Mechanism of β-cypermethrin metabolism by Bacillus cereus GW-01

Abstract

Pesticide residues in soil and food are of concern for human health. Biodegradation is an attractive option for reducing these residues, but more insight into the mechanism of degradation is necessary to ensure that toxic deadend products are not produced in the process. In this study, a β-cypermethrin (β-CY) degrading bacterium which we named GW-01 was isolated from a sheep’s rumen chyme. HPLC analyses of culture extracts revealed that train GW-01 degraded ∼ 60 % of 100 mg/L β‑CY within 7 d. Strain GW-01 transiently accumulated 3-phenoxybenzoic acid (3-PBA), phenol, and benzoic acid during β-CY degradation. Genomic, transcriptomic, and proteomic analyses of GW-01 during degradation of β-CY and its metabolites provided evidence that an α/β- hydrolase and a cytochrome aa3 quinol oxidase were responsible for the degradation of β-CY and 3-PBA, respectively. Chlorohydrolase was implicated in the degradation of phenol to catechol. Transcriptional and proteomic evidence was also found for upregulation of the benzoic acid degradation pathway and meta-pathway (catechol-2,3-dioxygenase), respectively. Based on these results a pathway for β-CY degradation is propose that provides greater insight into the mechanism of pyrethroid degradation by microorganisms.