Biodegradation of Carbofuran by Naturally Occurring Soil Borne Bacteria

Abstract

Biodegradation of carbofuran (Furadan) used as a pesticide, was investigated using microorganisms isolated from carbofuran treated rice field soil with a history of pesticide application. Samples of carbofuran treated soil were incubated in mineral salts medium supplemented with Standard carbofuran (99% purity) at 2 μg/ml,4 μg/ml, 8μg/ml and 16 μg/ml concentration for 7 days at 30°C and bacterial strain were isolated from the soil sample which were supplemented with standard carbofuran at 2 μg/ml and 4 μg/ml. No viable growths were found at 8μg/ml and 16μg/ml carbofuran concentrated MS media. The isolated bacteria were examined microscopically for their morphological and measured optical density (OD) to determine physiological characteristics at various temperature and pH. Morphological, physiological characteristics and biochemical properties indicated that the bacterium was gram negative, aerobic, lactose fermenting, catalase positive, oxidase negative, indole negative, methyl red negative, triple sugar iron test positive. The optimal culture condition of the bacterium for carbofuran degradation was pH 7.0 and temperature at 30°C. The antibiotic resistance pattern is generally used for strain identification in ecological studies. It is evident from the present investigation that the isolated bacteria were resistance to nalidixic acid(NA30) and cefuroxime sodium(CXM30) and have the ability to utilize different carbohydrates viz.glucose, lactose, sucrose, mannose, arabinose and cellulose. The MIC of gentamycine against the isolated bacteria was also determined and the concentration was 400μg/ml. Viable cell counts were also done and 459×107 CFU/ml. Carbofuran toxicity was also evaluated on Artemia salina and LC50 value was 9.103558μg/ml for the A. salina and the regression equation was Y = 3.942777 + 1.102179 X, while the 95% confidence limits were 3.810799 to 21.74736 μg/ml for 12h of exposure only . The antagonistic effect of the isolated bacteria was tested against some pure culture strain of bacteria and fungi. Unfortunately the bacteria did not show any antagonistic effect on plant pathogenic fungi and fortunately it exhibited no effect on Rhizobacteria. Thus, future application of the carbofuran degrading bacteria at field level would not be harmful against any plant growth promoting Rhizobium sp. Biodegrading ability of the isolated bacterium indicate a positive role of microorganism in pesticide contaminated sites bioremediation. So, the study recommends possible application of the isolate in the In vivo bioremediation of pesticide contaminated soils and assure pesticides hazards free better environment.