Isolation and characterization of chlorpyriphos degrading bacteria

Twenty six bacterial isolates were obtained from chlorpyriphos contaminated soil samples by enrichment culture technique. Out of these, four isolates showed growth up to 30,000 ppm and four up to 40,000 ppm chlorpyriphos amended in Mineral salt medium (MSM) containing glucose (0.2%). Out of these eight isolates, four produced yellow coloured colonies on MSM agar plates containing chlorpyriphos (50 ppm) and bromo thymol blue (BTB) indicator and also showed the reduction of 2,3,5-triphenyltetrazolium chloride (TTC) in MSM that confirmed their chlorpyriphos degrading capability. These four isolates were tested for different carbon and nitrogen source utilization pattern on MSM agar plates (containing 100 ppm chlorpyriphos). With all the isolates, good growth was observed in presence of five carbon and five nitrogen sources. Therefore, these carbon and nitrogen sources were usedfor chlorpyriphos utilization inliquid medium. Bacterial countand protein content was found to be more in the medium amended with 100 ppm chlorpyriphos containing glucose as carbon source and ammonium chloride as nitrogen source as compared to medium containing other carbon and nitrogen sources with all the four isolates at 7 days of growth. Maximum utilization of chlorpyriphos was observed with the isolate SB1(80.1%) followed by HIC2 (76.2%), SGB2 (65.2%) and HIIGA2 (58.1%) in liquid medium. Two isolates(SB1 and HIC2) which showed more utilization of chlorpyriphos in liquid medium as compared to others, were characterized using morphological, biochemical and physiological tests. Isolate SB1 was identified as Pseudomonas and HIC2 as Xanthomonas.