Isolation, characterization and fingerprinting of some chlorpyrifos- degrading bacterial strains isolated from Egyptian pesticides-polluted soils

Abstract

Five bacterial isolates (B-CP5- B-CP6 - B-CP7- B-CP8- B-CP9) were isolated from pesticides-contaminated soil in Egypt. The capability of these isolates to degrade chlorpyrifos was investigated using enrichment mineral salt (MS) medium containing chlorpyrifos. Two different PCR-based techniques, RAPD-PCR and PCR-RFLP for amplified16S rRNA fragment were used to conduct genetic fingerprinting and obtain specific molecular markers for the studied isolates. The isolates exhibited substantial growth in mineral salt medium supplemented with 100-300 mg/L chlorpyrifos as a sole source of carbon and energy. Based on their morphological, cultural and biochemical characters, the isolates have been identified as Pseudomonas stuzeri, Enterobacter aerogenes, Pseudomonas pseudoalcaligenes, Pseudomonas maltophila and Pseudomonas vesicularis respectively. Pseudomonas stuzeri was the most potent degrader strain. Five specific markers for this strain were determined. The highest genetic similarity was observed between CP8 and CP7 (66%), while the lowest genetic similarity was detected between CP8 and CP6 (37%). All isolates had the same pattern after digestion of 16S rRNA amplified fragment with two restriction enzymes (EcoRI and AluI) except Enterobacter aerogenes, which generate two monomorphic bands at 420 and 130 bp, respectively. In conclusion, the strain Pseudomonas stuzeri could be used to clean up the areas contaminated with Chlorpyrifos. Obtained molecular markers might be used for identifying and tracking the most potent bacterial isolate. The used PCR techniques represent a powerful tool and could be used for rapid typing of this strain.