Sulfate respiration

The anaerobic decomposition of organic matter by fermentation, methanogenesis (methane formation) and sulfate respiration is exemplified in Table 3.2. 

As shown in Figure 6.8, the most important part of the anaerobic sulfur cycle in terms of the sulfate respiration process can be integrated with the anaerobic carbon cycle. A fractionation of the readily biodegradable substrate (Ss) into SF and SA fits well to the anticipation that mainly SF is used by the sulfate-reducing biomass in sewer biofilms. By integrating the sulfide formation in this way, a simple conceptual approach is obtained instead of the traditional empirical descriptions as depicted in Table 6.1. 

Sorenson, J., 1984. Seasonal variation and control of oxygen, nitrate and sulfate respiration in coastal marine sediments. In M.3. Klug and C.A. Reddy (eds), Current Perspectives in Microbial Ecology. American Society for Microbiology, Washington, D.C., pp. 447-453. 

In benthic environments, ranging from the rhizosphere of shallow water macrophyte communities such as Zostera, Thalassia and Spartim hundreds of different diazotrophic strains have been isolated, and these are typically microaerophyUic or anaerobic, and often are sulfate respiring bacteria. These diazotrophs make significant contributions to the nitrogen economy of their respective plant communities. 

Mafias PM, Coelho AV, Valente FM, Placido D, LeGall J, Xavier AV, Pereira lA, Carrondo MA. Sulfate respiration in Desulfovibrio vulgaris Hildenborough. Structure of the 16-heme cytochrome c HmcA AT 2.5-A resolution and a view of its role in transmembrane electron transfer. J. Biol. Chem. 2002 277 47907-47916. 

Wagner M., Roger A. J., Flax J. L., Brusseau G. A., and Stahl D. A. (1998) Phylogeny of dissimilatory sulfite reductases supports an early origin of sulfate respiration. J. Bacterial. 180, 2975-2982. 

Of more immediate geochemical relevance is the dissimilatory reduction of sulfate to hydrogen sulfide which is a major topic for discussion in Chapter 6.2. Sometimes called sulfate respiration the process involves oxidation of organic matter (or hydrogen) with the transfer of electrons to sulfate instead of oxygen as in the majority of respiratory systems. The process is accompanied by a net release of free enei which is utilized by the org m-ism for growth (e.g. eqn (1), Wake et al., 1977). 

Zehr, J., and Oremland, R. S. (1987). Reduction of selenate to selenide by sulfate-respiring bacteria experiments with cell suspensions and estuarine sediments. Appl. Environ. Microbiol. 53, 1365-1369. 

Since sulfate instead of oxygen serves as an oxidant for organic compounds like CH2O in the above back reaction, the dissimilatory process may be regarded as a form of anaerobic respiration or sulfate respiration. In the early Earth s history this reaction would have played a cmcial role as it would have been responsible for large-scale transformations of sulfide to sulfate in biological mediation of the sulfur cycle. 

Fig. 1.3. A schematic presentation of the mechanisms which yield energy and biosynthesize organic compounds by the sulfate respiration...

Fig. 1.11. A schematic presentation of the mechanisms which yield energy and biosynthesize organic compounds in the lithoautotrophic sulfate respiration. Note that organic compounds are oxidized with sulfate to yield energy, in the sulfate respiration shown in Fig. 1.3...

Liu M-C, Costa C, Coutinho IB, Moura I, Xavier AV, LeGall J (1988) Cytochrome components of nitrate- and sulfate-respiring Desulfovibrio desulfuricans ATCC 27774. J Bacteriol 170 5545-5551... 

Cadmium Sulfate Respirator, goggles, rubber gloves. Remove victim from exposure and call physician. Wash with soap and water. Rush with water for at least 10 minutes consult physician. 

A smaller amount of free energy is released from oxidation by nitrate than by O2, and under standard thermodynamic conditions, sulfate oxidation of H2 requires an uptake of free energy. Although living organisms do not operate under standard conditions (1 M concentration, pH 0), sulfate respiration always will be less energy producing than nitrate or O2. 

Fig. 40. Probable intermediate steps and dismutation reactions in the reduction of sulfur compounds during sulfate respiration, after references 36S and 438. The first reduction step, sulfate to sulfite, also requires ATP.

Free Energies and Reduction Potentials in Sulfate Respiration... 

Sulfate respiration is probably only a distant relative of the other types of respiration and photosynthesis. The sequence Clostridium-De-suljotomaculum Desuljovibrio represents a probable line of evolutionary development marked by increasing elaboration of cytochrome-using electron transport chains. 

The chief argument for unrelatedness is the dissimilarity of the cytochromes of sulfate respirers with those of other organisms. 

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