Technology can really wonderful this time. But I wonder if too
much phosphor around the area will harm the plants. 
http://www.gatech.edu/news-room/release.php?id=919
Bacteria Aid in Clean-Up of Uranium
Contamination
Research shows organisms found in soil can immobilize radioactive
material
Atlanta (March 30, 2006) In research that could help control
contamination from the radioactive element uranium, scientists have
discovered that some bacteria found in the soil and subsurface can
release phosphate that converts uranium contamination into an
insoluble and immobile form.
Martial Taillefert and Patricia Sobecky
Based on laboratory studies, Georgia Institute of Technology
researchers report promising results using bacterial species from
three genera isolated from subsurface soils collected at a U.S.
Department of Energy (DOE) Field Research Center site in Oak Ridge,
Tenn. Researchers conducted preliminary screenings of many
bacterial isolates and found several candidate strains that
released inorganic phosphate after hydrolyzing an organo-phosphate
source the researchers provided.
The bioremediation research project, funded for three years by
DOEs Environmental Remediation Sciences Division, is in its early
stages. Research team member Melanie Beazley, a Ph.D. student in
the Georgia Tech School of Earth and Atmospheric Sciences,
presented preliminary findings on March 30 at the 231st American
Chemical Society National Meeting in Atlanta.
These organisms release phosphate into the medium, but the
precipitation (of uranium phosphate) occurs chemically, explained
Assistant Professor of Earth and Atmospheric Sciences Martial
Taillefert, co-director of the study. That is the
biomineralization of uranium and the novelty of this
approach.
The process begins when the bacteria from the genera Rhanella,
Bacillus and possibly Arthrobacterdegrade an organo-phosphate
compound such as glycerol-3-phosphate (G3P) or phytic acid (IP6),
which can be present in subsurface soils.
During their growth, the organisms liberate phosphate they derive
from the organo-phosphate compound, said project co-director
Patricia Sobecky, an associate professor of biology. The free
phosphate is released to the surrounding media, which is a solution
in the lab. Then we conduct assays to see how much uranium is
mineralized by the phosphate released by the bacteria.
The bacterias role is crucial in this process because uranium
cannot dissociate the organo-phosphate compound chemically,
Taillefert explained. So uranium in the presence of
organo-phosphate alone does not result in significant uranium
precipitation.
Sobecky and her Ph.D. student Robert Martinez are conducting the
microbiological and physiological component of the research, while
Taillefert and Beazley study the uranium chemistry and analyze
distribution of different forms of uranium during incubation in the
lab.
The devils in the details with the chemistry of uranium: There
are numerous forms of uranium in the environment, which are all
influenced by the natural properties of soils and groundwater,
Taillefert said.
Sobecky added, What were doing now is optimizing the assay
conditions and the techniques to analyze the distribution of
uranium species in the lab.
Traditionally, DOE has funded research investigating the chemical
reduction of uranium contamination. But there are two approaches to
immobilizing uranium. One strategy reduces uranium (VI) to uranium
(IV), which is, in principle, immobile. But the uranium can
re-oxidize even with traces of oxygen from rainwater seeping into
the groundwater. The Georgia Tech approach biomineralizes uranium
(VI) into an insoluble form of uranium via phosphate
precipitation.
As they work toward a bioremediation strategy that will work in the
field, researchers must design a mechanism to deal with competing
organisms in the soil that might sequester the free phosphate,
Sobecky noted. Though their current grant does not cover the cost
of a field study, researchers hope to obtain funds in the future to
test their strategy at Oak Ridge and potentially other DOE sites.
Uranium contamination is a concern at DOE sites because it can
migrate to groundwater in surrounding areas, Taillefert
noted.
At this point, we know the organisms were studying are active in
precipitating uranium phosphate, he said.
. Now we need to
determine how chemically stable it is.
Researchers also have learned that when the bacteria are releasing
phosphate from G3P, the bacteria can tolerate the toxic uranium and
can continue to grow once the uranium is precipitated by the
released phosphate.
Our challenge now is fine-tuning the conditions around the
bacterium so eventually it can thrive and work chemically in a
natural setting, Taillefert said.
