SCIENTISTS have discovered live bacteria several miles below ground that have apparently lived off energy from the Earth's core for millions of years. Other researchers have previously reported microbes living at about 200 metres below the seabed, but this is the first time that live bacteria have been discovered at great depths in ancient granite rock.
The discovery of the deepest living organisms could upset existing theories on the origin of life, which invoke the importance of the Sun's energy in sustaining organisms. Unlike life-forms on the surface of the planet, the subterranean bacteria seem not to have relied on the Sun's energy for their survival. They could be a model for possible underground life on other planets, Thomas Gold, emeritus professor of astronomy at Cornell University, New York, said yesterday.
The amount of life existing deep underground could exceed that living on or near the Earth's surface, he said. 'We do not know at present how to make a realistic estimate of the subterranean mass of material now living, but all that can be said is that one must consider it possible that it is comparable to all the living mass at the surface . . . . There are certainly very major life-forms down there.'
There are at least ten other planets or their moons in the Solar System where similar subterranean microbes could exist, he said.
Ulrich Szewzyk, a microbiologist at Sweden's National Bacteriological Laboratory in Stockholm, has cultured several strains of new bacteria from samples of granite rock taken from a borehole at depths of between five and six kilometres, Professor Gold says in the current issue of the Proceedings of the National Academy of Sciences.
The borehole was drilled in an ancient crater in central Sweden called the Siljan Ring, caused by the impact of a massive meteorite millions of years ago. Because the rock is granite, and not sedimentary deposits such as sandstone, it is unlikely the microbes originated from life on the surface, Professor Gold said. The bacteria do not need oxygen and live at very high temperatures of about 100C.
Dr Szewzyk has written a 'very substantial' scientific paper on the discovery and, co-operating with Carl Woese, Professor of Microbiology at the University of Illinois, will submit it later this year to the US National Academy of Sciences for publication.
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