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Response of Methanogens in Arctic Sediments to Temperature and Methanogenic Substrate Availability.

PloS one (2015-06-18)
Lynsay I Blake, Alexander Tveit, Lise Øvreås, Ian M Head, Neil D Gray
ABSTRACT

Although cold environments are major contributors to global biogeochemical cycles, comparatively little is known about their microbial community function, structure, and limits of activity. In this study a microcosm based approach was used to investigate the effects of temperature, and methanogenic substrate amendment, (acetate, methanol and H2/CO2) on methanogen activity and methanogen community structure in high Arctic wetlands (Solvatnet and Stuphallet, Svalbard). Methane production was not detected in Stuphallet sediment microcosms (over a 150 day period) and occurred within Solvatnet sediments microcosms (within 24 hours) at temperatures from 5 to 40°C, the maximum temperature being at far higher than in situ maximum temperatures (which range from air temperatures of -1.4 to 14.1°C during summer months). Distinct responses were observed in the Solvatnet methanogen community under different short term incubation conditions. Specifically, different communities were selected at higher and lower temperatures. At lower temperatures (5°C) addition of exogenous substrates (acetate, methanol or H2/CO2) had no stimulatory effect on the rate of methanogenesis or on methanogen community structure. The community in these incubations was dominated by members of the Methanoregulaceae/WCHA2-08 family-level group, which were most similar to the psychrotolerant hydrogenotrophic methanogen Methanosphaerula palustris strain E1-9c. In contrast, at higher temperatures, substrate amendment enhanced methane production in H2/CO2 amended microcosms, and played a clear role in structuring methanogen communities. Specifically, at 30°C members of the Methanoregulaceae/WCHA2-08 predominated following incubation with H2/CO2, and Methanosarcinaceaeand Methanosaetaceae were enriched in response to acetate addition. These results may indicate that in transiently cold environments, methanogen communities can rapidly respond to moderate short term increases in temperature, but not necessarily to the seasonal release of previously frozen organic carbon from thawing permafrost soils. However, as temperatures increase such inputs of carbon will likely have a greater influence on methane production and methanogen community structure. Understanding the action and limitations of anaerobic microorganisms within cold environments may provide information which can be used in defining region-specific differences in the microbial processes; which ultimately control methane flux to the atmosphere.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Methane-12C, 13C-depleted, 99.9 atom % 12C
Sigma-Aldrich
Carbon nanofibers, graphitized (iron-free), composed of conical platelets, D × L 100 nm × 20-200 μm
Sigma-Aldrich
Carbon nanofibers, graphitized, platelets(conical), >98% carbon basis, D × L 100 nm × 20-200 μm
Carbon - Vitreous, rod, 200mm, diameter 1.0mm, glassy carbon
Carbon - Vitreous, foil, 100x100mm, thickness 2.0mm, glassy carbon
Carbon - Vitreous, foil, 8x8mm, thickness 0.5mm, glassy carbon
Carbon - Vitreous, foil, 100x100mm, thickness 1.0mm, glassy carbon
Carbon - Vitreous, rod, 200mm, diameter 10mm, glassy carbon
Carbon - Vitreous, foil, 100x100mm, thickness 6.0mm, glassy carbon
Carbon - Vitreous, foil, 10mm disks, thickness 0.2mm, glassy carbon
Carbon - Vitreous, foam, 150x150mm, thickness 2.5mm, bulk density 0.05g/cm3, porosity 96.5%
Carbon - Vitreous, rod, 200mm, diameter 3.0mm, glassy carbon
Carbon - Vitreous, rod, 200mm, diameter 5.0mm, glassy carbon
Carbon - Vitreous, foil, 8mm disks, thickness 1.0mm, glassy carbon
Carbon - Vitreous, rod, 200mm, diameter 7.0mm, glassy carbon
Carbon - Vitreous, foil, 10x10mm, thickness 4.0mm, glassy carbon
Carbon - Vitreous, foil, 50x50mm, thickness 4.0mm, glassy carbon
Carbon - Vitreous, rod, 100mm, diameter 1.0mm, glassy carbon
Carbon - Vitreous, foam, 275x330mm, thickness 3.2mm, bulk density 0.05g/cm3, porosity 96.5%
Carbon - Vitreous, rod, 50mm, diameter 1.0mm, glassy carbon
Carbon - Vitreous, foam, 275x330mm, 0.05g.cmué, porosity 96.5%, 24 pores/cm
Carbon - Vitreous, foam, 150x150mm, 0.05g.cmué, porosity 96.5%, 24 pores/cm
Carbon - Vitreous, rod, 5mm, diameter 3.0mm, glassy carbon
Carbon - Vitreous, foil, 25x25mm, thickness 0.5mm, glassy carbon
Carbon - Vitreous, foam, 300x300mm, thickness 20mm, bulk density 0.05g/cm3, porosity 96.5%
Carbon - Vitreous, foil, 10x10mm, thickness 1.0mm, glassy carbon
Carbon - Vitreous, tube, 100mm, outside diameter 10mm, inside diameter 3mm, wall thickness 3.5mm, glassy carbon
Carbon - Vitreous, foil, 25x25mm, thickness 4.0mm, glassy carbon
Carbon - Vitreous, foam, 150x150mm, thickness 3.2mm, bulk density 0.05g/cm3, porosity 96.5%
Carbon - Vitreous, tube, 50mm, outside diameter 10mm, inside diameter 3mm, wall thickness 3.5mm, glassy carbon