Chapter 13 : Acetate-Based Methane Production

Figure 1

The global carbon cycle in nature. (A) Fixation of CO2 into organic matter; (B) aerobic decomposition of organic matter to CO2; (C) anaerobic decomposition of organic matter to fermentative end products; (D) anaerobic conversion of fermentative end products to methane and escape into aerobic environments; (E) aerobic oxidation of methane to CO2 by O2-requiring methylotrophs.

Figure 2.

Methane-producing freshwater consortia.

Figure 3.

Phase-contrast micrographs of Methanosarcina mazei showing cells in pseudosarcinal aggregates (left) and single cells (right). Bars, 10 μm. Reprinted from Applied and Environmental Microbiology ( Sowers et al., 1993 ) with permission of the publisher.

Figure 4.

Thin-section electron micrograph of Methanosarcina thermophila showing a cell aggregate enclosed by an outer membrane. Bar, 1 μm. Reprinted from International Journal of Systematic Bacteriology ( Zinder et al., 1985 ) with permission of the publisher.

Figure 5.

Scanning electron micrograph of Methanosaeta concilii strain T-3 filaments. Reprinted from Bioscience, Biotechnology, and Biochemistry ( Mizukami et al., 2006 ) with permission of the publisher.

Figure 6.

Thin section of “Methanothrix” (Methanosaeta) concilii. Spacer plugs are indicated by arrows, and “M” indicates the amorphous granular layer. Bar, 1 μm. Reprinted from Canadian Journal of Microbiology ( Beveridge et al., 1986 ) with permission of the publisher.

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Figure 2.

Cofactors and coenzymes utilized in the pathway for aceticlastic methanogenesis.

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Figure 8.

Overview of the aceticlastic and CO2 reduction pathways. H4M(S)PT, tetrahydromethanopterin (H4MPT) or tetrahydrosarcinapterin (H4SPT); CoM, coenzyme M; CoB, coenzyme B.

Figure 9.

Proposed mechanism of sodium translocation by the methyl-H4M(S)PT:coenzyme M methyltransferase. Reprinted from Biochimica et Biophysica Acta ( Gottschalk and Thauer, 2001 ) with permission of the publisher.

Figure 10.

Mechanism proposed for methyl-coenzyme M methylreductase. Adapted from Ermler et al., 1997.

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Figure 11.

Pathways for conversion of acetate to methane by M. mazei (A) and M. acetivorans (B). Ack, acetate kinase; Pta, phosphotransacetylase; CoA-SH, coenzyme A; H4SPT, tetrahydrosarcinapterin; Fdr, reduced ferredoxin; Fdo, oxidized ferredoxin; Cdh, CO dehydrogenase/acetyl-CoA synthase; CoM-SH, coenzyme M; Mtr, methyl-H4SPT:CoM-SH methyltransferase; CoB-SH, coenzyme B; Cam, carbonic anhydrase; Ech, H2-evolving hydrogenase; Vho, H2-consuming hydrogenase; Ma-Rnf, M. acetivorans Rnf; MP, methanophenazine; Hdr-DE, heterodisulfide reductase; Mrp, multiple resistance/pH regulation Na+ /H antiporter; Atp, H -translocating A1A0 ATP synthase. Adapted from Li et al., 2006.

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Figure 12.

The A cluster of Acs from Moorella thermoacetica. Reprinted from Critical Reviews in Biochemistry and Molecular Biology ( Ragsdale, 2004 ) with permission of the publisher.

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