[meteorite-list] Locked in Glaciers, Ancient Microbes May Return to Life

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Tue, 7 Aug 2007 14:05:04 -0700 (PDT)
Message-ID: <200708072105.OAA16797_at_zagami.jpl.nasa.gov>

http://ur.rutgers.edu/medrel/viewArticle.html?ArticleID=5898

Locked in Glaciers, Ancient Microbes May Return to Life
Rutgers, State University of New Jersey
August 06, 2007

New Brunswick, N.J. - The DNA of ancient microorganisms, long frozen in
glaciers, may return to life as the glaciers melt, according to a paper
published online this week in the Proceedings of the National Academy of
Sciences by scientists at Rutgers, The State University of New Jersey,
and Boston University. The article is scheduled to appear in the print
edition on Tuesday, Aug. 14.

The finding is significant, said Kay Bidle, assistant professor of
marine and coastal sciences at Rutgers, because scientists didn't know
until now whether such ancient, frozen organisms and their DNA could be
revived at all or for how long cells are viable after they've been
frozen. Bidle is lead author of the article, "Fossil Genes and Microbes
in the Oldest Ice on Earth."

Bidle and his co-authors, Rutgers colleague Paul Falkowski, SangHoon Lee
of Korea's Polar Research Institute and David Marchant of Boston
University - melted five samples of ice ranging in age from 100,000 to 8
million years old to find the microorganisms trapped inside.

The researchers wanted to find out how long cells could remain viable
and how intact their DNA was in the youngest and oldest ice.

"First, we asked, do we detect microorganisms at all?" Bidle said. "And
we did - more in the young ice than in the old. We tried to grow them in
media, and the young stuff grew really fast. We recovered them [the
microorganisms] easily; we could plate them and isolate colonies. They
doubled every couple of days." By contrast, Bidle said, the
microorganisms from the oldest ice samples grew very slowly, doubling
only every 70 days.

Not only were the microorganisms in oldest ice slow to grow, the
researchers were unable to identify them as they grew, because their DNA
had deteriorated. In fact, the DNA in the five samples examined showed
an "exponential decline" after 1.1 million years, "thereby constraining
the geological preservation of microbes in icy environments and the
possible exchange of genetic material to the oceans."

"There is still DNA left after 1.1 million years,' Bidle said. "But 1.1
million years is the 'half-life' - that is, every 1.1 million years, the
DNA gets chopped in half."

Bidle said the average size of DNA in the old ice was 210 base pairs -
that is, 210 units strung together. The average genome size of a
bacterium, by comparison, is 3 million base pairs.

The researchers chose Antarctic glaciers for their research because the
polar regions are subject to more cosmic radiation than the rest of the
planet and contain the oldest ice on the planet.

"It's the cosmic radiation that's blasting the DNA into pieces over
geologic time, and most of the organisms can't repair that damage."

Because the DNA had deteriorated so much in the old ice, the researchers
also concluded that life on Earth, however it arose, did not ride in on
a comet or other debris from outside the solar system. "...(T)he
preservation of microbes and their genes in icy comets may have allowed
transfer of genetic material among planets," they wrote. "However, given
the extremely high cosmic radiation flux in space, our results suggest
it is highly unlikely that life on Earth could have been seeded by
genetic material external to this solar system."

The five ice samples used in the experiment were taken from two valleys
in the Transantarctic Mountains by Marchant, the Boston University
glaciologist. "He sent us blocks of ice,' said Bidle of Marchant.
"Without them, we couldn't have done the work. Dave is also one of the
few researchers who is knowledgeable about the age of the ice, and also
important information about the formation and geology of the ice."

The actual melting of the ice, growing of microorganisms and examination
of DNA was carried out by Bidle and Lee, who was a visiting researcher
at Rutgers at the time. Falkowski co-directed the research and helped to
write the paper. The work was funded by a grant to Falkowski and Bidle
from the Gordon and Betty Moore Foundation.

Ken Branson
Media Relations
732-932-7084, ext. 633
E-mail: kbranson at ur.rutgers.edu
Received on Tue 07 Aug 2007 05:05:04 PM PDT