DNA >99% identical to that of candidatus Desulforudis audaxviator was found in the U.S. Great Basin—half a world away from the organism’s best known home beneath South Africa . Duane Moser of the Desert Research Institute in Nevada made the discovery through his research project associated with the DCO’s Census of Deep Life (CoDL), which is mapping Earth’s deep biosphere. Moser’s CoDL project is investigating microbial ecosystems beneath two North American geological provinces (the Canadian Shield and the Basin and Range), both of which have been little explored for microbiology in the past.
Candidatus D. audaxviator appears to dominate isolated microbial communities in the water-filled crystalline rock fracture systems that scientists have accessed via the world’s deepest mines in South Africa, up to 4 to 5 kilometers below surface. Although relatives (e.g., about 95% identity) are prominent in subseafloor habitats, with very few exceptions, South Africa’s Witwatersrand Basin has been the generally accepted geographic limit of D. audaxviator at the species level.
Moser’s CoDL study found the organism, which relies primarily on hydrogen and sulphate, in boreholes 900 meters deep near Death Valley in eastern California. The finding, which Moser reported at the 2012 Fall AGU Meeting, gives the microbiology community the opportunity to consider a number of fascinating possibilities for such close microbial relations to exist so far apart.
Figure: Southam, G. (University of Queensland); Wanger, G. (J. Craig Venter Institute)