Microbial reduction of nitrous oxide (N 2 O) in soil plays an important role in mitigating N 2 O emission, and it is the only known biological process for N 2 O sink. However, it is not clear about the mechnisms of differential N 2 O reducing function of N 2 O reducers. In this study, the N 2 O reducing activities and nosZ gene transcript abundance of two N 2 O reducers named P. veronii DM15 (DM15) and P. frederiksbergensis DM22 (DM22) were determined under varied temperature and oxygen

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... ation conditions, as well as the whole genomes were sequenced by Illumina sequencing. The results showed that DM15 generally exhibited significantly higher abilities in N 2 O reduction than DM22 in regardless of low or high temperature and aerobic or anaerobic conditions. Coincidently, DM15 expressed significantly more nosZ gene transcripts under above environments. Genomic analysis further revealed that DM15 possessed about 30% more transcription related genes than DM22 and the nos cluster of the former contained a transcriptional regulator gene of dnr which not found in that of the later. Additionally, the nos genes of DM15 possessed obviously higher expression potentials (CAI value). In conclusion, the transcriptional regulation of nos gene region would be a crucial factor in determining the differences of N 2 O reducing abilities of the two N 2 O reducing isolates.