Life From the Oldest Ice?

From ScienceNOW Daily News
6 August 2007

By Hannah Devlin

When Captain Robert Falcon Scott discovered the Dry Valleys as part of the British Antarctic Expedition in 1905, he described them as "valleys of the dead." But beneath their desolate, icy surface life goes on, according to a new study suggesting that microbes can remain alive for millions of years when frozen.

Previous studies of ancient ice samples taken from Antarctic subglacial lakes indicate that ice can preserve microorganisms for up to 300,000 years. In the new study, appearing online this week in the Proceedings of the National Academy of Sciences, molecular biologist Paul Falkowski of Rutgers University in New Brunswick, New Jersey, and his colleagues examined ice they had collected from the Upper Beacon Valley in Antarctica. They used a range of dating techniques, including measuring the isotope ratios in the ice, to show that samples ranged from about 100,000 years old to 8 million years old, making the latter ice the oldest sample ever studied.

After melting the samples that were 100,000 and 8 million years old, the researchers found signs of live bacteria in the water from both. Adding nutrients to the meltwater led to bacteria growth in both samples, although the microbes in the oldest ice grew much more slowly, doubling every 1 to 2 months versus every week. In another experiment examining how quickly DNA degenerates over time while frozen, the team examined any bits of DNA--whether from living or dead microbes--found within five ice samples of various ages.

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