January 29, 2014
4:00 - 5:00 PM
Hosted by: Prof. Louis Brus
Speaker: Dr. Leonard M. Tender, Center for Bio/Molecular Science and Engineering, NRL
Geobacter spp. are microorganisms that can acquire energy by coupling intracellular oxidation of organic matter such as acetate with extracellular electron transfer to solid phase electron acceptors such as iron oxide particles. This is a distinct capability - microbes generally utilize soluble metabolic oxidants that are reduced inside the cell. Geobacter can also use electrodes (graphite, gold, etc.) as electron acceptors. When grown on an electrode, they form a multi-cell thick biofilm in which the distance electrons are transported from cells comprising the biofilm to the underlying electrode surface can exceed 20 microns - enormous for a biological system. One model puts forth that long-distance electron transport in Geobacter biofilms occurs by incoherent multi-step hopping through a network of bound redox cofactors which appear to be hemes of outer membrane and extracellular matrix c-type cytochromes. Here I will describe voltammetric, spectroscopic, and conductivity measurements performed on actively respiring Geobacter sulfurreducens biofilm-modified electrodes that support this model. This model is not without controversy and I will discuss what information is lacking, a competing model of biofilm long-range electron transport, and where that model fails.
Leonard M. Tender earned a BS in chemistry from MIT where he was fortunate to be mentored by Mark Wrighton, and a PhD from UNC Chapel Hill where he was again fortunate to be mentored by Royce Murray. He has been at the Naval Research Laboratory since 1999 where he is a research chemist and branch head.