Inhibition of -galactosidase and -glucosidase synthesis in petroleum refinery effluent bacteria by zinc and cadmium

摘要

Inhibition of α-glucosidase (EC 3.2.1.20) and β-galactosidase (EC 3.2.1.23) biosynthesis by zinc and cadmium inEscherichia coli,BacillusandPseudomonasspecies isolated from petroleum refinery wastewater was assessed.At sufficient concentrations, exposure of the cells to zinc and cadmium resulted in repression ofα-glucosidase and β-galactosidaseinduction. The extent of inhibition varied among the test bacteria, metal and enzyme.Bacilluswith IC50of 0.125± 0.004 and 0.120 ± 0.007mM is most sensitive to cadmium inhibition ofα-glucosidase and β-galactosidase respectively. Biosynthesis of β-galactosidase inBacillusspecies is most sensitive to toxicity of zinc.The patterns of these toxic effects can be mathematically described with logistic or sigmoid dose-response models. The coefficients of inhibitionKi correlated with the IC50andindicate that inhibition coefficient can be used in addition to the EC50values as a measure of toxicity.The information could have a bearing on the development of bacterial models for acute toxicity assays.