The New York Times, October 19, 2000, Thursday, Page A25

HEADLINE: Ancient Bacterium Is Reported Found

BYLINE:  By NICHOLAS WADE

    A bacterium that last flourished before dinosaurs tore flesh or the
Appalachian Mountains emerged has been revived from a drop of fluid
trapped in a crystal of rock salt for 250 million years, say biologists at
West Chester University in Pennsylvania. But their result was immediately
challenged by another biologist.

    The crystal was excavated from 1,850 feet below the earth's surface,
from the air duct supplying a radioactive waste dump deep underground near
Carlsbad, N.M., in the thick salt beds left by a vanished Permian-age
ocean.

       The authors of the new report are Dr. Russell H. Vreeland and Dr.
William D. Rosenzweig, together with Dr. Dennis W. Powers, a consulting
geologist from Anthony, Tex. In an article in today's issue of Nature,
they say they sterilized the surface of the salt crystal, one of 53 they
examined, and drilled into a tiny pocket of fluid trapped within it.  When
the fluid was mixed with nutrients, a lawn of bacteria appeared.

    Because the crystal was intact, and comes from a salt bed known to
have been formed 250 million years ago, the authors say they believe a
bacterium was "trapped inside a crystal at that time and survived within
the crystal until the present."

    Though other biologists claim to have isolated living bacteria from
ancient salt beds in Europe, some experts do not believe that DNA, the
genetic material, can survive for more than a few thousand years at best,
let alone millions.

    "I just find it a silly and unbelievable report," said Dr. Tomas
Lindahl, an expert on the stability of DNA who works at the Imperial
Cancer Research Fund in London.

    Dr. Bill Grant, a microbiologist at the University of Leicester in
England, said he found the new result plausible because he and others had
made living bacteria grow from salt beds as ancient as the one in New
Mexico. Though critics would always explain such results as contamination
of the sample by present day bacteria, the rigorous sterilization
procedures followed by the West Chester biologists was "nudging closer and
closer to the situation where you say it can't really be contamination,"
Dr. Grant said.

    DNA in living cells is under constant attack from chemicals and
radiation. Every cell in the human body loses 5,000 letters a day from the
sequence that makes up the genetic code, but the damage is repaired by a
suite of repair enzymes. After a cell dies, the DNA is usually degraded
although fragments of meaningful sequence can survive in special
conditions. Short DNA sequences about 40,000 years old have been recovered
from the bones of Neanderthals.

    Bacteria can form spores, a tough, hunkered down form in which most
metabolism stops. Dr. Lindahl said that spores could survive a few hundred
years, maybe even a few thousands, but not for longer. There are no active
repair enzymes in a spore, he said, and radioactivity alone would
eventually break the DNA into pieces that would make a spore no longer
viable.

    For even a spore to survive 250 million years is "just incredible,"
Dr. Lindahl said.

    The West Chester biologists found that one gene of the bacteria that
grew from their crystal was 99 percent similar to that of Bacillus
marismortui, a present day bacterium isolated from near the Dead Sea.

    Dr. Lindahl said the sequence similarity was evidence of contamination

because through evolution and random change a bacteria that lived 250
million years ago would have a very different DNA sequence from that of
present day bacteria.

    Despite the sterilization procedures undertaken by the West Chester
biologists, a present day bacteria might have survived in some invisible
crack in the crystal, Dr. Lindahl suggested.

    "I am sorry to see that Nature still publishes papers in this vein,"
he said, referring to previous reports of ancient DNA that have been
discredited.

    Dr. Henry Gee, a Nature editor, said that the experts he consulted
were "absolutely satisfied that this is a bacterium cultured from spores
deposited in a salt deposit some 250 million years ago."

    Dr. Rosenzweig said he believed that the bacterium from the crystal
survived as a spore. He said that it differed in three aspects of its
metabolism from Bacillus marismortui and that the similarity of one gene
did not mean that all were similar. In any event, the DNA sequence of the
gene in question might be almost identical to that of Bacillus marismortui
because that bacterium, too, he suggested, might have been trapped in salt
for millions of years and only recently released into the environment.

    He was unable to look for any spore or bacterium in the fluid trapped
in the crystal because to have placed the fluid under the microscope would
have exposed it to contamination, Dr. Rosenzweig said.

    In response to Dr. Lindahl's criticism, Dr. Rosenzweig said there were

no apparent cracks in the crystal. "All I can say is that our sterility
checks indicate there was no contamination here," he said.

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