Bacteria for Brains

Problem: Some math problems can only be solved by throwing exponentially more computer processors at them.

Solution: Grow your processors like bacteria — literally.

Just ask the scientists who recently engineered bacteria to glow yellow when they stumbled upon a correct solution to a three-stop version of the "traveling postman" problem (where a postman takes the shortest path among a number of stops on his route).

How'd they do it? By treating green- and red-glowing genes as locations on the postman's route. The scientists chopped these genes in half, stuck them randomly into the DNA of bacteria and then grew up the microbes; those that glowed yellow signaled that the pieces correctly lined up in the shortest overall "path."

The researchers think their method could be used to solve increasingly complex problems. No word yet on the U.S. Postal Service's interest level. [More on computing with bacteria.]