Methanogen communities and Bacteria along an ecohydrological gradient in a northern raised bog complex

Abstract

Mires forming an ecohydrological gradient from nutrient-rich, groundwater-fed mesotrophic and oligotrophic fens to a nutrient-poor ombrotrophic bog were studied by comparing potential methane (CH(4)) production and methanogenic microbial communities. Methane production was measured from different depths of anoxic peat and methanogen communities were detected by detailed restriction fragment length polymorphism (RFLP) analysis of clone libraries, sequencing and phylogenetic analysis. Potential CH(4) production changed along the ecohydrological gradient with the fens displaying much higher production than the ombrotrophic bog. Methanogen diversity also decreased along the gradient. The two fens had very similar diversity of methanogenic methyl-coenzyme M reductase gene (mcrA), but in the upper layer of the bog the methanogen diversity was strikingly lower, and only one type of mcrA sequence was retrieved. It was related to the Fen cluster, a group of novel methanogenic sequences found earlier in Finnish mires. Bacterial 16S rDNA sequences from the fens fell into at least nine phyla, but only four phyla were retrieved from the bog. The most common bacterial groups were Deltaproteobacteria, Verrucomicrobia and Acidobacteria.

Nitrogen and methanogen community composition within and among three Sphagnum dominated peatlands in Scandinavia

“…This observation supports a previous study, which showed that Methanoregulaceae was the dominant family in two acidic peatlands (Sun et al, 2012). This family also belongs to the 'Fen cluster' originally detected by Galand et al (2002), and this type of methanogens have later been detected in several Nordic peatlands (Galand et al, 2003;Juottonen et al, 2005;Putkinen et al, 2009). The family belongs to the order Methanomicrobiales, which produces methane by the reduction of carbon dioxide and oxidation of hydrogen (Deppenmeier, 2002;Liu and Whitman, 2008).…”

“…Our study sites also showed relatively lower diversity of the mcrA gene compared to minerotrophic peatlands Juottonen et al, 2005;Merila et al, 2006). Those studies performed a direct comparison between peatland types and found the ombrotrophic sites to have lower methanogen diversity.…”

Stable carbon isotope fractionation during methanogenesis in three boreal peatland ecosystems

“…In MES, acetate concentrations were larger, so that further fractionation is feasible. This fractionation should be on the order of less than 10‰ as typical for Methanosaeta (Valentine et al, 2004;Penning et al, 2006), which was the prevailing acetoclastic methanogen in MES (Juottonen et al, 2005) . Therefore, we assumed values of δ 13 C CH 4 −ac being 5-10‰ smaller than δ 13 C org .…”

“…These layers exhibited the highest potential CH 4 production rates (Galand et al, 2002). The hydrological conditions and vegetation cover of the sites have already been described in detail (Juottonen et al, 2005). Briefly, MES is a mesotrophic fen, the vegetation of which is a mosaic of lawn and minerotrophic hollow level communities with high diversity.…”

Microbial dark matter ecogenomics reveals complex synergistic networks in a methanogenic bioreactor

“…Syntrophs specifically form obligate mutualistic interactions with methanogens to metabolize organic compounds whose degradation otherwise rapidly becomes thermodynamically unfavorable (DG40) as by-products accumulate (Schink, 1997;Schink and Stams, 2006). Despite such low-energy conditions, engineered and natural methanogenic environments harbor a wide diversity of uncharacterized microorganisms from known phyla and candidate phyla without cultivated representatives (microbial dark matter; Rinke et al, 2013; also see Juottonen et al, 2005;Nemergut et al, 2008;Griebler and Lueders, 2009;Riviere et al, 2009;Glockner et al, 2010;Kong et al, 2010;Kim et al, 2011;Lykidis et al, 2011;Nelson et al, 2011;Rinke et al, 2013). Their presence indicates many undiscovered microbial niches and interactions.…”