The primary objective of this study was to assess whether reactive oxygen species produced during the metabolism of mitomycin C are responsible for, or contribute to, the induction of the cytotoxic response. 2. Escherichia coli wild-type and superoxide dismutase mutants were grown either anoxically or euoxically, in K medium or minimal glucose medium, and treated with mitomycin C in K medium or M9 salts. The cytotoxic response did not vary significantly between the wild-type and the SOD mutants. 3. The toxicity of mitomycin C was not affected by the hydroxyl radical scavengers, dimethyl sulphoxide or ethanol, whereas protection was afforded by thiourea. 4. It is concluded that oxygen radical species do not play a significant role in mediating mitomycin C inactivation of normally growing bacteria.
