Genomics and Ecology of Novel N₂O-Reducing Microorganisms

Microorganisms with the capacity to reduce the greenhouse gas nitrous oxide (N₂O) to harmless dinitrogen gas are receiving increased attention due to increasing N₂O emissions (and our need to mitigate climate change) and to recent discoveries of novel N₂O-reducing bacteria and archaea. The diversity of denitrifying and nondenitrifying microorganisms with capacity for N₂O 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 N₂O reducers, which could be N₂O sinks without major contribution to N₂O formation. We review the recent advances about fundamental understanding of the genomics, physiology, and ecology of N₂O reducers and the importance of these findings for curbing N₂O emissions.