isolation and characterization of a quincloracdegrading actinobacteria streptomyces sp strain ahb and its implication on microecology in contaminated soil quinclorac a highly selective auxin herbicide is widely used for controlling weeds in rice field however the residual quinclorac is toxic to many crops vegetables and aquatic animals resulting in one of the major problems in crop rotation here we investigated the degradation of quinclorac by strain ahb which was isolated from longterm quincloraccontaminated soil using continuous circulating fluidized bed reactor and subjected to atmospheric and room temperature plasma mutation morphological examination 16s rrna gene sequencing and phylogenetic analysis revealed that strain ahb was streptomyces sp the quinclorac degradation efficiency of ahb in liquid medium was 972 after 18 days when the initial quinclorac concentration was 20mgl1 the degradation products were 3chloro7methoxy8quinolinecarboxylic 3chloro7methyl8quinolinecarboxylic 3chloro7oxyethyl8quinolinecarboxylic and 37dichloro6methyl8quinolinecarboxylic the inoculum size initial quinclorac concentration ph and temperature were found to affect quinclorac degradation efficiency of ahb highperformance liquid chromatographyelectrospray ionization tandem mass spectrometry analysis revealed that quinclorac degradation by ahb produced many products in soil with initial quinclorac content of 1mgkg1 dry soil addition of ahb resulted in 875 quinclorac degradation after 42 days while that in the control without ahb was 224 furthermore microecological analysis using nextgeneration sequencing of 16s rrna geneshowed that some bacterial species such as bacterioides and proteobacteria could survive in quincloraccontaminated soil while some bacteria such as firmicutes were very sensitive to quinclorac besides some fungal species such as basidiomycota could also survive quincloraccontamination after 42 days the diversity of bacteria and fungi in soil treated with ahb was higher than that in the control implying that bioaugmentation with strain ahb could reduce quinclorac toxicity to microorganisms in soil