Microbe discovery that may be more precious than gold
David Brown / Washington Post | October 21 2006
THEY are the microbes from hell, or at least hell's postcode.
A team of scientists has found bacteria living almost three kilometres underground, dining on sulfur in a world of steaming water and radioactive rock - completely independent of the sun.
The organisms, which have been there for millions of years, will probably survive as long as the planet does, drawing energy from the stygian world around them.
Found in water spilling out of a fissure in a South African goldmine in 2003, they are among the most primitive life forms described, researchers reported in yesterday's issue of the journal Science.
What is unusual is that their underground home contains no nutrients traceable to photosynthesis, the sunlight-harnessing process that fuels all life on earth's surface. Such a community is an oddity on this planet - and is of interest to people looking for life on other ones.
"There is an organism that dominates that environment by feeding off an essentially inexhaustible source of energy, radiation," said Tullis Onstott, a geoscientist at Princeton University who led the team.
"The bottom line is: water plus rocks plus radiation is enough to sustain life for millennia."
The research was mainly done by Li-Hung Lin, of National Taiwan University.
Professor Li-Hung descended three times to the fissure in East Driefontein Gold Mine, south-west of Johannesburg, to get samples. It was 2.7 kilometres underground, and the temperature of the rock was 50 degrees.
The surfaces of other rocky bodies in the solar system are all too cold, too hot, too dry or too toxic to support the kind of life known on earth. But their subterranean environments are likely to be more hospitable and stable. More important, many may contain the shortlist of ingredients that seem to be all the South African microbes need.
"This is a very nice potential model of the habitability of Mars, Jupiter's Europa and other moons," said Steven D'Hondt, an astrobiologist at the University of Rhode Island.
"The sorts of ecosystems you could get there could certainly be something like this."
Mars is known to have both subsurface water and uranium. The findings of Professor Onstott's team suggest that even without volcanos to warm the Martian environment, organisms that evolved in a more temperate time might survive there.
"This really increases the likelihood that we will find life beneath the surface of Mars," Professor Onstott said.
For more than 20 years microbiologists have retrieved colonies of bacteria living hundreds thousands of metres below ground. Most of the environments contained carbon-based molecules from decayed plants or animals. The energy in those molecules' chemical bonds was all traceable to the sun.
The microbes from the South African mine appear to exist outside this food chain.
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