An important point recently highlight is the general misconception that the bacteria on the electrode gain energy from the electron shuttle or the electrode directly itself . The bacterial cells gain energy from the pumping of protons across the inner membrane to form a proton gradient, which drives the formation of ATP from ADP through ATPase. As such, extracellular electron transfer acts to move the electron to the anode surface but does not gain any further energy for bacterial growth. It is the creation of a proton gradient that drives the synthesis of ATP and provides metabolic energy for the bacterium.