Abstract: This work is designed to obtain soil microorganisms that can efficiently degrade diuron,to systematically elucidate the characteristics of this strain degrading diuron and its metabolic pathway,and to explore the practical application potential of the isolated strain. Sole carbon source method was applied for enrichment,domestication and isolation of diuron-degrading soil microbes. Then single factor test was used to investigate the strain’s environmental adaptability. Further mass spectrometry analysis of metabolic intermediates was to deduce the metabolic pathway of the strain degrading diuron. And simulating in situ soil remediation was to investigate the application potential of the isolated strain in soil remediation. As results,one bacterial strain LX-C-06 that effectively degraded diuron was isolated from cotton fields with long-time diuron application. The strain LX-C-06 was identified as Achromobacter xylosoxidans via morphological,physiological and biochemical characteristics and 16S rRNA gene analysis. The results of single factor tests indicated that the optimal temperature and pH for diuron degradation by strain LX-C-06 were 30℃ and 7.0,respectively. The strain LX-C-06 showed high tolerance to NaCl concentration. The degradation rates of 50 mg/L diuron within 120 h were 100%,100% and 87.8% when NaCl concentration was 1%,3% and 5%,respectively. The strain LX-C-06 also showed good degradation ability towards high concentration of diuron,and the degradation rate of the strain LX-C-06 to diuron was above 100% within 120 h when diuron concentration was ≤ 400 mg/L. The degradation rate of diuron was 92.1% within 120 h when diuron concentration increased to 600 mg/L. Based on the identification of metabolic intermediates,it was speculated that the strain LX-C-06 transformed diuron into 3,4-dichloroaniline via hydrolyzing ester bond. And 3,4-dichloroaniline was further transformed into succinic acid by deamination,hydroxylation and ring-cleavage. Within 30 d,the maximum degradation rate of 50 mg/kg diuron in soil was 90.7% with bioaugmentation of the strain LX-C-06. In conclusion,the strain LX-C-06 is identified as Achromobacter xylosoxidans that efficiently degrades diuron. The strain LX-C-06 demonstrates tolerance to environmental temperature,pH,and salinity concentration. The strain LX-C-06 transforms and utilizes diuron by hydrolyzing ester bond,deamination,hydroxylation,ring-cleavage,etc. The strain LX-C-06 also shows promising application potential.

Key words: diuron, Achromobacter xylosoxidans, biodegradation, bioremediation, metabolic pathway