Aerobic and denitrifying methanotrophs: Dual wheels driving soil methane emission reduction

The greenhouse gas methane in soils has been considered to be consumed mainly by aerobic methane-oxidizing bac-teria for a long time. In the last decades, the discovery of anaerobic methanotrophs greatly complemented the methane cycle, but their contribution rates and ecological significance in soils remain undescribed. In this work, the soil samples from forest, grassland and cropland in four different climatic regions were collected to investigate these conventional and novel methanotrophs. A dual-core microbial methane sink, responsible for over 80 % of soil methane emission re-duction, was unveiled. The aerobic core was performed by aerobic methanotrophic bacteria in topsoil, who played im-portant roles in stabilizing bacterial communities. The anaerobic core was denitrifying methanotrophs in anoxic soils, including denitrifying methanotrophic bacteria from NC10 phylum and denitrifying methanotrophic archaea from ANME-2d clade. They were ubiquitous in terrestrial soils and potentially led to around 50 % of the total methane re-moval. Human activities such as livestock farming and rice cultivation further promoted the contribution rates of these denitrifying methanotrophs. This work elucidated the emission reduction contribution of different methanotrophs in the continental setting, which would help to reduce uncertainties in the estimations of the soil methane emission.

Automated summary

For a long time, it was believed that aerobic methane-oxidizing bacteria were the main consumers of methane in soils. However, the discovery of anaerobic methanotrophs in recent decades has greatly improved our understanding of the methane cycle. This study collected soil samples from different climatic regions to investigate both conventional and novel methanotrophs and found that a dual-core microbial methane sink, consisting of aerobic and anaerobic methanotrophs, was responsible for over 80% of soil methane emission reduction. These findings contribute to reducing uncertainties in the estimation of soil methane emissions.