One idea for biosensors and bioenergy is to combine living cells with inorganic materials. Researchers have taken a step towards this goal by engineering the bacterium Escherichia coli to transmit electrons to inorganic materials.
Cell membranes act as insulators and thus hinder the movement of electrons between cells and inanimate materials. Caroline Ajo-Franklin at the Lawrence Berkeley National Laboratory in Berkeley, California, and her colleagues overcame this by introducing genes for electron-shuttling proteins into E. coli. The genes occur naturally in another bacterium, Shewanella oneidensis, which can transfer charge to non-living materials in oxygen-free environments.
The engineered E. coli cells were able to reduce iron in culture six to eight times faster than normal strains. The authors say that these genes could be transferred to other microbes to create, for example, low-cost photobatteries — by inserting them into bacteria that generate electrons in response to light.