March 7, 2005

While bacteria cannot speak or hear, their livelihood and ability to cause infections rest on effective communication skills. Large assemblies of networked bacteria called biofilms communicate by quickly trading chemical messages back and forth through a process known as quorum sensing. Scientists know that certain harmful bacteria use quorum sensing to evade the human immune system, and they also understand a good deal about how biofilms form and function. Until now, though, researchers were not aware that the human body could defend itself against quorum-sensing bacterial behaviors.

E. Peter Greenberg, Ph.D., of the University of Iowa in Iowa City discovered that one type of human lung cell, called an epithelial cell, has the means to cope with the potentially harmful quorum sensing that occurs within certain biofilms. He grew epithelial and other types of mammalian cells in laboratory dishes, then added molecules used in quorum sensing by Pseudomonas aeruginosa, the bacterium that causes most of the fatal lung infections in people with cystic fibrosis. Greenberg found that only the epithelial cells were capable of short-circuiting quorum sensing through the actions of an enzyme that blocked the bacterial signal.

The work is noteworthy because it suggests the existence of a built-in human defense system against certain serious bacterial infections, including those common in people with cystic fibrosis. Scientists could capitalize on this new knowledge in searching for medicines to boost the body's natural ability to stop quorum-sensing signals. The research may also point to other innovative approaches to treating chronic infections linked to biofilm formation.