ISOLATION AND IDENTIFICATION OF CHLORPYRIFOS DEGRADING BACTERIA FROM AGRICULTURAL SOIL.

Abstract

The extensive use of pesticides in agricultural fields for pest control pose a serious problem in contaminating soil and water ecosystems. Chlorpyrifos is the major broad spectrum organophosphorus insecticide used in paddy fields against sucking, chewing, boring insects. Due to its toxicity and persistence in the environment, there is an immediate need to eliminate them from contaminated sites by biodegradation. Two pesticide degrading bacteria were screened and isolated from chlorpyrifos contaminated soil by enrichment culture technique and were identified as Kocuria kristinae and Staphylococcus aureus. The growth response and degradation of chlorpyrifos by the isolates in MSM broth supplemented with 0.5% chlorpyrifos was monitored every 48-72 hrs in spectrophotometer at 600nm. Kocuria sp showed maximum growth in 7 days than Staphylococcus aureus. The degradation efficiency of the strains were determined and estimated by the removal percentage of chlorpyrifos from the liquid culture. Both the isolate showed the degrading capability of chlorpyrifos in MSM. The isolate, S. aureus was more potent in degrading the 80% of the total compound from the media in 2 weeks of incubation than K. kristinae which shows 35 % of degradation. These results were further confirmed by GCMS, in which S. aureus has degraded 82.06% and K. kristinae has degraded 30.78% of chlorpyrifos in the medium. This study indicates that the isolate, Staphylococcus aureus is more potent in degrading chlorpyrifos in liquid culture and can also be used in bioremediation of chlorpyrifos contaminated soils.