Effect of Commercial Grade Methyl Parathion on the Survival of Pseudomonas at Varying Temperature and pH

Abstract

The wide-spread use of methyl parathion as an agricultural insecticide has been causing an increased level of contamination in soil, vegetation and groundwater reservoirs and as well as adverse effects on human, flora, fauna and ecosystems. Therefore, eco-friendly and cost-effective bioremediation system are needed to remove these pollutants from the contaminated sites and mitigate its hazardous. For this purpose, a lab scale study was conducted to investigate the effect of high concentrations of commercial grade methyl parathion (50 EC) on growth of indigenous soil Pseudomonas IES-Ps-1 under different environmental conditions such as pH and temperature. To determine the tolerance limit, Pseudomonas IES-Ps-1 was grown in nutrient broth supplemented with methyl parathion (0, 200, 400, 600, 800, 1000 and 1200 mg/l). The detailed pH (6, 7, 9) and temperature (25, 30 and 35 oC) studies were conducted using higher methyl parathion (400 and 800 mg/l). No growth was observed at 1000 and 1200 mg/l of pesticide after 96 hrs of incubation compared to other concentrations of 200, 400, 600 and 800 mg/l. The maximum growth for both 400 and 800 mg/l of pesticide was observed at pH 7 and 30 °C. The maximum removal of total organic carbon and chemical oxygen demand for 400 mg/lof pesticide were found 50 and 52 % while those for 800 mg/l were 46 and 49 % respectively. Hence, this study concluded that indigenous soil bacterium Pseudomonas IES-Ps-1 could serve as an efficient candidate at 30 °C and pH 7 in development of a bioremediation system for the removal of toxic effects of methyl parathion like pesticides from contaminated sites.