Investigation of Electron Transfer by Geobacter sulfurreducens Biofilms by using an Electrochemical Quartz Crystal Microbalance

Both the short- and long-term electron-transfer processes of electrode-respiring Geobacter sulfurreducens biofilms are demonstrated by using an electrochemical quartz crystal microbalance (QCM). The QCM monitors the frequency shift from the initial resonant frequency (background) in real time, while the current increases, because of biofilm growth. In the short term, the frequency shift is linear with respect to current for the biofilm. In long-term biofilm growth up to the exponential phase, a second linear region of frequency shift with respect to current is observed. In addition to the frequency shift response at constant polarization, the frequency shift response is coupled to cyclic voltammetry experiments. During cyclic voltammetry, a reproducible, negative increase in frequency shift is observed at oxidizing potentials. The results suggest that a QCM can be used in applications in which it is useful to find the most efficient current producer.