Immobilizing metals under study at UGA's Savannah River Ecology Laboratory

October 18, 2005

Metals and radionuclides in the environment are a continuing source of concern to the public and scientists alike. Ridding the environment of metals is often costly, if it can be done at all. Immobilizing metals, so that they do not migrate into new areas, may be a more realistic treatment, according to many scientists. Now, two University of Georgia scientists have received a grant of $232,000 to begin a three-year study of the fundamental mechanisms by which bacteria may help immobilize contaminants in the environment.

Andrew Neal of the University of Georgia Savannah River Ecology Laboratory and Thomas DiChristina of the Georgia Institute of Technology are co-investigators on the project (titled "Molecular Mechanism of Bacterial Attachment to FeIII - Oxide Surfaces") funded by the U.S. Department of Energy (DOE). Using bacteria that are naturally occurring in soils and in subsurface environments the two will aim to identify proteins involved in the adhesion of cells to iron mineral surfaces. They will use targeted and random mutagenesis to eliminate proteins likely to be involved in the adhesion process. There are some parallels between mechanisms thought to be used by iron-reducing bacteria to attach to mineral surfaces and those used by pathogenic bacteria to attach to surfaces in the body.

"This is like using both tweezers and a shotgun," said Neal of the dual strategy he and DiChristina will employ. "Some proteins will be pinpointed but random mutagenesis will knock out many other genes and may reveal other gene products that are involved in the cell adhesion process. We believe one or both of these processes will reveal proteins or genes that allow cells to attach to iron minerals and reduce them."

DiChristina will perform the mutagenesis work at Georgia Tech; Neal will then study the mutants' biophysical properties, measuring forces of adhesion generated between the mutants and mineral surfaces and the cells' tendency to attach to mineral surfaces.

"This is part pure science and part practical application," said Neal. "Adhesion of bacterial cells to surfaces is a fundamental aspect of microbiology with relevance to environmental and medical science. But also, understanding how bacteria and minerals interact is essential to being able to engineer a process to better immobilize metals in the environment. This is basic stuff but with an exciting, practical side."

By the end of the proposed work, the pair hopes to apply their gained knowledge to the suit of seven metal-reducing bacteria to have had their genomes sequenced by the DOE. This will help identify common themes of cell attachment in the environment. The work is expected to provide a better understanding of genetic, biochemical and regulatory processes, which control cell attachment to iron oxide surfaces and therefore the biotransformation of iron and indirectly, other metals and radionuclides.
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University of Georgia

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