Cable bacteria as long-range biological semiconductors

TL;DR

This study characterizes cable bacteria as biological semiconductors with resistive, thermally activated electron transport, demonstrating their potential for bioelectronic applications due to their high conductivity and n-type behavior.

Contribution

It provides the first detailed electrical characterization of cable bacteria, revealing their semiconductor-like properties and establishing them as a new class of biological electronic materials.

Findings

Charge transport is thermally activated and follows an Arrhenius relation.

Cable bacteria exhibit n-type charge transport in field-effect transistors.

Electron mobilities are comparable to organic semiconductors.

Abstract

Filamentous cable bacteria exhibit unprecedented long-range biological electron transport, which takes place in a parallel fibre structure that shows an extraordinary electrical conductivity for a biological material. Still, the underlying electron transport mechanism remains undisclosed. Here we determine the intrinsic electrical properties of individual cable bacterium filaments. We retrieve an equivalent electrical circuit model, characterising cable bacteria as resistive biological wires. Temperature dependent experiments reveal that the charge transport is thermally activated, and can be described with an Arrhenius-type relation over a broad temperature range (-196{\deg}C to +50{\deg}C), thus excluding metal-like electron transport. Furthermore, when cable bacterium filaments are utilized as the channel in a field-effect transistor, they show n-type transport, indicating that electrons rather than holes are the charge carriers. Electron mobilities are in the order of 10$^{-1}$ cm$^2$/Vs, comparable to many organic semiconductors. This new type of biological centimetre-range semiconductor with low resistivity offers new perspectives for both fundamental studies and applications in (bio)electronics.