bacterial solution from step (2) was inoculated into MRS liquid culture medium at an inoculation amount of 2% by volume, and cultured with shaking at 180 rpm and 37±2℃ for 24 h to obtain plant lactobacillus T-7a bacterial solution.

[0022] Example 3: Salt tolerance test of Lactobacillus plantarum T-7a MRS liquid culture media with NaCl concentrations ranging from 0 mM (0%), 20 g / L (2%), 40 g / L (4%), 60 g / L (6%), 80 g / L (8%), and 100 g / L (10%) were prepared. *Lactobacillus plantarum* T-7a, NO. A331014, and NO. A333630 were inoculated into the aforementioned MRS liquid culture media containing different NaCl concentrations and incubated at 37°C for 24 h. The OD of the culture medium was then measured. 600 Value (characterizing growth amount), results are as follows Figure 1 As shown.

[0023] Depend on Figure 1 It was found that the growth of the three Lactobacillus plantarum strains T-7a, NO.A331014, and NO.A333630 under different salt stress concentrations did not differ significantly, and all of them could tolerate a salt environment with a maximum NaCl concentration of 6%.

[0024] In addition to its salt tolerance, strain T-7a can also tolerate alkaline environments with a maximum pH of 10.

[0025] Example 4: Effect of *Lactobacillus plantarum* T-7a on wheat seed germination rate under salt stress Lactobacillus plantarum T-7a, NO.A331014, and NO.A333630 were cultured in MRS liquid medium to the logarithmic growth phase. The culture was centrifuged at 6000 rpm for 5 min, and the bacterial pellet was collected. The bacterial pellet was resuspended in 300 mM NaCl aqueous solution and the OD was adjusted. 600 The value was adjusted to 1.0 to obtain T-7a bacterial suspension, NO.A331014 bacterial suspension, and NO.A333630 bacterial suspension.

[0026] Select wheat seeds of uniform size and plumpness. First, rinse with distilled water to remove surface impurities, then blot dry with sterile filter paper. Next, soak in 2% sodium hypochlorite solution for 15 minutes for surface disinfection. After disinfection, rinse three times with sterile water to remove residual disinfectant, and then soak in sterile water for 2 hours. Place the soaked wheat seeds evenly in sterile petri dishes lined with two layers of sterile filter paper, with 30 seeds in each dish. Add 5m³ of LT-7a bacterial suspension, NO.A331014 bacterial suspension, and NO.A333630 bacterial suspension to each petri dish, respectively. Use petri dishes containing the same volume of 300mM sterile NaCl solution as a blank control group (CK). All treatment groups were designed with three biological replicates. Place all petri dishes in a 25℃ constant temperature incubator, using a light-protected environment to simulate the dark environment for seed germination. To maintain stable germination conditions, the filter paper and bacterial suspension / sterile NaCl solution were changed every two days during the experiment to ensure adequate moisture throughout the seed germination process. The experiment lasted for 5 days. The number of germinated wheat seeds in each petri dish was recorded, and the germination rate was calculated. The results are as follows: Figure 2 As shown.

[0027] Depend on Figure 2 It was found that under salt stress with a NaCl concentration of 300 mM, the germination rate of wheat seeds in the blank control group (CK) did not exceed 80%, and the addition of salt-tolerant Lactobacillus plantarum NO.A331014 and NO.A333630 had no significant effect on the germination rate of wheat seeds; after the addition of Lactobacillus plantarum T-7a, the germination rate of wheat seeds increased by 16.7% compared with the blank control group, which indicates that strain T-7a can significantly improve the germination rate of wheat seeds.

[0028] Example 5: Growth-promoting effect of Lactobacillus plantarum T-7a on wheat seedlings under salt stress Lactobacillus plantarum T-7a, NO.A331014, and NO.A333630 were cultured in MRS liquid medium to the logarithmic growth phase. The culture was centrifuged at 6000 rpm for 5 min, and the bacterial pellet was collected. The bacterial pellet was resuspended in sterile water and the OD was adjusted. 600 The value was adjusted to 1.0 to obtain T-7a bacterial suspension, NO.A331014 bacterial suspension, and NO.A333630 bacterial suspension.

[0029] Select wheat seeds of uniform size and plump kernels. First, rinse with distilled water to remove surface impurities, then soak in a 2% sodium hypochlorite solution for 15 minutes for surface disinfection. After disinfection, rinse three times with sterile water to remove residual disinfectant, and then soak in sterile water for 12 hours for vernalization. The vernalized wheat seeds were planted in soil with a NaCl concentration of 100 mM. Every two days, a bacterial suspension was poured around the wheat roots at a volume of 60 mL. Simultaneously, an equal volume of sterile water was added as a blank control group (CK). All treatment groups were designed with three biological replicates. All treatment groups were cultured under the same environment for 21 days. After culture, wheat seedlings were collected, and the plant height, root length, and fresh weight of each group were measured. The results are as follows: Figures 3-5 As shown. After the measurement, fresh wheat leaves were collected for later use.

[0030] Figures 3-5 The effects of *Lactobacillus plantarum* T-7a, NO. A331014, and NO. A333630 on wheat seedling height, root length, and fresh weight under salt stress were investigated, in descending order. Figures 3-5 It was found that under salt stress with a NaCl concentration of 100 mM, the addition of salt-tolerant *Lactobacillus plantarum* NO.A331014 and NO.A333630 did not significantly promote the root length of wheat seedlings. However, the addition of *Lactobacillus plantarum* T-7a significantly increased the plant height, root length, and fresh weight of wheat seedlings compared to the blank control group and NO.A331014 and NO.A333630, indicating that strain T-7a has a significant effect on promoting wheat growth under salt stress.

[0031] Example 6: Effects of *Lactobacillus plantarum* T-7a on chlorophyll content in wheat leaves under salt stress Fresh wheat leaves were collected in Example 5, and the total chlorophyll (Ct) content in the leaves was determined using the acetone-ethanol mixture extraction method. The results are as follows: Figure 6 As shown.

[0032] Depend on Figure 6 It was found that under salt stress with a NaCl concentration of 100 mM, the addition of salt-tolerant Lactobacillus plantarum NO.A331014 and NO.A333630 had no significant effect on the chlorophyll content in wheat leaves. However, the addition of Lactobacillus plantarum T-7a significantly increased the chlorophyll content in wheat leaves compared with the blank control group. This indicates that strain T-7a has the effect of significantly increasing the chlorophyll content in wheat leaves under salt stress.

[0033] Example 7: Effects of *Lactobacillus plantarum* T-7a on the antioxidant capacity of wheat leaves under salt stress Fresh wheat leaves were collected in Example 5. The malondialdehyde (MDA) content, superoxide dismutase (SOD) activity, and peroxidase (POD) activity in the wheat leaves were determined using a dedicated malondialdehyde (MDA) assay kit, a dedicated superoxide dismutase (SOD) assay kit, and a dedicated peroxidase (POD) assay kit, respectively. The results are shown below. Figures 7-9 As shown.

[0034] Figures 7-9 The effects of *Lactobacillus plantarum* T-7a, NO. A331014, and NO. A333630 on MDA content, SOD activity, and POD activity in wheat leaves under salt stress were investigated, in descending order. Figures 7-9 It was found that under salt stress with a NaCl concentration of 100 mM, the addition of salt-tolerant *Lactobacillus plantarum* NO.A331014 and NO.A333630 had no significant effect on the MDA content, SOD activity, and POD activity of wheat seedlings. However, the addition of *Lactobacillus plantarum* T-7a significantly reduced the MDA content of wheat seedlings compared to the blank control group, while significantly increased the SOD and POD activities. This indicates that strain T-7a can significantly improve the antioxidant capacity of wheat leaves under salt stress.

[0035] The above results indicate that the salt tolerance of strains NO.A331014 and NO.A333630 does not necessarily guarantee their ability to exert beneficial effects on plants, such as promoting growth, increasing chlorophyll content, and providing antioxidant effects, under saline conditions. This invention provides a strain of *Lactobacillus plantarum* T-7a, which can tolerate a maximum salt concentration of 6% and significantly promotes wheat seed germination, seedling growth, and enhances the photosynthetic and antioxidant capacity of wheat leaves under saline conditions. This is of great significance for improving wheat yield and quality in saline-alkali land.

Claims

1. A strain of *Lactobacillus plantarum* T-7a, wherein *Lactobacillus plantarum* ( Lactiplantibacillus plantarum T-7a was deposited on November 28, 2025, at the China General Microbiological Culture Collection Center, located at No. 3, Courtyard 1, Beichen West Road, Chaoyang District, Beijing, with accession number CGMCC No. 36806.

2. The culture method of Lactobacillus plantarum T-7a according to claim 1, characterized by, The method comprises the following steps: (1) inoculate Lactiplantibacillus plantarum T-7a on MRS solid medium, and activate the culture at 37±2°C to obtain an activated strain; (2) inoculate the activated strain in step (1) into MRS liquid medium, and shake culture at 180-200 rpm and 37±2°C to obtain an activated bacterial liquid; (3) inoculate the activated bacterial liquid in step (2) into MRS liquid medium at a volume percentage of 2-4%, and shake culture at 180-200 rpm and 37±2°C to obtain Lactiplantibacillus plantarum T-7a bacterial liquid.

3. Application of Lactiplantibacillus plantarum T-7a in claim 1 in promoting wheat seed germination in a salt environment.

4. Application of Lactiplantibacillus plantarum T-7a in claim 1 in promoting wheat growth in a salt environment.

5. Application of Lactiplantibacillus plantarum T-7a in claim 1 in increasing wheat leaf chlorophyll content in a salt environment.

6. Application of Lactiplantibacillus plantarum T-7a in claim 1 in improving wheat leaf antioxidant capacity in a salt environment.

7. A viable bacterial preparation with Lactiplantibacillus plantarum T-7a in claim 1 as an effective component.

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