WASHINGTON, Sept. 5 (Xinhua) -- Bacteria known as Geobacter can produce conductive hair-like filaments on their surfaces to remove dissolved uranium from groundwater, according to a study published on Monday in the Proceedings of the National Academy of Sciences.
The filaments, called pili, reduce the soluble form of uranium into a less-soluble form that may allow for easier removal.
Gemma Reguera, assistant professor of Michigan State University and colleagues grew Geobacter at temperatures that either induced or did not induce pili formation, and compared the bacteria with a mutant lacking a pili-producing gene and an engineered strain into which the gene had been reintroduced.
The researchers found that bacteria expressing pili removed considerably more uranium from a solution than did bacteria without pili. Piliated bacteria deposited uranium outside of their cells and prevented it from permeating their periplasm -- the space between the bacteria's inner and outer membranes. In contrast, non-piliated bacteria incorporated more uranium into their periplasms and cell membranes than did piliated bacteria.
The authors then used a fluorescent dye to measure the activity of some of the cell's respiratory enzymes in response to uranium exposure. They found that piliated bacteria had greater respiratory activity and thus were more viable than non-piliated bacteria. In addition, piliated Geobacter also recovered from uranium exposure and grew faster than pili-deficient strains.
The findings may help researchers design better uranium bioremediation strategies, according to the authors.
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