Electrically conductive pili: Biological function and potential applications in electronics

Abstract

Electrically conductive pili (e-pili) enable long-range electron exchange between microorganisms and their extracellular environment and show promise as a ‘green’ electronic material. Most studies have focused on the e-pili of G. sulfurreducens, which play a role in Fe(III) oxide reduction and interspecies electron transfer, and confer conductivity to current-producing biofilms. However, a diversity of other microorganisms have recently been found to possess e-pili, including e-pili with unique structures. Aromatic amino acids are key elements in electron transport along the length of e-pili and the conductivity of synthetic e-pili can be tuned by manipulating aromatic content. e-Pili are attractive as an electronic material because they can be produced from renewable feedstocks and are biodegradable, yet they are also highly robust for device fabrication. Basic information on the structure of e-pili, mechanisms for electron transport, and other electronic properties is required in order to better understand their biological function and to guide the design of synthetic e-pili for applications as electronic components.