Mohamed El-Naggar and co-workers promoted the production of nanowires by growing the bacteria Shewanella oneidensis under anaerobic conditions in a laminar-flow-perfusion imaging platform. The nanowires were on average 2.5 μm long, but could reach up to 9 μm. Atomic force microscopy showed that the nanowires can be in the form of a chain of vesicles, a continuous filament or a partially smooth filament containing vesicles, as shown by the atomic force microscope (main) and in vivo fluorescence (inset) images. By labelling the bacterial cells with a dye, the authors showed that the production of nanowires correlated with an increase in reductase activity, suggesting increased respiratory activity. Membrane stain experiments and quantitative gene expression analysis demonstrated that the entire length of the nanowire was composed of bacterial membranes and proteins, rather than of the fibrous proteins (called pilin) as suggested previously.
Immunofluorescence experiments showed that cytochrome proteins lined the nanowires. Understanding electron transport in bacterial nanowires and bacterial energy conversion strategies is useful for the development of microbial fuel cells and electrofuels.
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