"For instance, if you could enhance this bacterium's ability to reduce uranium by having it make more of these key proteins, that could perhaps be one way to clean up these sites that are contaminated," he said.
The danger at such waste sites is that the toxic metals are soluble, and so can leak into the local water supply. But these bacteria naturally convert the metals into an insoluble form. Though the metals would remain in place, they would be stable solids instead of unstable liquids.
For this study, Lower and his colleagues used an atomic force microscope (AFM) to test how the bacterium responded to the metallic mineral hematite.
An AFM works somewhat like a miniaturized phonograph needle: a tiny tip dangles from a cantilever above a surface that's being studied. The cantilever measures how much the tip rises and falls as it's dragged over the surface. It can measure features smaller than a nanometer (billionth of a meter), and detect atomic forces between the probe tip and the surface material.
They combined the AFM with an optical microscope to get a precise map of the bacteria's location on the hematite.
Though the bacteria are very small -- several hundred thousand of them could fit inside the period at the end of a sentence -- they are still thousands of times bigger than the tip of an AFM probe. So the microscope was able to slide over the surface of individual bacteria to detect protein molecules on the cell surface and in contact with the metal.
The researchers coated their probe tip with antibodies for the protein OmcA, which they suspected Shewanella would use to "breathe" the metal.
Whenever the probe slid over an OmcA protein, the antibody coating would stick to the protein. By measuring the tiny increase in force needed to pull the two apart, the researchers could tell where on the bacter
|Contact: Brian Lower|
Ohio State University