Paraquat is not bacteriostatic under anaerobic conditions

To test the hypothesis that bacteriostasis by Paraquat (N, N′-dimethyl bipyridylium chloride) is dependent on its effect on electron transport, we exposed log-phase cultures of obligate and facultative anaerobes to 10^?3 molar Paraquat. In the absence of the ultimate electron acceptor, oxygen, millimolar Paraquat failed to inhibit bacterial growth, while aerobic growth was inhibited. Biological injury by Paraquat requires the presence of oxygen in green plants and bacteria. These findings lend weight to reports that severity of Paraquat-induced lung injury in mammals is related to oxygen tension.