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Electronic Conductivity Found in Bacteria Nanowires

Transmission electron micrograph of Geobacter sulfurreducens cells synthesizing a network of protein nanofilaments.

Transmission electron micrograph of Geobacter sulfurreducens cells synthesizing a network of protein nanofilaments. (Anna Klimes and Ernie Carbone, UMass Amherst)

A team of microbiologists and physicists at University of Massachusetts in Amherst have discovered the ability of nanowires in a common microbe to transport electrons across long distances. The researchers published their findings online in the journal Nature Nanotechnology (paid subscription required).

Microbiologist Derek Lovley with physicists Mark Tuominen, Nikhil Malvankar and colleagues found this conductive property in the bacterium Geobacter sulfurreducens. Geobacter is a rod-shaped microbe with flagella and was already known to have potential industrial applications with its the ability to transfer electrons, as well as other environmental restorative capabilities.

Lovley’s team found that networks of microbial nanowires running through biofilms are connected aggregates of billions of cells. The capability to form networks of cells give this biological material a conductivity comparable to synthetic conducting polymers, commonly used in the electronics industry.

A key observation by the UMass team was the metallic-like carrying of an electrical charge along a protein filament. Previously, this capability was believed to require a a series of other proteins known as cytochromes that act as relays for electrons making short hops from one cytochrome to the next. In this new research, the UMass team demonstrated long-range conductivity without cytochromes, where the Geobacter filaments function like a true wire.

Lovley and colleagues also found they could adjust the conductivity of the Geobacter bacteria by manipulating internal and external factors, such as gene expression and temperature. They found as well that they could create a simple configuration like a  transistor, adding a third electrode acting as a switch, turning it on and off by applying a voltage.

Potential commercial or industrial applications for microbial nanowires include systems that cross solid-state electronics and biological domains, such as medical diagnostics or biometric security. Another benefit to industry is its ability to be made of freely available natural materials, rather than exotic minerals or rare earths imported from unstable regimes or subject to sharp market price fluctuations.

Read more: Silver Nanoparticles Generated in Natural Environment

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