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Archaea
Volume 2017, Article ID 1654237, 22 pages
https://doi.org/10.1155/2017/1654237
Review Article

Reverse Methanogenesis and Respiration in Methanotrophic Archaea

1Laboratory of Microbiology, Wageningen University, Stippeneng 4, 6708 WE Wageningen, Netherlands
2Wetsus, European Centre of Excellence for Sustainable Water Technology, Oostergoweg 9, 8911 MA Leeuwarden, Netherlands
3Soehngen Institute of Anaerobic Microbiology, Heyendaalseweg 135, 6525 AJ Nijmegen, Netherlands
4Department of Microbiology, Radboud University, Heyendaalseweg 135, 6525 AJ Nijmegen, Netherlands
5Laboratory of Systems and Synthetic Biology, Wageningen University, Stippeneng 4, 6708 WE Wageningen, Netherlands
6TU Delft Biotechnology, Julianalaan 67, 2628 BC Delft, Netherlands
7Centre of Biological Engineering, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal

Correspondence should be addressed to Peer H. A. Timmers; ln.ruw@sremmit.reep

Received 3 August 2016; Revised 11 October 2016; Accepted 31 October 2016; Published 5 January 2017

Academic Editor: Michael W. Friedrich

Copyright © 2017 Peer H. A. Timmers et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Anaerobic oxidation of methane (AOM) is catalyzed by anaerobic methane-oxidizing archaea (ANME) via a reverse and modified methanogenesis pathway. Methanogens can also reverse the methanogenesis pathway to oxidize methane, but only during net methane production (i.e., “trace methane oxidation”). In turn, ANME can produce methane, but only during net methane oxidation (i.e., enzymatic back flux). Net AOM is exergonic when coupled to an external electron acceptor such as sulfate (ANME-1, ANME-2abc, and ANME-3), nitrate (ANME-2d), or metal (oxides). In this review, the reversibility of the methanogenesis pathway and essential differences between ANME and methanogens are described by combining published information with domain based (meta)genome comparison of archaeal methanotrophs and selected archaea. These differences include abundances and special structure of methyl coenzyme M reductase and of multiheme cytochromes and the presence of menaquinones or methanophenazines. ANME-2a and ANME-2d can use electron acceptors other than sulfate or nitrate for AOM, respectively. Environmental studies suggest that ANME-2d are also involved in sulfate-dependent AOM. ANME-1 seem to use a different mechanism for disposal of electrons and possibly are less versatile in electron acceptors use than ANME-2. Future research will shed light on the molecular basis of reversal of the methanogenic pathway and electron transfer in different ANME types.