600,000-year-old bacteria found

The oldest living thing has been discovered in the form of 600,000-year-old bacteria extracted from ice cores, scientists claim. The finding gives hope that if Mars or other frigid worlds ever supported life similar to these ancient bacteria, they might be alive still. The trick, the discovery suggests, is for organisms to keep some metabolism going over the millennia, so that they can keep their DNA in repair while awaiting a more favorable environment in which to multiply. The other approach, complete dormancy, would cause DNA to be damaged and perhaps destroyed over such long periods of time. The scientists isolated long chains of active DNA from the bacteria. "The colder you make the environment, the longer [DNA] survives," said study team member Thomas Gilbert of the University of Copenhagen. "In places like Mars and [Jupiter's moon] Europa, which are really, really cold, DNA may very well be surviving there for a hell of a long time." Recently in separate work, scientists collected the oldest ever recovered DNA, estimated to be up to 800,000 years old, below more than a mile of Greenland ice. However, the DNA was not active inside a living organism. The new discovery involves extremely persistent life.

The secret to the longevity of the bacteria and DNA, the scientists write in the current issue of the Proceedings of the National Academy of Sciences, is the capacity of the DNA to continuously repair itself as it degrades over time. Sarah Stewart Johnson of MIT and her colleagues uncovered the bacteria from cores drilled in northeastern Siberia, northwestern Canada and Antarctica. They isolated genetic material from the samples, finding the DNA was relatively intact. "Normally with old samples of this kind of age, if you get any DNA at all, which is unlikely, you'll be getting maybe 30, 40, 50, maybe 100 nucleotide sequences," Gilbert told LiveScience. "Here they were getting 4,000 base pairs, no problem, which suggests the DNA is pretty good."