Earthworm activity in a simulated landfill cover soil shifts the community composition of active methanotrophs

Landfills represent a major source of methane into the atmosphere. In a previous study, we demonstrated that earthworm activity in landfill cover soil can increase soil methane oxidation capacity (Héry et al., 2008). In this study, a simulated landfill cover soil mesocosm (1 m x 0.15 m) was used to observe the influence of earthworms (Eisenia veneta) on the active methanotroph community composition, by analyzing the expression of the pmoA gene, which is responsible for methane oxidation. mRNA-based pmoA microarray analysis revealed that earthworm activity in landfill cover soil stimulated activity of type I methanotrophs (Methylobacter, Methylomonas, Methylosarcina spp.) compared to type II methanotrophs (particularly Methylocystis spp.). These results, along with previous studies of methanotrophs in landfill cover soil, can now be used to plan in situ field studies to integrate earthworm-induced methanotrophy with other landfill management practises in order to maximize soil methane oxidation and reduce methane emissions from landfills.