Monday, 13 Aug, 2007 Science
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Ancient Microorganisms May Revive in Melting Glaciers

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The DNA of ancient microorganisms frozen for millions of years in glaciers, may revive in the melting glaciers, as concluded by scientists at Rutgers, The State University of New Jersey.

According to Kay Bidle, an assistant professor of marine and coastal sciences at the university, until the present time the scientists didn't posses the exact information whether it is possible to revive the DNA of such ancient, for-centuries-frozen microorganisms. The scientists didn't know for what period of time cells could stay viable after they've been frozen. Bidle and his colleagues melted five samples of ice that were 100,000 - 8 million years old to discover the microorganisms kept inside the ice.

First, the researchers made sure that they were able to detect microorganisms at all – it turned out there were more organisms in the young ice samples than in the old ones. The scientists tried to grow the organisms in media, and were surprised to see that the younger microorganisms grew really fast and it was easy to recover them. The researchers plated the revived microorganisms and then isolated colonies. The young microorganisms doubled every few days, while those taken from the oldest ice samples grew very slowly, and doubled once in 70 days.

Moreover, the researchers were not able to identify the oldest growing microorganisms as their DNA deteriorated. The scientists concluded that the DNA in the five ice samples they examined proved to pass through an 'exponential decline' after 1.1 million years. It constrained the microbes' geological preservation in ice and the possible genetic material's exchange to the oceans. Still, the scientists have at their disposal the DNA left after 1.1 million years.

The researchers stopped their choice at Antarctic glaciers as the polar regions are exposed to greater cosmic radiation than the rest of the planet. The cosmic radiation makes the DNA blast into pieces over geologic time. As a result, the microorganisms are subject to irreversible damage.

The greatly deteriorated DNA in the old ice samples lead the researchers to one more significant conclusion - life on Earth could not be brought by a comet or other cosmic debris from outside our solar system. The microbes and their DNA preservation in icy comets could have resulted in genetic material's transfer among planets. However, if to take into account the extremely high levels of cosmic radiation in space, the results of the research suggest it is highly unlikely that life on our planet could have been seeded by genetic material from outside our solar system.

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