Geobacter sulfurreducens pili support ohmic electronic conduction in aqueous solution

Area of Science:

• Microbiology
• Bioelectrochemistry
• Materials Science

Background:

• Geobacter sulfurreducens is a model organism for microbial electrochemical devices, forming conductive biofilms.
• The role of Type IV pili in electrical conduction within these biofilms is debated: conductive proteins or inert scaffolds.
• Previous studies on pilus conductivity were limited to dry or vacuum conditions.

Purpose of the Study:

• To investigate the electronic conduction mechanism of G. sulfurreducens pili under physiologically relevant aqueous conditions.
• To compare the conductivity of live biofilms versus purified pili networks.
• To elucidate the role of pili in charge transport for bioelectronic applications.

Main Methods:

• Isolation of G. sulfurreducens pili.
• Characterization of electronic conduction in purified pili networks and live biofilms under dry and aqueous conditions using solid-state I-V characteristics and electrochemical gating.
• Analysis of conductivity dependence on temperature.

Main Results:

• Purified pili films exhibit electronic transport consistent with a fiber percolation network.
• Live biofilms show redox currents dominating conduction, as previously suggested.
• Purified pili films display inherent, non-redox-mediated electronic conduction in aqueous conditions, with conductivity increasing as temperature decreases.

Conclusions:

• Isolated G. sulfurreducens pili possess inherent conductivity, supporting a metallic-like charge transport model.
• Pili function as electronically conductive biomaterials, not merely inert scaffolds.
• This research establishes a platform for studying biomaterial electronic transport and highlights pili as a model for bioelectronic interface design.