"These bacteria should not be able to live in the mouth," says Quivey, "but they adapt to the acidic environment and thrive, thanks to the special defenses they use. Not only that, but the acid they produce harms other bacteria, allowing S. mutans to dominate. We're trying to make the human mouth, the only hospitable environment that S. mutans has ever found, inhospitable."

S. mutans is one of hundreds of types of bacteria in the human mouth. When people eat sugary foods, S. mutans eats the sugars, coats the teeth, excretes acids, and forms a pudding-like goo plaque that consists of bacteria, sugars, and other substances all locked together in a matrix that sticks to teeth. As the crowd of bacteria gathers, it becomes tough for saliva, a healthful substance that bathes the teeth in nutrients and fights cavities, to reach and cleanse the teeth.

"Within an hour after you eat, you can run your tongue over your teeth and feel a sort of film. That's plaque really, a community of bacteria making themselves comfortable for a long-term stay in your mouth. It can really get disgusting in there," says Quivey."

With S. mutans comfortably lodged along our tooth surfaces, the pH in our mouths quickly plummets, becoming 100 to 1,000 times more acidic than normal. Without frequent brushing and flossing, the assault on our teeth results in cavities quickly.

Like S. mutans, other bacteria have the ability to change their cell membranes to cope with harsh conditions. E. coli bacteria happily ensconced in red meat perform a similar trick as they travel through the human digestive system. Another harmful bacterium, Listeria, changes its membrane properties to allow it to live even in the cool temperatures of the refrigerator.

Matching the bacteria's abilities, however, are various human strategies to kill the microbes. Many cu
'"/>

Contact: Tom Rickey
trickey@admin.rochester.edu
585-275-7954
University of Rochester Medical Center
25-Jun-2004