Thermochemical studies of the toxic action of heavy metal ions on<Emphasis Type="Italic">Escherichia coli</Emphasis> by microcalorimetry

By using an LKB2277, BioActivity Monitor (heat conduction microcalorimeter), stopped-flow method, the thermogenetic curves of Escherichia coli growth at 37°C inhibited by four kinds of heavy metal ions are determined, and parameters such as growth rate constants, inhibitory ratio, half-inhibitory concentration etc. were obtained. The experimental results show that heavy metal ions can inhibit Escherichia coli growth obviously, but low concentration of Cu²⁺ has a promoting action. The half inhibitory concentrations of Zn²⁺, Cd²⁺, Hg²⁺ and Cu²⁺ are 28.3, 10.9, 3.19 and 69.6 μg. mL⁻¹, respectively. Judged from the rate constant, the half-inhibitory concentration and the molecular mass, the inhibitory sequence is Hg²⁺>Cd²⁺>Zn²⁺>Cu²⁺. This microclorimetric bioassay for acute cellular toxicity is based on metabolic heat evolution from cultured cells. The assay is quantitative, inexpensive, and versatile; moreover, toxicological information can be obtained with cell from other species of interest. Li Xi: Born in 1968 Funded by the National Natural Science Foundation of China (29973030 and 30170010)