Two enzyme assays, namely beta-galactosidase in Escherichia coli (E.C.3.2.1.23) and alpha-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 alpha-amylase biosynthesis in the Gram-positive bacteria was more sensitive to heavy metals, particularly to mercury as low as 0.1 ppm, compared to beta-galactosidase in the Gram-negative bacteria. The results of organic pesticide treatment were more clear-cm 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 beta-galactosidase system up to as high as 100 ppm. The effect of organic insecticide endosulfan on alpha-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. (C) 2003 Elsevier Science Inc. All rights reserved.