Issue 32, 2017

Geobacter sulfurreducens pili support ohmic electronic conduction in aqueous solution

Abstract

The bacterium Geobacter sulfurreducens is a model biological catalyst in microbial electrochemical devices. G. sulfurreducens forms electrically conductive, electrode-associated biofilms, but the biological structures mediating electrical conduction from cells to the electrodes are a matter of debate. Bacteria in these communities produce a network of fiber-like Type IV pili, which have been proposed to act either as inherent, protein-based electronic conductors, or as electronically inert scaffolds for cytochromes mediating long-range charge transport. Previous studies have examined pilus conduction mechanisms under vacuum and in dry conditions, but their conduction mechanism under physiologically relevant conditions has yet to be characterized. In this work, we isolate G. sulfurreducens pili, and compare the electronic conduction mechanism of both live biofilms and purified pili networks under dry and aqueous conditions. Solid-state IV characteristics indicate that electronic transport in films of purified pili is representative of conduction in a fiber percolation network. Electrochemical gating measurements in a bipotentiostat device configuration confirm previous results suggesting redox currents dominate live biofilm conduction. Purified pili films, however, exhibit non-redox electronic conduction under aqueous, buffered conditions, and their conductivity increases with decreasing temperature. These findings show that isolated pili possess inherent, non-redox-mediated conductivity consistent with a metallic-like model of charge carrier transport. The results demonstrate an experimental platform for studying electronic transport in biomaterials and suggest that pili serve as an exemplary model for designing bioelectronic interfaces.

Graphical abstract: Geobacter sulfurreducens pili support ohmic electronic conduction in aqueous solution

Associated articles

Supplementary files

Article information

Article type
Paper
Submitted
31 May 2017
Accepted
31 Jul 2017
First published
31 Jul 2017

Phys. Chem. Chem. Phys., 2017,19, 21791-21799

Geobacter sulfurreducens pili support ohmic electronic conduction in aqueous solution

N. L. Ing, T. D. Nusca and A. I. Hochbaum, Phys. Chem. Chem. Phys., 2017, 19, 21791 DOI: 10.1039/C7CP03651E

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