Diversity of organophosphorus pesticide-degrading bacteria in a polluted soil and conservation of their organophosphorus hydrolase genes

Seven methyl parathion-degrading bacteria were isolated from a long-term methyl parathion contaminated soil and were found to belong to the genera Pseudaminobacter, Achromobacter, Brucella, and Ochrobactrum. Southern blot analysis using an mpd gene probe revealed that their hydrolase genes were similar to the mpd gene from Plesiomonas sp. strain M6 and were all located on the chromosome. Gene libraries were constructed from genomic DNA of each of the 7 organophosphorus pesticide-degrading bacteria, and their mpd genes were cloned and sequenced. Sequence analysis revealed that their hydrolase genes were conserved, and that the G+C content of the mpd genes were distinctly different from that of the chromosome-located 16S rRNA gene, suggesting that the mpd gene could be transferred and expressed among a variety of bacterial hosts.