N20 Accumulation and Inhibition of N20 Reduction by DenitrifyingPseudomonassp. 220A in the Presence of Oxygen

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Abstract
Denitrifying bacteria, strain 220A and G59, belonging to the genus Pseudomonas, were isolated from soils percolated anaerobically with nitrate sewage. In denitrifying cultivation in the presence of 0.05 atm oxygen, strain 220A accumulated N20, whereas strain G59 did not. Both strains produced dinitrogen alone in the absence of added oxygen. In resting cell suspension experiments, 0.1 —0.2 atm oxygen inhibited the reduction of N20 to N2 in strain 220A but not in strain G59. Production of N20 from N02 in the presence of 0.1 atm C2H2 was not influenced by 0.1 — 0.2 atm oxygen in either strain. Production of N2 from N02 ˜ in the absence of C2H2 by strain G59 was not inhibited by the amounts of added oxygen. From these results, accumulation of N20 in denitrifying cultivation of strain 220A in the presence of oxygen could be due to the inhibition of N20 reduction prior to any depression in N02 ˜ reduction to N20 by oxygen.