Anaerobic methane oxidation coupled with denitrification mitigates soil nitrous oxide emissions

Abstract

The impact of anaerobic oxidation of methane (AOM) coupled with denitrification on the emission of the denitrification intermediate N₂O remains poorly understood. Here, we investigated the influence of AOM coupled with nitrate and nitrite reduction on soil N₂O emissions and the associated microbial interactions. We show that AOM coupled with denitrification markedly reduces soil N₂O emissions, with the type I methanotroph Methylobacter species collaborating with the Methylophilaceae and Gemmatimonadaceae families to perform key roles. The suppression of N₂O emissions by AOM primarily stems from its role in supplying electrons and carbon sources, fueling complete denitrification by associated bacteria. In addition, we uncovered distinct microbial interaction strategies for AOM-coupled nitrate and nitrite reduction. While nitrite reduction necessitates both bacterial cooperation and extracellular electron transfer during its initial stages, nitrate reduction predominantly depends on methanotrophic bacteria alone at the outset. These findings advance our understanding of carbon-nitrogen cycle coupling and underscore AOM’s potential to simultaneously mitigate both CH₄ and N₂O emissions.