| At present,serious diseases and insect pests occur in the process of vegetable planting in our country,resulting in increasing the amount of pesticide input.Carbendazim and acetamiprid are widely used in facility agriculture due to their low toxicity and high efficiency.However,with the expansion of the planting area,the soil residue problems of carbendazim and acetamiprid are becoming more and more prominent,which brings potential risks to the ecological environment.The use of microorganisms to remediate pesticide residue pollution is a safe,cheap,and efficient method with great development potential and application value.At present,most of the research on pesticide residue remediation is the isolation of highly efficient degrading microorganisms of pesticide pollutants and the study of their degradation mechanism.Fermentation of degrading bacteria into degrading bacteria agent is the main application method at present,but there are still many limitations,such as only being able to degrade a single pesticide residue,inconvenient transportation,short storage time,and easy pollution.Therefore,in this paper,the carbendazim-degrading strain Rhodococcus qingshengii djl-6 and the acetamiprid-degrading strain Pigmentiphaga sp.D-2 isolated from the soil in the early stage of the laboratory were used as the test strains,and an efficient organic fertilizer was used as the carrier.Single and composite solid degrading inoculants were developed,and the preliminary application of the inoculants and the microecological effects of the degrading inoculants on the remediation of pesticide residues in contaminated soil were studied,providing some basis for the application of solid degrading inoculants.The main research contents and results are summarized as follows:A high-efficiency organic fertilizer was selected as the carrier,and two strains of degrading bacteria,djl-6 and D-2,were inoculated respectively.The degrading bacteria were made into a single solid degrading bacteria agent,and djl-6 and D-2 were mixed and inoculated into the organic fertilizer carrier at a volume ratio of 5:3 to make a composite solid degrading bacteria agent.When stored for 120 days,the number of viable bacteria in each solid microbial agent was maintained at 107 cfu/g.and the number of viable bacteria in a single acetamiprid degrading inoculum of acetamiprid was the highest,which was 5.73×107 cfu/g.Degradation experiments of pesticide residues in minimal medium showed that the solid degrading inoculum with djl-6 as inoculating microorganisms could degrade 99.3%of carbendazim at a concentration of 5 mg/L within 48 h and the acetamiprid degrading microbial inoculum could degrade 98.5%of acetamiprid at a concentration of 10 mg/L within 64 h after storage for 30 days.Moreover,the degradation rate of 10 mg/L acetamiprid by the composite degrading bacteria agent reached 97.2%,and the degradation rate of 5 mg/L carbendazim reached 98.7%within 64 hours.Through the pot test of the remediation of pesticide residues and the promotion of plant growth,it was found that the compound pesticide residues of carbendazim and acetamiprid would inhibit the normal growth of green vegetables,resulting in the root length,stem leaf length and fresh weight of small green cabbage being only about 50%of the control group on the 24th day.The compound biodegradation agent could effectively degrade compound pesticide residues,so that the growth of green vegetables is the same as that of the control group on the 16th day.What’s more,the use of degrading bacteria agent can promote the growth of green vegetables,and the fresh weight of green vegetables increased by about 16%on the 16th and 24th days compared with the control group.The results of pot degradation experiments showed that the carbendazim degrading microbial inoculum could degrade 97.4%of the carbendazim at a concentration of 5 mg/kg within 12 d,and the acetamiprid degrading microbial inoculum could degrade 98.6%within 16 d.The composite degrading bacteria agent can degrade 98.8%of carbendazim at a concentration of 5 mg/kg in 12 days,and degrade 99.8%of acetamiprid at 10 mg/kg in 16 days.The specific primers of the esterase genes aceA and edo in the degrading strains were designed,and the survival of the degrading strains in the soil was quantitatively determined by the absolute quantitative method of fluorescence quantitative PCR.The results showed that D-2 and djl-6 could survive in soil under natural conditions for about 12 days and 16 days respectively.Through the high-throughput sequencing results of the remediation of pesticide residues contaminated soil by degrading bacteria agent,Alpha diversity analysis,Beta diversity analysis,and relative species abundance at the phylum and genus levels were obtained under different treatment conditions.Alpha diversity analysis results showed that degrading bacteria agent in the process of remediation of pesticide residues in the soil would increase the number of species,diversity and richness of soil bacterial communities.Beta diversity results showed that respectively adding carbendazim single degrading agent,acetamiprid single degrading agent,and carbendazim compound degrading agent,the difference between the bacterial community structure at the same treatment for different times is small,and the difference between different treatments is large.After adding the above three treatments,the difference from the 0 d sample is relatively large,indicating that three treatments have impacts on the community structure.The results of relative species abundance at the gate level indicated that the remediation of pesticide residue soil by degrading bacteria would increase the relative abundance of Proteobacteria and Bacteroidetes,and decrease the relative abundance of Firmicutes and Acidobacteria.Genus level relative species abundance results showed that the degrading strains in the degrading bacterial agent could survive for at least 16 days in the soil.The degrading bacteria agent could promote the increase of the relative abundance of the genus Sphingomonas,Rhodococcus and Pigmentiphaga,and reduce the relative abundance of the flora of Pullulanibacillus. |
PDF Full Text Request