Microbacterium paraoxidans and application thereof

Abstract

The invention belongs to the field of microorganisms, and particularly discloses a microbacterium paraoxidans strain and application thereof, the microbacterium paraoxidans strain TYQ7 is preserved in the China General Microbiological Culture Collection Center (CGMCC), the preservation number is CGMCC No.27216, and the preservation number is CGMCC No.27216. The microbacterium paraoxidans strain TYQ7 has the advantages that the microbacterium paraoxidans strain TYQ7 is preserved in the China General Microbiological Culture Collection Center (CGMCC); the applicant finds that the microbacterium paraoxidans can secrete auxin, can promote growth of cucumber seedlings, also has the capabilities of interfering tropism migration of nematodes and killing nematodes, has the effect of remarkably relieving stress of root-knot nematodes, also finds that the microbacterium paraoxidans has the capability of inhibiting normal growth of fusarium oxysporum, and has the effect of remarkably relieving stress of root-knot nematodes. Furthermore, the microbacterium paraoxidans have the capability of degrading vegetable straws and the capability of dissolving phosphorus, so that the applicant considers that the microbacterium paraoxidans have a remarkable application prospect in the fields of agriculture and environmental protection.

Description

Technical Field

[0001] The present invention belongs to the field of microorganisms, and specifically discloses a Microbacterium paraoxydans and its application. Background Art

[0002] Plant growth-promoting rhizobacteria (PGPR) play a crucial role in the process of modern agriculture pursuing sustainable development and high-efficiency production. Through various mechanisms such as nitrogen fixation, phosphorus solubilization, and potassium solubilization, plant growth-promoting bacteria increase the content of plant-available nutrients in the soil, thus significantly promoting plant growth. They can also secrete various plant hormones, such as auxin, etc., to regulate the physiological processes of plants, stimulate root development, enhance the ability of plants to absorb water and nutrients, and improve crop yield and quality. Therefore, exploring and utilizing efficient plant growth-promoting bacteria resources is of great significance for improving agricultural production efficiency, reducing the use of chemical fertilizers, ensuring the safety of agricultural products, and the health of the ecological environment.

[0003] Root-knot nematodes (Meloidogyne) and Fusarium oxysporum are two types of highly destructive plant pathogens that seriously threaten the safe production of global crops. Root-knot nematodes invade plant roots, form root knots, hinder the absorption of water and nutrients by roots, resulting in weak and stunted plant growth, and even death of the whole plant in severe cases. Fusarium oxysporum can cause wilt diseases in a variety of plants, and rapidly reproduce under suitable conditions, destroying the vascular system of plants and causing the plants to wither due to water loss. Currently, for these two pathogens, chemical agents are mainly used for control, but problems such as their residual toxicity, poor environmental compatibility, and the risk of drug resistance are becoming increasingly prominent. Although there have been studies attempting to use antagonistic microorganisms for biological control, most strains have limitations such as unstable control efficacy, single action target, or unclear interaction mechanism with plants, and it is difficult to meet the needs of sustainable agricultural development.

[0004] Crop straw is a large amount of by-product of agricultural production. Traditional straw treatment methods, such as burning, not only cause waste of resources, but also produce a large amount of soot, polluting the atmospheric environment. Reasonable degradation and conversion of straw into organic fertilizer is a key link in realizing agricultural ecological cycle. Microorganisms with efficient straw degradation function can decompose complex organic substances such as cellulose, hemicellulose, and lignin in straw into small molecule substances such as humus, amino acids, and sugars. These substances can improve soil fertility, improve soil structure, promote the growth and reproduction of soil microorganisms, enhance the water and fertilizer retention capacity of the soil, and create a good soil environment for crop growth.

[0005] Although some microorganisms have been applied in the agricultural field, there is still a shortage of microbial strains that can simultaneously possess multiple excellent characteristics, such as promoting plant growth, biological control, straw degradation, soil nutrient release, enhancing plant stress resistance and strong adaptability. Therefore, the development and utilization of multifunctional microbial strains have important practical significance and broad application prospects. A strain of Microbacterium paraoxydans provided by the present invention exhibits excellent performance in the above aspects and is expected to bring new breakthroughs to agricultural production. Summary of the Invention

[0006] In view of the above problems, the present invention discloses a strain of Microbacterium paraoxydans and its application.

[0007] In order to achieve the above invention purposes, the technical solutions of the present invention are as follows:

[0008] A strain of Microbacterium paraoxydans, the strain TYQ7 of Microbacterium paraoxydans is preserved in the China General Microbiological Culture Collection Center, and the preservation number is CGMCC No. 27216.

[0009] The present invention also discloses a microbial inoculum containing the cells of the above-mentioned Microbacterium paraoxydans and / or its metabolites and / or its fermentation broth.

[0010] The present invention also discloses the use of the above-mentioned bacterium or bacterium agent in the preparation of a preparation for enhancing the growth promotion of cucumber seedlings.

[0011] The present invention also discloses the use of the above-mentioned bacterium or bacterium agent in the preparation of a preparation for interfering with the migration of Meloidogyne incognita.

[0012] The present invention also discloses the use of the above-mentioned bacterium or bacterium agent in the preparation of a preparation for controlling Meloidogyne incognita.

[0013] The present invention also discloses the use of the above-mentioned bacterium or bacterium agent in the preparation of a preparation for inhibiting the growth of Fusarium oxysporum.

[0014] The present invention also discloses the use of the above-mentioned bacterium or bacterium agent in the preparation of a preparation for dissolving phosphorus.

[0015] The present invention also discloses the use of the above-mentioned bacterium or bacterium agent in the preparation of a preparation for straw degradation.

[0016] The present invention has the following beneficial effects:

[0017] The present invention discloses a strain of Pseudomonas krebsiensis and its applications. In terms of promoting growth, the Microbacterium paraoxydans TYQ7 disclosed by the present invention has the growth-promoting characteristics of dissolving inorganic phosphorus and secreting auxin. TYQ7 can utilize tryptophan to produce IAA, and the measured content is 43.98 μg / mL. Moreover, it significantly promotes the growth of cucumbers, with the dry weight of the above-ground part increasing by 32.18%, the root volume expanding by 64.10%, and the strong seedling index increasing by 36.29%. In addition, TYQ7 shows a significant effect on the migration and lethality of nematodes. Especially in terms of the lethality to the second-stage larvae of root-knot nematodes, its effect is significantly better than that of the control strain. And TYQ7 has a significant effect on alleviating the stress of root-knot nematodes. Compared with the cucumbers infected by the same root-knot nematodes, the dry weights of the above-ground part and the underground part increase by 23.81% and 28.89% respectively, the number of root knots per unit root weight decreases by 40.57%, and the chlorophyll content increases by 160.54%. In the growth inhibition experiment of Fusarium oxysporum, it shows a strong antagonistic effect. Within two weeks, the degradation rates of TYQ7 on tomato, cucumber, pepper, and eggplant straws reach 66.14%, 37.72%, 26.23%, and 30.18% respectively. Biolog analysis shows that it can utilize 71 carbon sources, shows resistance to nalidixic acid, lithium chloride, and aztreonam, and has broad-spectrum metabolic ability and environmental adaptability. To sum up, the TYQ7 strain shows good application potential in promoting plant growth, enhancing plant stress resistance, soil improvement, and environmental remediation, etc.

[0018] The information of strain preservation is as follows:

[0019] The name of the preservation unit: General Microbiology Center, China Committee for Culture Collection of Microorganisms;

[0020] The address of the preservation unit: No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing;

[0021] The preservation date: April 27, 2023

[0022] The preservation number is CGMCC No. 27216,

[0023] Taxonomic nomenclature: Microbacterium paraoxydans. Description of the drawings

[0024] Figure 1 It is the colony morphology of TYQ7;

[0025] Figure 2 It is the phylogenetic evolution tree diagram of TYQ7:

[0026] Figure 3 It is the effect diagram of the influence of TYQ7 inoculation on cucumber plants and roots;

[0027] Figure 4 It is the effect diagram of TYQ7 producing auxin;

[0028] Figure 5 It is a schematic diagram of the tropotactic migration experiment of Meloidogyne incognita after inoculation with TYQ7;

[0029] Figure 6 It is a diagram showing the influence of TYQ7 on the tropotactic migration of Meloidogyne incognita;

[0030] Figure 7 It is an effect diagram of the tropotactic migration of Meloidogyne incognita after inoculation with TYQ7;

[0031] Figure 8 It is a diagram showing the influence of the original fermentation supernatant of TYQ7 on the in vitro contact toxicity of Meloidogyne incognita;

[0032] Figure 9 It is an effect diagram of the in vitro contact toxicity of the original fermentation supernatant of TYQ7 on Meloidogyne incognita;

[0033] Figure 10 It is an effect diagram showing the influence of TYQ7 on cucumber plants and roots under the infection of Meloidogyne incognita after inoculation;

[0034] Figure 11 It is an effect diagram of the confrontation antagonism between TYQ7 and Fusarium oxysporum on a plate;

[0035] Figure 12 It is an effect diagram of the degradation of TYQ7 on four kinds of vegetable straws;

[0036] Figure 13 It is a phosphorus solubilization characteristic diagram of TYQ7;

[0037] Figure 14 It is a phosphorus solubilization ability diagram of TYQ7 under gradient salt concentration and gradient pH;

[0038] Figure 15 It is a fingerprint diagram of the utilization ability of TYQ7 for different carbon sources. Specific implementation manners

[0039] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0040] The following detailed description of the embodiments of the present invention provided is not intended to limit the scope of the claimed present invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0041] Example 1

[0042] 1.1 Isolation and purification of Microbacterium paraoxydans TYQ7:

[0043] The Microbacterium paraoxydans TYQ7 strain of the present invention was isolated from the rhizosphere soil of cucumber infected with root-knot nematodes in the laboratory of China Agricultural University. The isolation method was the soil dilution method. The specific steps are as follows:

[0044] Using the soil dilution method, 4 portions of 1 g of mixed soil samples were collected from the rhizosphere of cucumber infected with root-knot nematodes in the facility vegetable laboratory of China Agricultural University, placed in a 50 ml centrifuge tube containing 9 ml of sterile water, and shaken at 180 rpm for 20 minutes. After gradient dilution, 100 μL was taken and spread on an LB plate, and cultured under light at 28 °C for 2 days. Single colonies were picked and purified by streaking three times.

[0045] 1.2 Identification of Microbacterium paraoxydans TYQ7 strain

[0046] (1) Microbiological characteristics

[0047] The obtained strain was inoculated on an LB medium plate and cultured at 28 °C for 2 days. The colony morphology was as Figure 1 shown. The single colony of Microbacterium paraoxydans was round, light yellow and opaque. The surface was smooth and moist, and the edge was irregular. The central part was slightly raised, and a biofilm would naturally form around the single spot. The Gram stain was positive.

[0048] (2) Molecular biological characteristics

[0049] Single colonies were picked into a 1.5 ml centrifuge tube containing 1 mL of LB medium, and cultured with shaking at 28 °C and 180 rpm / min for 24 h. Using this bacterial solution as a template, 16S rRNA sequence amplification was performed with primers 27F and 1492R.

[0050] The PCR amplification reaction system was 50 μL, including 25 μL of 2x Taq enzyme, 1 μL of 27F primer, 1 μL of 1492R primer, 1 μL of bacterial solution and 22 μL of ddH2O. The amplification conditions were: pre-denaturation at 95°C for 3 min, denaturation at 94°C for 25 s, annealing at 55°C for 25 s, extension at 72°C for 1 min, 32 cycles, extension at 72°C for 5 min, and the amplification products were stored at 4°C. The amplification products were separated and identified by 1% agarose gel electrophoresis, and the PCR products were sent to Beijing Tsingke Biotechnology Co., Ltd. for bidirectional sequencing. The 16S rDNA of strain TYQ7 is shown as the following SEQ ID NO: 1:

[0051]

[0052]

[0053] The determination results were subjected to BLAST homology alignment, and the results showed that the similarity of this strain to Microbacterium paraoxydans reached 99.86%. Therefore, as shown in the phylogenetic tree of TYQ7 Figure 2 This strain was identified as a strain of the genus Microbacterium, named Microbacterium paraoxydans TYQ7, and it was deposited in the General Microbiological Center of the China Committee for Culture Collection of Microorganisms with the deposit number CGMCC.27216.

[0054] Example 2

[0055] Growth promotion effect of TYQ7 on cucumber

[0056] Using cucumber as the test material, through pot experiments, the ability of TYQ7 to promote plant growth was measured. The treatments set in this example were: ① Conventional control treatment (CK); ② Inoculation with TYQ7 inoculant (TYQ7). The specific implementation steps are as follows:

[0057] The specific implementation steps are as follows:

[0058] 2.1 Seed disinfection

[0059] Select cucumber seeds with plump grains and no mechanical damage, and perform surface disinfection according to the following process:

[0060] (1) Immerse in 75% ethanol for 30 seconds and rinse 3 times with sterile distilled water;

[0061] (2) Transfer to 3% NaClO solution and soak for 10 minutes, and rinse with sterile distilled water until there is no residue;

[0062] (3) After soaking the seeds in sterile water for 6 hours, place them in a petri dish lined with sterile wet filter paper;

[0063] (4) Carry out germination acceleration treatment in an incubator at a constant temperature of 28°C.

[0064] 2.2 Strain inoculation

[0065] Preparation of sterilized soil

[0066] After collecting forest soil and passing it through a sieve, sterilize it at 120°C under high pressure for 1 hour, and repeat the sterilization once after an interval of 24 hours.

[0067] Preparation of bacterial suspension

[0068] Inoculate strain TYQ7 into LB liquid medium, and shake-culture it at 28°C and 180 rpm until the OD600 reaches 0.8. Centrifuge at 8000 rpm for 5 min to collect the bacteria, and resuspend them with an equal volume of 10 mM MgSO4 buffer to prepare the bacterial agent.

[0069] Inoculation operation

[0070] After the radicle germinates, sow it in a 50-hole tray filled with sterilized soil. Start the treatment when the first true leaf of the seedling appears: irrigate 10 mL of bacterial suspension per plant, once a week for 3 consecutive weeks.

[0071] 2.3 Plant measurement

[0072] Take samples (n = 20) 21 days after the treatment, and measure the following parameters:

[0073] (1) Morphological indexes: Measure the stem diameter (mm) with a vernier caliper and the plant height (cm) with a meter stick

[0074] (2) Biomass: Weigh the fresh weight of the aboveground / underground parts with a percentile balance

[0075] (3) Dry matter: Measure the dry weight of each part after drying at 65°C to a constant weight

[0076] (4) Root system analysis: After scanning with a root scanner, analyze the total root length, root surface area, average root diameter and root volume with the WinRHIZO system

[0077] The seedling quality index (SQI) is calculated according to the following formula.

[0078] SQI = TDW / (PH / SD + SDW / RDW)

[0079] Where TDW, SDW and RDW represent the dry weight of the whole plant (g), the dry weight of the aboveground part (g) and the dry weight of the underground part (g) respectively, and PH (cm) and SD (mm) represent the plant height and stem diameter respectively.

[0080] 2.4 Result analysis

[0081] The effects of TYQ7 inoculation on the growth indexes and roots of cucumber seedlings are shown in Table 1-2, and the effects of TYQ7 inoculation on cucumber plants and roots are shown in Figure 3 , as shown in the chart:

[0082] (1) Stem diameter development: The TYQ7 treatment group was significantly increased by 9.47% compared with the control

[0083] (2) Dry matter accumulation: The above-ground dry weight and the whole-plant dry weight increased by 32.18% and 27.7% respectively

[0084] (3) Root development: The total root length, root surface area, root average diameter and root volume increased by 2.66%, 29.40%, 26.31% and 64.10% respectively

[0085] (4) Seedling vigor index: The TYQ7 treatment group was increased by 36.29% compared with the control

[0086] It shows that TYQ7 has a significant growth-promoting and seedling-strengthening effect on cucumbers

[0087] Table 1 Effects of TYQ7 inoculation on the growth indexes of cucumber seedlings

[0088]

[0089] Table 2 Effects of TYQ7 inoculation on the roots of cucumber seedlings

[0090]

[0091] Example 3

[0092] The Salkowski colorimetric method was used to qualitatively and quantitatively analyze the indole-3-acetic acid (IAA) production ability of the strain. The specific process is as follows:

[0093] 3.1 Qualitative detection

[0094] 3.1.1 Preparation of chromogenic reagent

[0095] Prepare the Salkowski chromogenic reagent according to the following steps:

[0096] (1) 0.5M FeCl3 solution: 0.811g of FeCl3 was dissolved in 10mL of sterile distilled water;

[0097] (2) Working solution: Take 1mL of 0.5M FeCl3 solution and mix it with 49mL of 35% HClO4, and mix well for later use.

[0098] 3.1.2 Bacterial liquid treatment

[0099] (1) Bacterial strain activation: Pick a single colony and inoculate it into 30mL of LB medium, and shake culture at 28°C and 180rpm until OD600 = 0.8;

[0100] (2) Induction culture: Transfer the bacterial liquid to LB medium containing 500 μg / mL of filter-sterilized tryptophan according to an inoculation amount of 1%, and use the uninoculated medium as a blank control. Culture at 28 °C and 180 rpm for 72 h;

[0101] (3) Centrifuge to obtain supernatant: Centrifuge at 10000 rpm for 10 min, and collect the cell-free supernatant.

[0102] 3.1.3 Color reaction

[0103] Mix 500 μL of the supernatant with 1 mL of the color reagent and let it stand at room temperature for 30 min. The effect diagram of auxin production by TYQ7 is shown in Figure 4 , and the pink color of the solution indicates the presence of IAA.

[0104] 3.2 Quantitative analysis

[0105] 3.2.1 Standard curve establishment

[0106] (1) Stock solution preparation: 100 mg / L IAA standard solution;

[0107] (2) Serial dilution: A series of concentrations of 0, 10, 20, 30, 40, 50, 60, 80, 100 mg / L;

[0108] (3) Standard measurement: Measure the OD values of each concentration at a wavelength of 530 nm, and establish a concentration-absorbance standard curve.

[0109] 3.2.2 Sample detection

[0110] (1) Reaction system: 500 μL of the strain supernatant + 4 mL of the color reagent, react in the dark for 30 min;

[0111] (2) Absorbance measurement: Detect the OD value of the sample at 530 nm and calibrate with the blank control;

[0112] (3) Concentration calculation: Calculate the IAA content through the standard curve, and set 3 replicates for the experiment.

[0113] 3.3 Experimental results

[0114] Quantitative detection shows that the strain TYQ7 can secrete IAA in the medium containing tryptophan, and the yield reaches 43.98 μg / mL.

[0115] Example 4

[0116] Effect of the fermentation supernatant of Microbacterium paraoxydans TYQ7 on the chemotactic migration of Meloidogyne incognita.

[0117] 4.1 Bacterial suspension preparation

[0118] Refer to the process of preparing the bacterial suspension in Example 2

[0119] 4.2 Cucumber root treatment

[0120] (1) Seed disinfection: Refer to the disinfection process in Example 2;

[0121] (2) Cucumber cultivation: Sow after germination. At the cotyledon flat stage (5 - 7 days), irrigate 10 mL of the bacterial suspension. Take the roots at the two - leaves - one - heart stage for the experiment.

[0122] 4.3 Obtaining second - instar larvae

[0123] (1) Egg mass separation: Pick the egg masses from the roots of diseased water spinach, and wash them by shaking with 0.6% NaClO;

[0124] (2) Sterile hatching: After filtering through a 600 - mesh sieve, place the egg masses in sterile water containing 0.004 mg / mL gentamicin and incubate at room temperature for 2 - 3 days;

[0125] (3) Density adjustment: After counting under a microscope, prepare a larval suspension of 100 larvae / 100 μL.

[0126] 4.4 Preparation of 23% Pluronic F - 127 gel

[0127] Dissolve 23 g of the powder in 80 mL of sterile water at 4°C, stir magnetically until completely dissolved, and store at 4°C for later use after preparation.

[0128] 4.5 Chemotactic migration experiment

[0129] (1) Experimental grouping: Set up an uninoculated control group (CK) and a TYQ7 treatment group, with 20 replicates each;

[0130] (2) Migration device: Place the roots of CK and the treatment group on both sides of the gel plate respectively, and preset a 0.5 - cm - diameter Oxford cup hole in the center. The schematic diagram of the experiment is as shown in Figure 5 shown;

[0131] (3) Nematode inoculation: Add 100 μL of the nematode suspension (about 100 nematodes) to the hole, and let it stand in the dark for 12 h;

[0132] (4) Data collection: Count the number of migrating nematodes on both sides under a microscope and calculate the migration percentage.

[0133] 4.6 Result analysis

[0134] The influence and effect of TYQ7 inoculation on the chemotactic migration of Meloidogyne incognita are shown in Figure 6 、 Figure 7; From the tropotaxis migration results, it can be seen that when TYQ7 is applied alone, it has a significant impact on the tropotaxis of nematodes. The percentage of nematodes migrating towards the cucumber root tips in the CK group reaches 5.359%, which is significantly higher than that on the side of cucumber roots with TYQ7. It has a significant impact on the tropotaxis of nematodes.

[0135] Example 5

[0136] Contact killing effect of the fermentation supernatant of Microbacterium paraoxydans TYQ7 on Meloidogyne incognita in vitro.

[0137] 5.1 Preparation of the supernatant of the strain fermentation broth

[0138] The tested strain is Microbacterium paraoxydans TYQ7, and the cell suspension is the same as in Example 2.

[0139] After the preparation of the cell suspension is completed, centrifuge at 10,000 rpm for 5 min. Use a syringe to aspirate the supernatant in the centrifuge tube and filter it through a 0.22 μm filter membrane. The solution obtained after filtration is the supernatant of the fermentation broth of Microbacterium paraoxydans TYQ7.

[0140] 5.2 Contact killing experiment in vitro

[0141] Add 400 μL of the fermentation supernatant of TYQ7 and the control strain into a 48-well cell culture plate respectively, and add 100 μL of a suspension of Meloidogyne incognita second-stage larvae containing 100 larvae to each well. The control group is replaced with 400 μL of sterile water.

[0142] Place it in a constant temperature incubator at 28 °C in the dark and let it stand. Observe the survival situation through a stereomicroscope after 12 h and 24 h respectively. Judgment criterion: After adding 1 mol / L NaOH solution, those that are rigid and motionless are dead, and those that are wriggling are alive. Count the number of dead and calculate the corrected mortality rate.

[0143]

[0144] 5.3 Result analysis

[0145] The influence and effect of the original solution of the TYQ7 fermentation supernatant on the contact killing effect of Meloidogyne incognita in vitro are shown in Figure 8 and Figure 9 , and the results show that the supernatant of the TYQ7 fermentation broth has a significant lethal effect on the second-stage larvae of Meloidogyne incognita, and the corrected mortality rate is significantly higher than that of the control group. As time prolongs, the lethality rate increases from 70.31% at 12 h to 83.67% at 24 h, indicating that its metabolites have a highly efficient and continuous lethal effect on the second-stage larvae of Meloidogyne incognita.

[0146] Example 6

[0147] Pot experiment on the control of Meloidogyne incognita by Microbacterium paraoxydans TYQ7.

[0148] Cucumber is the most sensitive vegetable crop to Meloidogyne incognita. In this example, cucumber was used as a model crop for research.

[0149] The treatments set in this example were as follows: ① inoculation with Meloidogyne incognita (CK+N); ② inoculation with TYQ7 bacterial agent (TYQ7+N). The specific implementation steps are as follows:

[0150] 6.1 Seed disinfection

[0151] The specific operation of seed disinfection was the same as that in Example 2.

[0152] 6.2 Bacterial strain inoculation

[0153] The specific operation of bacterial strain inoculation was the same as that in Example 2.

[0154] 6.3 Inoculation with second-stage juveniles of Meloidogyne incognita

[0155] When the cucumber seedlings were at the one-leaf and one-heart stage, inoculation with second-stage juveniles of Meloidogyne incognita began. Two small holes about 1 cm deep were poked around the roots of the cucumber seedlings with a pipette tip, and the suspension of Meloidogyne incognita was added to them. Each seedling was inoculated with 250 second-stage juveniles of Meloidogyne incognita.

[0156] 6.4 Plant measurement

[0157] On the 21st day after inoculation with nematodes, samples were taken to measure and statistically analyze the growth indexes of cucumber plants (plant height, stem diameter, above-ground fresh weight, underground fresh weight, above-ground dry weight, underground dry weight, chlorophyll content), and the roots of cucumber seedlings were scanned with a root scanner and analyzed using WinRHIZO analysis system software.

[0158] 6.5 Result analysis

[0159] Tables 3 and 4 show the results of the effects of TYQ7 inoculation on the growth indexes and roots of cucumber under the infection of Meloidogyne incognita. Figure 10 The effect diagrams of TYQ7 inoculation on cucumber plants and roots under the infection of Meloidogyne incognita. Figure 10 And the results in Tables 3 and 4 show that inoculation with TYQ7 strain significantly promoted the growth and development of cucumber plants under the infection of Meloidogyne incognita. The plant height and stem diameter increased by 30.80% and 0.63% respectively compared with the control; the above-ground and underground dry weights increased by 23.81% and 28.89% respectively, and the chlorophyll content increased by 160.54%. The root morphological indexes were comprehensively optimized, and the total root length, root surface area, average root diameter, and root volume increased by 50.01%, 76.93%, 17.07%, and 10.645% respectively. At the same time, TYQ7 treatment significantly inhibited the infection of Meloidogyne incognita, and the number of root knots per unit root weight decreased by 40.57% compared with the control, indicating that this strain has significant dual effects of promoting growth and resisting nematodes.

[0160] Table 3. Effects of TYQ7 inoculation on cucumber growth indexes under the infection of Meloidogyne incognita

[0161]

[0162]

[0163] Table 4. Effects of TYQ7 inoculation on cucumber root indexes under the infection of Meloidogyne incognita

[0164]

[0165] Example 7

[0166] Plate antagonism of TYQ7 against Fusarium oxysporum

[0167] 7.1 Preparation of strain suspension

[0168] The specific operation of preparing the strain suspension is the same as that in Example 3.

[0169] 7.2 Preparation of Fusarium oxysporum plate

[0170] The Fusarium oxysporum used in the present invention is the strain stored in the laboratory strain bank. Pick the bacterial mass and inoculate it on the solid PDA medium plate, and culture it at 28 °C for 3 days.

[0171] 7.3 Experiment on antagonism of TYQ7 against Fusarium oxysporum

[0172] Cut the activated Fusarium oxysporum plate into 3×3 mm bacterial blocks and inoculate them at 1 / 4 of the diameter of the new PDA plate. Dip a sterilized toothpick into the TYQ7 bacterial liquid adjusted to a specific OD value and streak inoculate it in the direction perpendicular to the diameter of the pathogen bacterial block. To ensure the full growth of TYQ7, streak inoculate 2-3 times. After the plate is cultured at 28 °C for 2-3 days, measure the long and short axis lengths (oval shape) of the Fusarium oxysporum bacterial circle, and calculate the eccentricity to quantify the inhibitory effect.

[0173]

[0174] 7.4 Result analysis

[0175] The effect of confrontation antagonism between TYQ7 and Fusarium oxysporum on the plate is shown in Figure 11 , the effect of TYQ7 on the growth of Fusarium oxysporum is shown in Table 5. The results show that after treatment with TYQ7, the shape of the Fusarium oxysporum bacterial circle changes from nearly circular to oval with an eccentricity > 0.5, indicating that its growth direction is significantly blocked. The area of the bacterial circle is reduced by 29.02% compared with the control, intuitively reflecting the antagonistic effect of TYQ7 against Fusarium oxysporum.

[0176] Table 5. Effects of TYQ7 on the growth of Fusarium oxysporum

[0177]

[0178] Note: The eccentricity in the table represents the growth of Fusarium oxysporum. The higher the eccentricity value, the flatter the ellipse, and the lower the eccentricity value, the more circular it is.

[0179] Example 8

[0180] Degradation characteristics of TYQ7 on vegetable straw

[0181] 8.1 Pretreatment of vegetable straw

[0182] In this example, four common fruit and vegetable straws, including cucumber, tomato, pepper, and eggplant straws, were cut into 3 - 4 cm segments, then dried in an oven, placed in a 250 ml Erlenmeyer flask, sealed with a sealing film, and put into an autoclave for sterilization at 121 °C for 15 minutes.

[0183] 8.2 Determination of the degradation rate of vegetable straw

[0184] 5 g of straw was added to each Erlenmeyer flask containing 125 ml of carbon - free liquid medium. The formula of the carbon - free liquid medium was the same as that in Example 3. Then, 5 ml of TYQ7 bacterial solution activated overnight was inoculated into the medium. After sealing the Erlenmeyer flask with a sealing film, it was placed on a shaker at a temperature of 28 °C and a rotation speed of 180 rpm / min for 15 hours. Then, the straw was recovered, washed, dried, and weighed. The degradation rates of the four straws were calculated respectively. The calculation formula is:

[0185]

[0186] 8.3 Results

[0187] The degradation effect of TYQ7 on the four vegetable straws is shown in Figure 12 , and the degradation rates of TYQ7 on the four vegetable straws are shown in Table 6. The analysis shows that TYQ7 shows degradation ability for all four vegetable straws. Among them, the degradation rate of tomato straw is the highest (66.14%), and the degradation rates of cucumber, pepper, and eggplant straws are relatively low. It is speculated that the higher lignification degree and lignin content of the latter three may make them more difficult to degrade.

[0188] Table 6 Degradation rates of TYQ7 on four vegetable straws

[0189]

[0190] Example 9

[0191] Phosphate - solubilizing characteristics of TYQ7

[0192] 9.1 Evaluation of the ability of TYQ7 to dissolve insoluble phosphorus using an inorganic phosphorus solid medium

[0193] Absorb 10 μL of the TYQ1 bacterial solution cultured overnight onto the surface of the inorganic phosphorus solid medium. Seal it with a sealing film and place it in an incubator at 28°C for 5 days. Observe whether a phosphorus-dissolving circle is formed around the colony.

[0194] 9.2 Results

[0195] The phosphorus-dissolving characteristics diagram of TYQ7 is shown in Figure 13 , after TYQ7 is cultured on the inorganic phosphorus solid medium for 5 days, an obvious transparent phosphorus-dissolving circle can be formed around the colony.

[0196] Example 10

[0197] Phosphorus-dissolving ability of TYQ7 at gradient salt concentrations and pH values

[0198] 10.1 Preparation of inorganic phosphorus liquid medium with gradient salt concentrations and pH values

[0199] Prepare the inorganic phosphorus liquid medium, add NaCl to set gradient salt concentration treatments of 0, 2, 4, 6, 8 g / L, and additionally use a pH meter to accurately add NaOH and HCl to set gradient pH value treatments of pH 5, 6, 7, 8, 9.

[0200] 10.2 Determination of dissolution ability

[0201] Evaluate the dissolution ability of TYQ7 for insoluble phosphorus using the inorganic phosphorus liquid medium with gradient salt concentrations: Absorb 50 μL of the TYQ7 bacterial solution cultured overnight into 5 ml of the inorganic phosphorus liquid medium. Seal it with a sealing film and place it in an incubator at 28°C for 5 days. Then, further quantitatively analyze the phosphorus-dissolving ability of TYQ7 using the molybdenum-antimony anti-colorimetric method. Take the supernatant as the test solution. Absorb 5 ml of the supernatant and add 2.5 ml of the molybdenum-antimony anti-color reagent. After standing at room temperature for 30 min, measure its absorbance at a wavelength of 700 nm.

[0202] 10.3 Results

[0203] The phosphorus-dissolving ability diagram of TYQ7 at gradient salt concentrations and gradient pH values is shown in Figure 14 , the results show that the phosphorus-dissolving ability of TYQ7 at gradient salt concentrations and gradient pH values shows a downward trend as the salt concentration increases or as the pH value deviates from neutral. The phosphorus-dissolving ability of TYQ7 is the largest at 77.33 mg / L when the salt concentration is 0 g / L, and the largest at 74.69 mg / L when the neutral pH = 7.

[0204] Example 11

[0205] Carbon source utilization ability of TYQ7

[0206] 11.1 Biolog GenIII microplate

[0207] Using the Biolog GenIII microtiter plate, the utilization or oxidation ability of strain TYQ7 to various pre-selected carbon sources was detected. This detection generated the metabolic fingerprint of TYQ7 for different carbon sources by measuring the absorbance value of the reaction solution at OD 590 nm.

[0208] 11.2 Results

[0209] The fingerprint diagram of the utilization ability of TYQ7 to different carbon sources is shown in Figure 15 . The results showed that TYQ7 exhibited varying degrees of utilization ability for 71 tested carbon sources, and the OD value directly reflected its metabolic activity. In the chemical resistance test, this strain showed significant insensitivity to nalidixic acid, lithium chloride, and aztreonam, indicating strong environmental adaptability and metabolic diversity.

[0210] Summary: It can be seen from the above examples that:

[0211] (1) This strain was isolated from the cucumber rhizosphere soil in the laboratory of China Agricultural University. Its taxonomic name is Microbacterium paraoxydans TYQ7, and it was deposited in the China General Microbiological Culture Collection Center on April 27, 2023, with the deposit number CGMCC.27216.

[0212] (2) The microbiological characteristics of Microbacterium paraoxydans TYQ7 are as follows: The colonies of this bacterium are round, light yellow and opaque. The surface is smooth and moist, and the edge is irregular. The central part bulges slightly, and a biofilm will naturally form around the single colony. The Gram stain is positive. The Gram stain is positive, and the optimum growth temperature is 28 - 37 °C.

[0213] (3) By amplifying the 16S rDNA fragment of this strain and performing BLAST homology alignment, the similarity of this strain to Microbacterium paraoxydans reached 99.86%. Therefore, this strain was identified as a strain of the genus Microbacterium, named Microbacterium paraoxydans TYQ7.

[0214] (4) Through qualitative and quantitative analysis, it was identified that TYQ7 can secrete auxin, and the concentration of IAA secreted by it in the presence of tryptophan is 43.98 μg / mL;

[0215] (5) The cucumber cultivation experiment inoculated with TYQ7 proved its significant growth-promoting effect: the above-ground dry weight and the whole-plant dry weight increased by 32.18% and 27.7% respectively, the total root surface area and volume increased significantly by 29.40% and 64.10% respectively, and the strong seedling index increased by 36.29%.

[0216] (6) TYQ7 interfered with the chemotactic migration of nematodes in plants: when the cotyledons of the seedlings flattened, the TYQ7 fermentation broth was watered on the rhizosphere soil, 10 ml for each seedling. This application made the migration tendency of Meloidogyne incognita to the control roots reach 53.59%.

[0217] (7) After the supernatant of the strain fermentation broth of TYQ7 was treated with the in vitro root-knot nematodes for 12 h and 24 h, the lethal rates to Meloidogyne incognita reached 70.31% and 83.67% respectively.

[0218] (8) The cucumber cultivation experiment inoculated with TYQ7 against Meloidogyne incognita infection proved its significant effect of alleviating the stress of root-knot nematodes: the above-ground and underground dry weights increased by 23.81% and 28.89% respectively, the number of root knots per unit root weight decreased by 40.57%, and the chlorophyll content increased by 160.54%.

[0219] (9) TYQ7 could effectively inhibit the normal growth of Fusarium oxysporum during the confrontation with the Fusarium oxysporum plate, and the area of the bacterial circle decreased by 48.58%. This was beneficial to prevent soil-borne diseases caused by Fusarium oxysporum during application.

[0220] (10) The degradation rates of TYQ7 to tomato, cucumber, pepper and eggplant straws reached 66.14%, 37.72%, 26.23% and 30.18% respectively within two weeks.

[0221] (11) The phosphorus-solubilizing ability of TYQ7 showed a downward trend with the increase of salt concentration or the deviation of pH from neutral. The phosphorus-solubilizing ability of TYQ7 was the largest at 77.33 mg / L when the salt concentration was 0 g / L, and the largest at 74.69 mg / L when the neutral pH = 7.

[0222] (12) The Biolog analysis of TYQ7 showed that it could utilize 71 carbon sources, showed resistance to nalidixic acid, lithium chloride and aztreonam, and had broad-spectrum metabolic ability and environmental adaptability.

[0223] There are several preferred embodiments of the invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the invention, several modifications and improvements can still be made, and these all belong to the protection scope of the invention.

Claims

1. A Microbacterium paraoxydans, characterized in that, The Microbacterium paraoxydans strain TYQ7 is preserved in the General Microbiological Center of the China Committee for Culture Collection of Microorganisms, with the preservation number of CGMCC No. 27216.

2. A microbial inoculum containing the Microbacterium paraoxydans cells and / or its metabolites and / or its fermentation broth as described in claim 1.

3. Use of the bacterium as described in claim 1 or the microbial inoculum as described in claim 2 in the preparation of a preparation for promoting the growth of cucumber seedlings.

4. Use of the bacterium as described in claim 1 or the microbial inoculum as described in claim 2 in the preparation of a preparation for interfering with the migration of Meloidogyne incognita.

5. Use of the bacterium as described in claim 1 or the microbial inoculum as described in claim 2 in the preparation of a preparation for controlling Meloidogyne incognita.

6. Use of the bacterium as described in claim 1 or the microbial inoculum as described in claim 2 in the preparation of a preparation for inhibiting the growth of Fusarium oxysporum.

7. Use of the bacterium as described in claim 1 or the microbial inoculum as described in claim 2 in the preparation of a preparation for straw degradation.

8. Use of the bacterium as described in claim 1 or the microbial inoculum as described in claim 2 in the preparation of a preparation for phosphorus solubilization.

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