Studies in the 1970s suggested that phages might time their escape by sensing the host cell’s electrical gradient. When researchers treated bacteria with cyanide, a poison that disrupts electrical currents, they observed that phage-induced lysis happened earlier than normal. A group of biophysicists at Texas A&M (Angelika Gründling, Michael Manson and Ry Young) finally answered these questions using a clever experiment that involved spinning bacteria. The flagellum is directly powered by the cell’s membrane potential; the larger this membrane potential is, the faster the flagellum spins. There are now charge-sensitive fluorescent proteins, such as pHluorin, whose color changes according to a cell’s electrical gradient.