Following the switch to a fumarate-free nutrient medium, EABs growth on the anode was monitored. Using a commercial potentiostat (Parstat MC 200, Princeton Applied Research, Oak Ridge, USA) to constinously record the voltage drop across the external resistor, Rext. The same setup was used to periodically performe a polarization test, from which polarization and power density curves were obtained. Polarization tests were achieved using a switched resistor approach (in the range Rext=100 to Rext=4 kΩ), utilizing a potentiostat connected directly across the anode/cathode. The changing voltage (V) across the external resistor after switching from OCV was monitored as a function of time and could be converted to current density (I ̅ ) using