The toxicity of copper to the marine bacterium Vibrio alginolyticus

Abstract

The toxicity of copper to the marine bacterium Vibrio alginolyticus was examined. Experiments were conducted with both aerobic and anaerobic cultures. Calorimetric and radiochemical techniques were used to examine the effect of copper on heat production, respiration, and carbon assimilation by the cultures. Plate counts were used to determine the number of viable cells present. Copper was more toxic to the bacterium in anaerobic culture (mean toxic concentration (TC50) = 2.1 μM)) than in aerobic culture (TC50 = 6.4 μM). Both cytotoxic and cytostatic effects were observed. The cytotoxic effect was not significantly different under aerobic and anaerobic conditions. The cytostatic effect, observed only in anaerobic culture, resulted in a decrease in the rate of metabolism of the surviving cells. The magnitude of the cytostatic and cytotoxic effects were dependent on the copper concentration, exhibiting saturation at higher concentrations. Organic chelators EDTA and nitrilotriacetic acid protected the anaerobic cultures from the copper, indicating that Cu–organic complexes are not toxic to the organism.