Isolation, characterization and identification of pesticide degrading bacteria from contaminated soil for...

In this study, malathion and chlorpyrifos degrading bacteria were isolated from agricultural soil samples taken from the Himachal region in India. A total of 52 organisms were isolated which were further screened for their efficiency for chlorpyrifos and malathion degradation. Screening was done by checking the growth on Nutrient Agar, Mineral Salt Medium and MacConkey agar plates containing chlorpyrifos and malathion; 37 isolates showed growth in these. Biomass assay and minimum inhibitory concentration (MIC) determination were carried out for the selection of most efficient bacterial isolates. Out of the seven isolates which showed good biomass assay and MIC, only three isolates (PDM-2, PDM-15 and PDM-20) were selected for further studies. These were characterized by various biochemical tests, Gram staining, indole test, methyl red test, Voges-Proskauer test, citrate utilization test and carbohydrate fermentation test. Out of three isolates, PDM-15 showed good resistance against the antibiotics such as erythromycin, chloramphenicol, ampicillin and penicillin and identified as Kocuria assamensis. Degradation of 71.3% of chlorpyrifos and 85% of malathion was observed by the gas chromatography. Therefore, the Kocuria assamensis can be used in the bioremediation of pesticide-contaminated soil.