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Project Progress

Samples for genome analysis were collected at a depth of about 8,000 ft below the surface from a South African gold mine in the Witwatersrand Basin. DNA was extracted from fracture water that is inferred to be 3 million years old based on noble gas contents. DNA was extracted also from microbial biofilms that were collected from within a borehole previously exposed to oxygenated mine air. Analysis of 16s rDNA (Figure 1) in the groundwater samples demonstrated the dominant presence of a sulfate reducer and a methylotroph with a few other thermophilic microbes. The borehole biofilm sample showed a number of other species including methanogens and oxidizers of sulfur, ammonia, and methane, a finding consistent with contamination during exposure to mine air. In addition, DNA was extracted from groundwater after concentration of biomass on filters and was subjected to metagenome analysis by complete direct sequencing of all of DNA in the sample or community DNA sequencing. This deep-subsurface metagenome is currently being annotated for comparison to the 16s rDNA analyses. The dominant Desulfotomaculum-like organism in the Witwatersrand community appears to represent a new species and new family. This deep-subsurface organism contains a number of differences from other thermophiles and sulfate reducers which may be related to biosustainability in deep-subsurface environments. The microbial community analyses using 16s suggest that Witwatersrand microbes have synergistic energy flux relationships allowing them to collectively use a broad array of electron donors and electron acceptors. This synergism may contribute to microbial biosustainability in deep-subsurface environments.

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Highlights:

• 16s rDNA analysis of deep subsurface microbic community
• Metagenome sequence of deep subsurface microbic community