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Methanogens and Methanogenesis in Hypersaline Environments

McGenity, Terry J and Sorokin, Dimitry Y (2018) 'Methanogens and Methanogenesis in Hypersaline Environments.' In: Stams, A and Sousa, D, (eds.) Biogenesis of Hydrocarbons. Handbook of Hydrocarbon and Lipid Microbiology . Springer. ISBN 978-3-319-53114-4

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Abstract

Methanogenesis is controlled by redox potential and permanency of anaerobic conditions; and in hypersaline environments, the high concentration of terminal electron acceptors, particularly sulfate, is an important controlling factor. This is because sulfate-reducing microbes, compared with methanogens, have a greater affinity for, and energy yield from, competitive substrates like hydrogen and acetate. However, hypersalinity is not an obstacle to methylotrophic methanogenesis; in many cases hypersaline environments have high concentrations of noncompetitive substrates like methylamines, which derive from compatible solutes such as glycine betaine that is synthesized by many microbes inhabiting hypersaline environments. Also, depletion of sulfate, as may occur in deeper sediments, allows increased methanogenesis. On the other hand, increasing salinity requires methanogens to synthesize or take up more compatible solutes at a significant energetic cost. Acetoclastic and hydrogenotrophic methanogens, with their lower energetic yields, are therefore more susceptible than methylotrophic methanogens, which further explains the predominance of methylotrophic methanogens like Methanohalophilus and Methanohalobium spp. in hypersaline environments. There are often deviations from the picture outlined above, which are sometimes difficult to explain. Identifying the role of uncultivated Euryarchaeota in hypersaline environments, elucidating the effects of different ions (which have differential stress effects and potential as electron acceptors), and understanding the effects of salinity on all microbes involved in methane cycling will help us to understand and predict methane production in hypersaline environments. A good demonstration of this is a recent discovery of extremely haloalkaliphilic methanogens living in hypersaline lakes, which utilize the methyl-reducing pathway and form a novel class “Methanonatronarchaeia” in the Euryarchaeota.

Item Type: Book Section
Subjects: Q Science > QR Microbiology
Divisions: Faculty of Science and Health > Life Sciences, School of
Depositing User: Elements
Date Deposited: 02 Jan 2019 10:53
Last Modified: 28 Aug 2019 21:16
URI: http://repository.essex.ac.uk/id/eprint/23701

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