A comparative study of bioassays based on enzyme biosynthesis in Escherichia coli and Bacillus subtilis exposed to heavy metals and organic pesticides

Abstract

Two enzyme assays, namely β-galactosidase in Escherichia coli (E.C.3.2.1.23) and α-amylase in Bacillus subtilis (E.C.3.2.1.1), were compared following exposure to various concentrations of heavy metals and organic pesticides. It was shown that α-amylase biosynthesis in the Gram-positive bacteria was more sensitive to heavy metals, particularly to mercury as low as 0.1 ppm, compared to β-galactosidase in the Gram-negative bacteria. The results of organic pesticide treatment were more clear-cut, when comparing both assays. Alpha-amylase test system can detect the inhibition by the organometallic fungicides Maneb and Mancozeb at as low as 0.1 ppm, while no inhibition with β-galactosidase system up to as high as 100 ppm. The effect of organic insecticide endosulfan on α-amylase was also seen at very low concentrations (0.048 ppm). The electrophoretic analysis also revealed the inhibition of enzyme biosynthesis at the tested toxicant concentrations.