Aug. 28, 2007 — Scientists say they can at last explain how bacteria stay alive in ice for hundreds of thousands of years.
Bacteria slow down their metabolism to the point where they produce just enough energy to repair their aging DNA, say Australian researcher Mike Bunce of Murdoch University in Perth and his international colleagues.
The researchers publish their findings today in the Proceedings of the National Academy of Sciences.
"We're looking at bacteria that have survived in the permafrost for hundreds of thousands of years. These aren't dead; these are viable cells," said Bunce, a molecular biologist.
"If the DNA wasn't being repaired the bacteria would accumulate too much damage to their genome and the cells just would not be viable."
The researchers collected bacteria in soil samples from the Siberian permafrost, put the samples in sealed containers and detected the release of carbon dioxide.
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"You can see they are actually respiring," said Bunce. "Samples up to about 600,000 years actually showed viable bacterial populations."
The researchers also extracted intact strands of bacterial DNA, which also supports the idea that they are alive.
"The longest ancient DNA study that's ever been produced got 1,000 base pairs of DNA from a dead specimen," says Bunce. "We're getting 4,000 base pairs."
Scientists already know bacteria can survive for many years in harsh conditions by switching off their metabolism, and protecting themselves in a hard coat called an endospore.
