Combined electrochemical and topographic characterization of Geobacter sulfurreducens cell surface under electrogenic conditions

ESTEVE NUÑEZ, ABRAHAM; BUSALMEN, JUAN PABLO; ROGERO, CELIA; FERNANDEZ, JORGE; MIGUEL FELIU, JUAN

Pennsylvania

Simposio; First International Symposium of Microbial Fuel Cells; 2008

University of Pennsylvania

The mechanism by which electricity-producing microorganisms interact with an electrode is poorly understood. Outer membrane cytochromes and conductive pili are being considered as possible players, but the available information does not concur to a consensus mechanism yet. In this work we demonstrate that Geobacter sulfurreducens cells are able to change the way in which they exchange electrons with a graphite electrode as a response to changes in the applied electrode potential. After several hours of polarization at 0.1 V (Ag/AgCl – KCl sat.), the voltammetric signature of the attached cells showed a single redox pair with a formal redox potential of about -0.08 V as calculated from chronopotentiometric analysis. However, new redox couples were detected after conditioning at 0.6 V. Importantly, when polarization was lowered again to 0.1 V the signals obtained at 0.6 V were found to greatly diminish in amplitude while those previously found at a potential of 0.1 V were recovered. Results clearly show the reversibility of cell adaptation to the electrode potential and point to the polarization potential as a key variable to optimize energy production from an electricity producing population. In addition, we have analyzed the microbial cell surface by Atomic Force Microscopy (AFM) in order to identify changes in the cell topography in response to the applied electrode potential.