As terminal electron acceptor

In 1987, the iron-sulfur clusters Fa and Fb acting as terminal electron acceptors in photosystem I have been shown to be located on a... 

Cervantes FJ, W Dijksma, T Dnong-Dac, A Ivanova, G Lettinga, JA Field (2001) Anaerobic mineralization of toluene by enriched sediments with qninones and hnmus as terminal electron acceptors. Appl Environ Microbiol 67 4471-4478. 

Lie TJ, W Godchaux, JR Leadbetter (1999) Sulfonates as terminal electron acceptors for growth of sulfite-reducing bacteria (Desulfitobacterium spp.) and sulfate-reducing bacteria effects of inhibitors of sulfidogenesis. A / Environ Microbiol 65 4611-4617. 

Lin WC, MV Coppi, DR Lovley (2004) Geobacter sulfurreducens can grow with oxygen as terminal electron acceptor. Appl Environ Microbiol 70 2525-2528. 

Tetrachoroethylene (perchloroethylene, PCE) is the only chlorinated ethene that resists aerobic biodegradation. This compound can be dechlorinated to less- or nonchlorinated ethenes only under anaerobic conditions. This process, known as reductive dehalogenation, was initially thought to be a co-metabolic activity. Recently, however, it was shown that some bacteria species can use PCE as terminal electron acceptor in their basic metabolism i.e., they couple their growth with the reductive dechlorination of PCE.35 Reductive dehalogenation is a promising method for the remediation of PCE-contaminated sites, provided that the process is well controlled to prevent the buildup of even more toxic intermediates, such as the vinyl chloride, a proven carcinogen. 

Mitochondria from body wall muscle and probably the pharynx lack a functional TCA cycle and their novel anaerobic pathways rely on reduced organic acids as terminal electron acceptors, instead of oxygen (Saz, 1971 Ma et al, 1993 Duran et al, 1998). Malate and pyruvate are oxidized intramitochondrially by malic enzyme and the pyruvate dehydrogenase complex, respectively, and excess reducing power in the form of NADH drives Complex II and [3-oxidation in the direction opposite to that observed in aerobic organelles (Kita, 1992 Duran et al, 1993 Ma et al,... 

These findings lead to (he conclusion that the reduction of MHb by its reductase requires a natural cofactor, which is abolished during the purification procedure and can be replaced by methylene blue (G5, H22, H23, K8, K14). Since methylene blue and the other effective dyes are redox intermediates, it is obvious that the postulated cofactor interacts in the electron transport sequence of the MHbR reaction (H23). This is confirmed by the finding that oxygen and cytochrome c serve as well as terminal electron acceptor as does MHb (H22, H23, K14). Nevertheless, it had been possible to separate a cytochrome c reductase from MHbR in yeast extracts (A6). 

Whereas the novel F thermautotrophicus" strains can reduce only Fe(III) among the tested ions, others such as B. infernus, T. siderophilus, and D. thermophilus can use Mn(IV) as terminal electron acceptor, and, similar to... 

Anaerobic metabolism occnrs nnder conditions in which the diffusion rate is insufficient to meet the microbial demand, and alternative electron acceptors are needed. The type of anaerobic microbial reaction controls the redox potential (Eh), the denitrification process, reduction of Mu and SO , and the transformation of selenium and arsenate. Keeney (1983) emphasized that denitrification is the most significant anaerobic reaction occurring in the subsurface. Denitrification may be defined as the process in which N-oxides serve as terminal electron acceptors for respiratory electron transport (Firestone 1982), because nitrification and NOj" reduction to produce gaseous N-oxides. hi this case, a reduced electron-donating substrate enhances the formation of more N-oxides through numerous elechocarriers. Anaerobic conditions also lead to the transformation of organic toxic compounds (e.g., DDT) in many cases, these transformations are more rapid than under aerobic conditions. 

Anaerobic conditions often develop in hydrocarbon-contaminated subsurface sites due to rapid aerobic biodegradation rates and limited supply of oxygen. In the absence of O, oxidized forms or natural organic materials, such as humic substances, are used by microorganisms as electron acceptors. Because many sites polluted by petroleum hydrocarbons are depleted of oxygen, alternative degradation pathways under anaerobic conditions tend to develop. Cervantes et al. (2001) tested the possibility of microbially mediated mineralization of toluene by quinones and humus as terminal electron acceptors. Anaerobic microbial oxidation of toluene to CO, coupled to humus respiration, was demonstrated by use of enriched anaerobic sediments (e.g., from the Amsterdam petroleum harbor). Natural humic acids and... 

Amazingly, some microorganisms are capable of using halogenated compounds as terminal electron acceptors (McCarty, 1997 Schumacher etal., 1997 Fetzner, 1998 Wohlfarth and Diekert, 1999). This amounts to these bacteria using compounds like tetrachloroethene instead of O2, NO3, or SO4- to breathe ... 

On the basis of this model, Lovley et al. (17) argued that reductive dissolution of ferric oxides must be a microbiological process because the zone of sulfide generation is distinct from the zone of maximum ferric oxide reduction. Highly eutrophic environments would be an exception. In these systems the zone of decomposition with oxygen as terminal electron acceptor directly overlies the zone of sulfate reduction. 

The respiratory systems of bacteria are of especial interest1435 and complexity in view of their ability in some cases to use alternative substrates as terminal electron acceptors, depending upon the environmental conditions. This will be illustrated with reference to E. coli, which has been reviewed recently.1436 The advantage of studying respiration in this organism is that, by choice of growth conditions, the pathways of electron transport can be manipulated. In addition, mutants are available which are defective in certain respiratory components. 

DOM can also act as an electron acceptor for biotically mediated oxidation reactions. Many active microorganisms, particularly phototrophs, produce reductants in excess of metabolic needs that must be regenerated by transfering electrons to acceptors in the environment via membrane-spanning reductases (Price and Morel, 1990). It has been discovered that some iron-reducing bacteria use humic and fulvic acids as terminal electron acceptors for their respiratory transport systems (Coates et al., 1998). 

These findings underscore the unique nature of the microbody-like particles of T. foetus. In contrast to mitochondria or peroxisomes, in which electron transfer is directed toward molecular oxygen, they utilize protons as terminal electron acceptors and thus produce molecular hydrogen. We propose the term hydrogenosome to designate this new biochemically defined subcellular entity. (p. 7728 in Lindmark and Muller 1973)... 

That is why anaerobic respiration, based on nitrate as a terminal electron acceptor, is more similar to oxygen-based (aerobic) respiration than it is to fermentation and is why it must by definition be clearly distinguished from the latter. The great pioneer in this area, Louis Pasteur, first and simply defined fermentation as life in the absence of oxygen. But today, a century after his pathbreaking work, fermentations are more precisely defined as those metabolic processes that occur in the dark and do not involve respiratory chains with either oxygen or nitrate as terminal electron acceptors. 

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