Minute-Speed Biodegradation of Organophosphorus Insecticides by X1.

Organophosphorus insecticides (OPs) have been widely used to control agricultural pests, which has raised concerns about OP residues in crops and the environment. In this study, we investigated the degradation kinetics and pathways of 8 OPs by X1 and identified the enzyme via gene cloning and in vitro assays. The degradation half-life of methyl parathion, triazophos, and phoxim was only 5, 9, and 43 min, respectively. It was 46 fold faster than that of triazophos by sp. TAP-1, a well-studied triazophos-degrader. Strain X1 completely degraded not only chlorpyrifos, methyl parathion, parathion, fenitrothion, triazophos, and phoxim at 50 mg/L within 48 h but also the phenolic metabolites. This was the fastest degradation of OPs by bacterial whole cells reported thus far. The OPs were first hydrolyzed by an OP hydrolase encoded by the gene in strain X1, followed by further degradation of the metabolites. The crude enzyme maintained a full activity.