Screening and Composition Analysis of Carbendazim-Decomposing Bacterial Community and Effect Test in Soil

【Objective】 The objective of this study is to screen carbendazim-decomposing bacterial communities and strains,understand the composition of carbendazim-decomposing bacterial communities and the phylogeny of isolated carbendazimdecomposing bacterial strains,test the degradation effect of screened carbendazim-decomposing bacterial communities and strains to soil carbendazim.【Method】 Mineral salt medium was used for enrichment and screen for carbendazim-decomposing bacterial communities and strains.Chromatography was used for effect test of carbendazim degradation by bacterial communities and strains.Denaturing gradient gel electrophoresis(DGGE) and band sequencing were used for composition analysis of carbendazimdecomposing bacterial communities.16S rDNA sequence blust and bacterial identification techniques wrer used for strain phylogeny.【Result】Nine carbendazim-decomposing bacterial communities were screened,which could degrade 23.14%-70.64% carbendazim with initial concentration of 600 mg.L-1 in liquid culture in 10 days.Five strains designed as 111-3,161-4,165-2,166-2,and 167-4 were further screened from the above bacterial communities,which could degrade 33.90%-72.66% carbendazim with initial concentration of 600 mg.L-1 in liquid culture in 15 days.Strains 111-3,165-2,166-2,and 167-4 were identified as Rhodococcus sp.,161-4 was identified as Stenotrophomonas sp..Under laboratory conditions,above 90% of the carbendazim in soil with initial concentration of 5 mg.kg-1 was decomposed after inoculation of anyone of the screened carbendazim-degrading bacterial communities or strains in 72 hours.The screened carbendazim-decomposing bacterial communities was composed of 6-10 dominent strains,the screened carbendazim-decomposing bacterial strains was only about 1/10 of bacterial communities.【Conclusion】 Nine carbendazim-decomposing bacterial communities and 5 strains were screened,which could decompose 90% of the 5 mg.kg-1 carbendazim in soil in 72 hours.Rhodococcus is the dominent species for carbendazim decomposition in natural environment.The screened carbendazim-decomposing bacterial strains are only a small part of the screened carbendazim-decomposing bacterial communities.Decomposing system is much meaningful to pesticide residue decomposition.