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ENVIRONMENTAL POLLUTANTS
EAST LANSING, Mich. – Scientists at Michigan
State University have found an elusive microbe whose world-class
pickiness is a key to one of the most nagging concerns in the
cleanup of a common type of environmental toxin.
In this week's
issue of Science, researchers from MSU's Center for Microbial
Ecology report the discovery of a microbe dredged from the
bottom of the Hudson River that has an insatiable appetite to
break down the environmental pollutant TCA.
"TCA was one
of the remaining groundwater pollutants for which biodegradation
had not been resolved," said James Tiedje, a University
Distinguished Professor of microbiology and molecular genetics
and of crop and soil sciences. "Till now, there wasn't good
evidence there was a biodegradable solution."
That means the
bacterium shows promise as the missing piece of the puzzle to
clean up soil and groundwater that is contaminated by multiple
chlorinated solvents. Microbes that munch other toxins have been
isolated, but TCA-eating bugs have remained a mystery.
"For a
while, people didn't think this bug existed," said
postdoctoral student and co-author Baolin Sun. "Now we've
solved it."
TCA –
1,1,1-Trichloroethane – is a common industrial solvent that's
found in half of the U.S. Superfund sites. As a pollutant, it
packs a double punch, contaminating groundwater as well as
eroding the ozone layer when released into the atmosphere.
In the Science
article "Microbial Dehalorespiration with
1,1,1-Trichloroethane," Tiedje's team identified TCA1, an
anaerobic bacterium with a single-minded taste for TCA.
"This is the
first bacterium that breathes the chlorinated solvent TCA,"
said MSU doctoral student Benjamin Griffin. "It breathes
TCA, and the only way we know how to grow the bacteria is to
feed it TCA."
The MSU group
found TCA1 in the sediment of the upper Hudson River in New
York. The bacterium also occurs naturally in Michigan's
Kalamazoo River.
TCA1 handily
chows on the toxin, converting it to chloroethane, a less toxic
substance that can then be easily degraded by aerobic microbes
in soil. The beauty of the newly discovered bacterium is that it
does its work under water, preventing the toxin from escaping
into the atmosphere and causing ozone depletion.
Finding TCA1 and
understanding how to make it thrive is a first step in devising
ways to put the bacterium to work cleaning up contaminated sites
that until now were left with a piece of the puzzle unsolved.
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Source:
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Michigan State University
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Date:
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2002-11-04
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