Effect of acetylene on autotrophic and heterotrophic nitrification

Abstract

Acetylene (C 2 H 2 ) strongly inhibited (K i 0.25 μM or 0.66 Pa) the oxidation of ammonia (NH 4 + ) to nitrite (NO 2 − ) by Nitrosomonas europaea but did not affect the oxidation of hydroxylamine (NH 2 OH) to NO 2 − by this organism. We suggest that the C 2 H 2 -sensitive step is associated with the ammonia oxygenase. Oxidation of NH 4 + 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 NO 2 − to nitrate (NO 3 − ) by Nitrobacter winogradskyi and of NH 4 + to NH 2 OH and NO 3 − by the heterotrophic nitrifier, Arthrobacter sp., was not affected by 3.83 mM (10 kPa) C 2 H 2 .