Methanogenesis and methanogenic pathways in a peat from subarctic permafrost

Abstract

Few studies have dealt so far with methanogenic pathways and populations in subarctic and arctic soils. We studied the effects of temperature on rates and pathways of CH4 production and on the relative abundance and structure of the archaeal community in a mildly acidic peat from a permafrost region in Siberia (67 degrees N). We monitored the production of CH4 and CO2 over time and measured the consumption of Fe(II), ethanol and volatile fatty acids. All experiments were performed with and without specific inhibitors [2-bromoethanesulfonate (BES) for methanogenesis and CH3F for acetoclastic methanogenesis]. The optimum temperature for methanogenesis was between 26 degrees C and 28 degrees C [4.3 micromol CH4 (g dry weight)(-1) day(-1)], but the activity was high even at 4 degrees C [0.75 micromol CH4 (g dry weight)(-1) day(-1)], constituting 17% of that at 27 degrees C. The population structure of archaea was studied by terminal restriction fragment length polymorphism analysis and remained constant over a wide temperature range. Acetoclastic methanogenesis accounted for about 70% of the total methanogenesis. Most 16S rRNA gene sequences clustered with Methanosarcinales, correlating with the prevalence of acetoclastic methanogenesis. In addition, sequences clustering with Methanobacteriales were recovered. Fe reduction occurred in parallel to methanogenesis. At lower and higher temperatures Fe reduction was not affected by BES. Because butyrate was consumed during methanogenesis and accumulated when methanogenesis was inhibited (BES and CH3F), it is proposed to serve as methanogenic precursor, providing acetate and H2 by syntrophic oxidation. In addition, ethanol and caproate occurred as intermediates. Because of thermodynamic constraints, homoacetogenesis could not compete with hydrogenotrophic methanogenesis.

Stable carbon isotope fractionation during methanogenesis in three boreal peatland ecosystems

“…Under these conditions, 2 CH 4 are derived from acetate and 1 CH 4 from H 2 /CO 2 . In fact, this path of CH 4 production has been demonstrated in various peat bogs ranging from Michigan (Avery et al, 1999), western Siberia (Kotsyurbenko et al, 2004) to the permafrost region of northwestern Siberia (Metje and Frenzel, 2007). In some peat ecosystems, however, acetoclastic methanogenesis is apparently impeded and CH 4 is mainly produced from H 2 /CO 2 (Lansdown et al, 1992;Horn et al, 2003;Metje and Frenzel, 2005;Prater et al, 2007).…”

Psychrophilic methanogenic community development during long-term cultivation of anaerobic granular biofilms

“…Three quarters of the Earth's biosphere is permanently exposed to low temperatures (Metje and Frenzel, 2007). Psychrotrophic and psychrophilic Archaea contribute significantly to the biomass in the predominantly cold biosphere (for example, c. 10 28 cells in the world's oceans) and typically, these habitats are characterized by hypoxic/anoxic conditions and are low in inorganic terminal electron acceptors (Horn et al, 2003).…”

“…It is proposed that the predicted increase in global temperatures will result in substantially increased methane emissions from cold biomes (Galand et al, 2003). As methane is a potent greenhouse gas, its increased emission will likely further accelerate climate change (Metje and Frenzel, 2007).…”

Temperature, inocula and substrate: Contrasting electroactive consortia, diversity and performance in microbial fuel cells

“…An appropriate choice of inoculum might influence performance in general, and temperature sensitivity in particular. Thus, although wastewater itself is known to be a satisfactory source of inoculum, soils, especially arctic soils, might be superior for systems that are expected to function at low temperatures: soils are inherently more diverse than wastewater [22], and display significant anaerobic activity at low temperatures [23,24]. Geobacter species are usually the dominant electrogens in acetate fed reactors [25].…”