Conventional methanotrophs are responsible for atmospheric methane oxidation in paddy soils

Abstract

Soils serve as the biological sink of the potent greenhouse gas methane with exceptionally low concentrations of ∼1.84 p.p.m.v. in the atmosphere. The as-yet-uncultivated methane-consuming bacteria have long been proposed to be responsible for this ‘high-affinity' methane oxidation (HAMO). Here we show an emerging HAMO activity arising from conventional methanotrophs in paddy soil. HAMO activity was quickly induced during the low-affinity oxidation of high-concentration methane. Activity was lost gradually over 2 weeks, but could be repeatedly regained by flush-feeding the soil with elevated methane. The induction of HAMO activity occurred only after the rapid growth of methanotrophic populations, and a metatranscriptome-wide association study suggests that the concurrent high- and low-affinity methane oxidation was catalysed by known methanotrophs rather than by the proposed novel atmospheric methane oxidizers. These results provide evidence of atmospheric methane uptake in periodically drained ecosystems that are typically considered to be a source of atmospheric methane.

Higher yields and lower methane emissions with new rice cultivars

“…Indeed, CH 4 oxidation in paddy soils only occurs at CH 4 concentrations ≥500 p.p.m.v. (Cai, Zheng, Bodelier, Conrad, & Jia, ), far higher than what was found in the fallow soil in experiment 3B. Thus, our results suggest that rice cultivars affect net CH 4 emissions by altering the availabilities of resources that affect microorganisms that both produce and consume CH 4 , and that the soil context determines the direction of the effect: High‐yielding rice cultivars promote CH 4 production and emissions by increasing C substrate availability for methanogens when soil C content is low, but facilitate CH 4 oxidation by increasing O 2 transport and promoting methanotrophic organisms when soil C availability is high.…”

Species interactions and distinct microbial communities in high Arctic permafrost affected cryosols are associated with the CH4 and CO2 gas fluxes

“…This has been attributed to an unculturable group of high affinity methanotrophs that can oxidize methane to methanol at atmospheric levels (~1.8 ppm CH 4 ) (Martineau et al, 2014;Christiansen et al, 2015;Lau et al, 2015). However, some studies suggest that conventional, low-affinity methanotrophs are able to perform atmospheric methane oxidation as well (Cai et al, 2016). However, the only methanotrophs at the IWP cryosol cite that we could detect were those closely related, based on their pmoA sequences, to uncultured methanotrophs belonging to the USCα cluster of suspected high-affinity methanotrophs (Pratscher et al, 2018).…”

Microbial energy and matter transformation in agricultural soils

“…This may be further complicated in that phenotypic activity can indeed be dependent on taxonomy. For example only specific methanotroph species, such as those within the Upland Soil Cluster-a group, appear to actively oxidise methane at atmospheric concentrations whereas other species, such as Methylosarcina spp., only actively oxidise atmospheric concentrations of methane after being induced with high concentrations of methane, for example in water-saturated rice paddy soils that favour methanogenesis (Baani and Liesack, 2008;Cai et al, 2016). Thus for certain ecosystem functions a combination of functional gene diversity, taxonomic diversity and knowledge of the conditions which induce protein expression between species may be necessary to elucidate a relationship between function and diversity.…”