Methane-Dependent Extracellular Electron Transfer at the Bioanode by the Anaerobic Archaeal Methanotroph " Candidatus Methanoperedens"

• Published in: Frontiers in microbiology Vol. 13; p. 820989
• Main Authors: Ouboter, Heleen T, Berben, Tom, Berger, Stefanie, Jetten, Mike S M, Sleutels, Tom, Ter Heijne, Annemiek, Welte, Cornelia U
• Format: Journal Article
• Language: English
• Published: Switzerland Frontiers Media S.A 12.04.2022
• Subjects: anaerobic methane oxidation; ANME-2d; bioelectrochemistry; biofilms; cytochromes; extracellular electron transfer; Microbiology; bioelectrochemistry; extracellular electron transfer; anaerobic methane oxidation; biofilms; ANME-2d; cytochromes
• ISSN: 1664-302X; 1664-302X
• DOI: 10.3389/fmicb.2022.820989

Anaerobic methanotrophic (ANME) archaea have recently been reported to be capable of using insoluble extracellular electron acceptors extracellular electron transfer (EET). In this study, we investigated EET by a microbial community dominated by " Methanoperedens" archaea at the anode of a bioelectrochemical system (BES) poised at 0 V vs. standard hydrogen electrode (SHE), in this way measuring current as a direct proxy of EET by this community. After inoculation of the BES, the maximum current density was 274 mA m (stable current up to 39 mA m ). Concomitant conversion of CH into CO demonstrated that current production was methane-dependent, with 38% of the current attributed directly to methane supply. Based on the current production and methane uptake in a closed system, the Coulombic efficiency was about 17%. Polarization curves demonstrated that the current was limited by microbial activity at potentials above 0 V. The metatranscriptome of the inoculum was mined for the expression of -type cytochromes potentially used for EET, which led to the identification of several multiheme -type cytochrome-encoding genes among the most abundant transcripts in " . Methanoperedens." Our study provides strong indications of EET in ANME archaea and describes a system in which ANME-mediated EET can be investigated under laboratory conditions, which provides new research opportunities for mechanistic studies and possibly the generation of axenic ANME cultures.