Scientists have long believed a certain biochemical pathway involved in the folding and delivery of proteins to cell membranes is essential for survival. Now University of Florida researchers have discovered that Streptococcus mutans, the decay-causing organism that thrives in many a mouth, can do just fine without it.

The findings, reported this month in the Proceedings of the National Academy of Sciences, have rocked the cellular biology scientific community, which has long considered the pathway to be crucial. The report may also explain why strains of the bacteria can survive in the harsh acidic environment they create in the mouth.

"We were met with skepticism because the dogma was that this biochemical pathway is key for all living cells," said study investigator Jeannine Brady, Ph.D., an associate professor of oral biology at the UF College of Dentistry. "As far as we know, this is the first example of any bacteria that can cope without this pathway; all of the existing literature indicated it is vital."

The signal recognition particle, or SRP, pathway is a primary mechanism by which proteins are chaperoned from cellular assembly lines, where they are made, to the protective outer surface of the cells, where they are inserted. Without a steady infusion of proteins, the membrane weakens and the cell - in this case, a bacterium - becomes unable to protect itself from harsh environmental conditions.

In the human mouth, its natural environment, it is typically S. mutans that goes on the attack. When sugary foods are eaten, the S. mutans population explodes, excreting lactic acid as it digests sugar. The acid makes life difficult for other helpful bacteria and demineralizes tooth enamel, causing decay.

According to the U.S. Centers for Disease Control and Prevention, 95 percent of adult American
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Contact: Lindy McCollum-Brounley
lbrounley@dental.ufl.edu
352-273-5782
University of Florida
13-Dec-2005