Cool DNA

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Science  16 Jul 1999:
Vol. 285, Issue 5426, pp. 327
DOI: 10.1126/science.285.5426.327a

Scientists say they have, for the first time, extracted DNA from ancient ice core samples in northern Greenland. The success may usher in a hunt for microbes trapped in ice around the world.

A team led by evolutionary biologist Peter Arctander of Copenhagen University used the polymerase chain reaction (PCR) to amplify fragments of a well-characterized ribosomal gene in ice cores dated to 2000 and 4000 years ago. After sequencing the recovered fragments, they compared them to known sequences in a database and found that the ice cores held the remains of a surprising diversity of lifeforms: at least 57 distinct organisms, including fungi, algae, protists, and a class of conifer, they report in the 6 July issue of the Proceedings of the National Academy of Sciences.

“No one expected such a variety of fungi to be present,” says Andrea Gargas of the University of Wisconsin, Madison, a specialist on fungal DNA. “You always think of the [arctic] environment as a bit more sterile because it's so remote and because of the lack of nutrients.” And there's more to come, says Arctander: So far they've only toted up the eukaryotic organisms—those with nuclei. The number of bacterial species, he says, should be far greater.

The study of ancient life in ice cores mostly has been limited to the identification of plant pollen and spores, but PCR has opened up a wealth of new possibilities, says Arctander. Members of his team have further probes planned, including a look at the DNA of plant material in 6000-year-old Greenland ice, to see what was available at the time when people are thought to have first migrated there from Canada.

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