A cadmium-resistant enterococcus Cd-2 and its culture method and application

Abstract

The present invention relates to the field of microbial application technology, and in particular to a cadmium-resistant enterococcus Cd-2 and a culture method and application thereof. The strain collection number of the cadmium-resistant enterococcus Cd-2 is CGMCC No.25220. It can be used to promote the growth and development of ryegrass and the restoration of cadmium-contaminated soil. The cadmium-resistant enterococcus Cd-2 provided by the present invention can increase the activity of soil luciferin hydrolase, increase the microbial activity of the soil, increase the ascorbic acid content in ryegrass, and promote the antioxidant system of ryegrass to remove excessive reactive oxygen in ryegrass, thereby reducing the superoxide dismutase activity and glutathione content in ryegrass leaves, alleviating the oxidative stress reaction of ryegrass under adverse stress, promoting the growth of ryegrass in cadmium-contaminated soil, increasing the biomass of ryegrass, and increasing the absorption and enrichment of cadmium by ryegrass, which helps to promote the restoration of ryegrass to cadmium-contaminated soil.

Description

Technical Field

[0001] The invention relates to the technical field of microbial application, and in particular to a cadmium-resistant enterococcus Cd-2 and a culture method and application thereof. Background Art

[0002] With the development of economy and society, the rapid development of mining, metal smelting and chemical industry has led to the release of a large amount of heavy metals into the natural environment, polluting the soil and water system, causing the heavy metals in the environment to exceed the standard. The heavy metals released into the soil and water system will be absorbed by plants, which will pose a serious threat to the ecosystem.

[0003] Cadmium is toxic and a heavy metal pollutant. It is not easily biodegraded or chemically degraded in the soil, and it is bioaccumulative. Cadmium distributed in the soil can be absorbed by plants. When the plants that absorb cadmium are eaten by herbivores, herbivores are eaten by carnivores, and herbivores and carnivores are eaten by humans, cadmium is transferred to the human body through the food chain and accumulates in the human body, causing people to suffer from diseases such as cancer, which directly endangers human health.

[0004] Microbial soil remediation technology is a method of using microorganisms to fix, move or transform heavy metals in the soil to change the content of heavy metals in the soil. In the existing technology, the tolerance concentration of cadmium in cadmium-contaminated soil by microorganisms is 20-40 mg / kg. In a higher concentration of cadmium contaminated environment, the survival rate of existing cadmium-resistant microorganisms is low.

[0005] Ryegrass is a perennial plant with a stem height of 30-90 cm and soft roots at the base nodes. When planted in cadmium-contaminated soil, it can absorb cadmium through its roots. Therefore, ryegrass can be used to repair cadmium-contaminated soil. However, the growth of ryegrass will be restricted under high cadmium concentrations, resulting in a decrease in biomass, which is not conducive to the absorption and accumulation of cadmium. Summary of the invention

[0006] In view of the above technical problems, the present invention provides a cadmium-resistant Enterococcus Cd-2, which can survive in cadmium pollution with a concentration of 0 to 100 mg / L, can increase the activity of soil luciferin hydrolase, reduce the basic respiration intensity of the soil, reduce the activity of sucrase, is conducive to the growth of soil microorganisms, and promotes the growth of ryegrass, thereby promoting the enrichment of cadmium in ryegrass, thereby achieving the purpose of repairing cadmium-contaminated soil.

[0007] To solve the above technical problems, the embodiments of the present invention adopt the following technical solutions:

[0008] In the first aspect, the present invention provides a cadmium-resistant Enterococcus Cd-2, whose strain preservation number is CGMCC No.25220. The strain belongs to Enterococcus sp. and was deposited in the General Microbiology Center of China National Microbiological Culture Collection Administration on July 1, 2022. The preservation address is No. 3, Yard No. 1, Beichen West Road, Chaoyang District, Beijing.

[0009] Compared with the prior art, the cadmium-resistant enterococci Cd-2 provided by the present invention can survive under a cadmium concentration of 0 to 100 mg / L, can increase the activity of soil luciferin hydrolase, increase the biological activity of the soil, increase the content of ascorbic acid in ryegrass, and promote the antioxidant system of ryegrass to remove excessive active oxygen in ryegrass, thereby reducing the superoxide dismutase activity and glutathione content in ryegrass leaves, alleviating the oxidative stress response of ryegrass under adverse conditions, and promoting the growth of ryegrass in cadmium-contaminated soil; increasing the biomass of ryegrass, increasing the enrichment of cadmium by ryegrass, and helping to promote the restoration of ryegrass to cadmium-contaminated soil.

[0010] The present invention obtains differentially expressed genes by transcriptional sequencing of the cadmium-resistant Enterococcus Cd-2, and obtains a total of 944 screened differentially expressed genes, of which 476 are up-regulated and 468 are down-regulated. After performing GO enrichment analysis and KEGG pathway enrichment analysis on the screened differentially expressed genes, it is found that the enrichment pathway of the differentially expressed genes is most significant in the glycolysis / gluconeogenesis pathway.

[0011] In a second aspect, the present invention provides a method for culturing the cadmium-resistant Enterococcus Cd-2, wherein the cadmium-resistant bacteria are cultured in a culture medium with a pH of 6 to 7.

[0012] Preferably, the cadmium-resistant Enterococcus Cd-2 is cultured at a temperature of 30-40°C.

[0013] In a third aspect, the present invention also provides the use of the cadmium-resistant Enterococcus Cd-2 in promoting the growth of ryegrass in cadmium-contaminated soil.

[0014] In a cadmium-contaminated environment, the increase in peroxidase content in ryegrass increases reactive oxygen, leading to oxidative stress in ryegrass, increasing the secretion of superoxide dismutase and glutathione to coordinate redox balance. Studies have found that cadmium-resistant Enterococcus Cd-2 can increase the ascorbic acid content in ryegrass leaves and promote the antioxidant system of ryegrass to remove excessive reactive oxygen in ryegrass, thereby reducing superoxide dismutase activity and glutathione content in ryegrass leaves. This result shows that cadmium-resistant Enterococcus Cd-2 can alleviate the oxidative stress response under adverse stress, allowing ryegrass plants to grow normally, thereby increasing the biomass of ryegrass and promoting the growth and development of ryegrass. The underground and aboveground parts of well-grown ryegrass have increased enrichment coefficients and transport coefficients for cadmium, thereby reducing the residual amount of cadmium in cadmium-contaminated soil and improving the removal rate of cadmium in contaminated soil.

[0015] In a fourth aspect, the present invention provides a method for promoting the growth of ryegrass in cadmium-contaminated soil, wherein the cadmium-resistant Enterococcus Cd-2 is inoculated into the cadmium-contaminated soil where ryegrass is grown.

[0016] Preferably, the concentration of cadmium in the cadmium-contaminated soil is ≤100 mg / L.

[0017] Preferably, the method further comprises, after inoculating the cadmium-resistant enterococci Cd-2, culturing according to light conditions of 10-14 h / d and darkness of 8-10 h / d.

[0018] Preferably, the moisture content of the cadmium-contaminated soil inoculated with cadmium-resistant Enterococcus Cd-2 is 40%-60%.

[0019] Preferably, the cadmium-resistant bacteria are inoculated before sowing ryegrass seeds.

[0020] In a fifth aspect, the present invention also provides a method for repairing cadmium-contaminated soil, wherein ryegrass is planted in cadmium-contaminated soil inoculated with cadmium-resistant Enterococcus Cd-2; ryegrass plants enriched with cadmium are collected to complete the repair of cadmium-contaminated soil. The method of planting ryegrass can be selected by directly planting ryegrass plants or sowing ryegrass seeds, and the planting time is preferably after inoculation with cadmium-resistant Enterococcus Cd-2. Cadmium-resistant Enterococcus Cd-2 can increase the activity of soil luciferase hydrolase and soil microbial activity in cadmium-contaminated soil, promote the growth of ryegrass into ryegrass plants, and ryegrass plants absorb cadmium in the enriched soil through the root system, and transfer the cadmium in the soil to the ryegrass plants. Finally, by collecting the ryegrass plants that absorb cadmium, the repair of cadmium pollution in the soil is completed. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a growth curve and pH change diagram of cadmium-resistant Enterococcus Cd-2 in the embodiment of the present invention;

[0022] Figure 2 is a graph showing the growth characteristics of cadmium-resistant Enterococcus Cd-2 under different cadmium concentrations in an embodiment of the present invention;

[0023] Figure 3 is a graph showing the growth characteristics of cadmium-resistant Enterococcus Cd-2 at different pH values ​​in an embodiment of the present invention;

[0024] Figure 4 is a graph showing the growth characteristics of cadmium-resistant Enterococcus Cd-2 at different temperatures in an embodiment of the present invention;

[0025] Figure 5 is a volcano map of differentially expressed genes in cadmium-resistant Enterococcus Cd-2 in the embodiment of the present invention;

[0026] Figure 6 is a GO functional classification diagram of differentially expressed genes of cadmium-resistant Enterococcus Cd-2 in an embodiment of the present invention;

[0027] Figure 7 is a GO function enrichment map of differentially expressed genes of cadmium-resistant Enterococcus Cd-2 in the embodiment of the present invention;

[0028] Figure 8 is a KEGG pathway enrichment map of cadmium-resistant Enterococcus Cd-2 in the embodiment of the present invention;

[0029] Fig. 9A It is the dynamic change of ryegrass biomass of cadmium-resistant Enterococcus Cd-2 under 4 mg / kg cadmium concentration in the embodiment of the present invention;

[0030] Fig. 9B It is the dynamic change of ryegrass biomass under 20 mg / kg cadmium concentration of cadmium-resistant Enterococcus Cd-2 in the embodiment of the present invention;

[0031] Fig. 10A It is the dynamic change of SOD activity of ryegrass in the cadmium-resistant Enterococcus Cd-2 in the embodiment of the present invention at a cadmium concentration of 4 mg / kg;

[0032] Fig. 10B It is the dynamic change of SOD activity of ryegrass in the cadmium-resistant Enterococcus Cd-2 in the embodiment of the present invention at a cadmium concentration of 20 mg / kg;

[0033] Fig.11A It is the dynamic change of POD activity of ryegrass under 4 mg / kg cadmium pollution in the cadmium-resistant Enterococcus Cd-2 in the embodiment of the present invention;

[0034] Fig. 11B It is the dynamic change of ryegrass POD activity of cadmium-resistant Enterococcus Cd-2 under 20 mg / kg cadmium pollution in the embodiment of the present invention;

[0035] Fig. 12A It is the dynamic change of GSH activity of ryegrass under 4 mg / kg cadmium pollution by cadmium-resistant Enterococcus Cd-2 in the embodiment of the present invention;

[0036] Fig. 12B It is the dynamic change of GSH activity of ryegrass under 20 mg / kg cadmium pollution in the cadmium-resistant Enterococcus Cd-2 in the embodiment of the present invention;

[0037] Fig.13A It is the dynamic change of ASH content in ryegrass under 4 mg / kg cadmium pollution by cadmium-resistant Enterococcus Cd-2 in the embodiment of the present invention;

[0038] Fig. 13B It is the dynamic change of ASH content in ryegrass under 20 mg / kg cadmium pollution by cadmium-resistant Enterococcus Cd-2 in the embodiment of the present invention;

[0039] Fig.14A It is the dynamic change of soil basal respiration of cadmium-resistant Enterococcus Cd-2 under 4 mg / kg cadmium pollution in the embodiment of the present invention;

[0040] Fig. 14B It is the dynamic change of soil basal respiration of cadmium-resistant Enterococcus Cd-2 under 20 mg / kg cadmium pollution in the embodiment of the present invention;

[0041] Fig.15A It is the dynamic change of soil sucrase of cadmium-resistant Enterococcus Cd-2 under 4 mg / kg cadmium pollution in the embodiment of the present invention;

[0042] Fig. 15B It is the dynamic change of soil sucrase of cadmium-resistant Enterococcus Cd-2 under 20 mg / kg cadmium pollution in the embodiment of the present invention;

[0043] Fig.16A It is the dynamic change of soil luciferase activity of cadmium-resistant Enterococcus Cd-2 under 4 mg / kg cadmium pollution in the embodiment of the present invention;

[0044] Fig. 16B It is the dynamic change of soil luciferase activity of cadmium-resistant Enterococcus Cd-2 under 20 mg / kg cadmium pollution in the embodiment of the present invention. DETAILED DESCRIPTION

[0045] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0046] Example 1

[0047] 1. Study on the growth characteristics and resistance mechanism of cadmium-resistant bacteria

[0048] 1.1 Experimental Materials

[0049] The test strains were screened from the tailings soil of Fenghuang Mountain in Yi'an District, Tongling City, Anhui Province.

[0050] 1) Cultivation of resistant bacteria:

[0051] Use CdCl2 to prepare a solution containing 5 mg / L Cd 2+ 50 mL of liquid LB medium was placed in a 250 mL conical flask and sterilized by high pressure steam at 121°C for 20 min. In the clean bench, a small amount of soil samples (5 g each of uncovered, shallowly covered, and deeply covered soil samples) were taken and placed in 50 mL of a flask containing Cd. 2+ The cells were cultured in a conical flask containing liquid LB medium, and the conical flask was placed in a shaking incubator (SHZ-82 air bath constant temperature oscillator) for 3 days. The shaking incubator was set at 30°C and 150 rpm.

[0052] 2) Purification of strains:

[0053] Dilution of culture medium: In the clean bench, take 0.5mL of bacterial solution from the conical flask culture medium and put it into a test tube containing 4.5mL of pure water, mix well, and the culture medium is diluted to 10 -1 After mixing, transfer the diluted solution to another tube containing 4.5 mL of pure water and dilute to 10 -2 Concentration, and so on, dilute step by step.

[0054] Coating plate: In the clean bench, dip the applicator into a small amount of alcohol and put it on the alcohol lamp to dry, then place it on the rack to cool. Take 100μL of bacterial solution and drop it on the sterile plate, and evenly coat it on the surface of the culture medium with the cooled applicator. After coating, burn it to sterilize, and cool it for the next use.

[0055] Plate streaking: In the clean bench, burn the alcohol-soaked inoculation loop with alcohol. After cooling, pick an independent colony from the plate and quickly streak back and forth on a quarter of a blank plate, then burn the inoculation loop. After cooling, streak the inoculation loop from the last part of the first streak to the second quarter of a circle and streak back and forth to form a second area, and burn the inoculation loop again. Repeat the above process to complete the streaking of the third interval, and the last streak does not touch the starting line. After completion, burn the inoculation loop.

[0056] 3) Domestication of strains:

[0057] Prepare the same concentration of Cd as the initial liquid LB medium. 2+ Solid LB medium. After 3 days of culture, the bacterial solution was diluted to 10 -3 , 10-4 , 10 -5 Concentration, coat 3 identical plates for each concentration, place them in a constant temperature incubator at 30℃ for 3 days, and observe the experimental results.

[0058] Double Cd 2+ The concentration is 10 mg / L, and liquid LB medium is prepared. 1 mL of the culture solution from the previous batch is drawn into the newly prepared medium, and the shaking culture is continued. The above screening process is repeated to obtain colony plates at different dilution concentrations. The cultured plates are observed in the clean bench, and all colonies with different morphological structures, colors, etc. are picked from the LB plates containing cadmium, and streaked into the solid LB plates. The plates are placed in an incubator and cultured at 30°C for 3 days, the morphology is observed, and the plates are temporarily stored in a refrigerator at 4°C.

[0059] The obtained different single colony plates were picked out and placed in liquid LB medium with a higher cadmium concentration for shaking culture. After each culture, the plates were tested by the dilution spread plate method to observe whether colonies grew at this concentration.

[0060] Pick a single colony from the streaked plate, add liquid LB medium containing double the cadmium ion concentration, and culture it in a shaker under the same conditions. After one week, use the spread plate method to test whether the strain can survive in the presence of cadmium ions at this concentration. -1 Concentration dilution, take 100 μL to coat the LB solid culture medium plate containing the cadmium concentration, place the coated plate in a 30°C incubator, and observe whether colonies can grow. If there are colonies, pick the colonies from the plate with a sterilized inoculation loop in the clean bench, add them to the culture medium with a higher concentration and continue to culture on the shaking table. If there are no colonies, abandon the culture of the strain. This screening process continues until the two strains with the strongest cadmium tolerance are screened out. Set Cd 2+ The concentration gradients from low to high are:

[0061] Cd 2+ :20mg / L, 40mg / L, 80mg / L, 150mg / L, 200mg / L, 300mg / L.

[0062] In the process of increasing the concentration step by step, different strains were inoculated into liquid LB medium at each concentration. After shaking culture, they were diluted and coated on plates and placed in an incubator for culture and detection. It was gradually found that some strains died. After a period of screening, the strain Cd-2 with the strongest tolerance was finally obtained. It was identified that strain Cd-2 belongs to Enterococcus sp. (as shown in SEQ ID NO.1), and its 16Sr DNA sequence is:

[0063]

[0064] 1.2 Experimental design

[0065] In order to understand the growth characteristics of cadmium-resistant Enterococcus Cd-2, the OD values ​​at 24h and 48h were measured under different temperatures, initial cadmium concentrations and initial pH conditions. 600 value and pH.

[0066] In order to explore the resistance mechanism of cadmium-resistant Enterococcus Cd-2, cadmium-resistant Enterococcus Cd-2 was cultured in normal LB medium and LB medium containing 50 mg / L cadmium. 2+ LB medium was added to the logarithmic growth phase, and the bacterial solution was centrifuged at 4°C and 5000r / min for 10min. The precipitate was washed with phosphate buffer and repeated 3 times. The cells were quick-frozen in liquid nitrogen and the cells were collected for transcriptome sequencing and numbered B2 and B2C respectively.

[0067] 2 Results Analysis

[0068] 2.1 Growth curve of cadmium-resistant Enterococcus Cd-2

[0069] Figure 1 It is a growth curve and pH change diagram of cadmium-resistant Enterococcus Cd-2 in the embodiment of the present invention;

[0070] like Figure 1 As shown, in the early stage of culture, the OD 600 The value did not change significantly. At the 4th hour, it began to grow rapidly and reached a peak of about 0.4 at the 12th hour. 600 The value began to decrease. When the cadmium-resistant Enterococcus Cd-2 began to accelerate its growth, the pH of the liquid culture medium also changed dynamically. During the growth process, the cadmium-resistant Enterococcus Cd-2 reduced the pH of the liquid culture medium from neutral to acidic. At the 36th hour, the pH was about 5.8.

[0071] 2.2 Growth characteristics of cadmium-resistant Enterococcus Cd-2 under different initial conditions

[0072] During the culture of cadmium-resistant Enterococcus Cd-2 under different cadmium concentrations, as the initial cadmium concentration increased, its OD 600 The value shows a slow downward trend, such as Figure 2 shown.

[0073] Figure 2 is a graph showing the growth characteristics of cadmium-resistant Enterococcus Cd-2 under different cadmium concentrations in an embodiment of the present invention;

[0074] from Figure 2 It can be seen that at 24h, the OD of cadmium-resistant Enterococcus Cd-2 600 The values ​​were all greater than those at 48h. At 24h, the OD values ​​of cadmium-resistant Enterococcus Cd-2 treated with each cadmium were600 The OD values ​​of the 10 mg / L cadmium treatment were significantly lower than those of the cadmium-free treatment. 600 The OD value of 20 mg / L cadmium treatment was significantly reduced by about 20.4%. 600 The OD value of 50 mg / L cadmium treatment was significantly reduced by about 9.1%, and the OD value of 50 mg / L cadmium treatment was significantly lower than that of no cadmium treatment. 600 The OD value of 100 mg / L cadmium treatment was significantly reduced by about 16.3%. 600 A decrease of about 13.3%.

[0075] Growth characteristics of cadmium-resistant Enterococcus Cd-2 in different pH ranges, such as Figure 3 shown.

[0076] Figure 3 : is a graph showing the growth characteristics of cadmium-resistant Enterococcus Cd-2 at the same temperature (35° C.) and different pH values ​​in the embodiment of the present invention; Figure 3 It can be seen that within the five pH ranges set, Cd-2 could not grow except at pH 4, but could grow in other pH environments. 600 The value was the largest at pH 7; the OD of the treatments at pH 6, 8, and 10 600 The values ​​were significantly reduced by about 17.6%, 41.0% and 52.4% respectively compared with the pH 7 treatment. The growth characteristics of cadmium-resistant Enterococcus Cd-2 at different temperatures, such as Figure 4 shown. Figure 4 : is a graph showing the growth characteristics of cadmium-resistant Enterococcus Cd-2 at the same pH (pH 7) and different temperatures in the embodiment of the present invention; Figure 4 It can be seen that within the set temperature range, temperature has a significant effect on the growth of cadmium-resistant Enterococcus Cd-2. Cadmium-resistant Enterococcus Cd-2 cannot grow at 20℃ and 25℃, and can grow normally when the temperature reaches 30℃. At 48h, the OD of cadmium-resistant Enterococcus Cd-2 treated at 35℃ and 40℃ was 600 The values ​​were significantly higher than those at 30℃ by about 24.9% and 27.6%, respectively. At the same time, the cadmium-resistant Enterococcus Cd-2 grown under three different initial conditions could reduce the pH of the liquid culture medium from neutral to a certain value of acidity, which was consistent with the law obtained in the growth curve of cadmium-resistant Enterococcus Cd-2.

[0077] 2.3 Differential expression of Cd-2 genes in cadmium-resistant Enterococci

[0078] 2.3.1 Sequencing data quality assessment and genome alignment

[0079] The average mass concentrations of samples B2 and B2C were 283.6 and 48 ng / μL, respectively; the integrity values ​​were 6.3 and 6.25, respectively, which met the requirements for library construction and sequencing. The transcriptome sequencing data are shown in Table 1.

[0080] Table 1 Data output quality statistics

[0081] Sample name Raw data Filtered data Error rate (%) Comparison ratio (%) GC content B2 15332007 15222874 0.03％ 77％ 74.16 B2C 16067824 15578938 0.02％ 81.4％ 71.74

[0082] As shown in Table 1, B2 and B2C obtained an average of 15332007 and 16067824 raw sequences respectively. After filtering the raw data, the CleanReads obtained were 15222874 and 15578938 respectively; their error rates were 0.03% and 0.02% respectively; the alignment results of genome positioning analysis of B2 and B2C were 77% and 81.4% respectively; and the GC contents were 43.17 and 45.15 respectively. This shows that the data has high accuracy and can be directly used for subsequent analysis.

[0083] 2.3.2 Differential gene expression analysis

[0084] The differentially expressed genes of each sample were screened based on the criteria of |Log2(FoldChange)|>1 and P<0.005. Figure 5 shown. Figure 5 is a volcano map of differentially expressed genes in cadmium-resistant Enterococcus Cd-2 in the embodiment of the present invention; Figure 5 In the figure, dots represent specific genes. The dots in region A represent significantly upregulated genes, the dots in region B represent significantly downregulated genes, and the dots in region C represent genes with non-significant differential expression. Figure 5 It can be seen that a total of 944 differentially expressed genes were screened from the B2 and B2C comparison groups, of which 476 were upregulated and 468 were downregulated.

[0085] 2.3.3 GO enrichment analysis and KEGG pathway analysis of differentially expressed genes

[0086] Figure 6 GO functional classification diagram of differentially expressed genes of cadmium-resistant Enterococcus Cd-2 in the embodiment of the present invention; Figure 6As shown in the figure, after GO functional annotation of the screened differentially expressed genes, it was found that the B2C / B2 group annotated 59 significantly enriched Goterms, mainly distributed in 7 secondary Goterms. Among them, there are 3 terms in biological process with a total of 2455 differential genes, which are mainly involved in cell processes, metabolic processes, biological regulation and other functions; there are 2 terms in cell composition with a total of 114 differential genes, which are mainly involved in cell anatomical entities and protein-containing complexes and other functions; there are 2 terms in molecular biology function with a total of 158 differential genes, which are mainly involved in binding and structural molecular activity and other functions. Figure 7 is a GO function enrichment map of differentially expressed genes of cadmium-resistant Enterococcus Cd-2 in the embodiment of the present invention; Figure 7 In the figure, the horizontal axis represents different GO functions; the vertical axis represents significance, and the larger the value, the more significant it is. Different colors represent different functional branches. Figure 7 As shown in the figure, the functions significantly enriched in biological processes are mainly cellular nitrogen-containing compound biosynthesis, macromolecular biosynthesis, cellular macromolecular biosynthesis, ATP biosynthesis, and nucleobase compound biosynthesis; the functions significantly enriched in cell composition are mainly cell periphery, plasma membrane, cell, cell part, protein-containing complex, ribosome, intracellular organelle, intracellular organelle without membrane boundary, intracellular part, and ribonucleoprotein complex; the functions significantly enriched in molecular biological functions are mainly flavin adenine dinucleotide binding, catalytic activity, acting on tRNA, oxidoreductase activity, ligase activity, aminoacyl tRNA ligase activity, carbon-oxygen bond formation, and ion binding. In order to determine the most important biochemical metabolic pathways and signal transduction pathways involved in differentially expressed genes, KEGG pathway enrichment analysis was performed on the differentially expressed genes, such as Figure 8 shown. Figure 8 is a KEGG pathway enrichment map of cadmium-resistant Enterococcus Cd-2 in the embodiment of the present invention; Figure 8 The horizontal axis represents the enrichment ratio. The larger the enrichment ratio, the greater the degree of enrichment. The vertical axis represents the pathway. The size of the dot represents the number of genes in this pathway. Figure 8 It can be seen that the 20 most significantly enriched pathways were plotted as differential gene KEGG pathway enrichment scatter plots. The top five pathways with the most enriched differentially expressed genes in cadmium-resistant Enterococcus Cd-2 under the culture conditions of 50 mg / L cadmium treatment and 0 mg / L cadmium treatment were: biosynthesis pathway of secondary metabolites, microbial metabolic pathways in different environments, carbon metabolic pathways, starch and sucrose metabolic pathways, and glycolysis / gluconeogenesis pathways. The number of enriched differentially expressed genes was 91, 62, 38, 35, and 3, respectively. Among them, the glycolysis / gluconeogenesis pathway was the most significantly enriched.

[0087] 3. Summary

[0088] Cadmium-resistant Enterococcus Cd-2 has good tolerance to cadmium and can grow normally in a 100 mg / L cadmium environment. Under the set environmental conditions, the optimum pH is 6-7, the temperature is 30-40°C, and the optimum temperature is 35-40°C. The functions of genes upregulated under different cadmium concentrations are mainly concentrated in compound synthesis and metabolism, cell membrane and its related components, transmembrane transport, heavy metal binding, etc. Specifically, the top five pathways enriched in differentially expressed genes are: biosynthesis pathway of secondary metabolites, microbial metabolic pathways in different environments, carbon metabolic pathways, starch and sucrose metabolic pathways, and glycolysis / gluconeogenesis pathways. Among them, the most significant pathway for differential gene enrichment in cadmium-resistant Enterococcus Cd-2 is the glycolysis / gluconeogenesis pathway, and the tolerance process of cadmium-resistant Enterococcus Cd-2 to cadmium may be greatly affected by the glycolysis / gluconeogenesis pathway.

[0089] Example 2

[0090] 1. Dynamic effects of inoculation with cadmium-resistant Enterococcus Cd-2 on the physiology and biochemistry of ryegrass in cadmium-contaminated soil

[0091] 1.1 Experimental Materials

[0092] The test soil was collected from clean soil in the 0-20 cm soil layer of a farmland. After the fresh soil was collected, stones, plant roots, large and medium-sized soil animals were removed, and the soil was air-dried and sieved through a 2 mm sieve for later use. The soil pH was 5.51, the total nitrogen content was 0.81 g / kg, the total phosphorus content was 0.48 g / kg, the total potassium content was 1.63 g / kg, and the cadmium content was not detected. The test plant was ryegrass (Lolium perenne L.), and ryegrass seeds were purchased from Suqian Horticulture Co., Ltd., Jiangsu Province.

[0093] 1.2 Experimental design

[0094] This experiment was designed with 4 treatments, each with 18 replicates, for a total of 72 pots. The experimental design is shown in Table 2.

[0095] Table 2 Experimental design

[0096]

[0097] The test soil was contaminated (cadmium was added in the form of CdCl2·2.5H2O solution), and 0.5 g / LCd was accurately prepared. 2+ As the mother solution, it was evenly irrigated into the potting soil, and the Cd pollution concentration was adjusted to 0.4 mg / kg (agricultural soil control value) and 20 mg / kg (a type of construction land screening value) according to the soil environmental quality standard (GB15618-2018). 2+Each pot (8cm×8cm×10cm) was filled with 500g of soil (dry weight), and 50 perennial ryegrass seeds were evenly planted in each pot. According to the conventional application rate of N 20kg / mu and P 10kg / mu, the water-soluble fertilizer was diluted and applied as basal fertilizer. Each pot was inoculated with 9mL of cadmium-resistant Enterococcus Cd-2 (10 9 CFU / mL), with 14h / d of light and 10h / d of darkness, for a 2-month indoor culture test. During this period, distilled water was added daily according to the soil moisture status of each pot, so that the soil moisture content of the potted plants was maintained at 60% of the saturated moisture content. Destructive collection sampling was carried out on the 20th, 40th and 60th days. Six replicates were randomly selected for each treatment each time, of which three replicates were used to analyze plant physiological and biochemical indicators and soil microbial activity, and the other three replicates were used to determine related indicators such as biomass and heavy metal content.

[0098] 2 Results Analysis

[0099] 2.1 Effects of cadmium-resistant Enterococcus Cd-2 on ryegrass biomass at different cadmium concentrations

[0100] Fig. 9A It is the dynamic change of ryegrass biomass of cadmium-resistant Enterococcus Cd-2 under 4 mg / kg cadmium concentration in the embodiment of the present invention; Fig. 9B The dynamic changes of ryegrass biomass under 20 mg / kg cadmium concentration of cadmium-resistant enterococci Cd-2 in the embodiment of the present invention; Figures 9A-9B It can be seen that the biomass of ryegrass treated with different cadmium concentrations showed an increasing trend over time, and there were certain differences in the biomass of ryegrass treated with different cadmium concentrations. Fig. 9A It can be seen that under the treatment of 4 mg / kg cadmium, at the 60th day, the treatment with cadmium-resistant Enterococcus Cd-2 significantly increased the ryegrass biomass by about 41.4% (P=0.007) compared with the treatment without cadmium-resistant Enterococcus Cd-2. Fig. 9B It can be seen that under the treatment of 20 mg / kg cadmium, on the 60th day, the treatment with cadmium-resistant Enterococcus Cd-2 significantly increased the ryegrass biomass by about 108.6% (P=0.001) compared with the treatment without cadmium-resistant Enterococcus Cd-2.

[0101] 2.2 Effects of cadmium-resistant Enterococcus Cd-2 on SOD activity of ryegrass at different cadmium concentrations

[0102] Fig. 10A It is the dynamic change of SOD activity of ryegrass in the cadmium-resistant Enterococcus Cd-2 in the embodiment of the present invention at a cadmium concentration of 4 mg / kg; Fig. 10B The dynamic changes of SOD activity of ryegrass in the cadmium-resistant Enterococcus Cd-2 in the embodiment of the present invention at a cadmium concentration of 20 mg / kg; Fig. 10A-B shows that under different cadmium concentrations, the activity of superoxide dismutase (SOD) in ryegrass generally increased with the increase of culture time. Fig. 10A It can be seen that under the treatment of 4 mg / kg cadmium, on the 60th day, the treatment with cadmium-resistant Enterococcus Cd-2 significantly reduced the SOD activity of ryegrass by about 26.2% (P=0.001) compared with the treatment without cadmium-resistant Enterococcus Cd-2. Fig. 10B It can be seen that under the treatment of 20 mg / kg cadmium, on the 40th day, the SOD activity of ryegrass inoculated with cadmium-resistant Enterococcus Cd-2 was significantly reduced by about 16.6% (P=0.002) compared with the treatment without cadmium-resistant Enterococcus Cd-2; on the 60th day, the SOD activity of ryegrass inoculated with cadmium-resistant Enterococcus Cd-2 was extremely significantly reduced by about 54.6% (P=0.001) compared with the treatment without cadmium-resistant Enterococcus Cd-2.

[0103] 2.3 Effects of cadmium-resistant Enterococcus Cd-2 on POD activity of ryegrass at different cadmium concentrations

[0104] Fig.11A It is the dynamic change of POD activity of ryegrass under 4 mg / kg cadmium pollution in the cadmium-resistant Enterococcus Cd-2 in the embodiment of the present invention; Fig. 11B The dynamic changes of the POD activity of ryegrass under 20 mg / kg cadmium pollution of cadmium-resistant Enterococcus Cd-2 in the embodiment of the present invention; Fig.11A -B shows that under different cadmium concentrations, the POD activity of ryegrass generally showed a downward trend with the increase of treatment time. Fig.11A It can be seen that under the treatment of 4 mg / kg cadmium, at the 20th day, the treatment with cadmium-resistant Enterococcus Cd-2 significantly increased the POD activity of ryegrass by about 86.4% (P=0.007) compared with the treatment without cadmium-resistant Enterococcus Cd-2; at the 40th day, the treatment with cadmium-resistant Enterococcus Cd-2 significantly increased the POD activity of ryegrass by about 150.7% (P=0.011) compared with the treatment without cadmium-resistant Enterococcus Cd-2. Fig. 11B It can be seen that under the treatment of 20 mg / kg cadmium, on the 20th day, the treatment with cadmium-resistant Enterococcus Cd-2 significantly increased the peroxidase (POD) activity of ryegrass by about 67.5% (P=0.002) compared with the treatment without cadmium-resistant Enterococcus Cd-2; on the 60th day, the treatment with cadmium-resistant Enterococcus Cd-2 significantly increased the POD activity of ryegrass by about 146.5% (P=0.001) compared with the treatment without cadmium-resistant Enterococcus Cd-2.

[0105] 2.4 Effects of cadmium-resistant Enterococcus Cd-2 on GSH content in ryegrass at different cadmium concentrations

[0106] Fig. 12AThis is the dynamic change of the GSH content of ryegrass in the cadmium-resistant Enterococcus Cd-2 under 4 mg / kg cadmium pollution in the embodiment of the present invention; Fig. 12B The dynamic changes of GSH content in ryegrass of cadmium-resistant Enterococcus Cd-2 under 20 mg / kg cadmium pollution in the embodiment of the present invention; Fig. 12A -B shows that under different cadmium concentration treatments, the GSH content of ryegrass generally increased with the increase of treatment time. Fig. 12A It can be seen that under the treatment of 4 mg / kg cadmium, at the 40th day, the glutathione content of ryegrass inoculated with cadmium-resistant Enterococcus Cd-2 was significantly increased by about 61.4% (P=0.001) compared with the treatment without cadmium-resistant Enterococcus Cd-2; at the 60th day, the glutathione content of ryegrass inoculated with cadmium-resistant Enterococcus Cd-2 was significantly reduced by about 27.1% (P=0.049) compared with the treatment without cadmium-resistant Enterococcus Cd-2. Fig. 12B It can be seen that under the treatment of 20 mg / kg cadmium, on the 20th day, the GSH content of ryegrass inoculated with cadmium-resistant Enterococcus Cd-2 was significantly reduced by about 63.6% (P=0.001) compared with the treatment without cadmium-resistant Enterococcus Cd-2; on the 60th day, the glutathione content of ryegrass inoculated with cadmium-resistant Enterococcus Cd-2 was significantly reduced by about 12.3% (P=0.024) compared with the treatment without cadmium-resistant Enterococcus Cd-2.

[0107] 2.5 Effects of cadmium-resistant Enterococcus Cd-2 on the ASA content of ryegrass at different cadmium concentrations

[0108] Fig.13A It is the dynamic change of ASA content in ryegrass of cadmium-resistant Enterococcus Cd-2 under 4 mg / kg cadmium pollution in the embodiment of the present invention; Fig. 13B The dynamic changes of ASA content in ryegrass of cadmium-resistant Enterococcus Cd-2 under 20 mg / kg cadmium pollution in the embodiment of the present invention; Fig.13A -B shows that under different cadmium concentration treatments, the ascorbic acid (ASA) content of ryegrass generally increased with the increase of cultivation time. Fig.13A It can be seen that under the treatment of 4 mg / kg cadmium, on the 40th day, the treatment with cadmium-resistant Enterococcus Cd-2 significantly increased the ascorbic acid (ASA) content of ryegrass by about 308.5% (P=0.001) compared with the treatment without cadmium-resistant Enterococcus Cd-2. Fig. 13BIt can be seen that under the treatment of 20 mg / kg cadmium, on the 40th day, the ASA content of ryegrass inoculated with cadmium-resistant Enterococcus Cd-2 was significantly increased by about 153.0% (P=0.001) compared with the treatment without cadmium-resistant Enterococcus Cd-2; on the 60th day, the ASA content of ryegrass inoculated with cadmium-resistant Enterococcus Cd-2 was significantly increased by about 6.2% (P=0.018) compared with the treatment without cadmium-resistant Enterococcus Cd-2.

[0109] 2.6 Effects of cadmium-resistant Enterococcus Cd-2 on cadmium accumulation characteristics in ryegrass

[0110] The accumulation characteristics of cadmium in ryegrass are shown in Table 3.

[0111] Table 3 Characteristics of cadmium accumulation and transport in ryegrass

[0112]

[0113] Note: On the 20th day, the underground biomass of ryegrass was insufficient to determine the Cd content in the underground part; Different letters in the same column indicate significant differences (P<0.05).

[0114] As shown in Table 2, at different sampling periods, with the increase of cadmium treatment concentration, the cadmium content in the underground and aboveground parts of ryegrass also increased, and there were significant differences between different cadmium concentration treatments, showing that the cadmium concentrations in the underground and aboveground parts of the 20 mg / kg treatment were higher than those in the 4 mg / kg treatment. At the same sampling time and the same cadmium concentration treatment, the cadmium concentrations in the aboveground and underground parts of the inoculated cadmium-resistant Enterococcus Cd-2 treatment were generally higher than those in the non-inoculated treatment. On the 40th day, the cadmium concentration in the aboveground part of the C1B2 treatment was extremely significantly higher than that in the C1B0 treatment by about 58.3% (P=0.005); the underground part was significantly lower than that in the C1B0 treatment by about 9.6% (P=0.023); the cadmium concentration in the underground part of the C2B2 treatment was significantly higher than that in the C2B0 treatment by about 30.5% (P=0.028). On the 60th day, the cadmium concentration in the aboveground part of the C1B2 treatment was significantly lower than that in the C1B0 treatment by about 11.5% (P=0.003); the cadmium concentration in the underground part of the C1B2 treatment was significantly lower than that in the C1B0 treatment by about 55.6% (P=0.004). The transport coefficient and enrichment coefficient also had certain differences under different sampling times and different cadmium concentration treatments. On the 40th day, the transport coefficient of the C1B2 treatment was significantly higher than that of the C1B0 treatment by about 75.0% (P=0.002); the enrichment coefficient of the C2B2 treatment was significantly higher than that of the C2B0 treatment by about 31.8% (P=0.05). On the 60th day, the transport coefficient of the C1B2 treatment was significantly higher than that of the C1B0 treatment by about 122.2% (P=0.001); the enrichment coefficient of the C1B2 treatment was significantly lower than that of the C1B0 treatment by about 43.2% (P=0.011). Except for the 60th day, when the cadmium-resistant bacteria were inoculated under the 4 mg / kg cadmium treatment, the other treatments could improve the ryegrass's cadmium transport coefficient and enrichment coefficient to a certain extent. The ryegrass cadmium accumulation and cadmium removal rate in the soil are shown in Table 4.

[0115] Table 4 Cd accumulation of ryegrass and its removal rate from soil

[0116]

[0117] * indicates that the difference between inoculated and non-inoculated treatments at the same Cd concentration is significant; ** indicates that the difference between inoculated and non-inoculated treatments at the same Cd concentration is extremely significant.

[0118] In different sampling periods and under different cadmium concentrations, inoculation with cadmium-resistant Enterococcus Cd-2 can generally increase the accumulation of cadmium in ryegrass, and there are certain differences between different cadmium concentrations. On the 20th day, the cadmium accumulation of the treatment with cadmium-resistant Enterococcus Cd-2 at 4 mg / kg cadmium concentration was significantly increased by 41.9% (P=0.035) compared with the treatment without inoculation; the cadmium accumulation of the treatment with cadmium-resistant Enterococcus Cd-2 at 20 mg / kg cadmium concentration was extremely significantly reduced by 77.4% (P=0.008) compared with the treatment without inoculation. On the 40th day, the cadmium accumulation of the treatment with cadmium-resistant Enterococcus Cd-2 at 4 mg / kg cadmium concentration was extremely significantly increased by 48.9% (P=0.001) compared with the treatment without inoculation; the cadmium accumulation of the treatment with cadmium-resistant Enterococcus Cd-2 at 20 mg / kg cadmium concentration was significantly increased by 75.1% (P=0.035) compared with the treatment without inoculation. On the 60th day, the cadmium accumulation in the treatment of cadmium-resistant Enterococcus Cd-2 at 4 mg / kg cadmium concentration was significantly reduced by 23.8% (P=0.037) compared with the treatment without inoculation; the cadmium accumulation in the treatment of cadmium-resistant Enterococcus Cd-2 at 20 mg / kg cadmium concentration was significantly increased by 167.5% (P=0.046) compared with the treatment without inoculation. The removal rate of cadmium in soil by ryegrass showed the same pattern.

[0119] 3 Summary

[0120] The experimental results show that inoculating cadmium-resistant Enterococcus Cd-2 in cadmium-contaminated soil with ryegrass can increase ryegrass biomass, peroxidase activity and ascorbic acid content; and reduce superoxide dismutase activity and glutathione content in ryegrass leaves. The reason for this phenomenon may be that in a cadmium-contaminated environment, the active oxygen in ryegrass continues to increase, causing ryegrass to produce oxidative stress, increasing the secretion of superoxide dismutase and glutathione to coordinate redox balance. The study found that inoculating cadmium-resistant Enterococcus Cd-2 in cadmium-contaminated soil with ryegrass can increase the ascorbic acid content in ryegrass leaves and promote the antioxidant system of ryegrass to remove excessive reactive oxygen in ryegrass, thereby reducing the superoxide dismutase activity and glutathione content in ryegrass leaves. This result shows that cadmium-resistant Enterococcus Cd-2 can alleviate the oxidative stress response under adverse stress, allowing ryegrass plants to grow normally, thereby increasing the biomass of ryegrass and promoting the growth and development of ryegrass. The underground and aboveground parts of well-grown ryegrass have increased enrichment coefficients and transport coefficients for cadmium, thereby reducing the residual amount of cadmium in cadmium-contaminated soil and improving the removal rate of cadmium in contaminated soil.

[0121] Example 3

[0122] 1. Effects of cadmium-resistant Enterococcus Cd-2 on microbial activity in cadmium-contaminated soil

[0123] 1.1 Materials and methods

[0124] The experimental materials are the same as those in Example 2.

[0125] 1.2 Experimental design

[0126] The experimental design is the same as that of Example 2.

[0127] 2 Results and analysis

[0128] 2.1 Dynamic effects of cadmium-resistant Enterococcus Cd-2 on basal respiration in cadmium-contaminated soil

[0129] Fig.14A It is the dynamic change of soil basal respiration of cadmium-resistant Enterococcus Cd-2 under 4 mg / kg cadmium pollution in the embodiment of the present invention; Fig. 14B The dynamic changes of soil basal respiration of cadmium-resistant Enterococcus Cd-2 under 20 mg / kg cadmium pollution in the embodiment of the present invention; Fig.14A -B shows that the soil basic respiration intensity generally shows a trend of first increasing and then decreasing with the increase of cultivation time. At the same cadmium concentration, inoculation of cadmium-resistant Enterococcus Cd-2 also has a certain effect on the soil basic respiration intensity. Fig.14A It can be seen that under the treatment of 4 mg / kg cadmium concentration, at the 20th day, the soil basic respiration intensity of the treatment inoculated with cadmium-resistant Enterococcus Cd-2 was significantly reduced by about 47.8% (P=0.012) compared with the treatment without cadmium-resistant Enterococcus Cd-2; at the 40th day, the soil basic respiration intensity of the treatment inoculated with cadmium-resistant Enterococcus Cd-2 was extremely significantly reduced by about 99.4% (P=0.001) compared with the treatment without cadmium-resistant Enterococcus Cd-2. Fig. 14B It can be seen that under the treatment of 20 mg / kg cadmium concentration, on the 40th day, the basic respiration intensity of the soil in the treatment of inoculation with cadmium-resistant Enterococcus Cd-2 was significantly reduced by about 59.6% (P=0.002) compared with the treatment without inoculation with cadmium-resistant Enterococcus Cd-2; on the 60th day, the basic respiration intensity of the soil in the treatment of inoculation with cadmium-resistant Enterococcus Cd-2 was significantly increased by about 48.9% (P=0.039) compared with the treatment without inoculation with cadmium-resistant Enterococcus Cd-2.

[0130] 2.2 Effects of cadmium-resistant Enterococcus Cd-2 on sucrase activity in soils contaminated with cadmium

[0131] Fig.15A It is the dynamic change of soil sucrase activity of cadmium-resistant Enterococcus Cd-2 under 4 mg / kg cadmium pollution in the embodiment of the present invention; Fig. 15B The dynamic changes of soil sucrase activity of cadmium-resistant Enterococcus Cd-2 under 20 mg / kg cadmium pollution in the embodiment of the present invention; Fig.15A-B shows that the soil sucrase activity generally shows an upward trend with the increase of culture time. There are certain differences in the soil sucrase activity under different cadmium concentrations. Inoculation of cadmium-resistant Enterococcus Cd-2 at the same cadmium concentration also has a certain effect on the soil sucrase activity. Fig.15A It can be seen that under the 4 mg / kg cadmium concentration treatment, at the 60th day, the soil sucrase activity in the treatment of cadmium-resistant Enterococcus Cd-2 was significantly reduced by about 28.1% (P=0.009) compared with the treatment without cadmium-resistant Enterococcus Cd-2. Fig. 15B It can be seen that under the treatment of 20 mg / kg cadmium concentration, on the 60th day, the soil sucrase activity in the treatment inoculated with cadmium-resistant Enterococcus Cd-2 was significantly reduced by about 31.8% (P=0.023) compared with the treatment not inoculated with cadmium-resistant Enterococcus Cd-2.

[0132] 2.3 Effects of cadmium-resistant Enterococcus Cd-2 on luciferase activity in soils contaminated with cadmium

[0133] Fig.16A It is the dynamic change of soil luciferase activity of cadmium-resistant Enterococcus Cd-2 under 4 mg / kg cadmium pollution in the embodiment of the present invention; Fig. 16B The dynamic changes of soil luciferase activity of cadmium-resistant Enterococcus Cd-2 under 20 mg / kg cadmium pollution in the embodiment of the present invention; Fig.16A -B shows that the activity of soil luciferase hydrolase (FDA) generally shows a downward trend with the increase of culture time, and the inoculation of cadmium-resistant Enterococcus Cd-2 also has a certain effect on the activity of soil luciferase hydrolase. Fig.16A It can be seen that under the treatment of 4 mg / kg cadmium concentration, at the 40th day, the soil luciferase activity in the treatment of cadmium-resistant Enterococcus Cd-2 was significantly reduced by about 37.9% (P=0.029) compared with the treatment without cadmium-resistant Enterococcus Cd-2; at the 60th day, the soil luciferase activity in the treatment of cadmium-resistant Enterococcus Cd-2 was extremely significantly increased by about 202.5% (P=0.032) compared with the treatment without cadmium-resistant Enterococcus Cd-2. Fig. 16B It can be seen that under the treatment of 20 mg / kg cadmium concentration, on the 20th day, the soil luciferase activity in the treatment of cadmium-resistant Enterococcus Cd-2 was significantly reduced by about 17.3% (P=0.002) compared with the treatment without cadmium-resistant Enterococcus Cd-2; on the 60th day, the soil luciferase activity in the treatment of cadmium-resistant Enterococcus Cd-2 was significantly increased by about 155.1% (P=0.002) compared with the treatment without cadmium-resistant Enterococcus Cd-2.

[0134] 3 Summary

[0135] The experimental results show that under cadmium pollution conditions, inoculating cadmium-resistant Enterococcus Cd-2 in cadmium-contaminated soil with ryegrass can reduce the activity of soil sucrase, reduce the soil basic respiration intensity, and increase the soil luciferase activity in the later stage of cultivation, that is, inoculating cadmium-resistant Enterococcus Cd-2 can increase the activity of soil microorganisms. From the above results, it can be seen that the cadmium-resistant Enterococcus Cd-2 provided by the present invention can increase the activity of luciferase, increase the microbial activity of soil, increase the content of ryegrass anti-cycloheptacid, and promote the antioxidant system of ryegrass to remove excessive active oxygen in ryegrass, thereby reducing the superoxide dismutase activity and glutathione content in ryegrass leaves, alleviating the oxidative stress reaction of ryegrass under adverse stress, promoting the growth of ryegrass in cadmium-contaminated soil, increasing the biomass of ryegrass, and increasing the enrichment of cadmium by ryegrass, which helps to promote the repair of ryegrass to cadmium-contaminated soil. The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modification, equivalent substitution or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An enterococcus ( Enterococcus ) Cd-2, characterized in that Its strain collection number is CGMCC No.25220.

2. The method for culturing Enterococcus Cd-2 according to claim 1, characterized in that: The Enterococcus Cd-2 is cultured in a culture medium with a pH of 6-7.

3. The method for culturing Enterococcus Cd-2 according to claim 2, characterized in that: The Enterococcus Cd-2 was cultured at a temperature of 30-40°C.

4. Use of the Enterococcus Cd-2 described in claim 1 in promoting the growth of ryegrass in cadmium-contaminated soil.

5. A method for promoting the growth of ryegrass in cadmium-contaminated soil, characterized in that: The Enterococcus Cd-2 described in claim 1 is inoculated into cadmium-contaminated soil where ryegrass is grown.

6. The method according to claim 5, characterized in that The concentration of cadmium in the cadmium-contaminated soil is ≤100 mg / L.

7. The method according to claim 5, characterized in that The method further comprises, after inoculating the enterococcus Cd-2, culturing according to light exposure of 10-14 h / d and darkness of 8-10 h / d.

8. The method according to claim 7, characterized in that The moisture content of the cadmium-contaminated soil inoculated with Enterococcus Cd-2 is maintained at 40%-60%.

9. The method according to claim 5, characterized in that: The time of inoculating the Enterococcus Cd-2 is before sowing ryegrass seeds.

10. A method for repairing cadmium-contaminated soil, characterized in that: Planting ryegrass in the cadmium-contaminated soil inoculated with the enterococcus Cd-2 described in claim 1; collecting ryegrass plants enriched in cadmium to complete the restoration of the cadmium-contaminated soil.

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