Bertagnolli AD, Konstantinidis KT, Stewart FJ. Non-denitrifier nitrous oxide reductases dominate marine biomes. Environmental Microbiology Reports. In press.
Our study examined diverse ocean metagenomes to quantify the diversity and abundance of nosZ genes encoding nitrous oxide reductase. Nos is the key enzyme for microbial consumption of nitrous oxide (N2O), a potent greenhouse house. The potential for biological consumption of N2O varies based on the type of Nos enzyme. Typical Nos variants are, in general, associated with lower N2O affinity and organisms capable of complete denitrification (nitrate to N2), whereas atypical variants are associated with higher N2O affinity and organisms lacking complete denitrification potential. Our analysis shows that atypical nosZ genes are widely distributed across diverse marine water columns and microbial taxa, consistently more abundant than typical variants, and particularly enriched in oxygen minimum zones (OMZs), systems well known for rapid N2O cycling. These results suggest that marine environments, and OMZs in particular, select for high N2O -scavenging ability. This finding is relevant to understanding the potential for oceans to buffer increases in N2O production, for example those predicted to occur as OMZs expand due to climate change.