The mode of action of nanaomycins D and A on a gram-negative marine bacterium Vibrio alginolyticus.

Nanaomycin (NNM) D had a higher growth inhibitory activity than NNM-A against a Gram-negative marine bacterium, Vibrio alginolyticus. These quinone antibiotics were reduced by the respiratory chain-linked flavin dehydrogenase of the organism and the reduced forms of NNMs were quickly autoxidized by molecular oxygen to produce superoxide radicals (O2-). NNM-D was more effective than NNM-A both in the induction of KCN-insensitive oxygen consumption with the intact cells and in the production of O2- by the redox cycling. The growth inhibitory activities of NNM-D and A were partly reduced by raising the superoxide dismutase level of the cells. Thus, the ability to produce O2- at the cell membrane was correlated to the antibacterial activities of NNM-D and A.