ELECTROCHEMICAL BIOASSAY SYSTEM - REDOX RESPONSES OF ESCHERICHIA-COLICULTURES TO ENVIRONMENTAL STRESSES

Redox responses of Escherichia coli based on the anaerobic metabolism of glucose to hydrogen are characteristic of the culture. Four unique E. coli strains and one resistant strain were monitored in a multichan nel electrochemical analyzer. The redox measurements and absorbance as well as their kinetics, observed during culture growth, were compared to differentiate strains and to correlate with phenotypes. Mixed cult ures of two strains to simulate the emergence of a resistant populatio n yielded two peak potentials. On increasing or decreasing the initial cell concentration of one strain or the other, the respective potenti al peak was moved forward or backward in the time-scale, thereby allow ing peak identification. The electrochemical bioassay system, calibrat ed by known cultures, was used to evaluate various environmental stres s factors: culture media without nutrients or substrates, extended cul turing under impoverished conditions, freezing, cooling, or heating cu ltures to lethal temperatures for different periods of time, and expos ing cultures to increasing doses of a phenolic toxicant. This system a ppears to be responsive to the stress factors in a quantitative and re producible manner, and hence may find use in environmental risk assess ments.