The first computers were biological: they had two arms, two legs and 10 fingers. “Computer” was a job title, not the name of a machine. The occupation vanished after programmable, electric calculating machines emerged in the late 1940s. We have thought of computers as electronic devices ever since.

Over the past 15 years or so, however, biology has been making a comeback of sorts in computing. Scientists in universities and biotech start-ups believe they are close to advancing the first biocomputers from mere research objects to useful, real-world tools. These systems, built out of genes, proteins and cells, include basic elements of computer logic: IF/THEN tests, AND and OR operations, even simple arithmetic operations. Some systems include primitive digital memories. Given appropriate biological inputs, these living computers generate (mostly) predictable outputs.

Within about the next five years, the first biological computers might be used as sensitive and accurate diagnostics and therapeutics for human diseases, including cancer, inflammatory diseases and rare metabolic disorders. We and others who are engineering these cellular logic systems envision a future — one not far off — in which they are safe and smart enough to treat disorders as well as identify them. The technology could make it possible to produce complex chemicals, such as biofuels and pharmaceuticals, in novel ways that are faster and less expensive than we can create today. It might allow us to respond to spills by lacing contaminated ecosystems with organisms designed to monitor and degrade toxins. ...