An electron spin resonance study of oxyradical generation in superoxide dismutase- and catalase-deficient mutants of Escherichia coli K-12

The response of superoxide dismuase- and catalase-deficient strains of Escherichia coli to redox active compounds was examined by electron spin resonance. Levels of radicals formed in response to pyocyanine in situ were extremely low and were found to be predominantly extracellular, even in a strain completely deficient in both superoxide dismutase and catalase. In cell-free extracts of superoxide dismutase-minus strains incubated with NADPH and pyocyanine, the primary accumulating radical was the superoxide anion (O 2 −), although low levels of the hydroxyl radical (.OH) were also detected. In contrast, extracts from strains lacking catalase were found to accumulate higher levels of hydroxyl radicals.