Ferricyanide (30 mM, in a pH 7.0 sodium phosphate buffer) flowed through the cathode compartment at flow rate Qc=0.5 mL h -1 . Inoculation lasted for 24 hours under the total flow rate of QT=Qa + Qc=1.0 mL h -1 . After inoculation, a sterile nutrient medium without fumarate was supplied to the channel at the same flow rate. This eliminated electron transfer to the solution, thus promoting G. sulfurreducens growth on the anode.