World's Oldest Known DNA Discovered

DNA from 419-million-year-old bacteria may have belonged to the descendants of the world's first life forms.

By Michael Reilly | Thu Dec 17, 2009 07:00 AM ET

It won't make Jurassic Park a reality, but scientists have discovered 419 million-year-old DNA intact inside ancient salt deposits.

The genetic material, the oldest ever found, belongs to salt-loving bacteria whose ancestors may have been among the first life forms on Earth.

Scientists have previously recovered similar genetic material from the Michigan Basin, the same region where the latest discovery was made. But the DNA was so similar to that of modern microbes that many scientists believed the samples had been contaminated.

Not so this time around.

A team of researchers led by Jong Soo Park of Dalhousie University in Halifax, Canada, found six segments of identical DNA that have never been seen before by science. Their work appears in the December issue of the journal Geobiology.

"We went back and collected DNA sequences from all known halophilic bacteria and compared them to what we had," Russell Vreeland of West Chester University in Pennsylvania said. "These six pieces were unique."

The team's finding reshuffles the family tree for salt-loving bacteria, organisms that trace their ancestors back to the dawn of life.

The first representative of the group, Halobacterium salinarum, was found living on a salt-cured buffalo hide in the 1930s. Scientists assumed it was a modern species, but the team's work has shown that H. salinarum is in fact a close genetic relative of bugs that lived between 121 and 419 million years ago.

Vreeland tracked down the origins of the buffalo skin and found that the salt probably came from a mine in Saskatchewan.

Rocks in the mine formed when a sea dried up around 300 million years ago, and Vreeland suspects those first H. salinarum spent the entire time living inside tiny brine-filled defects in salt crystals, waiting for the right moment to re-emerge.

It's a bold claim, but evidence suggests the creatures may be nature's Rip Van Winkles, hunkering inside salt deposits for eons until natural forces -- or in this case, humans -- bring them back to the surface.

"There is better and better evidence that these organisms can somehow survive for these amazing amounts of time," and then repopulate in the planet's vast saltwater basins whenever conditions allow, Melanie Mormile of Missouri University of Science and Technology said.

Salt-loving bacteria living underground have likely survived several mass extinctions, Vreeland said, only to re-seed the planet with life as conditions improved.

"It's a perfect example of how it's not just organisms staying alive, but how Earth has a way of keeping itself alive," he said.

From: http://news.discovery.com/earth/oldest-dna-bacteria-discovered.html