Magazine article Natural History

Viruses on Ice

Magazine article Natural History

Viruses on Ice

Article excerpt

Viruses infect all life fortu-including microorganisms. Yet their evolutionary history is largely hidden from us, because few traces of early viruses have endured the passage of time. The recent fortuitous discovery of ancient viral genetic sequences preserved in an ice core provides a rare snapshot of the past.

In the mountains of Canada's Northwest Territories, researchers uncovered layers of caribou dung sandwiched within ice more than five feet below the surface. As revealed by radiocarbon techniques, the dung dates from 700 to as much as 4,400 years ago. Historically, caribou have retreated to alpine ice patches during summer months to escape heat and diminish insect bites. Virologist Eric Delwart of the Blood Systems Research Institute in San Francisco and the University of California, San Francisco, together with an international team of fifteen researchers, recovered genetic material from 700-year-old caribou feces found in a permanently frozen ice patch.

They team created a large library of the random fragments of ancient genetic material-some of which turned out to come from ancient viruses, not from caribou or caribou gut bacteria. They then compared the genetic sequences with those of other viruses, including viruses found in modern-day caribou feces. The researchers recovered genetic material from two unknown viruses: the complete small circular genome of a DNA virus-which they called ancient caribou feces associated virus (aCFV)-and the partial genome of an RNA virus, ancient Northwest Territories cripavirus (aNCV). …

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