Genomics and Ecology of Novel NO-Reducing Microorganisms.

Microorganisms with the capacity to reduce the greenhouse gas nitrous oxide (NO) to harmless dinitrogen gas are receiving increased attention due to increasing NO emissions (and our need to mitigate climate change) and to recent discoveries of novel NO-reducing bacteria and archaea. The diversity of denitrifying and nondenitrifying microorganisms with capacity for NO reduction was recently shown to be greater than previously expected. A formerly overlooked group (clade II) in the environment include a large fraction of nondenitrifying NO reducers, which could be NO sinks without major contribution to NO formation. We review the recent advances about fundamental understanding of the genomics, physiology, and ecology of NO reducers and the importance of these findings for curbing NO emissions.