Methanogens organization

Methanogenic organisms are placed among the archaea, and they differ significantly from the other two domains of life, the eukarya and bacteria. The... 

Freshwater sediment slurries debrominated 2-bromobenzoate to benzoate that was then degraded by methanogenic organisms (Horowitz et al. 1983). 

The terminal step in methane generation by several methanogenic organisms, of which the best studied is the archaeon Methanobacterium thermoautotrophicum, is catalyzed by the enzyme S-methyl coenzyme M reductase (methylreductase, EC 1.8.-.-). This enzyme contains a macrocyclic tetrapyrrole-derived cofactor, F430, at the active site coordinating Ni(II) in the resting state. A Ni(I) state (Ni1F430) has been proposed as the active form of the cofactor. Extensive mechanistic and spectroscopic studies have been performed on the holoenzyme, isolated cofactor, and various synthetic model compounds. These studies are summarized in... 

Fascinating communities of methanogens, organisms that can use methane for a food source, have developed on these ice fields. These creatures live under great pressures, at extremely low temperatures, and with no light. But these unusual communities are not the major focus of interest in the methane ice fields. Scientists would like to "mine" this ice to use the methane as a fuel. In fact, the U.S. Geological Survey estimates that the amount of methane hydrate in the United States is worth over two hundred times the conventional natural gas resources in this country ... 

Figure 2 Theoretical temperature dependence of H2 activity, when maintained by methanogenic organisms operating at a constant free energy yield HCO3" + 4 H2 + -> CH4 + 3H2O at AGmp = -10 kJ mol Conditions HCOa = 10 M, CH4 = M H+ = 10 M, P = 1.0 bar.

Methanogen (Section 2 5) An organism that produces methane... 

The sulfite reductase from the hyperthermophilic methanogen Methanocaldococcus jannashii is able to reduce the otherwise toxic sulfite to sulfide that is required for growth. In contrast to most organisms that use nicotinamides and cytochromes as electron carriers, this organism uses a coenzyme p42o-dependent reductase (Johnson and Mukhopadhyay 2005). 

Pnre cnltnres of organisms that can oxidize propionate either in the presence of a methanogen or nsing snlfate as electron acceptor have been obtained. These include both Syntrophobacter wolinii and Syntrophobacter pfenigii (Wallrabenstein et al. 1995). The interaction of two organisms, therefore, is clearly not obligatory for the ability to degrade these carboxylic acids under anaerobic conditions. 

The procedure is particularly suited to the study of anaerobic transformations since there are no problems resulting from problems with oxygen limitation. A good example is provided by the application of C NMR to the intricate relations of fumarate, succinate, propionate, and acetate in a syntrophic organism both in the presence (Houwen et al. 1991), and in the absence of methanogens (Plugge et al. 1993 Stams et al. 1993). 

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