Bacterial colonies can now add signals and direct them, like an electronic circuit, but alive.
To achieve this, MIT researchers modified the bacterium Pantoea agglomerans, commonly found on plants. The study was published on August 17, 2026, in Nature Chemical Biology.
To understand how it works, an electronic transistor acts as a switch that controls the flow of current. Here, no electrical current flows between the bacterial colonies. Instead, two bacterial strains act as chemical switches. Depending on the molecules they detect, they either produce or do not produce another molecule that serves as a signal.
Colonies of modified bacteria are arranged on a growth medium to form biological circuits whose function depends on their spatial organization.
Credit: MIT researchers, image edited by MIT News
Three other strains serve as relays. They receive a chemical signal, convert it, and then transmit it to the next stage. The researchers use five cell strains here, and only their spatial arrangement determines the "calculation" performed.
In the demonstration, the colonies are arranged by printing them on agar, a gelled medium where bacteria can grow. They are spaced about 5 mm apart. This distance limits the diffusion of molecules toward neighboring colonies. The information can then follow the path planned by the researchers, moving from relay to relay.
By simply changing the arrangement of the five strains, the team carried out several logical operations. Some configurations add two or three inputs. Another directs an incoming signal toward a chosen destination. The circuit that adds two inputs contains 24 chemically connected bacterial colonies.
The comparison with an electronic chip nevertheless has its limits. An operation takes about eight hours, compared with an infinitesimal amount of time on a computer. The method is therefore clearly not intended to replace processors: its interest lies in the possibility of directly integrating simple decisions into living systems.
One envisioned application concerns agriculture. Bacteria placed on roots or leaves could detect several signs of stress and then trigger an appropriate response. The researchers cite, for example, the production of a product against fungi when certain conditions are met.
This architecture mainly makes it possible to modify the circuit's behavior by moving existing strains rather than rewriting the bacteria's genome. Future research will need to transform these demonstrations on a growth medium into systems capable of functioning sustainably in real biological environments.