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David Brown '10 and Amy Allen '10.
David Brown '10 and Amy Allen '10.

Amy Allen '10 and David Brown '10 Probing Bacterium

By Allison Eck '12
Posted July 9, 2009
Tags Student Research
Some organisms breathe gases. But others don't. While it may seem plausible that certain bacteria can "inhale" solids as part of the respiratory process, our preconceived notions of some solids – like iron – are rigidly robust. Never would we consider a solid such as iron a breathable entity. But it is, at least for one bacterium known to biologists as Shewanella oneidensis. David Brown '10 and Amy Allen '10 are probing through previous research on the organism this summer. With Associate Professor of Biology Michael McCormick, they will look at what makes its iron intake possible, and they will expand on whatever sparse information is already available to the scientific community. 

"Sparse" is not an exaggeration. Only one paper has been published on the subject (Haas & DiChristina, 2002). It explained that Shewanella oneidensis reduces ferric iron, or Fe (III), to ferrous iron, or Fe (II) during respiration. Substances called ligands bind to the iron and move it into the solution. The bacterium is then able to reduce it. The study's principle discovery was that weaker ligands help the cell function better, but it failed to address how the ligands bind to iron (a process called metal chelation). 

Brown and Allen want to identify the properties of ligands that make this biological anomaly possible. Their research is funded by the New York State Department of Energy because this species' respiration could create microbial fuel cells that can produce electricity from waste water. In addition, a better understanding of what goes on at the microscopic level could lead to more expansive knowledge of bioremediation. The story behind the process is what matters. 

The stories behind the researchers merit an explanation as well. Brown says that he has been interested in research for as long as he can remember. This is his fourth summer doing research at Hamilton – he even participated as an entering first-year student. He feels the experience he has gained is diverse. He has taken both biology and chemistry courses, and will apply for graduate school in biochemistry in the fall. 

Allen says she was "all over the map" her freshman year. After taking a variety of courses, her plan to major in biology gradually morphed into a geoscience major. But her interest in biology lingered, and when she heard that Professor McCormick was a geomicrobiologist, she thought working with him over the summer would help her decide whether or not she should go in that direction. 

She says that the part of their project that relates to geoscience is the mineral aspect. 

"These bacteria are using a solid to breathe," she said. "What's really going on is a change in the chemical composition of minerals. Most people don't know that minerals can change into other minerals. It's really astounding because it shows how the organic can be connected to the inorganic." 

The students say that Shewanella oneidensis is a multi-talented creature. It can also reduce chromium (VI) to a less toxic variation. Chromium (VI), or hexavalent chromium, made an appearance in the movie Erin Brockovich as the pesky element that threatens to poison a small town's water supply. Brockovich was the legal assistant who investigated the town's mysterious illnesses. She revealed Pacific Gas and Electric's responsibility for the illnesses, but all she really needed to do was introduce a bit of bacteria.

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