Saliva's Defenders Fight Tooth Decay

It's a war in there but MUC5B is on defense in your mouth fighting tooth decay by weakening rather than annihilating the enemy, Streptococcus mutans. The oral battle zone or microbiome is better preserved when naturally occurring species aren't killed outright, scientists say.

MUC5B offers salivary defense against S. mutans, according to research published in Applied and Environmental Microbiology, an American Society for Microbiology publication. "We chose to study the interaction of MUC5B with Streptococcus mutans because it is the primary cavity-causing bacteria in the oral cavity," said first author Erica Shapiro Frenkel of Harvard University.

Just who are these defenders and how do they defend against tooth decay? Scientists describe them as one of the salivary mucins, key components of mucus, among the glycoprotein families that lubricate and protect the body. The research grew from the scientists' previous work demonstrating protective effects of gastric and other types of mucins.

"We wanted to apply these emerging ideas to a disease model that is a widespread, global public health problem, cavities," Frenkel said.

"We focused on the effect of the salivary mucin, MUC5B, on S. mutans attachment and biofilm formation because these are two key steps necessary for cavities to form. We found that salivary mucins don't alter S. mutans' growth or lead to bacterial killing over 24 hours. Instead, they limit biofilm formation by keeping S. mutans suspended in the liquid medium. This is particularly significant for S. mutans because it only causes cavities when it is attached, or in a biofilm on the tooth's surface."

The American Society for Microbiology represents more than 39,000 scientists and health professionals.

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