Microbial sulfate reduction

Pallud, C. and P. Van Cappellen, 2006, Kinetics of microbial sulfate reduction in estuarine sediments. Geochimica et Cosmochimica Acta 70, 1148-1162. 

Rouxel O, Galy A, Elderfield H (2006) Germanium isotope variations in igneous rocks and marine sediments. Geochim Cosmochim Acta 70 3387-3400 Rouxel O, Ono S, Alt J, Rumble D, Ludden J (2008) Sulfur isotope evidence for microbial sulfate reduction in altered oceanic basalts at ODP Site 801. Earth Planet Sd Lett 268 110-123 Rozanski K, Sonntag C (1982) Vertical distribution of deuterium in atmospheric water vapour. Tellus 34 135-141... 

Shen Y, Buick R (2004) The antiquity of microbial sulfate reduction. Earth Sci Rev 64 243-272 Sheppard SMF (1986) Characterization and isotopic variations in natural waters. In stable isotopes in high temperature geological processes. Rev Miner 16 165-183 Sheppard SMF, Epstein S (1970) D/H and 0 /0 ratios of minerals of possible mantle or lower crustal origin. Earth Planet Sci Lett 9 232-239... 

Wortmann UG, Bemasconi SM, Bdttcher ME (2001) Hypersulfldic deep biosphere indicates extreme sulfur isotope fractionation during single-step microbial sulfate reduction. Geology 29 647-650... 

Wortmann UG, Chemyavsky B, Bemasconi SM, Bmnner B, Bottcher ME, Swart PK (2007) Oxygen isotope biogeochemistry of pore water sulfate in the deep biosphere dominance of isotope exchange reactions with ambient water during microbial sulfate reduction (OOP Site 1130). Geochim Cosmochim Acta 71 4221 232... 

These examples convincingly demonstrate that specific OSC are formed during the early stages of diagenesis by reactions of reduced sulfur species with specific biogenic substrates. The reactive substrates are proposed to contain either carbon-carbon double bonds or other reactive functional groups that react with either hydrogen sulfide or polysulfides to form the OSC (88). These views are consistent with evidence from sulfur isotopes that H2S produced by microbial sulfate reduction is the major source of reduced sulfur in sediments... 

Sulfur isotopes can effectively be used to examine important geochemical processes associated with redox changes in sedimentary environments. The speciation of sulfur is strongly affected by redox potential, pH, productivity, microbial sulfate reduction, and iron availability (Berner, 1984). More details are provided on the sulfur cycle in chapter 12. In general, during microbial dissimilatory sulfate reduction there is fractionation of sulfur... 

Schroth M. H., Kleikemper J., Bollinger C., Bemasconi S. M., and Zeyer J. (2001) In situ assessment of microbial sulfate reduction in a petroleum-contaminated aquifer using push-pull tests and stable sulfur isotope analyses. J. Contamin. Hydrol. 51, 179-195. 

It is not surprising that the geochemical cycle of sulfur during the I0W-O2 Archean differed from that of the present day. As shown in Figure 5, the mass-dependent fractionation of the sulfur isotopes in sedimentary sulfides was smaller prior to 2.7 Ga than in more recent times. Several explanations have been advanced for this observation. The absence of microbial sulfate reduction is one. However, the presence of... 

Konopka A., Gyure R. A., Doemel W., and Brooks A. (1985) Microbial sulfate reduction in extremely acid lakes. Purdue University Water Resources Research Center, Technical Report 173, West Lafayette, pp. 1—50. 

Alt J. C. and Shanks W. C. (1998) Sulfur in serpentinized oceanic peridotites serpentinization processes and microbial sulfate reduction. J. Geophys. Res. 103, 9917-9929. 

Bak F. and Pfennig N. (1991) Microbial sulfate reduction in littoral sediment of Lake Constance. FEMS Microbiol. Ecol. 85, 31-42. 

Elsgaard L., Jannasch H. W., Isaksen M. F., Jorgensen B. B., and Alayse A. M. (1994) Microbial sulfate reduction in deep-sea sediments at the Guay mas Basin hydrothermal vent area influence of temperature and substrates. Geochim. Cosmochim. Acta 58, 3335-3343. 

Fortin D. and Beveridge T. J. (1997) Microbial sulfate reduction within sulfidic mine tailings formation of diageneticFe sulfides. Geomicrobiol. J. 14, 1-21. 

SRB are essentially ubiquitous in aqueous environments that contain organic carbon and sulfate (e.g., subsurface aquifers and lake sediments). Moreover, analysis of a key gene associated with sulfate reduction (dissimilatory sulfite reductase) indicates that microbial sulfate reduction is an ancient trait, suggesting that organisms may have contributed to sulfide mineral formation throughout much of Earth history (Wagner et al. 1998). SRB are tolerant to environmental extremes of heat (some are hyperthermophiles) and salinity (some are halophiles). 

Table II summarizes the results for degradation of the CP isomers in East River cultures under sulfate-reducing conditions based on the stoichiometry in equation 11. Sulfate loss in the background controls were subtracted from the cultures to which CPs were added. As noted in Table II, the measured sulfate depletion corresponded to that calculated and provided evidence that CP metabolism was coupled to sulfate reduction. In these studies sulfate reduction is supported by two additional experimental observations. First, molybdate, which is a specific inhibitor of microbial sulfate reduction, was documented to stop the CP degradation. Active controls that did not receive molybdate continued to degrade CP. Second, radiolabeled 35S042 formed 35 S2 in active cultures and not in control cultures (33).

Sulfur isotope fractionation is important in the study of atmospheric gases, sulfur in the oceans (Section 5.4.4.1) and in living organisms. Microbes use 32S in preference to 34S during microbial sulfate reduction providing a sulfur isotope fingerprint for a... 

Microbial sulfate reduction is known from 3.47 Ga barites, from North Pole, Australia (Shen Buick, 2004). Petrological arguments constrain the temperature of sulfate reduction to below about 60°C and so limit the type of sulfate reducing bacteria to mesophiles. This argument is used to place sulfate reducing bacteria just above Thermodesulfobacterium.on the RNA tree (Shen Buick, 2004). There are important implications in this finding, for sulfate reduction is a complex metabolic process. This means that even by 3.47 Ga microbes had developed many of the key cellular systems found in their modern relatives and implies that even at 3.47 Ga they had had a long history. 

In this chapter I will propose a kinetic estimate for the thermodynamics of reactions like Eq (lb). The solid phases listed in Table 1 may act as a reductant or an oxidant. One of the prominent geochemical electron donors is pyrite. From an estimate of global pyrite weathering of 36 Tgy"1 (Garrels et al., 1973) we may deduce an average electron flux on the land surface in the order of 0.02 mol m 2 y1. At redox boundaries in salt marshes and in lake sediments microbial sulfate reduction will intensify this electron cycling. Luther (Chapter 6, this volume) discusses the details of sulfide redox mechanisms. 

Sulfur is treated in Chapter 13 and discussed only briefly here. The dominant reaction in the sedimentary sulfur cycle is microbial sulfate reduction. This gives rise to the formation of hydrogen sulfide which, by precipitating iron as "black unstable sulfide", will give the reduced sediment its characteristic blackish color ... 

Aharon, P. and Fu, B. (2000) Microbial sulfate reduction rates and sulfur and oxygen isotope fractionations at oil and gas seeps in deepwater Gulf of Mexico. Geochimica et Cosmochimica Acta, 64, 233—246. 

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