Manganese- and Iron-Dependent Marine Methane Oxidation

Abstract

Electrons Accepted Here Methane is produced in large quantities in marine sediments during the breakdown of organic matter. Methane is a powerful greenhouse gas that plays a large role in the regulation of climate. Methane is also an energy source for the abundant anaerobic methanotrophs that consume most of it before it ever reaches the atmosphere. The anaerobic oxidation of methane in marine systems depends on the presence of sulfate, which acts as an electron acceptor and is often considered essential for the reaction to proceed. Beal et al. (p. 184 ) report that anaerobic methane oxidation in marine sediments can be facilitated by iron and manganese, as well as by sulfate. Thus, anaerobic methane oxidation using iron and manganese could have been an important methane sink, and energy source, for the early biosphere.

Microbial characterization of a subzero, hypersaline methane seep in the Canadian High Arctic

“…Although the mechanisms of AOM metabolism are not fully understood, AOM is believed to occur through either reverse methanogenesis (Hallam et al, 2004;Caldwell et al, 2008), a type of acetogenesis (Valentine and Reeburgh, 2000;Caldwell et al, 2008) or methylogenesis (Caldwell et al, 2008;Moran et al, 2008). It has been shown that ANME cells (including ANME-1) form consortia with SRB cells to couple AOM with sulfate reduction (Valentine and Reeburgh, 2000;Orphan et al, 2002) and very recently it has been shown that AOM can also be coupled to denitrification (Raghoebarsing et al, 2006) or to the use of manganese and iron oxidants (Beal et al, 2009). Alternatively, it has also been theorized that ANME cells may undertake AOM autonomously (Orphan et al, 2002;Strous and Jetten, 2004) as some ANME cells have been observed alone.…”

Changing redox conditions at cold seeps as revealed by authigenic carbonates from Alaminos Canyon, northern Gulf of Mexico

“…Typically, the manganeseand iron-reduction zones overly the zone of sulfate reduction (Froelich et al, 1979), where sulfate-dependent AOM occurs. Beal et al (2009) showed that AOM can be coupled not only to sulfate reduction but also to iron and manganese reduction. The biomarkers of these newly discovered bacterial partners in AOM are not known yet, which impedes their recognition in archives like seep carbonates.…”

Ferromanganese nodules and micro-hardgrounds associated with the Cadiz Contourite Channel (NE Atlantic): Palaeoenvironmental records of fluid venting and bottom currents

“…Fe3+ and Mn 4 + reduction processes partial or totally mediated by microorganisms are common in the redox zone (e.g. Hein and Koski, 1987;Nealson and Myers, 1992;Lovley, 1993;Fortin et al, 1997;Tebo et al, 1997;Kohn et al, 1998;Stein et al, 2001;Frankel and Bazylinski, 2003;Webb et al, 2005;Beal et al, under reducing conditions, appear in the most internal parts of the nodules. Similarly, some redox-sensitive trace elements such as Mo, Pb and As are enriched in the nuclear zones of the nodules.…”