Bacteria frozen in permafrost for hundreds of thousands of years slowly respirate and repair their DNA, according to a report in the Proceedings of the National Academy of Sciences this week. The strategy may explain how life persists over geologic time scales, the authors say.Other scientists have claimed to recover viable microbes that have been trapped in amber, salt or buried deep within the earth for tens to hundreds of millions of years, but how these ancient bacteria remained alive for so long under extreme conditions has remained a mystery.Researchers have postulated that they persist as dormant endospores in which metabolic activity has all but ceased. But those resting cells would still be buffeted by physical and chemical degradation, said Eske Willerslev of the University of Copenhagen in Denmark, who led the current effort. DNA, in particular, would become fragmented unless it could be repaired."Many people, including myself, have...

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