Molecular mechanism of the antimicrobial action of pyocyanin

Abstract

The mechanism by which pyocyanin inhibits bacterial growth was investigated. Several organisms possessing varying levels of superoxide dismutase were analyzed for their sensitivity to pyocyanin to test the possibility that reduced pyocyanin univalently reduces oxygen to superoxide, thus causing cell death. No correlation was found between the amount of superoxide dismutase possessed by an organism and resistance to pyocyanin. In addition, it was demonstrated that organisms growing anaerobically with nitrate as a terminal electron acceptor were as sensitive as, or more sensitive to the action of pyocyanin than organisms grown under aerobic conditions. We thus rule out the possibility that excess superoxide generation is the primary mechanism by which pyocyanin exerts its antibiotic effect. Oxygen electrode and radioisotope studies demonstrated that pyocyanin does inhibit bacterial respiration and active transport of solutes. Thus, it was concluded that the mechanism of action is the result of pyocyanin interacting with the cell membrane respiratory chain in such a way to render the cell unable to perform energy-requiring, membrane-bound metabolic processes such as active transport.