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“Methanogenesis 2020 – An update”

EGU General Assembly 2020 Online | 7 May 2020

Frank Keppler

Institute of Earth Sciences Heidelberg University

Germany

Methanogenesis – traditional view

biotic abiotic

biomass burning

serpentinisation

rice paddies, mires, lakes, wetlands, landfills …

archaea

geological

anoxic

decay of organic matter

guts of ruminants

or termites

biomass burning fossil sources

energy production

Fischer-Tropsch-process

industry

microbial

CO2 + 4H2 CH4 + 2H2O

CH3COOH CH4 + CO2

Well known processes of methane formation on Earth

ocean floor

Prokaryotes Archaea

The final step of methanogenesis by archaea

Me-S-CoM + CoB-SH → CH4 + CoB-S-S-CoM

Ellermann et al., Eur. J. Biochem, 1988

The enzyme Methyl-coenzyme M reductase (MCR) catalyzes the final step in CH4 formation…a phylogenetic marker

Novel eukaryotic sources recently discovered…

as described e.g. by Abdulmajeed &, Qaderi 2017, 2019, 2020, Althoff et al. 2014; Boros & Keppler, 2019; Bruhn et al. 2012; Carmichael et al. 2014; Hartmann et al. 2020, Keppler et al. 2006, 2009; Klintzsch et al. 2019; Lenhart et al. 2012, 2015, 2016; Liu et al. 2015; Wang et al. 2013, 2016,…

Phylogenetic Tree of Life Three domain system

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[Phylogenetic Tree of Life taken from Wikimedia Commons]

Widespread formation of methane by Cyanobacteria in aquatic and terrestrial environments

Bižić et al., Science Advances, 2020

Thomas Klintzsch, Heidelberg University

Thomas Klintzsch, Heidelberg University

Reported formation rates - from culture experiments:

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Bižić et al., Science Advances, 2020

Methanogenesis 2020

8 [Phylogenetic Tree of Life taken from Wikimedia Commons]

biomass burning

serpentinisation

decay of organic matter

From https://contemplativepathways.files.wordpress.com/2012/08/cornwalls_glendurgan_lowres.jpg?w=640&h=480

Detailed pathways of non-archaeal methane formation have yet to be discovered…