Links between methanotroph community composition and CH4 oxidation in a pine forest soil

Authors


  • Editor: Kornelia Smalla

  • Present addresses: Per Bengtson, Department of Microbial Ecology, Ecology Building, Sölvegatan 37, 223 62 Lund, Sweden.
    Marc G. Dumont, Max Planck Institute for Terrestrial Microbiology, Marburg D-35043, Germany.
    Nathan Basiliko, Department of Geography, University of Toronto Mississauga, 3359 Mississauga Road North, Mississauga, ON, Canada L5L 1C6.

Correspondence: Per Bengtson, Department of Forest Sciences, University of British Columbia, 2424 Main Mall, Vancouver, BC, Canada V6T 1Z4. Tel.: +46 46 222 3760; fax: +46 46 222 3800; e-mail: per.bengtson@mbioekol.lu.se

Abstract

The main gap in our knowledge about what determines the rate of CH4 oxidation in forest soils is the biology of the microorganisms involved, the identity of which remains unclear. In this study, we used stable-isotope probing (SIP) following 13CH4 incorporation into phospholipid fatty acids (PLFAs) and DNA/RNA, and sequencing of methane mono-oxygenase (pmoA) genes, to identify the influence of variation in community composition on CH4 oxidation rates. The rates of 13C incorporation into PLFAs differed between horizons, with low 13C incorporation in the organic soil and relatively high 13C incorporation into the two mineral horizons. The microbial community composition of the methanotrophs incorporating the 13C label also differed between horizons, and statistical analyses suggested that the methanotroph community composition was a major cause of variation in CH4 oxidation rates. Both PLFA and pmoA-based data indicated that CH4 oxidizers in this soil belong to the uncultivated ‘upland soil cluster α’. CH4 oxidation potential exhibited the opposite pattern to 13C incorporation, suggesting that CH4 oxidation potential assays may correlate poorly with in situ oxidation rates. The DNA/RNA-SIP assay was not successful, most likely due to insufficient 13C-incorporation into DNA/RNA. The limitations of the technique are briefly discussed.

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