Methanotrophic communities in a landfill cover soil as revealed by [13C] PLFAs and respiratory quinones:: Impact of high methane addition and landfill leachate irrigation

The soil microbial communities of a landfill cover substrate, which was treated with landfill gas (1001CH(4)m(-2) d(-1)) and landfill leachate for 1.5 years, were investigated by phospholipid fatty acid (PLFA), ergosterol and respiratory quinone analyses. The natural C-13 depletion of methane was used to assess the activity of methanotrophs; and carbon turnover in the soil system. Under methane addition, the soil microbial community was dominated by PLFAs (14:0 and 16:1 isomers) and quinones (tibiquinone-8 and 18-methylene-ubiquinone-8) related to type I methanotrophs, and 18:1 PLFAs contained in type 11 methanotrophs. While type I methanotrophic PLFAs were C-13 depleted, i.e. type 1 methanotroplis were actively oxidising and assimilating methane, C-13 depletion of 18:1 PLFAs was low and inconsistent with their abundance. This, possibly reflects isotopic discrimination, assimilation of carbon derived from type I methanotrophs and a high contribution of non-methanotrophic bacteria to the 18:1 isomers. Landfill leachate irrigation caused the methanotrophic community to shift closer to the soil surface. It also decreased 18:1 PLFAs, while type I methanotrophs were probably stimulated. Gram positive bacteria, but not fungi, were also C-13 depleted and consequently involved in the secondary turnover of carbon originating front methanotrophic bacteria. Cy 17:0 PLFA was C-13 depleted in deep soil layers, indicating anaerobic methane oxidation. (c) 2007 Elsevier Ltd. All rights reserved.