Abundance and Diversity of Methanogens in German Fen and Peat Bog Soils
O 2.4 in Biodiversity: Patterns, Function and Protection
11.10.2012, 10:15-10:30, H8
Natural wetlands such as bogs and fens contribute up to 40% to the global emission of methane (2). Biopolymers in wetland soils are anaerobically degraded via intermediary events that terminate in the emission of methane, collectively termed ‘intermediary ecosystem metabolism’; i.e., IEM (1). The objective of this study was to investigate the terminal event of the IEM and evaluate the abundance and diversity of methanogens in regional peatland soils.
Five peatland soils (three fens, two bogs) and roots of Carex rostrata, Molinia caerula and Eriophorum vaginatum were diluted with mineral medium and incubated in the dark under anoxic conditions. Soil microcosms were treated with acetate, or H2-CO2; untreated soils served as controls. Soil-free roots were treated with formate or butyrate and propionate; untreated roots and soils served as controls. Microbial communities were evaluated by analyzing mcrA genes (encode for the alpha-subunit of methyl-CoM reductase). Abundances were determined by most probable number and qPCR analysis.
H2-CO2 and acetate stimulated methane production in all peatland soils. Formate was more stimulatory for methanogenesis than butyrate and propionate for all three plant roots and their surrounding soils. The roots of C. rostrata and the surrounding soils showed the highest potential of methane production, whereas no methane production has been observed with E. vaginatum. Up to 4.9-10.3 x 107 mcrA genes per g[soilFW]-1and 1.0-32.2 x 107 mcrA genes per g[soilFW]-1 were detected in fen and bog soils, respectively. Fen-derived methanogens in root-free soil and attached to plant roots were equal (i.e., 9.3 x 101 living cells per g[soil/rootFW]-1). The abundance of bog-derived methanogens was higher in root-free soil than attached to plant roots (i.e., 4.3 x 101 living cells per g[soilFW]-1 and 2.3 x 101 living cells per g[rootFW]-1). The methane producing taxa Methanobacteriaceae, Methanosarcinaceae, Methanomicrobiaceae, Methanosaetaceae as well as Methanoregula-related taxa and novel taxa were detected in fen and bog soils. Methanocellaceae were only detected in fen soils.
The collective results reinforce the likelihood that H2-CO2, formate, acetate, propionate and butyrate stimulated the methane production in the analyzed peatland soils or roots, similar taxa are responsible for methanogenesis in different peatland soils, and that Methanocellaceae are more important to the IEM of fen soils then of bog soils.
(1) Drake et al. 2009. Environ Microbiol Reports 1:307
(2) Hein et al. 1997. Global Biogeochem Cycles 11:43
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