An improbable microbe, , has been glimpsed half a world away in California.
Candidatus Desulforudis audaxviator was found in water-filled fractures in South Africa鈥檚 deep gold mines, where it lives isolated from every other life form on Earth.
Uniquely, the bacterium has evolved to do without the sun鈥檚 energy, relying only on hydrogen and sulphate, which can form naturally in its subterranean home.
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Until recently, biologists thought that the species was confined to South Africa鈥檚 depths 鈥� although and in igneous crust below the sea floor.
Now, a project to map Earth鈥檚 deep biosphere 鈥� the 鈥� has found DNA 99 per cent identical to that of D. audaxviator tens of thousands of kilometres away, in boreholes 900聽metres deep near Death Valley in eastern California.
at the Desert Research Institute in Las Vegas, Nevada, discussed the find at the in San Francisco on 6 December. 鈥淲e鈥檙e reasonably sure we鈥檙e looking at the same bug,鈥� he says.
Life can find a way
If so, D. audaxviator 鈥� literally, 鈥渂old traveller鈥� 鈥� merits its name. If the bacterium came from South Africa, it probably started out at shallow depths and evolved to live in ever-greater isolation as it descended, says Moser. But then some bacteria may have made the return journey and reached the surface, perhaps through water springs. From there they may have surfed the winds before raining down on the US and begun to descend once more.
The scenario is certainly possible, says at Princeton University, who has worked extensively on the South African D. audaxviator populations.
Alternatively, the horizontal flow of water underground may allow deep microbes to colonise new regions without returning to the surface, says at the University of Southern California in Los Angeles. The move between South Africa and the New World must have happened before the Atlantic opened between them, though.
鈥淲e鈥檙e taught in school that all life needs some input from the sun,鈥� says Moser. 鈥淲hat we鈥檙e seeing in D. audaxviator is that even where the sun hasn鈥檛 shone for hundreds of millions of years 鈥� like the interior of Earth or Mars 鈥� life can find a way.鈥�
