According to IRNA’s science desk, a report by *SciTechDaily* states:
In electronic devices, a transistor acts like a switch that turns the flow of electricity on and off. In this biological system, engineered bacteria play a similar role; by producing small molecules, they either transmit messages to subsequent parts of the circuit or halt them.
The team developed two types of switch-like bacteria and three types of intermediary bacteria that relay messages from one point to the next. Together, these five bacterial types function like components that can be arranged in various configurations to build diverse circuits.
In a new study, researchers used this system to construct circuits capable of combining two or three inputs and sending a signal to a specific destination.
Hamid Doosthosseini, a postdoctoral researcher at MIT and the lead author of the study, says: "We have built some of the fundamental components of a computer, but virtually any operation can be constructed using these five types of bacteria."
Future Application: Biological Circuits on Plants
Ultimately, the researchers hope to create biological circuits that can be placed on plant leaves or roots. These circuits could process information regarding environmental conditions—such as drought or pest infestations—and trigger an appropriate response. Christopher Voigt, head of the Department of Biological Engineering at the Massachusetts Institute of Technology (MIT), is the senior author of this paper, which was published in the journal *Nature Chemical Biology*.
Why is it difficult to build these circuits within a single cell?
Synthetic biology circuits are typically created by engineering cells to produce proteins that act like on/off switches to control genes. However, the number of such switches is limited, and packing multiple circuits into a single cell places a strain on its structure.
Instead of fitting the entire circuit into one cell, the research team engineered individual cells so that each functions as a transistor. To construct these transistors, they used a bacterium called *Pantoea agglomerans*, which commonly grows on surfaces such as plants. They created two types of bacterial transistors controlled by a molecule known as OC-6: one is activated by the molecule, while the other is deactivated by it.
Connecting Bacteria
The team also engineered three additional types of bacteria to act as intermediaries. These bacteria receive a signal from one transistor, convert it into a new form, and pass it on to the next transistor. In this way, researchers can connect the bacteria much like components on an electronic circuit board.
To assemble these circuits, the researchers used a specialized printer to deposit bacterial clusters onto a layer of agar (a nutrient-rich gel medium that supports bacterial growth). Neighboring clusters were spaced approximately 5 millimeters apart. This spacing ensures that each signal reaches only the nearest cluster, thereby controlling the path of information flow.
From Bacteria to Computation; What do living circuits do?
Researchers demonstrated that a single transistor—depending on its position within the circuit—can perform various logic operations (such as AND, OR, and IF). They also combined transistors into more advanced systems. These circuits were capable of summing two signals and functioning as a demultiplexer (a unit that directs a single input signal to one of several possible outputs). The largest circuit in the study consisted of 24 interconnected bacterial clusters.
Voigt says, "This work shows that we can achieve complex functions by linking simpler functions within individual cells. From a computational standpoint, there is nothing a smartphone can do that these circuits cannot."
These living circuits operate much more slowly than conventional computers. Each calculation takes about eight hours; however, this speed is sufficient for the researchers' intended applications.
Voigt notes, "We aren't trying to replace computers. Our goal is to endow plants and living organisms with decision-making capabilities. Imagine bacteria situated on a plant's roots; if they monitor the plant's condition overnight, that timeframe is incredibly fast compared to a growing season—which spans several months."
He adds, "In agriculture, these circuits could be placed on plant roots to detect issues such as drought, pest infestations, or disease. Once a problem is identified, the circuit could trigger a response, such as the production of a natural fungicide."