Anaerobic oxidation of methane

The overall syntrophic process involves a transfer of electrons from methane to sulphate, e.g. 

Methane-derived intermediates (possibly acetate or C02) and hydrogen from methane-consuming Archaea are transferred to their sulphate-reducing bacterial partners (Orphan etal., 2001). 

Teske etal. (2002) recently demonstrated that anaerobic methane oxidation occurs in Guaymas Basin. Although this site is influenced by active hydrothermal venting, the abundant hydrocarbon-rich sediments make the system similar to cold seeps. These authors suggest that such anaerobic methanotrophy is likely a significant and widely occurring process at methane-rich hydrothermal vents. 

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Schouten S, SG Wakeham, EC Hopmans, JSS Damste (2003) Biogeochemical evidence that thermophilic archaea mediate the anaerobic oxidation of methane. Appl Environ Microbiol 69 1680-1686. 

These redox reactions are abiogenic, whereas the methane sinks are thought to be biogenic, such as the anaerobic oxidation of methane by archaea as observed at the Lost City vent fields (Figure 19.20). Microbial production of methane has also been observed at this site. 

Strous, M., andjetten, M. S. M. (2004). Anaerobic Oxidation of Methane and Ammonium. Annual Review of Microbiology. 58, 99-117. 

Anaerobic CH4 oxidation, now referred to as anaerobic oxidation of methane (AOM), has received renewed attention with introduction of new organic geochemical and molecular techniques. Hinrichs et al. (1999) applied compound-specific isotope analyses of lipid biomarker molecules associated with specific archea and culture-independent techniques involving 16S rRNA identification studies to samples collected from an Eel River Basin seep. This work showed that the biomarker compounds were so strongly depleted in that CH4 must be the source rather... 

Boetius A., Ravenschlag K., Schubert C. J., Rickert D., Widdel F., Gieseke A., Amann R., Jprgensen B. B., Witte U., and Pfankuche O. (2000) A marine microbial consortium apparently mediating anaerobic oxidation of methane. Nature 407, 623-626. 

Nauhaus K., Boetius A., Kruger M., and Widdel E. (2002) In vitro demonstration of anaerobic oxidation of methane coupled to sulfate reduction in sediment from a marine gas hydrate area. Environ. Microbiol. 4, 296—305. 

A second newly recognized group of prokaryotes are the methane oxidizing archea. Nearly 90% of the methane produced in anoxic marine sediments is recycled through anaerobic microbial oxidation processes (Cicerone and Oremland, 1988 Reeburgh et al., 1991). However, the organisms and biochemical processes responsible for the anaerobic oxidation of methane (AMO)... 

Bian E., Hinrichs K.-U., Xie T., Brassell S. C., Iversen N., Eossing H., Jprgensen B. B., Sylva S. P., and Hayes J. M. (2001) Algal and archaeal polyisoprenoids in a recent marine sediment molecular isotopic evidence for anaerobic oxidation of methane. Geochem. Geophys. Geosys. 2, 2000GC000112. 

Murase J. and Kimura M. (1994a) Methane production and its fate in paddy fields 6. Anaerobic oxidation of methane in plow layer soil. Soil Sci. Plant Nutr. 40, 505-514. 

It has been inferred from carbon and sulfur dating that the concentration of oxygen in the Earth s atmosphere was less than I part per million volume (ppmv) prior to around 2.4 billion (Ga) years ago, whereas methane would have been present at levels of around 10 to 10 ppmv (compared with its present value of around 1.7 ppmv). Methane is generated in signihcant amounts by the anaerobic decomposition of organic matter in modem marine sediments, but is oxidised by sulfate under the ocean sea floor and never reaches the atmosphere. Prior to the watershed constituted by the appearance of oxygenic photosynthesis, the ocean had little sulfate to support anaerobic oxidation of methane, but as atmospheric oxygen and seawater sulfate levels rose, the consequent anaerobic oxidation of methane would have steadily reduced the net release of methane. 

Elvert, M., Boetius, A., Knittel, K. and Jorgensen, B.B., 2003. Characterization of specific membrane fatty acids as chemotaxonomic markers for sulfate-reducing bacteria involved in anaerobic oxidation of methane. Geomicrobiol. J., 20 403-419. 

Wakeham, S.G, Lewis, C.M., Hopmans, E.C., Schouten, S. and Sinninghe Damste, J.S., 2003. Archaea mediate anaerobic oxidation of methane in deep euxinic waters of the Black Sea. Geochim. Cosmochim. Acta, 67 1359-1374. 

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