Inside the human mouth, bacteria are in near constant communication. Roughly 700 bacterial species live there, and many exchange chemical messages through a process called quorum sensing. Some of these microbes communicate using signaling molecules known as N-acyl homoserine lactones (AHLs).

Researchers from the College of Biological Sciences and the School of Dentistry set out to investigate how these bacterial signals shape the oral microbiome and whether interrupting those signals could help prevent harmful plaque buildup while preserving healthy bacteria. Their findings, published in npj Biofilms and Microbiomes, could eventually influence treatments far beyond dentistry.

Scientists Target Bacterial Communication

The research team discovered several important patterns in how mouth bacteria interact:

• Bacteria living in dental plaque produce AHL signals in aerobic environments (such as above the gumline), and those signals can still affect bacteria in anaerobic environments (beneath the gumline).
• Removing AHL signals using specialized enzymes called lactonases increased populations of bacteria associated with good oral health.
• The findings suggest that 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.”

Oxygen Levels Change Bacterial Behavior

The researchers also found that oxygen plays a surprisingly important role in determining how these bacterial messages influence 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.”

This discovery suggests that bacterial communication works differently depending on where bacteria live inside the mouth. That insight could help researchers design more targeted approaches to controlling gum disease and maintaining a healthier balance of microbes.

Future Treatments Could Protect Healthy Bacteria

The next phase of the research will examine how bacterial signaling differs across various 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,” said Elias.

Researchers believe this strategy could eventually be expanded beyond oral health. Imbalances in the microbiome, known as dysbiosis, have been linked to numerous diseases throughout the body, including certain cancers. Scientists hope these findings could help lay the groundwork for future therapies that guide microbial communities toward healthier states rather than eliminating bacteria altogether.

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