Physiological studies with the only comammox pure culture Nitrospira inopinata revealed that it tightly controls its aerobic nitric oxide (NO) production and releases much less nitrous oxide (N2O) than ammonia-oxidizing proteobacteria. Furthermore, we show in this publication that the NO scavenger PTIO inhibits comammox bacteria and should not longer be used as "specific" inhibitor of ammonia-oxidizing archaea (it is also cytotoxic to members of the genus Nitrospira at higher concentrations). Shifting nitrifying microbial communities in wastewater treatment plants or agricultural soils to higher comammox abundances might help reducing emissions of the strong greenhouse gas nitrous oxide from these systems. The study was conducted in the framework of the Comammox Research Platform by members of the nitrification research groups led by Holger Daims and Michael Wagner, and in collaboration with colleagues in Germany and Canada.
