Isolation and Characterisation of Paraquat Degrading Bacteria from Agricultural Soil in Rigachikun Area of Kaduna Metropolis, Nigeria

Abstract

Paraquat is a compound that, in spite of its benefits, may produce a wide range of toxic side effects which pose a potential threat to the environment. This study was conducted to isolate and identify paraquat degrading bacteria from herbicide contaminated soil in Kaduna. The bacteria were isolated, identified and characterized using phenotypic characterization and Agarose gel electrophoresis. The agarose gel electrophoresis confirmed the presence of Bacillus subtilis, Escherichia coli and Staphylococcus aureus in the soil obtained from the sample site. A concentration effect of 0.05%, 0.10%, 0.15%, 0.20% was observed and the initial and final cell mass was calculated. In microbial tolerance, it shows that 0.20% of paraquat in both Bacillus subtillis and Staphylococcus aureus, 0.10% of paraquat in Escherichia coli have the highest cell mass while 0.15%, 0.20%, 0.10% have the lowest cell mass respectively. Highest cell mass for each species shows the higher tolerance to paraquat, thus selected for biodegradation test. The spectrophotometric absorbance at 600nm wavelength was measured. Bacillus subtilis and Escherichia coli had an increase in absorbance for the first 48hours and later start decreasing while staphylococcus aureus had an increase in absorbance for the first 72hours then later started decreasing. Bacillus subtilis had the highest paraquat degrading capabilities, followed by Escherichia coli and Staphylococcus aureus. However, the optimal conditions for paraquat degradation have to be further studied to maximize the ability of the isolates.