Biodegradation of dimethachlon by Arthrobacter sp. K5: Mechanistic insights and ecological implications

Abstract

Dimethachlon, an agricultural fungicide, poses a potential risk to both the ecosystem and human health. Microbial degradation provides a safe, efficient, and environmentally friendly method for eliminating pesticide residues from the environment. In this study, a dimethachlon-degrading bacterium, Arthrobacter sp. K5, was isolated and characterized by the enrichment technique. Strain K5 was observed to initially convert dimethachlon into 4-(3,5-dichloroanilino)-4-oxobutanoic acid, which was subsequently transformed into 3,5-dichloroaniline and succinic acid. Strain K5 effectively utilized dimethachlon as the sole carbon source, converting 100 mg L−1 dimethachlon to 3,5-dichloroaniline within 36 h at 30°C. The optimum degradation conditions were pH 7.0, a temperature of 30°C, and a NaCl concentration range of 0–0.1 % (w/v). In addition, 1 mM Cd2+, Cu2+, and Zn2+ could considerably decrease the dimethachlon degradation activity. Enzyme activity analysis revealed that strain K5 contains intracellular enzymes that can metabolize dimethachlon into 3,5-dichloroaniline. The strain K5 genome was sequenced, and four putative dimethachlon-degrading enzymes were hypothesized in strain K5. In addition, the genus Arthrobacter is extensively dispersed in metagenomes from various soil environments. This study enhances our understanding of the role of the genus Arthrobacter in dimethachlon degradation.