Study of soil microflora indicating pesticide contamination of Cauvery River belt in India

Abstract

The usage of microbial responses as an indicator of herbicide toxicity in soil residue is well known. The present study is aimed to analyze the heterotrophic and pesticide degrading bacteria in sediment samples of Cauvery River bed, where the farmers are using methyl parathions as a potent pesticide in paddy and vegetable fields. We report, higher incidence of methyl parathion degrading bacterial population in the river bed which can able to utilize the pesticide at a concentration of 5μl/ml. The heterotrophic and methyl parathion degrading bacterial counts in soil sediment samples was carried out on monthly basis from Oct. 2007 to Nov. 2008. The total heterotrophic bacterial count was in the range of 12-20 × 10 4 CFU / gm and the total pesticide degrading bacterial count was 50-90 × 10 3 CFU/gm. Among the pesticide degrading bacterial population, Bacillus sp. was found to be dominant followed by Pseudomonas sp., Micrococcus sp. and Yersinia sp. No marked fluctuation was noticed in total heterotrophic count and pesticide degrading bacterial count irrespective of seasonal variation. The pesticide degrading ability was studied in presence of various parameters. The optimum temperature for the methyl parathion degradation was 37°C, pH7 and there was no change due to the increase in glucose level. Cauvery is one of the main riparian water sources in South India supporting the agrarian activities and susceptible for pesticide contamination due to run off from the agri-lands during monsoon season. The study indicates the presence of pesticide contamination in the riparian water which is the source for drinking and agricultural activity. Hence there is a need for an alternate pest management in this area as environmental protection point of view.