Commentary on ‘Inhibition by acetylene of ammonia oxidation in Nitrosomonas europaea’

Abstract The discovery that acetylene inhibited ammonia oxidation by Nitrosomonas europeae came about by studying linkages of microbial Nitrogen cycling processes in laboratory soil columns. Continuous addition of ammonium chloride (25 μg N/ml) to the soil columns resulted in steady state nitrification of all of the ammonia to nitrate. Acetylene (10.1 kPa) was introduced to detect nitrous oxide, a product of denitrification of nitrate, however, nitrification was inhibited and washout and disappearance of nitrate in the column effluent was detected. Concomitantly, ammonium levels in the effluent rose. Nitrification of nitrite was not affected by acetylene. Summary Acetylene inhibited the metalloenzyme, ammonia monooxygenase in the obligate chemoautotrophic nitrifier, Nitrosomonas europeae.