EXPERIMENTAL AND FIELD INVESTIGATIONS IN SEARCH OF BIOSIGNATURES IN EARLY PROTEROZOIC MANGANESE DEPOSITS
Preliminary analysis shows that both Bacillus subtilis and Escherichia coli DNA is preserved less over time in samples which contain up to 1000 ppm Mn(II). After two days of exposure to Mn(II) Bacillus subtilis showed near complete cell death in 10, 100, and 1000 ppm Mn(II), but DNA from ~106 microorganisms could still be recovered. Total lipids extracted from Bacillus subtilis samples showed a complete conversion to hydrocarbons (n-alkanes) after 72 days exposure to 1000 ppm Mn(II). Samples collected from Mamatwan Mine of the Kalahari Manganese Field have been microdrilled along a length of core and carbon isotopes have been analyzed. A range of carbonate carbon isotopic values from -6 δ13C to -15 δ13C have been documented. Further analysis using scanning electron microscopy coupled with energy-dispersive x-ray analysis has confirmed the presence of barite in the Kalahari samples, as well as nanometer-size tube structures of unidentified composition.