E. coli has no wires that scientists can pull apart to learn how its circuits work. Instead, they must do experiments of the sort Jacob and Monod carried out. They observe how quickly the bacteria respond to their environment, how quickly they make a certain protein or clear another one away. Scientists combine the results of experiment after exper

The deadly beauty of restriction and modification enzymes is that restriction enzymes are durable, whereas modification enzymes are short-lived. If E. coli loses the P1 virus, it quickly loses its shields and cannot make new ones.

Bernhard Palsson, a biologist at the University of California, San Diego, has overseen the construction of a model of E. coli’s metabolism.