Methanogenesis
The biological formation of methane, methanogenesis, is an essential link in the global carbon cycle. Organic matter is decomposed anaerobically into carbon dioxide (plus hydrogen), formate, and acetate, which would, if not reduced to gaseous methane, oth
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Genetics of Biogenesis
36 Methanogenesis M. Rother Institut fu¨r Molekulare Biowissenschaften, Molekulare Mikrobiologie & Bioenergetik, Johann Wolfgang Goethe-Universita¨t Frankfurt am Main, Frankfurt, Germany [email protected] 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 484 2 Hydrogenotrophic Methanogenesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 486 3 Methylotrophic Methanogenesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 492 4 Acetotrophic Methanogenesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 494 5 Research Needs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 495
K. N. Timmis (ed.), Handbook of Hydrocarbon and Lipid Microbiology, DOI 10.1007/978-3-540-77587-4_36, # Springer-Verlag Berlin Heidelberg, 2010
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Methanogenesis
Abstract: The biological formation of methane, methanogenesis, is an essential link in the global carbon cycle. Organic matter is decomposed anaerobically into carbon dioxide (plus hydrogen), formate, and acetate, which would, if not reduced to gaseous methane, otherwise accumulate. The only organisms producing significant amounts of methane are methanogenic archaea, strictly anaerobic members of the Euryarchaeota. All methanogens investigated thus far depend on the process of methanogenesis for energy conservation and most of them are only capable to reduce CO2 with H2 or formate to methane. In these so called hydrogenotrophic methanogens, all factors involved are therefore essential and regulation of the respective genes is moderate, mostly affecting differential expression of isogenes and fine tuning of gene expression in response to growth phase and/or substrate concentration. However, many members of the order Methanosarcinales have a broader substrate spectrum and are able to grow with, beside H2 + CO2, methylated compounds, such as methanol, methylamines, or methyl-sulfides, and acetate. Methanogenesis from these substrates employs distinct yet overlapping pathways. Consequently, expression of the genes encoding one of the pathways is very stringently regulated in response to substrate availability, its concentration, and other substrates present. This section aims at summarizing current knowledge about the organization and regulation of expression of genes encoding factors involved in the different pathways of methanogenesis.
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Introduction
Methane is the most abundant hydrocarbon present in our atmosphere. Its current concentration of ca. 1750 ppb (Dlugokencky et al., 2003, and see http://www.epa.gov/methane) has more than tripled since pre-industrial times and an estimated 5 1014 g of biologically produced methane are annually released into our atmosphe
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