Electron donors, sulfate-reducing bacteria

To establish the stoichiometry of the sulfide formation, Equation (6.3) must be combined with the oxidation process for the organic matter that is the actual electron donor for the heterotrophic sulfate-reducing bacteria. The procedure for the combination of the oxidation and the reduction process steps is the same as outlined in Section 2.1.3. If organic matter is considered simply as CH20, the combination of the oxidation process as depicted in Example 2.2 and the reduction reaction for sulfate shown in Equation (6.3) result in the following redox process ... 

Sulfate-reducing bacteria are able to use a variety of organic compounds as both electron acceptors and electron donors. For example, Desulfovibrio species can ferment fumarate or malate, but will reduce these species to succinate if an additional electron donor is available (Miller and Wakerley, 1966). 

Smith R. L. and Klug M. J. (1981) Electron donors utilized by sulfate-reducing bacteria in eutrophic lake sediments. Appl. Environ. Microbiol. 42, 116—121. 

Biebl, H. and Pfennig, N., 1977. Growth of sulfate-reducing bacteria with sulfur as electron donor. Arch. Microbiol., 112 115—117. 

In the sulfate-reducing bacteria there is another cytochrome which resembles cytochrome c3 in the spectral properties and redox potential but differs from this cytochrome in molecular mass this is cytochrome c3 (26 kDa) which has eight heme C molecules in the molecule. The cytochrome molecule is composed of two polypeptides of 13 kDa (Loufti et al., 1989). On the basis of the amino acid sequence, however, the 13 kDa polypeptide differs from cytochrome c3 (Guer-lesquin et al., 1982 LeGall and Peck, 1987 Loufti et al., 1989). Desulfovibrio gigas cytochrome c3 (26 kDa) molecule is composed of two 13 kDa molecules bound to each other by an S-S bond (Bruschi et al., 1996). It is claimed that cytochrome c3 (26 kDa) is very effective as the electron donor for thiosulfate reductase (Hat-chikian et al., 1972). 

Apart from microenvironments, an explanation for the concurrent dissimilatory sulfate and iron reduction was provided by Postma and Jakobsen (1996). They demonstrated that the stabilities of iron oxides are decisive with respect to iron and/or sulfate reduction assuming that the fermentative step and not the overall energy yield is overall rate limiting. Additionally, it shall be noted that the typical sulfate reducing bacteria Desulfovibrio desulfuricans was found to reduce iron oxide enzymatically contemporarily or optionally (Coleman et al. 1993). When only very small concentrations of as sole electron donor were available iron oxide instead of sulfate was used as electron acceptor by D. desulfuricans. 

Can sulfate-reducing bacteria utilize complex carbon compounds as electron donors during sulfate reduction ... 

In the H2 reactor, sulfate-reducing bacteria convert ZnS04(aq) ZnS(s) using H2 as an electron donor. 

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