CN114134063B

CN114134063B - Strain Serratia sp.X10 for reducing cadmium accumulation in rice and application thereof

Info

Publication number: CN114134063B
Application number: CN202111009673.XA
Authority: CN
Inventors: 李明顺; 王孟杰; 范蓉荣; 王革娇
Original assignee: Huazhong Agricultural University
Current assignee: Huazhong Agricultural University
Priority date: 2021-08-31
Filing date: 2021-08-31
Publication date: 2023-03-21
Anticipated expiration: 2041-08-31
Also published as: CN114134063A

Abstract

The invention belongs to the technical field of agricultural microorganisms and discloses a strain for reducing cadmium accumulation in riceSerratiaX10 and uses thereof, saidSerratiaThe preservation number of the sp strain is CCTCC NO: m2021738. The bacteria are directly sprayed or irrigated in soil. X10 can reduce the absorption and accumulation of the rice to the cadmium in the soil and relieve the inhibition effect of the heavy metal cadmium on the growth of the rice by the change of the cadmium adsorption of the strain per se and the bioavailability of the cadmium in the soil. Bacterial strainsSerratiasp.x10 can passivate cadmium in soil with high efficiency so as to reduce the accumulation of cadmium in rice, and the diversity of original microorganisms in soil can not be changed. The method is simple to operate, economic and efficient, has obvious effect, can reduce the harm of cadmium-polluted soil to rice, and has high application value and potential.

Description

Strain Serratia sp.X10 for reducing cadmium accumulation in rice and application thereof

Technical Field

The invention belongs to the technical field of agricultural microorganisms, and relates to a strain Serratia sp.X10 for reducing cadmium accumulation in rice and application thereof.

Background

Cadmium (Cd) is a silver toxic metal with strong ductility, is easily soluble in acid but not soluble in alkali, and has the valence of Cd (II) and Cd (I). The cadmium form in soil can be divided into four forms: the acid is in an extractable, reducible, oxidizable and residuum state. The acid extractable cadmium and the reducible cadmium are the most easily utilized by plants in the four forms, the oxidizable cadmium and the residual cadmium have the highest stability and are not easily absorbed and utilized by the plants, and the cadmium in various forms can be mutually converted. Cadmium in soil has strong mobility, is easy to be accumulated by plants into a food chain, is further enriched in a human body and generates irreversible toxic action. In addition, cadmium in the air can also enter the human body through the respiratory tract. Cadmium not only has adverse effects on human beings, but also has great harm to plant growth, such as: if the rice grows in cadmium-polluted soil for a long time, a large amount of cadmium is enriched near the root, and after a certain amount of cadmium is accumulated, oxidative stress of the rice is caused, and photosynthetic response and related gene expression are inhibited; cadmium also inhibits the conversion of sucrose to adenodiphosphoglucose in rice, resulting in lack of glucose donor in rice and thus inhibiting the synthesis of starch; after the cadmium is accumulated in the rice, the ratio of the branched chain to the amylose of rice grains of the rice is changed, so that the quality of the rice is reduced.

The current cadmium pollution remediation modes are mainly divided into three types: (1) physical repair: physical remediation refers to the treatment of cadmium pollution in the environment by using a physical method, so that the concentration of cadmium in the environment is reduced. Although the method has quick response, the method has high cost, wastes time and labor, and can cause the problems of change of soil structure, reduction of soil fertility and the like. (2) chemical repair: chemical remediation generally refers to the use of an improver or an inhibitor in heavy metal contaminated soil, and the heavy metal ion form, the soil pH or the oxidation-reduction potential and the like are changed through the actions of heavy metal ion oxidation reduction, adsorption and the like, so that the concentration of heavy metals in the contaminated soil is finally reduced. This method is easy to operate, but heavy metals in soil may be activated due to instability to cause secondary pollution, and the properties of soil may be changed by chemical agents to cause other soil problems. (3) bioremediation: bioremediation includes animal remediation, phytoremediation, and microbial remediation. Compared with the first two heavy metal restoration methods, the microbial restoration belongs to a new environment-friendly restoration method, and the heavy metal pollution is restored mainly through the action modes of the redox action, coprecipitation, surface adsorption, biological accumulation and the like of the microbes on the heavy metals. Most of microorganisms used for repairing the heavy metal contaminated soil are separated from original contaminated soil and prepared into microbial inoculum to be put back into the original soil to treat pollution, so that microbial remediation is a novel green remediation mode, is not easy to cause secondary pollution, is economical and efficient, is suitable for various soils, and can realize in-situ remediation of the contaminated soil.

Serratia (Serratia) was originally attributed to a single Serratia which was newly identified after correction due to confusion between BacteriumEhrenberg and BacillusCohn. To date, there are 32 strains of this genus that have been effectively characterized, and some studies have shown that: the serratia RSC-14 can obviously increase the biomass of the black nightshade under the cadmium stress and reduce the cadmium content in the black nightshade leaves; the Serratia liquefaciens CL-1 is added into the lead-cadmium polluted soil, and the lead-cadmium content of the edible part of the carrot is reduced by 37-81 percent; the serratia marcescens HB-4 is inoculated in rhizosphere soil of the houttuynia cordata which is a cadmium-hyper-enriching plant, and the combined action of the serratia marcescens HB-4 and the rhizosphere soil can increase the cadmium content of the overground part and the root part of the houttuynia cordata by 34.48 percent and 59.13 percent; the Serratia CP-13 can obviously improve the growth, biomass and chlorophyll content of the flax under the cadmium stress and obviously reduce the cadmium content of flax plants, and subsequent researches further find that the CP-13 can also reduce the cadmium absorption of the corn by influencing the physiology and biochemistry of the corn. The serratia liquefaciens H12 can obviously reduce the absorption of the pakchoi on lead and cadmium in the soil. The above disclosure illustrates that the effect of Serratia on cadmium content in different plants is different.

In addition to the function of passivating cadmium, the serratia liquefaciens F2 is found to reduce the arsenic content in brown rice by 23-36%; the mixed microbial inoculum of the Serratia S41 and the Arthrobacter J122 can effectively carry out bioremediation on a polluted water body in a water culture system by biodegradation and Cr (VI) reduction of pyrene in the water body; the serratia has the effects of generating the erythromycin and killing insects besides the effects of resisting and repairing various heavy metals: serratia marcescens PG12 can be synthesized into colistin with protozoan resisting, malaria resisting, immunosuppression resisting and anticancer properties; serratia marcescens PS-1 has insecticidal effect on beet armyworm which is a multi-feeding agricultural pest. Meanwhile, researches show that the serratia marcescens S2I7 has the capacity of reducing the strong carcinogenic substance BaP (benzopyrene) in the root of the melia azedarach; serratia KG-2-1 has the ability to produce a highly active fibrinolytic protease and is useful as a potential therapeutic agent against various thrombolytic disorders.

As the Serratia has plant selectivity, no report aiming at the Serratia capable of reducing the cadmium accumulation in rice exists at present.

Disclosure of Invention

The invention aims to provide a serratia (Serratia sp.) X10 strain which has high cadmium resistance and can efficiently reduce cadmium accumulation in rice, and the preservation number is CCTCC NO: m2021738.

Another objective of the invention is to provide an application of Serratia sp X10 in reducing cadmium accumulation in plants.

The third purpose of the invention is to provide the strain Serratia sp.X10 which can relieve the inhibition effect of heavy metal cadmium on plants and promote the growth of the plants.

In order to achieve the purpose, the invention adopts the following technical measures:

separating and screening a strain which has the functions of efficiently passivating heavy metal cadmium in soil and reducing the absorption and accumulation capacity of rice to cadmium from cadmium-polluted soil (the total cadmium content in a soil sample is 0.5 mg/kg) in Shaoguan city, guangdong province, china, and delivering the strain to a China Center for Type Culture Collection (CCTCC) for preservation in 2021, 06 and 21 days, wherein the preservation number is CCTCC NO: m2021738, class name: serratia sp.x10, address: wuhan university in Wuhan, china.

The specific characteristics of the strain are as follows:

A. morphological characteristics

The cell shape of the strain X10 is short rod-shaped, the length is 1.1-1.3 μm, and the width is 0.5-0.9 μm.

B. Culture characteristics

The strain X10 is cultured on an LB agar plate culture medium at 28 ℃ for 48h, and the colony is white, has a protruding middle part, and has a complete and smooth edge and is opaque.

The strain X10 has high resistance to Cd (II), and the MIC (minimum inhibitory concentration) of the strain can reach 5mM.

The strain X10 is used as a bacterium for efficiently passivating heavy metal cadmium in soil, and can remarkably reduce the content of cadmium in rice.

The strain X10 can relieve the inhibition effect of heavy metal cadmium on rice or Chinese cabbage and promote the growth of the rice or Chinese cabbage.

Compared with the prior art, the invention has the following advantages:

(1) The obtained strain Serratia sp.X10 has the capability of efficiently passivating heavy metal cadmium in soil, and has the advantages of economy, high efficiency, environmental friendliness compared with other cadmium pollution treatment means.

(2) The addition of the microbial liquid prepared from Serratia sp.X10 can obviously reduce the accumulation of heavy metal cadmium in rice, and the bacterial strain is classified into Serratiasp, so that the content of cadmium in cadmium-polluted soil which is easily utilized by plants is reduced, and the content of cadmium in cadmium-polluted soil which is difficult to be utilized by plants is increased, so that the content of cadmium in brown rice is reduced to below the national safety standard (0.02 mg/kg), and the effect of in-situ remediation is achieved.

(3) The microbial liquid prepared from Serratia sp.X10 is simple and convenient to add, economic and environment-friendly, and cannot destroy the diversity of original soil microorganisms.

(4) Compared with other bacteria of Serratia, the invention not only can be widely applied to pot experiments and field experiments, but also obtains remarkable results.

(5) The Serratia sp.X10 has high growth speed and large biomass, can be cultured to the concentration required by the strain feeding in a short time, and saves time and production cost.

(6) X10 can stably survive in dry farmland soil, can be detected for over 15 days in flooded soil, and can stably play a role in soil.

(7) X10 has high resistance to Cd (II), the MIC of the Serratia sp can reach 5mM, and the Serratia sp can be applied to soils with different cadmium pollution degrees.

(8) The Serratia sp.X10 strain has obvious effect of reducing the cadmium accumulation in rice, but has no obvious effect of reducing the cadmium content in the leaves of the Chinese cabbage.

Drawings

FIG. 1 is a schematic diagram of a growth curve of a strain Serratia sp.X10;

the curve with solid circles in FIG. 1 represents the growth curve of strain X10 in LB medium without Cd; the square-dot curve represents the growth curve of X10 in LB medium with 0.2mM CD (II).

Fig. 2 is a schematic representation of the colonization of the strain Serratia sp.x10 in soil;

"Add strain X10" in FIG. 2 indicates that the X10 bacterial liquid was applied to the soil surface three times in 50 days, and was supplemented every 1 day to 5 days at a bacterial concentration of 10 ⁸ CFU/g。

Fig. 3 is a graph showing the ability of strain Serratia sp.x10 to reduce cadmium accumulation in rice;

a shows the content change of cadmium in each part of rice under the condition of laboratory pot culture; b shows the content change of cadmium in each part of rice under the field condition. In both figures, control indicates the treatment group to which no microbial agent was added, and X10 indicates the treatment group to which a microbial agent was added.

FIG. 4 is a schematic diagram showing the comparison of agronomic traits of rice in cadmium contaminated soil by applying the strain Serratia sp.X10;

cd represents the agronomic characters of the rice without adding the microbial agent, and Cd + X10 represents the agronomic characters of the rice with adding the microbial agent.

Fig. 5 is a schematic diagram of the diversity of the soil microbial community for the application of the strain Serratia sp.x 10;

b1 to B3 represent the diversity of the soil microbial communities before the addition of the microbial agent, and E1 to E3 represent the diversity of the soil microbial communities after the addition of the microbial agent X10.

FIG. 6 is a schematic diagram showing the heavy metal content of the leaf of the pakchoi after the strain Serratia sp.X10 is added into the cadmium-contaminated soil;

the Control group is a treatment group without adding a microbial inoculum, and the X10 group is a treatment group with adding Serratia sp.X10. 0mg/kg of original soil without additional cadmium addition, and 5mg/kg of soil with additional cadmium addition of 5 mg/kg.

FIG. 7 is a schematic diagram showing the comparison of agronomic traits of pakchoi after applying a strain Serratia sp.X10 in cadmium contaminated soil;

wherein A is a fresh weight graph of the pakchoi, and B is a plant height graph of the pakchoi. Wherein the Control group is a treatment group without adding a microbial inoculum, and the X10 group is a treatment group with adding Serratia sp.X10. 0mg/kg of original soil without additional cadmium addition, and 5mg/kg of soil with additional cadmium addition of 5 mg/kg.

Fig. 8 is upland soil colonization by the strain Serratia sp.x10:

"Add strain X10" in FIG. 8 indicates that the bacterial suspension X10 was applied to the soil surface twice within 21 days and supplemented once every 1 day, and the bacterial concentration was 10 ⁸ CFU/g。

Detailed Description

The present invention will be described in further detail with reference to specific examples. The embodiments are implemented on the premise of the technical scheme of the invention, and detailed implementation modes and specific operation processes are given, but the protection scope of the invention is not limited by the following embodiments. The methods used in the following examples are conventional methods unless otherwise specified.

Cadmium added in the embodiment of the invention is Cd (II) ions.

Example 1:

acquisition of Serratia sp.x 10:

the applicant separates and screens a strain with the capacity of efficiently passivating heavy metal cadmium in soil and reducing the absorption and accumulation of cadmium by rice from cadmium-polluted soil (the total cadmium content in soil samples is 0.5 mg/kg) in Shaokuan city, guangdong province in China, and the strain has 99.86% homology with Serratia nematophila (Serratia nematodiphila) DSM21420 (JPUX 0100 0001) through 16s R NA gene identification, so that the strain is Serratia nematodiphila (Serratia nematodiphila). The strain is delivered to China Center for Type Culture Collection (CCTCC) for preservation in 2021, 21/06/21, and the preservation number is CCTCC NO: m2021738, class name: serratia sp.x10, address: wuhan university in Wuhan, china. In the present invention, serratia sp.x10 or simply strain X10.

The specific characteristics of the strain are as follows:

A. morphological characteristics

B. Characteristics of cultivation

The strain X10 is cultured on an LB agar plate culture medium at 28 ℃ for 48h, and the bacterial colony is white, has a convex middle part, and has complete and smooth edge and is opaque. The strain X10 has high resistance to Cd (II), and the MIC (minimum inhibitory concentration) of the strain can reach 5mM.

Growth curves of the strain Serratia sp.X10

(1) Inoculating a fresh bacterial liquid Serratia sp.X10 cultured overnight at the inoculation amount of 1% into 100mL of LB culture medium and LB culture medium containing 0.2mmol/L Cd (II), and culturing in a constant-temperature shaking table at 28 ℃ and 150 rpm/min.

(2) Samples were taken at 3h, 6h, 12h, 24h, 36h, 48h, 60h, 72h, 84h, 108h, 132h, diluted and spread on LB plates, counted and growth curves were plotted.

The results are shown in FIG. 1, serratia sp.X10 enters into stationary growth phase at 36-84 h, and the effective bacteria concentration can reach 10 ¹⁰ CFU/ml. After 84h, gradually entering decay phase, but the decay speed is slower, and the effective bacteria concentration can still be maintained at 10 until 132h ⁹ CFU/ml。

Example 2:

soil colonization curve of strain Serratia sp.X10

The method comprises the following specific steps:

(1) Fresh bacterial liquid Serratia sp.X10 cultured overnight was inoculated at 1% inoculum size into LB medium and cultured at 28 ℃ for 12 hours on a constant temperature shaker at 1 50rpm/min.

(2) Centrifuging at 4000rpm/min for 10min, collecting thallus, suspending with ultrapure water, and treating the suspended thallus at 10 deg.C ⁸ CFU/g is the standard and is added into the soil, and the adding day is regarded as the 0 th day.

(3) At 1,3,5,7,9, 12, 15 days 5g rhizosphere soil was taken and antibiotic plate colony counts were performed.

(4) Every 15 days, the microbial inoculum is generally supplemented in the synchronous step (1).

The results are shown in FIG. 2: serratia sp.X10 can survive in rice soil for about 11 days in a large amount (as shown in the table below), the viable count is reduced after 11 days, so the detection is difficult, the experiment replenishes bacteria in 15 days and 36 days, and the colonization curve after the supplementation is similar to that in 0-15 days.

Table of colonization of Serratia sp.X10 in rice soil

Example 3:

determination of cadmium content in each part of rice

The method comprises the following specific steps:

(1) Two treatment groups (control group without added bacteria, X10 group with added Serratia sp.x10 bacteria) were set up for the rice potting experiment, and five groups were paralleled.

Cadmium balance is carried out on soil before planting: 5mg/kg of cadmium is added into each pot, and the balance is carried out for one week after the excessive water is added to immerse the whole soil.

(2) Transplanting 3 rice seedlings with consistent growth vigor in each pot after soil balance is finished, resuspending Serratia sp.X10 strain with normal saline, and evenly applying to five pots of soil of X10 group after resuspension with normal saline, wherein the final concentration of Serratia sp.X10 strain in each pot is 10 ⁸ CFU/g (dry soil), control group added equal amount of saline per pot.

(3) Two treatment groups (a control group without bacteria and an X10 group with bacteria) are set in the rice field experiment, each group is three-parallel, and each parallel group occupies 20m of land ² The cell of (2).

(4) After base fertilizer (compound fertilizer 1.5 kg) is applied to each cell, the strain Serratia sp.X10 is added into the cells of the bacterium adding treatment group, 4L of bacterium liquid is added into each cell, and the bacterium adding concentration reaches 4X 10 ¹¹ And CFU/g, uniformly mixing the bacterial liquid with plough layer soil.

(5) Transplanting the rice seedlings with the same size into each cell, wherein the quantity of the rice seedlings in each cell is basically the same, and the line spacing is kept at 20cm multiplied by 25cm. On the 45 th day after the transplantation, the microbial inoculum was again supplemented as in step (4).

(6) And (4) harvesting rice after the 90-day grouting period of both the pot culture experiment and the field experiment, separately treating each part of the rice, and performing the next determination experiment of the cadmium content.

(7) Grinding rice roots, rice husks, rice and stalks into uniform samples, wherein the granularity is not more than 0.425mm. The samples were stored in clean plastic bottles and stored at room temperature for testing.

(8) 2.000g of sample were weighed into 50mL Teflon beakers, and 10mL of mixed acid (HC lO) was added to each beaker ₄ :NHO ₄ = 1:9) on hot plate until clear and transparent at 180 ℃.

(9) And (4) determining the cadmium content in each part of the rice by using a TAS-990 atomic absorption spectrophotometer after digestion.

As shown in FIG. 3, the cadmium content in the brown rice of the X10 bacteria-added group rice in the potting experiment (A in FIG. 3) was 0.16mg/kg, which was reduced to the edible range (0.2 mg/kg) of the national cereal safety cadmium content (GB 2762-2017). The cadmium content of the brown rice in the group without the added bacteria is 0.75mg/kg, and the result shows that the cadmium content of the brown rice in the group with the added bacteria is obviously reduced by 78.7 percent compared with the cadmium content of the brown rice in the group without the added bacteria. In the field test (B in figure 3), the cadmium content of the brown rice in the group without adding the bacteria is 0.28mg/kg, while the cadmium content of the brown rice in the group with adding the bacteria X10 is 0.16mg/kg, which is remarkably reduced by 43.9 percent compared with the control group. Meanwhile, the cadmium content of the fungus groups added in roots, stems and leaves of the rice is obviously lower than that of the fungus groups not added in the roots, stems and leaves of the rice in a pot culture experiment or a field experiment. The results show that the microbial inoculum X10 can obviously reduce the cadmium content in the brown rice.

Example 4: measurement of agronomic traits in rice

The method comprises the following specific steps:

(1) Two treatment groups (control group without added bacteria, X10 group with added bacteria) were set up for the rice potting experiment, and five groups were in parallel. Cadmium balance is carried out on the soil before planting: 5mg/kg cadmium is added into each pot, and the soil is balanced for one week after being immersed by excessive water.

(2) Transplanting 3 rice seedlings with consistent growth vigor in each pot after soil balance is finished, resuspending Serratia sp.X10 strain with normal saline, and applying to five pots of soil of X10 group on average, wherein the final concentration of Serratia sp.X10 strain in each pot is 10 ⁸ CFU/g (dry soil), control group added equal amount of saline per pot.

(3) The rice of the two treatment groups 90 days after planting was taken and the ear length thereof was measured with a meter ruler.

(4) 1000 grains of rice with husks were randomly selected from the rice plants of the two treatment groups 90 days after planting, and the thousand grain weight thereof was measured on an electronic balance.

(5) The rice plants of the two treatment groups 90 days after the planting were taken, and the total number of rice (including no empty rice husks) and the number of real rice (excluding no empty rice husks) per plant were counted.

As shown in FIG. 4, the ear length of the treated group was longer and the growth was better in the rice pot test than that of the non-treated group. Meanwhile, the full rice rate of the bacteria-added treatment group is 6.1 percent higher than that of the bacteria-not-added treatment group, and the thousand grain weight is increased by 3 percent.

Example 5: soil microbial diversity analysis

The method comprises the following specific steps:

(1) The soil samples after cadmium balance are set into B groups, and each group is 3 in parallel; adding bacteria after cadmium balance, and the final concentration of Serratia sp.X10 bacteria is 10 ⁸ CFU/g (dry soil), setting soil samples for planting rice on day 40 as E groups, and setting each group to be 3 in parallel; the two groups of soil samples are stored in a refrigerator at the temperature of 80 ℃ below zero.

Balancing cadmium: 5mg/kg of cadmium is added into each pot, and the balance is carried out for one week after the excessive water is added to immerse the whole soil.

(2) The extraction of total bacterial DNA from rhizosphere Soil samples was carried out according to the instructions of the MN NucleoSpin 96Soil kit (MN macherey-nagel, germany). The V3-V4 region of the bacterial 16S rRNA gene was PCR amplified using forward primer 338F (5'-ACTCCTACGGGAGGC AGCA-3') and reverse primer 806R (5 '-GGACTACHVGGGTWTCTAAT-3'). And (3) performing column purification on the PCR amplicon by using an OMEGA DNA purification kit, quantitatively homogenizing after cutting gel and recovering to establish a sequencing library, performing sequencing by using Illumina HiSeq 2500, splicing sequencing original data, performing quality filtration, and removing chimeras to obtain a high-quality Tags sequence.

(3) Bioinformatics analysis of the diversity of the native soil bacteria was done and plotted by beijing behamier company.

As a result, as shown in FIG. 5, the bacterial contents of Bacteroides and firmicutes increased after the addition of the strain X10, because the substances produced by the strain X10 during the inactivation of cadmium had a growth-promoting effect on the microorganisms therein. The addition of the strain X10 does not affect the diversity abundance of original microorganisms in the potting soil in the whole, so that the species abundance of the original environmental microorganisms in the soil to which the strain X10 is put cannot be greatly affected during practical application.

Example 6:

determination of cadmium content in leaf part of pakchoi

The method comprises the following specific steps:

(1) The Chinese cabbage pot experiment is provided with four treatment groups, wherein each group is divided into five groups:

treatment group 1: original soil without extra cadmium is not added with bacteria;

treatment group 2: original soil bacterium without additional cadmium

Treatment group 3: soil free bacterium added with 5mg/kg of cadmium additionally

Treatment group 4: soil bacteria with 5mg/kg of cadmium is additionally added;

treatment groups 3 and 4, among others, were cadmium balanced in the soil before planting: 5mg/kg cadmium is added into each pot, and the balance is carried out for two weeks after the excessive water is added to immerse the whole soil.

(2) Transplanting 3 plantlets of Brassica rapa with consistent growth vigor (variety Shanghaiqing, seedling growth to two true leaves) in each pot after soil balance is over, resuspending Serratia sp.X10 strain with normal saline, and applying in ten pots of soil of treatment groups 2 and 4 averagely, wherein the final concentration of Serratia sp.X10 strain in each pot is 10 ⁸ CFU/g (dry soil), treatment 1 and treatment 3 were supplemented with the same amount of physiological saline per pot.

(3) And (5) supplementing the primary bacterium solution on the 16 th day of planting, wherein the method is as in the step (2). Chinese cabbage was harvested 21 days after planting and subjected to the next measurement.

(4) The leaf of pakchoi was ground to a uniform sample with a particle size of no more than 0.425mm. The samples were stored in clean plastic bottles and stored at room temperature for testing.

(5) A sample (1.000 g) was weighed into 50mL polytetrafluoroethylene beakers, and 10mL of mixed acid (HC lO4: NHO4= 1:9) was added to each beaker and digested on a hot plate at 180 ℃ until clear and transparent.

(6) And (4) determining the cadmium content in the leaf of the pakchoi by using a TAS-990 atomic absorption spectrophotometer after digestion.

The results are shown in fig. 6, and no matter in the treatment group additionally added with 5mg/kg cadmium or the treatment group not additionally added with cadmium, the addition of the microbial inoculum X10 has no significant reduction of the cadmium content in the leaves of the pakchoi, which indicates that the microbial inoculum X10 has no effect on the pakchoi planted in the dry land but has significant effect on the rice growing in the flooding way.

Example 7:

measurement of agronomic characters of pakchoi

The method comprises the following specific steps:

(1) Four treatment groups are set in a Chinese cabbage pot experiment, and five treatment groups are parallel to each other:

treatment group 2: adding bacteria to original soil without adding extra cadmium;

treatment group 3: 5mg/kg of cadmium is additionally added into the soil without adding bacteria;

treatment group 4: soil bacteria with 5mg/kg cadmium is additionally added.

Treatment groups 3 and 4, among others, were cadmium balanced to the soil before planting: 5mg/kg cadmium is added into each pot, and the balance is carried out for two weeks after the excessive water is added to immerse the whole soil.

(2) Transplanting 3 plantlets of Brassica rapa with consistent growth vigor (variety Shanghaiqing, seedling growth to two true leaves) in each pot after soil balance is over, resuspending Serratia sp.X10 strain with normal saline, and applying in ten pots of soil of treatment groups 2 and 4 averagely, wherein the final concentration of Serratia sp.X10 strain in each pot is 10 ⁸ CFU/g (dry soil), treatment 1 and treatment 3 added equal amounts of saline per pot.

(3) And (3) supplementing the primary bacterium liquid on the 16 th day of planting, wherein the method is as in the step (2). And harvesting the Chinese cabbages 21 days after planting, and carrying out the next determination of the agronomic characters.

(4) The fresh weight of the harvested pakchoi matured for 21 days is measured on an electronic balance.

(5) The height of the mature and harvested pakchoi in 21 days is measured by a rice ruler.

As shown in FIG. 7, the fresh weight of the pakchoi after the microbial inoculum X10 is added reaches 13.19-24.11 g/plant, and is increased by 28.2-32.9% (FIG. 7 (A)) and the plant height is significantly increased by 13-19% (FIG. 7 (B)) compared with the blank group. The microbial inoculum X10 has obvious promotion effect on the growth of the pakchoi.

Example 8:

colonization of Serratia sp.X10 in upland soil

The method comprises the following specific steps:

(1) Fresh bacterial liquid Serratiasp. X10 cultured overnight was inoculated at an inoculum size of 1% to LB medium and cultured on a constant temperature shaker at 28 ℃ and 15 rpm/min for 12 hours.

(2) Centrifuging at 4000rpm/min for 10min, collecting thallus, suspending with ultrapure water, and concentrating to final concentration of 10 ⁸ CFU/g is added into soil according to the standard, and the addition day is regarded as the 0 th day.

(3) At 1,3,5,7,9, 5g of rhizosphere soil was taken at 12 days and antibiotic plate colony counts were performed.

(4) On day 13, the bacteria were replenished and synchronization step (1) was typically supplemented with microbial inoculum and counted.

The results are shown in FIG. 8:

x10 in soil, the viable count is still 10 after 12 days ⁴ CFU/g, compared with rice, the flooded soil, survives for a longer time in dry farmland.

Claims

1. An isolated strain of serratia (Serratia sp.）X10，The preservation number of the serratia X10 is CCTCC NO: m2021738.

2. Use of the serratia X10 strain of claim 1 for reducing the accumulation of heavy metal cadmium in rice.

3. The use of the serratia X10 strain of claim 1 for the relief of the inhibition of heavy metal cadmium on rice or cabbage while promoting growth.