Efficient biodegradation of multiple pyrethroid pesticides by Rhodococcus pyridinivorans strain Y6 and its degradation mechanism

Pyrethroids are one of the most widely used insecticides, which have adverse biological effects and poses a serious threat to ecological environments and human health. In this study, a novel pyrethroid-degrading strain Rhodococcus pyridinivorans Y6 was isolated from activated sludge contaminated by multiple pesticides. Within 36 h, the Y6 strain was able to completely metabolize multiple pyrethroid pesticides including prallethrin, allethrin, D-cyphenothrin, fenvalerate, and beta-cypermethrin (50 mg.L-1). The results of the soil remediation indicated that the Y6 strain could effectively remove prallethrin from soil and slurry with indigenous microbes. Moreover, 16S high-throughput sequencing of the soil demonstrated that the strain Y6 had no adverse effects on the soil community structure and diversity of indigenous microbes after it entered the soil. A p-nitrophenyl esterase gene (pnbA1564) containing conserved pentapeptide motif Gly190-X-Ser192-X-Gly194 was cloned from the Y6 genome, in which Ser192 was the active center of the catalytic triad of Ser192-His416-Asp314. RT-PCR and enzyme activity analysis showed that PnbA1564 was involved in the hydrolysis of prallethrin. GC-MS results further confirmed that prallethrin could be hydrolyzed via ester bond by PnbA1564. Taken together, these original findings provide a comprehensive assessment of R. pyridinivorans strain Y6 and contribute to a better understanding of the molecular mechanism responsible for the pyrethroid biodegradation.