VPI4330-1 is an anaerobic organism which has no superoxide dismutase, catalase or peroxidase. It can be protected from the toxic effects of oxygen by catalase in the culture medium. In order to elucidate its mechanisms of oxygen tolerance, the effect of oxygen on the metabolic activity of the organism was studied.

In salt solution supplemented with glucose or pyruvate the organism had a more rapid metabolic rate under aerobic conditions than under anaerobic conditions. There were also significant differences in metabolic end-products obtained under aerobic and anaerobic conditions. The crude cell-free extract had NADH oxidase activity, which reduced oxygen to water, and NADPH oxidase activity, which reduced oxygen to superoxide radicals and hydrogen peroxide. The former specific activity was much higher than the latter.

The results indicate that the main product of intracellular oxygen reactions was water. Deleterious products such as superoxide radicals and hydrogen peroxide were only formed to a limited extent. NADH oxidase may fulfil an important protective role in this organism.


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