It turns out the bacteria in dental plaque are talking to each other, and University of Minnesota researchers say interrupting those messages may shift the mix of microbes toward better oral health.

The team found that some plaque bacteria use chemical signals called N-acyl homoserine lactones, or AHLs, to coordinate growth. In the study, published in npj Biofilms and Microbiomes, researchers tested how those signals shape the oral microbiome and what happens when they are blocked.

They reported that bacteria in dental plaque produce AHL signals in aerobic environments, such as above the gumline, and that those signals can still affect bacteria in anaerobic environments beneath the gumline.

The researchers also found that removing AHL signals with specialized enzymes called lactonases increased populations of bacteria associated with good oral health.

The findings suggest carefully selected enzymes may be able to reshape dental plaque communities and support a healthier oral microbiome.

“Dental plaque develops in a sequence, much like a forest ecosystem,” said Mikael Elias, associate professor in the College of Biological Sciences and senior author of the study.

“Pioneer species like Streptococcus and Actinomyces are the initial settlers in simple communities , they’re generally harmless and associated with good oral health. Increasingly diverse late colonizers include the ‘red complex’ bacteria like Porphyromonas gingivalis, which are strongly linked to periodontal disease. By disrupting the chemical signals bacteria use to communicate, one could manipulate the plaque community to remain or return to its health-associated stage.”

The researchers said oxygen levels also changed how the signals affected plaque growth.

“What’s particularly striking is how oxygen availability changes everything,” said lead author Rakesh Sikdar.

“When we blocked AHL signaling in aerobic conditions, we saw more health-associated bacteria. But when we added AHLs under anaerobic conditions, we promoted the growth of disease-associated late colonizers. Quorum sensing may play very different roles above and below the gumline, which has major implications for how we approach treatment of periodontal diseases.”

The next phase of the research will examine how bacterial signaling differs across areas of the mouth and in people with different stages of periodontal disease.

“Understanding how bacterial communities communicate and organize themselves may ultimately give us new tools to prevent periodontal disease , not by waging war on all oral bacteria, but by strategically maintaining a healthy microbial balance,” Elias said.

Funding for the study was provided by the National Institutes of Health.

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