Bacteria are often pictured as lone cells moving randomly about. In fact, millions of bacteria frequently stick together in well-organized colonies. This is slime-or, as microbiologists prefer to call it, "biofilm." A research team at the Center for Biofilm Engineering at Montana State University (MSU) in Bozeman has now identified the chemical signal secreted by bacteria that tells the microbes when to form-and when to desert-these bacterial structures.

The discovery could provide clues on ways to shut down the formation of biofilms. And that could mean a potful of applications-including controlling bacterial infections in hospitals and controlling contamination of water supplies. As a result of these implications, the findings "are of considerable significance," says molecular geneticist John Geiger, group leader for biotechnology at Olin, a Cheshire, Conn.-based producer of industrial biocides.