ABSTRACT
A biofilm that can interact electrochemically with an electrode and regulate its microbial metabolism using the electrode either as a source or as a sink for electrons transported in the metabolic chain of reactions is known as an electrochemically active biofilm (EAB). Structurally, EABs look and act just as all other biofilms described in this book do; the name EABs refers to their most prominent function, the ability to exchange electrons with metal electrodes or with redox-sensitive minerals. EABs are also known under several other names, such as electricigens, electrochemically active microbes, exoelectrogenic bacteria, and anode-respiring or anodophilic species. Because the hallmark of these biofilms is their ability to exchange electrons with solid surfaces, such as electrodes in electrochemical cells, we believe that the term electrochemically active biofilms refers directly to the function of these biofilms, and we use it in this book. As we pointed out above, when EABs grow on electrodes, electrons from metabolic reactions can be exchanged with the electrode by (1) direct electron transfer from the microorganisms through membrane proteins or nanowires and (2) electron transfer mediated by soluble exogenous, or electron transfer, mediators (Figure 7.1).
