[Consumption Capacity of NO in Paddy Soil and the Response Mechanism of -containing Communities].

The long-term flooding anaerobic environment in paddy soils is conducive to denitrification, which is one of the most important reasons for NO emissions. NO can be transformed to nitrogen gas (N) by bacteria and archaea containing nitrous oxide reductase (NOR) encoded by the gene, which is the only known biological pathway of NO consumption in soil. is known to be typical in denitrifying bacteria, which is one of the clades of the gene and is mainly possessed a Tat signal peptide motif. Although many researchers have studied NO emission characteristics of paddy soil, the capacity of NO consumption and the response mechanism of related functional microorganisms in paddy fields is not yet clear. To verify the effect of exogenous NO on NO consumption and gene, a pot trial experiment was performed under anaerobic conditions. We collected intact soil cores from flooding paddy fields at a 0-5 cm depth, and exogenous NO gas was input through the bottom of flooding paddy soil cores. Meanwhile, a control treatment (CK) with no additional NO gas was also performed. The dynamic characteristics of the added exogenous NO concentration through the intact soil cores, the content of inorganic nitrogen, and DOC were systematically monitored. In addition, the change in the population diversity and community composition were investigated by high-throughput sequencing approaches, with the purpose of revealing the NO uptake ability of flooded paddy soil and the response mechanism of the population. The results showed that 97.39% of exogenous NO diffused into the soil cores, and only 0.72%-7.75% of exogenous NO escaped from the soil surface. The NO released in the headspace of soil cores could continue being absorbed and consumed by the flooding soil column. In addition, 67.10% of the NO escaped to the headspace was consumed in exogenous NO treatment after 192 h of incubation, which was higher than that in CK treatment, and the NO consumption rate increased by 144.2% than that in CK treatment. Meanwhile, the consumption of NH-N, NO-N, and DOC consumed during exogenous NO addition treatment was 19.65%, 16.29%, and 8.41% higher than that in CK treatment, respectively. However, the diversity of the gene community had no significant difference; the community composition of -containing bacteria changed significantly after 192 h when exogenous NO was input. The abundances of OTU5004, OTU5065, OTU960, and OTU1282 () significantly increased, which were the dominant bacterial strain of gene on the OTU level. Compared with the initial sample and CK, the abundance of the OTU5004 strain increased by 7.3% and 4.63%, and the abundance of the OTU5265 strain ( sp.) increased by 0.33% and 0.15%, respectively. The result indicated that the flooding paddy soil column at the soil layer of 0-5 cm has a strong NO absorption and consumption ability. In summary, compared with CK, the addition of exogenous NO significantly accelerated the NO consumption rate, improved the consumption potential of flooding paddy soil column, promoted carbon and nitrogen conversion, and changed community composition. These results would provide a new reference for reducing atmospheric NO emissions.