Diversity of chlorpyrifos-degrading bacteria isolated from chlorpyrifos-contaminated samples

Chlorpyrifos as an agricultural insecticide has been widely used and caused great pollution. As the toxicity of chlorpyrifos in the environment, exploration of various chlorpyrifos-degrading bacteria to clean-up the pollutant is of immense importance. Seven chlorpyrifos-degrading bacteria, named Dsp-1 to Dsp-7, were isolated from organophosphate pesticide-contaminated soil and water using a culture method with chlorpyrifos as the sole carbon source. Comparative studies were performed to study their morphological, physiological and biochemical characteristics. Based on these analysis, strains Dsp-2, Dsp-4, Dsp-6 and Dsp-7 were identified as Sphingomonas sp., Stenotrophomonas sp., Bacillus sp. and Brevundimonas sp., respectively, while all other strains were members of Pseudomonas sp. ERIC (enterobacterial repetitive intergenic consensus)-PCR fingerprints were used to distinguish strains Dsp-1 and Dsp-3 which had only 1 bp difference in 16S rDNA sequences. Significant differences in the ability of the bacteria to degrade chlorpyrifos and other organophosphate pesticides were found. The organophosphate pesticide hydrolase gene mpd were cloned from strains Dsp-1 to Dsp-4 with the PCR technique. Differences in amino acid sequence of mpd gene from the four bacteria strains were compared. These results showed that there were diversities of chlorpyrifos-degrading strains in the contaminated environment, and the chlorpyrifos-degrading strains had the potential to clean up the organophosphate pesticide-contaminated environment. (C) 2008 Published by Elsevier Ltd.