Electronic gene control could let us plug bacteria into devices

We don’t usually welcome bugs in digital technology, but that’s about to change. Researchers have developed a way to control bacterial genes at the flick of a switch using electricity. 

The ability of custom-made microbes to sense the environment and make biological molecules would be particularly valuable for devices that work inside the body, says William Bentley at the University of Maryland.

For example, a device could use an organism to sense chemicals produced by harmful bacteria in the body and secrete an antibiotic when it detects them.

To get specific genes in bacteria to respond to electrical stimulation, Bentley’s team took advantage of what are called redox molecules. These biological molecules are found in all cells and can pick up and pass on electrons. They are said to have a reduced state when they gain electrons, and an oxidised state when they lose electrons.

The team also made use of naturally occurring genetic components in E. coli that respond to oxidative stress, which occurs when too many molecules in the cell are oxidised, making them dangerously reactive.

To apply electrical input, the researchers submerged an electrode in a liquid containing the bacteria. When the electrode supplies a positive charge, certain redox molecules get oxidised and trigger the genetic mechanisms that respond to oxidative stress.

The bacteria can be engineered so that these mechanisms switch on any genes researchers want to target. When the electrode is negatively charged, the molecules get reduced and the genes switch off again. Using this principle, Bentley’s team showed they can use electrical inputs to make E. coli swim or fluoresce on demand.