Abstract:Nitrous oxide (N2O) is a powerful greenhouse gas which can destroy the ozone layer. Nitrous oxide reductase coded by nosZ gene in microorganisms, can reduce N2O to harmless N2, thus the study on nosZ gene in the environments becomes a research hotspot. A recent study of genome sequence comparative analysis revealed that a new class of nosZ gene (atypical nosZ II gene) is present in diverse nitrogen metabolism microbes. This type of nosZ gene encodes a functional nitrous oxide reductase and is found in variety of natural environments. However, the research on microbes containing atypical nosZ II genes is still incomplete, and the environmental conditions in which these microorganisms act and characteristics of N2O reduction process is still unknown. This paper reviews the differences between atypical nosZ II and typical nosZ I, and their distribution in environment. We also propose the direction of future research on the nosZ II gene.