New biological transistors use living bacteria to compute logic inside live plants

MIT researchers have engineered bacteria that can perform the basic switching functions of transistors. The breakthrough lets them build biological circuits from living cells instead of electronic components. The team printed bacterial colonies onto agar inside Petri dishes. Chemical signals then travel between the colonies, allowing the cells to process information and perform logic operations. The approach could eventually bring computation directly into biological environments. Researchers envision bacteria on plant leaves or roots that detect stress and trigger responses without conventional electronics. Bacteria become switches The researchers used Pantoea agglomerans, a bacterium commonly found on plants and other surfaces. They engineered two versions of the bacterium to work as biological transistors. One transistor switches on when it receives a chemical signal. The other performs the opposite function. Both can detect another molecule and produce a separate chemical output. Three additional bacterial strains act as relays between the transistors. They translate one chemical signal into another that the next circuit component can recognize. That setup gives researchers a way to connect individual cells into larger networks. Electronic circuits move electrical signals through wires, while these biological circuits move molecules between bacterial colonies. The team printed colonies onto agar with about 5 millimeters separating neighboring cells. That spacing helps signals move toward the intended downstream colony. Researchers can then change the circuit’s layout without redesigning every component. The researchers demonstrated several logic functions using their bacterial transistors. Their circuits can process multiple inputs and direct signals toward specific outputs. One system adds two inputs together using 24 bacterial colonies. Other configurations can perform OR and implication operations. The team also built a demultiplexer. This circuit takes one incoming signal and directs it toward different destinations based on another control signal. The modular design addresses a limitation in conventional synthetic biology. Researchers often place many functions inside a single cell. That strategy can eventually overload the cell’s protein-making machinery. It also creates problems when different biological components interfere with one another. Separating functions across multiple cells offers another path toward more complex biological computing. Computing inside plants These circuits remain dramatically slower than electronic computers. A bacterial circuit takes about eight hours to complete a calculation. That limitation matters less for applications tied to biological processes. Plants operate across hours, days and entire growing seasons. MIT researchers want to eventually place these circuits on plant roots or leaves. The bacteria could detect signals associated with drought, pests or disease. A detected condition could then trigger a biological response. One proposed application involves producing a fungicide after the circuit detects plant stress. “We’re not trying to replace computers,” said Christopher Voigt, head of MIT’s Department of Biological Engineering. The goal is to givebiological systems their own computational control. The work points toward a different kind of computing architecture. Instead of bringing biology into electronic systems, researchers are starting to put computation directly into living systems.The research appeared in Nature Chemical Biology and received partial funding from DARPA and IARPA.Get the latest in engineering, tech, space & science - delivered daily to your inbox.Aamir is a seasoned tech journalist with experience at Exhibit Magazine, Republic World, and PR Newswire. With a deep love for all things tech and science, he has spent years decoding the latest innovations and exploring how they shape industries, lifestyles, and the future of humanity.