MIT builds living circuit boards from bacteria in the lab

A Petri dish can now host a rudimentary circuit board. MIT researchers printed colonies of engineered Pantoea agglomerans bacteria onto agar and connected them with chemical signals, creating living circuits that can switch, relay and process information in the laboratory.

The key move was to split the job across cells. Two bacterial designs act as transistors: one switches on in response to the molecule OC-6, the other switches off. Both also detect OC-12 and, depending on the combination of inputs, release OHC-14. Three additional bacterial strains translate that signal so it can feed the next transistor. The result is a biological version of wiring components together rather than forcing one cell to carry an entire circuit.

The researchers demonstrated multi-input, “or” and “imply” logic gates, along with circuits that add two signals, process several signals at once or route one signal to a selected destination. The largest circuit contained 24 bacterial colonies. Each colony was printed about 5 millimeters from its nearest neighbor, allowing the signal to move in one direction through the layout.

The limitation is speed. These living circuits take about eight hours to perform each calculation, far slower than an electronic computer. MIT’s researchers say that timing could still make sense for biology, where a response measured overnight may be fast enough compared with a plant’s growth season.

So what does this change in practice? Not smartphones: the team says the circuits are meant to add computation to biology, not replace computers. The longer-term idea is to place bacteria on plant leaves or roots, where they could detect environmental stress such as drought or pest attack and potentially trigger a response such as synthesizing a fungicide. For now, that application remains a goal; the demonstrated system is a printed laboratory circuit on agar.