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Old 16-09-2003, 04:20 AM
David Kendra
 
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Default UGA researchers use transgenic trees to help clean up toxic waste site

UGA researchers use transgenic trees to help clean up toxic waste site

Contact: Kim Carlyle

706-583-0913
University of Georgia

Can genetically engineered cottonwood trees clean up a site contaminated
with toxic mercury? A team of researchers from the University of Georgia -
in the first such field test ever done with trees - is about to find out.

The results could make clearer the future of phytoremediation - a
technique of using trees, grasses and other plants to remove hazardous
materials from the soil. UGA scientists and city officials in Danbury,
Conn., planted on July 16 some 60 cottonwoods with a special gene at the
site of a 19th-century hat factory in that northeastern city.

"We hope to see a significant difference in the levels of mercury in the
soil within 18 months, perhaps as much as a twofold reduction," said
Richard Meagher, professor of genetics at UGA.

The field test is a collaboration between UGA, Western Connecticut State
University, Applied PhytoGenetics, Inc., of Athens and the City of
Danbury.

While the technology now being used in Danbury does not apply to all
sites, mercury pollution is a pervasive problem in Georgia as it is
elsewhere. The site of a former chemical factory near Brunswick, for
example, is polluted with mercury and other toxic chemicals. Mercury
contamination has been reported around the sites of former gold mines in
north Georgia, and advisories have been issued during the past decade for
mercury-contaminated fish in more than 80 streams, lakes and creeks in the
state.

Meagher's team did the first-ever field trial of a genetically engineered
plant to sequester mercury when it grew transgenic tobacco in a New Jersey
field trial in 2001, but this is the first such trial using trees, whose
larger root systems and year-round life cycle makes them better candidates
for long-term cleaning of polluted soil.

Phytoremediation is a relatively new field and one gaining international
interest. A team of photographers working for National Geographic, for
instance, recently spent considerable time with Meagher capturing on film
his work as part of a four-part documentary that will be aired some time
next winter.

Meagher has for more than a decade been a pioneer in phytoremediation, and
he was the first to demonstrate that a gene called merA can be inserted
into plants and used to detoxify mercury in the environment. While no
plant can break mercury down, since it is an element, less toxic forms can
be created, and that has been the goal of Meagher's lab - to find ways to
let plants or trees grow on polluted sites, draw such heavy metals as
mercury into the plants themselves and then either transpire the much less
toxic forms of the metal into the air where they are quickly diffused or
trap the metal aboveground for later harvest.

The project with Danbury came about because Danbury's environmental
coordinator, Jack Kozuchowski, had in 1977 published an early study that
showed how native plants could transfer mercury from contaminated soils
into the atmosphere. Kozuchowski, aware of Meagher's work, convinced
officials in Danbury that the so-called Barnum Court site in that town
would be a perfect site for a field trial of the genetically engineered
trees that Meagher and his collaborator Scott Merkle developed.

The city was awarded a grant of some $55,162 from the Environmental
Protection Agency to explore use of the technology, and the trial was set
up - though most costs for the work are being born by those involved in
it.

"It is our hope that the research will lead to a cleansing of the Barnum
Court property so the city can transfer the property for development,"
said Mark Boughton, mayor of Danbury.

Meagher's mercury phytoremediation technology is exclusively licensed to
Applied PhytoGenetics, or APGEN as it is called, and that Athens company
has been instrumental in helping set up the field trial. (Meagher is a
consultant to and cofounder of APGEN.)

Postdoctoral associate Andrew Heaton of Meagher's lab and one other of
Meagher's students traveled to Danbury in July to supervise planting the
genetically engineered trees on the site in enclosed plastic containers
buried on the site.

Because the mercury on the site ranges, depending on location, from five
to more than 300 parts per million, trials were set up to measure the
effects of the cottonwood trees on progressively more polluted samples of
soil. Forty-five plots, most planted with four trees each, are located on
the site, which is in a mixed-use urban area and whose total area is less
than an acre. (Some 15 plots have four merA trees, 15 are nonengineered or
"wild-type" trees and 15 received no trees at all, so there are 120 trees
in the field test.)

The form of mercury at the Danbury site is ionic mercury, a species that
can be sequestered and transformed into less toxic metallic mercury in the
transgenic trees and then transpired into the atmosphere. (Several forms
of mercury were used in hat-making in the 19th century, but their toxic
effects often sickened workers and led to the phrase "mad hatter," which
described the process of neurological degeneration that came from working
with the metal. In this part of New England, the symptoms of mercury
poisoning were called the "Danbury shakes.")

Meagher's lab actually has two genes that can effect phytoremediation,
merA and merB, but since the merA is active on ionic mercury, the
cottonwoods trees chosen for the Danbury trial express the merA gene.

"This is a field test, not a cleanup," said Meagher. "And we will be
measuring mercury in both the soil and the trees to see just how much
success we have in reducing the mercury levels in the soil. We are very
optimistic that this technology will work."

While the trees at the site will have to be watered, the costs of that
pale in comparison to traditional clean-up methods - digging up the
polluted soil and hauling it off for storage at another site, possibly
greater than $1 million.

A team of researchers from Western Connecticut State University will be
studying the role of soil microorganisms in the potential clean-up of
mercury on the site. According to the City of Danbury, the field test will
run through the 2004 growing season, and if results are positive,
genetically engineered cottonwood trees will be used to clean the whole
site.