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Microbial nitric oxide dismutation reaction (NOD), involved in the biogeochemical nitrogen cycle on Earth, has been implemented to N removal in laboratory-scale wastewater treatment systems, but microorganisms from relatively a few lineages have been implicated to be associated with this biochemical process. Detection of abundant putative (or novel) nitric oxide dismutase-encoding gene PCR products could confer the diversity of nitric oxide dismutase in additional microbial groups other than the two known lineages, but the distribution pattern of nod gene is unclear in different environments including oil reservoirs. Here, we surveyed the distribution and diversity of nod genes by clone library sequencing together with the inference of 16S rRNA gene-based taxonomy by amplicon sequencing in diverse samples including wastewater treatment plants (WWTP), wetland, hydrocarbon-contaminated soil, and oil reservoirs. A total of 730 phylogenetically diverse nod -related sequences recovered from these samples were clustered into 42 operational taxonomic units (OTUs) showing a considerably high diversity of nod gene in these different ecosystems. The abundance of nod gene in five environmental samples were ∼1.80 × 107–2.62 × 108 copies g−1 soil (sludge) and ∼9.67 × 106 copies l−1 water. The dominant microorganisms were Bacteroidetes, Firmicutes , Actinobacteria , and Chloroflexi. Our results expanded significantly the diversity of microbial groups potentially involved in nitric oxide dismutation, suggesting the ubiquity of microbial members in the different ecosystems carrying out NO dismutation reaction. Further studies on the functional capacity of this new microbial group will advance a better understanding of the microbially-driven nitrogen cycling and provide thorough information on N-removal processes and potential applications.
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