Electron transfer of exoelectrogens

To date, two EET mechanisms have been found. One is indirect EET, relying on electron shuttles, which can be either self-secreted or externally added. Electron shuttles are redox-driven and have two states oxidized and reduced states. Driven by redox, the oxidized shuttles become reduced via the acquisition of electrons at the exoelectrogen outer membrane. The reduced shuttles are then driven to the anode and release electrons to the anode and become oxidized. This process repeats to transfer electrons from the exoelectrogens to the anode. For instance, Shewanella oneidensis MR-1 is reported to mainly rely on electron shuttles named flavins (Marsili et al, 2008). 

Once electrons reach an anode, they flow to a cathode, oxidized by an electron acceptor, such as oxygen, ferricyanide, etc., driven by a high potential at the cathode. By coimecting a load between 

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