Some bacteria that can transmit electricity turn out to have a hidden talent: when grown on a copper electrode, they construct a network of copper sulfide compounds that boosts their conductivity.
Copper is hostile to microorganisms, and as a result has long been used in antibacterial cladding for ships’ hulls, and in pots and pipes for drinking water. But while studying electrically conductive Geobacter sulfurreducens bacteria for use in fuel cells, Uwe Schröder and his colleagues at the Technical University of Braunschweig in Germany found that the microbes flourished on copper, forming tough layers known as biofilms.
What’s more, G. sulfurreducens biofilms on a copper electrode produced double the electrical current of those on a graphite electrode. Chemical analysis revealed copper sulfide solids deposited throughout the biofilms. The team concluded that the bacteria promote chemical reactions between the copper electrode and sulfate ions in their food source to form copper sulfide ‘wires’, which enhanced the flow of electricity within the biofilm.
The researchers hope their findings can help to improve the design and performance of fuel cells that take advantage of such electrically conductive bacteria.