Methane oxidation in alpine meadow and wetland soils on the Qinghai-Tibet Plateau: Roles of USCγ and conventional methanotrophs

Methane is a potent greenhouse gas, and understanding its microbial uptake mechanisms in natural environments is crucial for mitigating its impact on global warming. This study investigated the role of atmospheric methanotrophs, particularly USCγ, in regulating methane oxidation in alpine meadow and wetland soils on the Qinghai-Tibet Plateau. Soils were incubated under varying methane concentrations (2, 200, 900, 10,000, and 45,000 ppm) to assess the effects of soil type and methane concentration on oxidation potentials and methanotrophic community composition. Bacterial 16S rRNA and pmoA gene sequencing, quantitative PCR, and DNA-SIP techniques were employed to analyze the potentially active microbial populations. The results showed significant differences in methane oxidation potential between meadow and wetland soils. Higher methane concentrations correlated with increased oxidation potentials across all soil types. In meadow soils, USCγ was dominant at low methane concentrations, but its relative abundance decreased with increasing methane concentration, giving way to conventional methanotrophs like Methylocystis and Methylobacter. In contrast, these conventional methanotrophs dominated wetland soils regardless of methane concentration, with USCγ playing no detectable role. These findings highlight the critical role of USCγ in low-methane environments and demonstrate the shifting dominance of methanotrophic groups in response to methane availability.