With a tweak to their genetic codes, bacteria have been coaxed to follow a chemical trail of a researcher's choosing.
Chemotactic bacteria, such as Escherichia coli, recognize and move toward certain chemicals. The chemicals bind to proteins on the microbe's surface, inducing an internal mechanism to drive the microbe's flagellum, a tail-like structure.
Chemists Justin P. Gallivan and Shana Topp of Emory University in Atlanta wanted bacterial cells "to follow things that we want them to follow," Gallivan says. Rather than engineering one of the bacterial-cell-surface proteins to recognize a new chemical, the researchers focused on one of the internal proteins that controls the E. coli flag