Sulphur isotopes Belingwe belt

Grassineau N. V., Nisbet E. G., Bickle M. J., Fowler C. M. R., Lowry D., Mattey D. P., Abell P., and Martin A. (2001) Antiquity of the biological sulphur cycle evidence from sulphur and carbon isotopes in 2700 million year old rocks of the Belingwe belt, Zimbabwe. Proc. Roy. Soc. London B268, 113-119. 

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). 

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