Old Salt

A West Chester U scientist finds ancient DNA — and new hope in the search for life on other planets.

by Andrew Thompson

The crystals and cinder-block-sized chunks of rock dug out of a cavernous salt mine in Michigan were really, really ancient, part of one of the oldest salt formations in the world. And Russell Vreeland knew that if those rocks contained any DNA, it too would be really, really old. What he found when he brought them back to the laboratory at West Chester University wasn't just old DNA; it was the oldest DNA ever discovered, clocking in at about 419 million years.

Popular scientists may be dismayed that the organism found by Vreeland, a professor of biology at WCU who led the team in Michigan, didn't have neon eyes or nine limbs. It was a microorganism called a haloarchaea, and the title of Vreeland's paper in the December 2009 issue of the journal Geobiology hardly heralds such a record-breaking event ceremoniously: "Haloarchaeal diversity in 23, 121 and 419 MYA salts."

So other than finding the oldest DNA in history, what's the big deal?

"It shows that there are systems that can protect DNA for that long; that DNA doesn't just fall apart after it's gone; that Earth does, in fact, preserve some of that stuff," says Vreeland. This means the prospect for finding evidence of life on now-lifeless planets is strong: Where there is water, there is salt. And where there is salt, there is a natural DNA preservative.

In fact, it may not have even been mere DNA that Vreeland found, but a living organism of a 400-million-year-old species, what Vreeland calls the "holy grail" sought after by every adventurous geomicrobiologist. Then again, it may not have been: The DNA strands recovered were 1,000 bases long, meaning that at the very least, it was preserved very well, and at most, there's a chance it was alive before they analyzed it."If they were alive ... the technique to extract the DNA would destroy the organism."

Vreeland can speculate a few rudiments of the haloarchaea — a salt-loving organism — from the DNA, but not much: It was probably red, probably a microbe and probably evolved into a similar type of organism seen in salt ponds today. That's about it.

What's more important is what it tells us about life today, and life in general: It hasn't changed much. Vreeland's team found a segment of the DNA molecule never before seen, which both helped to prove the specimen's age and made the study "the first time anyone has been able to track the evolutionary record of a group of microorganisms," says Vreeland.

But they also found a lot of DNA similar to what they see today, meaning that other than a few tweaks over hundreds of millions of years, a salt-loving microorganism today is much like it was back then. And on the most fundamental level, says Vreeland, this concept applies to pretty much everything on Earth.

"While the organisms have changed over the years — some of the big ones — some of the small ones have not," he says. "What has changed has been the topography of that life as opposed to vast differences in that life itself, and I think that's one of the big things scientists are starting to appreciate." In other words, a Tyrannosaurus rex is genetically similar to an emu. And the smaller you get on the scale of life,the more likely you are to find things haven't changed over time.

The discovery of the ancient organism has launched what Vreeland calls "the paleontology of microorganisms." Using the samples they found in Michigan, Vreeland and his team can return and pinpoint when and where these organisms existed. "What we can do now is go back to the salt formations and look at them and isolate more and more pieces of DNA and more and more organisms and other genes that may still be sitting there," says Vreeland. "And that would allow us to track microorganism development in the same way we track dinosaurs."

(andrew.thompson@citypaper.net)