So-called bio-batteries or microbial fuel cells took a tiny step toward reality with the announcement of research at the University of East Anglia showing that proteins on the surface of bacteria can produce an electric current by simply touching a mineral surface. The result demonstrates that it is possible for bacteria to lie directly on the surface of a metal or mineral and transfer electrical charge through their cell membranes. According to the researchers, this effect can be used to build a biologically based battery but it also appears clear this work is a long way from fruition as working technology in mass production for use in cars.
|Shewanella oneidensis bacteria. Credit: Alice Dohnalkova.|
The research team created a synthetic version of Shewanella oneidensis using only those proteins the researchers believed would shuttle the electrons from inside the microbe to rock. They inserted the proteins into the lipid layer of the bacterial membrane. They then tested how well electrons flowed between an “electron donor” inside the bacteria, and metal-bearing minerals in the rock.
Lead researcher Dr Tom Clarke from UEA’s school of Biological Sciences said: “We knew that bacteria can transfer electricity into metals and minerals, and that the interaction depends on special proteins on the surface of the bacteria. But it was not been clear whether these proteins do this directly or indirectly though an unknown mediator in the environment.
“Our research shows that these proteins can directly ‘touch’ the mineral surface and produce an electric current, meaning that is possible for the bacteria to lie on the surface of a metal or mineral and conduct electricity through their cell membranes.
“This is the first time that we have been able to actually look at how the components of a bacterial cell membrane are able to interact with different substances, and understand how differences in metal and mineral interactions can occur on the surface of a cell.
“These bacteria show great potential as microbial fuel cells, where electricity can be generated from the breakdown of domestic or agricultural waste products.
“Another possibility is to use these bacteria as miniature factories on the surface of an electrode, where chemicals reactions take place inside the cell using electrical power supplied by the electrode through these proteins.”
The technology clearly is a long way from anything practical but sure is interesting basic scientific research. Most likely this line of research will lead to some sort of “battery” or “fuel cell” based on biological principles but using completely custom-designed materials.
More information: ‘Rapid electron exchange between surface-exposed bacterial cytochromes and Fe(III) minerals’ by Thomas A Clarke, Gaye White, Julea N Butt, and David J Richardson (all UEA, UK), and Zhri Shi, Liang Shi, Zheming Wang, Alice C Dohnalkova, Matthew J Marshall, James K Fredrickson and John M Zachara (all PNNL, USA) is published by PNAS on Monday, March 25. (Will be available at www.pnas.org/lookup/doi/10.1073/pnas.1220074110 )
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