Microfossils bacteria

There is some hope, since certain sediments are thought to be produced only by biological activities. Obviously many of the involved reactions, if not mediated by biocatalysts would require the addition of too much time and heat. In these cases it is plausible to conclude that bacteria had provided the necessary catalysts. Especially, if a specific inorganic formation is found to be associated with organic chemofossils and microfossils, it is very likely a result of biological activities. This is exemplified by stromatolltic formations. When such deposits are found, one can deduce the nature of the biological activities from the characteristics of the mineral formation. 

Late Archaean stromatolites Younger stromatolites have been described from 3.0 Ga rocks at Steep Rock in Canada (Wilks St Nisbet, 1985), from the 2.7 Ga Cheshire formation of the Belingwe Greenstone belt (Martin et al., 1980) and from 2.52 Ga shelf carbonate sediments in the Campbellrand subgroup, South Africa. In this latter locality there are also well-documented calcified microfossils of cyanobacteria (Kazmierczak St Altermann, 2002). It is also possible that at this locality the mineralization of the dead bacteria was the result of the action of het-erotrophic bacteria. 

Plectonema terebrans, a species of filamentous marine cyanobacteria, accumulates gold in its sheath from an aqueous solution of AuCls. Sheaths are among the few stmctures likely to be preserved in some form in microfossils of ancient bacteria. In marine media, it is expected that AuCls (2.0 g Au/L) will formAuCl4, AuOJ, andAuClJ Biosorption of Au+, as AUCI4, by dried Pseudomonas strains of bacteria was inhibited by palladium, as Pd+, and possibly other metal ions. 

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