. coli have a bad rap. The very name conjures up mental images — and sounds and smells — of diarrhea and vomiting, but that species of bacterium is actually a kind of golden goose. Even as you’re reading these words, they are teeming in your gut, producing helpful vitamins; in labs around the world, they are filling Petri dishes with offspring, allowing for all kinds of experiments. And at the Massachusetts Institute of Technology, a team of scientists engineered them so that they would turn bright green when they came into contact with certain chemicals.
That sounds really useful, but there is a catch: It was all happening in liquid-filled lab dishes, which hampered many of the real-world applications.