Mechanism of the antibiotic action pyocyanine

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Abstract
Exposure of Escherichia coli growing in a rich medium to pyocyanine resulted in increased intracellular levels of superoxide dismutase and of catalase. When these adaptive enzyme syntheses were prevented by nutritional paucity, the toxic action of pyocyanine was augmented. The antibiotic action of pyocyanine was dependent upon O2 and was diminished by superoxide dismutase and by catalase, added to the suspending medium. Pyocyanine slightly augmented the respiration of E. coli suspended in a rich medium, but greatly increased the cyanide-resistant respiration. Pyocyanine was able to cause the oxidation of NADH, with O2- production, in the absence of enzymatic catalysis. Apparently, pyocyanine diverts electron flow and thus increases the production of O2- and H2O2 and the antibiotic action of this pigment is largely a reflection of the toxicity of these products of O2 reduction.