March 25, 2013 
Electrons conduct through bacterial proteins directly to minerals containing iron
RICHLAND, Wash. - Certain bacteria can breathe iron like we breathe oxygen. Understanding how they do so will help researchers use the microbes for cleaning up soil contaminants, for trapping carbon dioxide or for making batteries out of bacteria. Now, a team of researchers report in the journal Proceedings of the National Academy of Sciences that proteins on the surface of bacteria produce an electric current by simply touching a mineral surface, allowing them to breathe the iron in the rock.
To do so, the team created a simulated bacterium using just the proteins thought to shuttle the electrons from the inside of the microbe to the rock. They inserted these proteins into lipid layers of vesicles, which are small bubbles of lipids such as the ones that make up a bacterial membrane. Using instruments and expertise at EMSL, the D.O.E.'s Environmental Molecular Sciences Laboratory, the team showed that the proteins protruded through the lipid bubbles in the same way they do in real bacteria, known as Shewanella oneidensis.
Then they tested how well electrons traveled between an electron donor on the inside and an iron-bearing mineral on the outside. The electron transfer rate they measured was fast enough to support bacterial respiration, showing that those proteins were the only ones the bacteria would need to conduct electricity.
In addition to contaminant cleanup and bio-batteries, the finding is important for understanding how carbon works its way through the atmosphere, land and oceans. If researchers understand electron transfer, they can learn how bacteria control the carbon cycle.
The team of researchers included Thomas A Clarke, Gaye White, Julea N Butt, and David J Richardson from the University of East Anglia and Zhi Shi, Liang Shi, Zheming Wang, Alice C Dohnalkova, Matthew J Marshall, James K Fredrickson and John M Zachara at the D.O.E.'s Pacific Northwest National Laboratory. This work was supported by the D.O.E. Office of Science and UK's Biotechnology and Biological Sciences Research Council.
Read the entire release from the University of East Anglia.
Tags: Energy, Environment, Fundamental Science, Batteries, Carbon Capture and Sequestration, Environmental Remediation
EMSL, the Environmental Molecular Sciences Lab, is a national scientific user facility sponsored by the D.O.E.'s Office of Science. Located at Pacific Northwest National Lab in Richland, Wash., EMSL offers an open, collaborative environment for scientific discovery to researchers around the world. Its integrated computational and experimental resources enable researchers to realize important scientific insights and create new technologies. Follow EMSL on Facebook, LinkedIn and Twitter.
Interdisciplinary teams at Pacific Northwest National Lab address many of America's most pressing issues in energy, the environment and national security through advances in basic and applied science. PNNL employs 4,500 staff, has an yearly budget of nearly $1 billion, and has been managed for the D.O.E. by Ohio-based Battelle since the laboratory's inception in 1965. For more information, visit the PNNL News Center, or follow PNNL on Facebook, LinkedIn and Twitter.
