Tunable metallic-like conductivity in microbial nanowire networks

Area of Science:

• Biotechnology
• Materials Science
• Nanotechnology

Background:

• Natural amino acid-based nanostructures are desirable due to low cost, ease of processing, and non-toxicity.
• However, most amino acid-derived materials are electronically insulating, limiting their applications.
• There is a need for conductive, biocompatible nanomaterials.

Purpose of the Study:

• To investigate the electronic conductivity of Geobacter sulfurreducens biofilms and extracted pilin nanofilaments.
• To explore the potential of these microbial nanowires as alternatives to synthetic metallic nanostructures.
• To understand the factors influencing the conductivity of these biological materials.

Main Methods:

• Cultivation of Geobacter sulfurreducens biofilms.
• Extraction and purification of pilin nanofilaments (microbial nanowires).
• Measurement of electronic conductivity using standard techniques.
• Analysis of conductivity dependence on temperature, gene expression, and gate voltage.

Main Results:

• Achieved metallic-like conductivity (∼5 mS cm⁻¹) in bacterial films and nanofilaments, comparable to synthetic materials.
• Demonstrated conductivity over centimeter-scale distances, significantly larger than bacterial size.
• Showed that conductivity can be tuned by regulating gene expression and gate voltage.
• Observed temperature dependence consistent with disordered metals, with conductivity enhanced by processing.

Conclusions:

• Geobacter sulfurreducens biofilms and microbial nanowires exhibit significant electronic conductivity.
• These biological materials present a promising, sustainable alternative to synthetic conductive nanostructures.
• Tunable conductivity and large-scale conduction open avenues for novel bioelectronic devices.