"These bacteria are truly unique, in the purest sense of the word," said Lin, now at National Taiwan University. "We know how isolated the bacteria have been because analyses of the water that they live in showed that it's very old and hasn't been diluted by surface water. In addition, we found that the hydrocarbons in the environment did not come from living organisms, as is usual, and that the source of the hydrogen needed for their respiration comes from the decomposition of water by radioactive decay of uranium, thorium and potassium."
Because the groundwater the team sampled to find the bacteria comes from several different sources, it remains difficult to determine specifically how long the bacteria have been isolated. The team estimates the time frame to be somewhere between three and 25 million years, implying that living things are even more adaptable than once thought.
"We know surprisingly little about the origin, evolution and limits for life on Earth," said biogeochemist Lisa Pratt, who led Indiana University Bloomington's contribution to the project. "Scientists are just beginning to study the diverse organisms living in the deepest parts of the ocean, and the rocky crust on Earth is virtually unexplored at depths more than half a kilometer below the surface. The organisms we describe in this paper live in a completely different world than the one we know at the surface."
That subterranean world, Onstott said, is a lightless pool of hot, pressurized salt water that stinks of sulfur and noxious gases humans would find unbreathable. But the newly discovered bacteria, which are distantly related to the Firmicutes division of microbes that exist near undersea hydrothermal vents, flourish there.
"The radiation allows for the production of lots of sulfur compounds that these bacteria can use as a high-energy source of food," Onstott said. "For them,
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Contact: Chad Boutin
cboutin@princeton.edu
609-258-5729
Princeton University
20-Oct-2006