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Methanogenesis (bacteria)

The microbial formation of methane, which is confined to anaerobic habitats where occurs the production of hydrogen, carbon dioxide, formic acid, methanol, methylamines, or acetate—the major substrates used by methanogenic microbes (methanogens). In fresh-water or marine sediments, in the intestinal tracts of animals, or in habitats engineered by humans such as sewage sludge or biomass digesters, these substrates are the products of anaerobic bacterial metabolism. Methanogens are terminal organisms in the anaerobic microbial food chain—the final product, methane, being poorly soluble, anaerobically inert, and not in equilibrium with the reaction which produces it.

Two highly specialized digestive organs, the rumen and the cecum, have been evolved by herbivores to delay the passage of cellulose fibers so that microbial fermentation may be complete. In these organs, large quantities of methane are produced from hydrogen and carbon dioxide or formic acid by methanogens. From the rumen, an average cow may belch 26 gallons (100 liters) of methane per day.

Methanogens are the only living organisms that produce methane as a way of life. The biochemistry of their metabolism is unique and definitively delineates the group. Two reductive biochemical strategies are employed: an eight-electron reduction of carbon dioxide to methane or a two-electron reduction of a methyl group to methane. All methogens form methane by reducing a methyl group. The major energy-yielding reactions used by methanogens utilize substrates such as hydrogen, formic acid, methanol, acetic acid, and methylamine. Dimethyl sulfide, carbon monoxide, and alcohols such as ethanol and propanol are substrates that are used less frequently. See Archaebacteria, Bacterial physiology and metabolism

McGraw-Hill Concise Encyclopedia of Bioscience. © 2002 by The McGraw-Hill Companies, Inc.


The biosynthesis of the hydrocarbon methane; common in certain bacteria. Also known as bacterial methanogenesis.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
Tannins also affect feed utilization and especially protect protein from fermentation including a shift in N excretion from urine to feces, and reduce ruminal methanogenesis [5,6].
With respect to batch digestion continuous digestion system getting nutrients on daily basis therefor methanogenesis process didn't disturbed and biogas production remain near to constant rate.
Therefore, it is important to understand how the morphophysiological variables of different irrigated rice cultivars may be related to the supply of root exudates that function as a source for the methanogenesis process in rice cultivation under the flood irrigation regime.
Methanogens associated with ciliates are responsible for 9-25% of the methanogenesis of the rumen fluid (Moss et al., 2000).
Methane emissions can be reduced by the selection of plant species that produce secondary metabolites to reduce methanogenesis, such as saponins, flavonoids and tannins.
Thus, the low methane production in the configuration without buffering agent (AIS + FW) and acidification of the medium (final pH of 5.38) can be an indication of methanogenesis inhibition through the hydrolytic and acetogenic step, whose microorganisms exhibit growth rate much higher than that of the methanogenic ones.
Satoh, "Organic removal by denitritation and methanogenesis and nitrogen removal by nitritation from landfill leachate," Water Research, vol.
There are a number of factors that control the rate of methanogenesis [19], including temperature [20], groundwater salinity [21], pH [22], and pore space [23].
Effect of gynosaponin on rumen in vitro methanogenesis under different forage-concentrate ratios.