Light-induced nanowire formation and extracellular electron transport (EET) in <i>Shewanella oneidensis</i> MR-1

Dissimilatory metal-reducing bacteria, such as Shewanella oneidensis MR-1, harness energy from diverse sources in the environment through the metabolic oxidation of electron donors, such as organic materials, and subsequent electron transfer to insoluble electron acceptors, such as minerals. The electron transfer from bacteria to solid-state minerals or electrodes outside the cell is referred to as extracellular electron transport (EET). Recent research has proposed a few strategies for how EET is mediated in these microbial systems, including soluble redox mediators (such as flavins) to shuttle electrons via diffusion, direct contact with membrane cytochromes to the solid surface, and production of bacterial nanowires to bridge the gap between the cell body and surface. We combine optical and fluorescence microscopy with concurrent on-chip electrochemical and electrical measurements on a epifluorescence microscope to monitor the bacteria’s motility, EET, and metabolic behavior. We show preliminary data where we directly control nanowire production and enhance EET in a subpopulation of cells.