Using bacteria to generate energy is a significant step closer following a breakthrough discovery by scientists from the School of Biological Sciences at the University of East Anglia (UEA).
Published May 31 by the leading scientific journal Proceedings of the National Academy of Sciences (PNAS), the research demonstrates for the first time the exact molecular structure of the proteins which enable bacterial cells to transfer electrical charge.
The discovery means scientists can now start developing ways to ‘tether’ bacteria directly to electrodes - creating efficient microbial fuel cells or ‘bio-batteries’. The advance could also hasten the development of microbe-based agents that can clean up oil or uranium pollution, and fuel cells powered by human or animal waste.
“This is an exciting advance in our understanding of how some bacterial species move electrons from the inside to the outside of a cell,” said Dr Tom Clarke.
“Identifying the precise molecular structure of the key proteins involved in this process is a crucial step towards tapping into microbes as a viable future source of electricity.”
The discovery means scientists can now start developing ways to ‘tether’ bacteria directly to electrodes - creating efficient microbial fuel cells or ‘bio-batteries’. The advance could also hasten the development of microbe-based agents that can clean up oil or uranium pollution, and fuel cells powered by human or animal waste.
“This is an exciting advance in our understanding of how some bacterial species move electrons from the inside to the outside of a cell,” said Dr Tom Clarke.
“Identifying the precise molecular structure of the key proteins involved in this process is a crucial step towards tapping into microbes as a viable future source of electricity.”
Bacteria called Shewanella can use metal ions in place of oxygen to live and grow. In the process, Shewanella can transform some metals and trap them in minerals, a useful skill for engineers who want to stop radioactive or toxic metals from migrating in soil or groundwater. The bacteria also help cycle metals used as nutrients through the biosphere.
Shewanella oneidensis uses an electron-shuttling conduit made up of proteins to live off of metal in minerals such as this hematite
But bacteria can't inhale solid metal like humans breathe oxygen. Instead of lungs, Shewanella send out tiny wires that contact metals and minerals. Within these wires are proteins that pass electrons outward, but no one knows what these proteins look like or how exactly they work together in a large complex. Now, a collaborative research team from the University of East Anglia and Pacific Northwest National Laboratory have determined the structure of the first of these protein components, providing insights into how bacteria live off minerals and rocks.
In earlier research published by PNAS in 2009, the team demonstrated the mechanism by which bacteria survive in oxygen-free environments by constructing electrical wires that extend through the cell wall and make contact with a mineral – a process called iron respiration or ‘breathing rocks’. (See http://www.uea.ac.uk/bio/news/rocknews)
In this latest research, the scientists used a technique called x-ray crystallography to reveal the molecular structure of the proteins attached to the surface of a Shewanella oneidensis cell through which electrons are transferred.
In this latest research, the scientists used a technique called x-ray crystallography to reveal the molecular structure of the proteins attached to the surface of a Shewanella oneidensis cell through which electrons are transferred.
In addition to cleaning up legacy radioactive waste, the information will help researchers tap bacteria to generate currents in fuel cells or for applications in synthetic biology. Researchers performed some of the work, which they reported in the Proceedings of the National Academy of Sciences' Early Edition, using instruments and expertise at EMSL, the Department of Energy's Environmental Molecular Sciences Laboratory on the PNNL campus.
Contacts and sources:
PNNL
University of East Anglia (UEA)
Citation: Thomas A. Clarke, Marcus J. Edwards, Andrew J. Gates, Andrea Hall, Gaye F. White, Justin Bradley, Catherine Reardon, Liang Shi, Alexander S. Beliaev, Matthew J. Marshall, Zheming Wang, Nicholas J. Watmough, James Fredrickson, John Zachara, Julea N. Butt, and David J. Richardson, Structure of a bacterial cell surface decaheme electron conduit. Proc Natl Acad Sci U S A, Early Edition online the week of May 23-28, 2011. DOI 10.1073/pnas.1017200108, (http://www.pnas.org/content/early/2011/05/16/1017200108).
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