Sensitivity of methanotrophic community structure, abundance, and gene expression to CH4 and O2 in simulated landfill biocover soil

- Both CH4 and O2 as substrates of methanotrophs is the first to be taken account.
- Increasing either CH4 or O2 would enhance activity of methanotrophs.
- Methanotrophs are more sensitive to CH4 than O2.
- CH4 mitigation have higher potential by controlling O2 and CH4 concentrations.

Pressure on mitigating CH4 emission in landfill requires better understanding of methanotrophs in landfill biocovers. Most previous studies focused on CH4 as the sole substrate. This study aims to understand the sensitivity of methanotrophs to both substrates CH4 and O2 concentrations in landfill biocovers. The estimated CH4 oxidation rates (4.66-98.7 × 10−16 mol cell−1 h−1) were evidently higher than the previous reports, suggesting that activity of methanotrophs was enhanced with both the increasing of O2 and CH4 concentrations. Denaturing gradient gel electrophoresis based on the amplification of pmoA genes suggested that methanotrophs were more sensitive to CH4 than O2. Quantification of methanotrophs using pmoA- and mmoX-targeted real-time polymerase chain reaction showed that Mbac and Mcoc as well as Mcys groups were significantly dominant. Mbac group with pmoA gene transcription was dominant. Results indicate that CH4 mitigation would have higher potential by increasing O2 at appropriate CH4 concentrations.