Sulphate/sulphide bacterial reduction

Bacterial reduction of sulfate in an anaerobic environment with large isotope fractionation between the residual sulphate and the sulphide is the source of sulphur and sulphide in many deposits. The recognition that many sulphur... 

Some isotope fractionations, notably those in biological systems, are primarily controlled by kinetic effects. For example, the bacterial reduction of seawater sulphate to sulphide proceeds 2.2 % faster for the light isotope than for S. -/For the reactions... 

To summarize, the isotopic and textural evidence collectively implies the activity in the Belingwe belt of a variety of prokaryotic processes (1) sulphate reduction and possibly photosynthetic sulphide oxidation (2) operation of rubisco both in cyanobacterial stromatolites (as expected) but also possibly in non-photosynthetic sulphur-bacterial mats (3) oxygenic photosynthesis (in stromatolites) (4) methanogenesis and methane oxidation. Most probably, other sulphur-based metabolic reactions (e.g. dissim-ilatory sulphate reduction) were also taking place. This complexity is consistent with the relative timing of the metabolic phylogeny deduced from rRNA studies (Woese 1987 Pace 1997). 

White. C., and Gadd, G. M. (1996b). A comparison of carbon/energy and complex nitrogen sources for bacterial sulphate-reduction potential applications to bioprecipitation of toxic metals as sulphides. J. Ind. Microbiol. 17, 116-123. 

The inter-dependency of bacterial species has been described for a number of cases. One example is the close dependency of sulphate-reducing bacteria on the presence of an associated heterotrophic microflora which supply the bacteria with additional growth factors and favour reduction of the medium (Cahet, 1965, 1966 LeGall and Postgate, 1974). Moreover, the production of hydrogen sulphide binds them to sulpho-oxidisers within the ecosystem (called sulphuretum by Baas-Becking, 1925). 

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