Nitrosomonas europaea ATCC25978 is the right ammonia-oxidizing bacterium for screening nitrification inhibitors

Abstract

To determine whether Nitrosomonas enropaea is adequate to assay nitrification inhibitors as representative of ammonia-oxidizing bacteria or not, the inhibitory activity exhibited by known nitrification inhibitors in soil and the susceptibility of recently isolated ammonia-oxidizing bacteria to the inhibitors in cell suspension were compared. Nitrapyrin, MAST and Br-MAST completely inhibited nitrification in soil at 15 ppm for 15 days, whereas dicyanodiamide and thiourea were weak inhibitors. In order of effectiveness, the inhibitiors ranked as follows; Br-MAST > MAST > nitrapyrin ≫ dicyanodiamide ≥ thiourea. Ammonia-oxidation by ammonia-oxidizing bacteria in cell suspension was strongly inhibited by nitrapyrin, MAST and Br-MAST, whereas dicyanodiamide and thiourea were weak inhibitors. N. europaea is adequate to assay nitrification inhibitors as representative of ammonia-oxidizing bacteria.