Thaindian News

Washington, March 17 (IANS) Not all soil bacteria are bad. Some of them act as good Samaritans as they “inhale” toxic metals, strip them of their toxicity and then “exhale” them, say researchers. In the foreseeable future, they might potentially clean-up toxic chemicals left over from nuclear weapons production decades ago.
Using a unique combination of microscopes, researchers at Ohio State University were able to glimpse how the Shewanella oneidensis bacterium breaks down metal to extract oxygen.

The study provides the first evidence that Shewanella manoeuvres proteins within the bacterial cell into its outer membrane to contact metal directly. The proteins then bond with metal oxides, which the bacteria utilise the same way we do oxygen.

The process is called respiration, and it’s how living organisms make energy, explained Brian Lower, assistant professor in the School of Environment and Natural Resources at Ohio State University.

With better knowledge of the bacterium’s abilities, scientists might one day engineer a Shewanella that would remediate nuclear waste more efficiently.

“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,” Lower said.

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 miniaturised 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 nanometre (billionth of a metre), 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, said a Ohio release.

These findings were published online this week in Applied and Environmental Microbiology.