Computers made from living cells, anyone? Two groups of researchers have independently built the first biological analogue of the transistor – an integral element of modern electronics.

It should make it easier to create gadgets out of living cells, such as biosensors that detect polluted water.

A transistor acts as a switch, converting electrical inputs into output signals via logic gates. Now, Drew Endy at Stanford University in California and colleagues have designed a transistor-like device that controls the movement of an enzyme called RNA polymerase along a strand of DNA, just as electrical transistors control the flow of current through a circuit.

A different enzyme acts as the input, which depending on the sequence of the logic gates, either stops or starts the flow of polymerase. The device can also amplify its flow, another important function of transistors, allowing them to power other components in the circuit.


Because combinations of transistors can carry out computations, this should make it possible to build living gadgets with integrated control circuitry.

A similar device has been built by Timothy Lu and colleagues at the Massachusetts Institute of Technology, but amplification gives Endy’s device the edge.

Such devices will be key building blocks in cellular machines, says Paul Freemont at Imperial College London, who was not involved in either study.

For example, bacterial cells are good at detecting pathogens or chemicals, such as heavy metals, says Freemont. By redesigning the circuitry that a bacterium uses to sense things, we could produce cheap biosensors that monitor water quality. “Underpinning all of that will be these foundational components, like in electronics,” he says.

For Endy, the applications are limited only by our imagination. He suggests we could one day have living bridges or buildings constructed by the self-directed growth of their natural materials, controlled by internal biological circuits, or even tiny medical “submarines” with on-board DNA computers navigating the insides of our bodies.

Journal reference: Science, 10.1126/science.1232758