Abstract：Acetochlor is a broad-spectrum and high-efficive chloroacetanilide herbicide. Because of its long degradation period, with the characteristics of difficult for volatilization, photolysis, and easy for residue, the overuse of acetochlor is toxic to human, plants and animals. In order to investigate the microbial degradation mechanisms of acetochlor, an acetochlor-degrading bacterium, named strain M-3 was isolated from acetochlor-contaminated samples using selective culture medium with acetochlor as the sole carbon source. The strain was identified based on its morphological, physiological and biochemical tests, with reference to Bergey’s Manual of Determinative Bacteriology combined with 16S rRNA gene sequence analysis. Strain M-3 was finally identified as Stenotrophomonas sp. . With HPLC and HPLC-MS method, degrading characteristics of strain M-3 were studied under laboratory conditions and the degrading pathway of acetochlor was researched preliminarily. The results showed that strain M-3 could degrade more than 76.6% of 50 mg/L acetochlor within 5 d. The best temperature and pH for the acetochlor degradation by strain M-3 were 30℃ and 7.0, respectively. Based on the identified products, the degrading pathway of acetochlor was speculated. The product was identified as 2-ethyl-6-methyl-2-chloroacetanilide. Our research provides theoretical basis for bioremediation technology of acetochlor pollution.
