Stress protein synthesis, a potential toxicity marker in Escherichia coli

Various chemicals were tested in Escherichia coli for the ability to modify the cellular growth rate and to induce the synthesis of heat shock and stress proteins. The toxicity of chemicals as observed by modification of the growth rate depended on concentration and duration of treatment, except for thiram. In this last case, no modification was observed up to a concentration of 10 micrograms.ml-1. In contrast, all toxicants tested enhanced the synthesis of heat shock and stress proteins. The stress response was similar but not identical. Heat shock proteins and stress proteins appear to be a more sensitive toxicity marker than growth inhibition. Suggestions for the use of stress proteins as a practical bioassay are made.