Betaproteobacterial clade II nosZ activated under high N₂O concentrations in paddy soil microcosms.

This article focuses on identifying microbial clades responsible for nitrous oxide (N₂O) reduction in flooded paddy soils, which act as significant sinks for this potent greenhouse gas. Using soil microcosms amended with external N₂O and rice straw, metatranscriptomic analyses revealed that Betaproteobacteria, particularly members of the orders Rhodocyclales and Nitrosomonadales harboring clade II nosZ genes (encoding N₂O reductase), dominated the active N₂O-reducing community and were associated with rapid N₂O consumption. However, metagenomic data from diverse paddy soils showed that these Betaproteobacteria are not dominant in native soil microbiomes, suggesting selective activation under experimental conditions. The findings highlight Rhodocyclales clade II nosZ carriers as potential targets for biostimulation or bioaugmentation strategies aimed at mitigating N₂O emissions from agricultural soils.