An effective chlorpyrifos-degrading bacterium (named strain YC-1) was isolated from the sludge of the wastewater treating system of an organophosphorus pesticides manufacturer. Based on the results of phenotypic features, phylogenetic similarity of 16S rRNA gene sequences and BIOLOG test, strain YC-1 was identified as the genus Stenotrophomonas. The isolate utilized chlorpyrifos as the sole source of carbon and phosphorus for its growth and hydrolyzed chlorpyrifos to 3,5,6-trichloro-2-pyridinol. Parathion, methyl parathion, and fenitrothion also could be degraded by strain YC-1 when provided as the sole source of carbon and phosphorus. The gene encoding the organophosphorus hydrolase was cloned using a PCR cloning strategy based on the known methyl parathion degrading (mpd) gene of Plesiomonas sp. M6. Sequence blast result indicated this gene has 99% similar to mpd. The inoculation of strain YC-1 (10(6) cells g(-1)) to soil treated with 100 mg kg(-1) chlorpyrifos resulted in a higher degradation rate than in noninoculated soils. Theses results highlight the potential of this bacterium to be used in the cleanup of contaminated pesticide waste in the environment.

Based on the results of phenotypic features, phylogenetic similarity of 16S rRNA gene sequences and BIOLOG test, a soil bacterium was identified as Bacillus sp. DM-1. Using either growing cells or a cell-free extract, it transformed parathion and methyl parathion to amino derivatives by reducing the nitro group. Pesticide transformation by a cell-free extract was specifically inhibited by three nitroreductase inhibitors, indicating the presence of nitroreductase activity. The nitroreductase activity was NAD(P)H-dependent, O(2)-insensitive, and exhibited the substrate specificity for parathion and methyl parathion. Reductive transformation significantly decreased the toxicity of pesticides.