Effect of acetylene on autotrophic and heterotrophic nitrification

Abstract

Acetylene (C2H2) strongly inhibited (Ki 0.25 μM or 0.66 Pa) the oxidation of ammonia (NH4+) to nitrite (NO2−) by Nitrosomonas europaea but did not affect the oxidation of hydroxylamine (NH2OH) to NO2− by this organism. We suggest that the C2H2-sensitive step is associated with the ammonia oxygenase. Oxidation of NH4+ was inhibited only approximately 50% by 0.4 mM (10 kPa) ethylene and by 2.1 mM (10 kPa) nitrous oxide and was unaffected by 0.1 mM (10 kPa) methane. The oxidation of NO2− to nitrate (NO3−) by Nitrobacter winogradskyi and of NH4+ to NH2OH and NO3− by the heterotrophic nitrifier, Arthrobacter sp., was not affected by 3.83 mM (10 kPa) C2H2.