Extracellular Electron Transfer in Microbial Bioelectrocatalysis

Connecting microorganisms to electrodes has led to a gamut of applications in bioenergy/bioproducts, wastewater treatment, biosensors, and bioelectronics. A crucial part of this connection relies on electrons being transported from individual cells to the electrode surface, a process coined extracellular electron transfer (EET). Over the past few decades, we have learned how bacteria have developed EET approaches to transfer electrons to solid electron donors/acceptors, transfer electrons within each other, or simply alleviate gradients within flocs or biofilms. In this chapter, two major EET mechanisms used by bacteria are discussed: extracellular electron shuttles (EES; using examples from Shewanella oneidensis , Pseudomonas aeruginosa , and exogenous electron shuttles) and solid conductive matrix through microbial nanowires (using Geobacter sulfurreducens as an example). For both mechanisms, we outline common approaches to predict and model electrical current generated by bacteria in response to electrode potential changes and the predicted electrochemical responses.