Methanogens terminators

As a result, the partial breakdown of the organic matter by fermentation yields organic products with a low molecular weight, e.g., VFAs, along with C02. Compared with the aerobic respiration, the fermentation is inefficient however, these fermentation products can to some extent, and in addition to fermentable substrate, be used by the sulfate-reducing bacteria that make use of sulfate as the terminal electron acceptor (Nielsen and Hvitved-Jacobsen, 1988). In the absence of sulfate, the methanogenic bacteria utilize the low molecular... 

Anaerobic reduction of CO2 to CH4 Carbon dioxide can serve as terminal electron acceptor in anaerobic hydrogen respiration. The product of this reduction is methane when certain members of the domain Archaea, the methanogens, are involved ... 

Leuders, T., and Friedrich, M. W. (2003). Evaluation of PGR amplification bias by terminal restriction fragment length polymorphism analysis of smaU-subunit rma and mcra genes by using defined template mixtures of methanogenic pure cultures and soil DNA extracts. Appl. Environ. Microbiol. 69, 320-326. 

The findings clearly indicate that the last step of the CO2 reduction pathway, the reduction of CoM-S-S-HTP by H2, is a coupling site for ATP synthesis. It is concluded that CoM-S-S-HTP is the terminal electron acceptor ( = —200 mV) of a membrane-bound electron transport chain, with molecular H2 ( ° = -414mV) being the electron donor in hydrogenotrophic methanogens [115]. The physiological electron donor for CoM-S-S-HTP reduction is not known (Fig. 5). 

Analysis of the sequences located upstream of archaeal rRNA genes has shown that archaeal rRNA promoters consist of the sequence TTTA(A/T)A located 20-30 nucleotides upstream of the transcription initiation site and a weakly conserved sequence, (A/T)TG(A/C) around the transcription initiation site [40]. Transcription of the rRNA genes terminates within pyrimidine-rich regions in the extreme thermophiles [30,41], in pyrimidine-rich regions followed by a short hairpin loop in the methanogens [27,34] and in AT-rich regions preceded by a GC-rich region in the extreme... 

Transcription usually ends within or after pyrimidine-rich regions [120,141,145,150]. Among the methanogens, inverted repeats that might form stem-loop structures, reminiscent of the rho-independent terminators of bacteria, have been identified close to the termination sites [100]. Usually, there are multiple transcription stops in the archaea. 

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