Heterotrophs methanogens

Heterotrophic methanogens use acetate directly for biosynthesis and as an energy source. During this process, methanogens convert acetate to carbon dioxide and methane by utilizing a different biochemical pathway than the autotrophic methanogens. The sequence of reactions involved are as... 

In combination with Eh, pH strongly influences the types of bacteria that will be present. High- to medium-pH, low-Eh environments will generally restrict bacterial populations to sulfate reducers and heterotrophic anaerobes.187 In reducing conditions, pH strongly affects whether methanogenic or sulfate-reducing bacteria predominate.43... 

Glu 6, a major constituent of dissolved free amino acids (DFAA) in marine sediments [71], has been detected in red algae (Rhodophyta) [72] and as a potential osmolyte in several marine bacteria, for example obligatory aerobic heterotrophs [70] and methanogenic archaebacteria [8], N-methyl-/ -glutamate has been reported solely as a natural product from the cyanobacterium Prochloron didemni [96]. 

In comparison to all other heterotrophs, the microorganisms oxidizing methane and other Cj compounds such as methanol, have a unique metabolic pathway which involves oxygenase enzymes and thus requires O. Only aerobic methane-oxidizing bacteria have been isolated and studied in laboratory culture, yet methane oxidation in marine sediments is known to take place mostly anaerobically at the transition to the sulfate zone. Microbial consortia that oxidize methane with sulfate have in particular been studied at methane seeps on the sea floor and the communities can now also be grown in the laboratory (Boetius et al. 2000 Orphan et al. 2001 Nauhaus et al. 2002) Anaerobic methane oxidation is catalyzed by archaea that use a key enzyme related to the coenzyme-M reductase of methanogens, to attack the methane molecule (Kruger et al. 2003 see Sect. 5.1). The best studied of these ANME (ANaerobic MEthane... 

Several micronutrients such as molybdenum, nickel, boron, iron, zinc, vanadium, and cobalt have been shown to affect the microbial activities, especially of methanogens, but to a lesser extent of heterotrophs. The bioavailability of many of these trace metals is affected by the redox and pH of wetland soils. The significance of micronutrient deficiency in microbial processes in wetlands is not well understood. (Howarth, 1993 Megonigal et al., 2004). 

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