Electrochemical Techniques and Applications to Characterize Single‐ and Multicellular Electric Microbial Functions

The biological electron transport process beyond the insulating lipid bilayer membrane of a microbe, referred to as extracellular electron transport (EET), is mediated by a transmembrane electron conduit. Interdisciplinary interest in the electrochemical properties of the membrane enzyme, and of electrically conductive nanowire and biofilm, led to the development of integrated methodology to study intact EET-capable bacterial cells. In this chapter, we summarize the techniques and their applications to Shewanella oneidensis MR-1 and Geobacter sulfurreducens PCA, both of which were discovered 30 years ago and have been widely investigated as model systems. Simple electrochemistry with flat electrodes directly characterizes the interfacial electron transport of cell-surface enzymes and electrodes; and, once combined with microscopic techniques, EET-associated metabolic processes also can be characterized. Interdigitated array (IDA) and nanoscale probe techniques will be introduced for conductivity characterization of biofilm and nanowire, respectively. Some technical challenges remaining in this field are also addressed.