Tunable Metallic-Like Conductivity in Microbial Nanowire Networks

Electronic nanostructures made from natural amino acids are attractive because of their relatively low cost, facile processing and absence of toxicity1, 2, 3. However, most materials derived from natural amino acids are electronically insulating1, 2, 3, 4, 5, 6. Here, we report metallic-like conductivity in films of the bacterium Geobacter sulfurreducens7 and also in pilin nanofilaments (known as microbial nanowires8, 9) extracted from these bacteria. These materials have electronic conductivities of ~5 mS cm−1, which are comparable to those of synthetic metallic nanostructures2. They can also conduct over distances on the centimetre scale, which is thousands of times the size of a bacterium. Moreover, the conductivity of the biofilm can be tuned by regulating gene expression, and also by varying the gate voltage in a transistor configuration. The conductivity of the nanofilaments has a temperature dependence similar to that of a disordered metal, and the conductivity could be increased by processing