
Under ultraviolet light in a Petri dish containing laundry whitener, symbiotic bacteria with a mutant bluB gene (lower right) fluoresce brightly, while the same bacteria with no mutation only glow slightly (top right), and bacteria with another mutation (in the exoY gene) are completely dark. Image: Michiko TagaFor decades, scientists have wondered how living organisms manufacture the essential vitamin B12. Now, using laundry whitener and dirt-dwelling bacteria--the everyday ingredients of an undergraduate science experiment--researchers may have found the major clue they need to solve the mystery.

