Researchers at Michigan
State University
have unraveled the mystery of how microbes generate electricity while cleaning
up nuclear waste and other toxic metals.
Details of the process, which can be improved and
patented, are published in the Proceedings
of the National Academy of Sciences. The implications could eventually
benefit sites forever changed by nuclear contamination, says Gemma Reguera, MSU
microbiologist.
“Geobacter
bacteria are tiny microorganisms that can play a major role in cleaning up
polluted sites around the world,” says Reguera, who is an MSU AgBioResearch
scientist. “Uranium contamination can be produced at any step in the production
of nuclear fuel, and this process safely prevents its mobility and the hazard
for exposure.”
The ability of Geobacter
to immobilize uranium has been well documented. However, identifying the Geobacters‘ conductive pili or nanowires
as doing the yeoman’s share of the work is a new revelation. Nanowires,
hair-like appendages found on the outside of Geobacters, are the managers of electrical activity during a
cleanup.
“Our findings clearly identify nanowires as being the
primary catalyst for uranium reduction,” Reguera says. “They are essentially
performing nature’s version of electroplating with uranium, effectively
immobilizing the radioactive material and preventing it from leaching into
groundwater.”
The nanowires also shield Geobacter and allow the bacteria to thrive in a toxic environment,
she adds.
Their effectiveness was proven during a clean up in a
uranium mill tailings site in Rifle, Colo. Researchers injected acetate into
contaminated groundwater. Since this is Geobacters‘
preferred food, it stimulated the growth of the Geobacter community already in the soil, which in turn, worked to remove
the uranium, Reguera says.
Reguera and her team of researchers were able to
genetically engineer a Geobacter
strain with enhanced nanowire production. The modified version improved the
efficiency of the bacteria’s ability to immobilize uranium proportionally to
the number of nanowires while subsequently improving its viability as a
catalytic cell.
Reguera has filed patents to
build on her research, which could lead to the development of microbial fuel
cells capable of generating electricity while cleaning up after environmental
disasters.
