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Associate professor Lesley A. Warren of the School of Geography & Geology at McMaster University, Hamilton, Ontario, is also studying the role microbes play in the fate of contaminants. She's particularly interested in microbes found in a stream that drains a mine site in northern Ontario. Despite the stream's harsh conditions--its pH often dips below 3, and it is laden with metals--microbes flourish, Warren reported at the ACS meeting. They live in complex communities called biofilms--the microbial equivalent of high-rise apartments--that form where water and sediment meet. In collaboration with professor Adam P. Hitchcock of McMaster's chemistry department, Warren and graduate student Elizabeth A. Haack are using a host of X-ray methods to characterize the three-dimensional architecture of these biofilms. A technique called scanning transmission X-ray microspectroscopy reveals that the biofilms are made up of small, diverse minicommunities of bacteria. It also shows that some of the bacteria in these minicommunities produce a mineral on the outside of their membranes. Using X-ray absorption fluorescence spectroscopy, Warren's team has shown that this biomineral is manganese oxyhydroxide--and that it sequesters trace toxic metals like nickel, cobalt, and chromium from the stream. Warren thinks that such bacterially produced manganese oxyhydroxide biominerals play a crucial role in whether metals are carried downstream, away from the mine. "If we understand how, then we will be able to target these metal-retention processes for bioremediation," Warren told C&EN. |
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