December
11, 2003
Energy
Department-funded Scientists Decode DNA of Bacterium
that Cleans Up Uranium Contamination and Generates
Electricity
WASHINGTON, DC – Department
of Energy-funded researchers have decoded and
analyzed the genome of a bacterium with the
potential to bioremediate radioactive metals
and generate electricity. In an article published
in the December 12th issue of Science, researchers
at The Institute for Genomic Research (TIGR)
and the University of Massachusetts, Amherst,
report that Geobacter sulfurreducens possesses
extraordinary capabilities to transport electrons
and "reduce" metal ions as part of
its energy-generating metabolism.
"The genome of this tiny
microorganism may help us to address some of
our most difficult cleanup problems and to generate
power through biologically-based energy sources,"
Secretary of Energy Spencer Abraham said. "Geobacter
is an important part of Nature's toolbox for
meeting environmental and energy challenges.
This genome sequence and the additional research
that it makes possible may lead to new strategies
and biotechnologies for cleaning up groundwater
at DOE and at industry sites."
The contamination of groundwater
with radionuclides and metals is one of the
most challenging environmental problems at Department
of Energy former nuclear weapons production
sites. Researchers at the University of Massachusetts
have previously found that Geobacter species
can precipitate a wide range of radionuclides
and metals (including uranium, technetium and
chromium) from groundwater, preventing them
from migrating to wells or rivers where they
may pose a risk to humans and the environment.
The analysis of the genome sequence
revealed a number of capacities that had not
been previously suspected from past research
on this microbe. "We’ve provided
a comprehensive picture that has led to fundamental
changes in how scientists evaluate this microbe,"
said Barbara Methe, the TIGR researcher who
led the genome project and is the first author
of the Science paper. "Research based on
genome data has shown that this microbe can
sense and move towards metallic substances,
and in some cases can survive in environments
with oxygen." G. sulfurreducens was previously
thought to be an anaerobic organism.
The other main project collaborator
was Derek Lovley, a professor of microbiology
at the University of Massachusetts, Amherst,
who discovered the Geobacter family of bacteria
and has led projects to assess their biology
and their potential for bioremediation. Lovley
said, "Sequencing the genome of Geobacter
sulfurreducens has radically changed our concepts
of how this organism functions in subsurface
environments." The genome analysis, he
said, "revealed previously unsuspected
physiological properties" of the bacterium
and also gave scientists insight into the metabolic
mechanisms that the organism uses to harvest
energy from the environment.
Geobacter reduces metal ions in
a chemical process during which electrons are
added to the ions. As a result, the metals become
less soluble in water and precipitate into solids,
which are more easily removed. Small charges
of electricity are also created through the
reduction process. Geobacter is also of interest
to the Department of Energy because of its potential
to create an electrical current in a "bio-battery."
Geobacter microbes are widely
distributed in nature and are commonly found
in subsurface environments contaminated with
radionuclides and metals. Researchers have demonstrated
that if they "feed" the microbes simple
carbon sources such as acetate they will grow
faster and precipitate more radionuclides and
metals. These findings are now serving as the
basis for a test of a bioremediation strategy
aimed at removing uranium from groundwater at
a Uranium Mill Tailings Remedial Action site
near Rifle, Colorado.
The Natural and Accelerated Bioremediation
Research (NABIR) and Microbial Genome Programs
in the department’s Office of Science
funded the $800,000 G. sulfurreducens sequencing
project. The genome sequence is now serving
as the basis for detailed investigations, supported
by the department’s Genomes to Life program,
into the ability of Geobacter to reduce radionuclides
and metals and to generate electricity. The
NABIR program’s mission is to provide
the fundamental science that will serve as the
basis for development of cost-effective bioremediation
and long-term stewardship of radionuclides and
metals in the subsurface at DOE sites. The focus
of the program is on strategies leading to long-term
immobilization of contaminants in place to reduce
the risk to humans and the environment. The
NABIR program encompasses both intrinsic bioremediation
by naturally occurring microbial communities,
as well as accelerated bioremediation through
the use of biostimulation -- addition of inorganic
or organic nutrients. More information on NABIR
is available at www.lbl.gov/NABIR and on the
Microbial Genome Program at http://doegenomes.org.
DOE’s Office of Science is the single
largest supporter of basic research in the physical
sciences in the nation, manages 10 world-class
national laboratories and builds and operates
some of the nation’s most advanced R&D
user facilities. Its web site address is www.science.doe.gov.
More detailed information on the
Science article is available in news releases
issued by TIGR and the University of Massachusetts.
To obtain those releases, visit www.eurekalert.org
or contact those institutions’ press offices.
NEWS MEDIA CONTACTS:
Jeff Sherwood (DOE), 202/586-5806 Thursday,
December 11, 2003
Robert Koenig (TIGR), 301/838-5880
Daniel Fitzgibbons (UMass), 413/545-0444
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