Bacteria are remarkably good at adapting. That ability helps them survive changing conditions, but it can also create problems when harmful species become resistant to antibiotics and disinfectants.
At the same time, bacteria are not simply enemies to eliminate. Many species play important roles in human health, including the hundreds of different microbes that live in the mouth. That raises an intriguing possibility: instead of trying to kill bacteria, could scientists influence how they behave and encourage healthier microbial communities?
Research published in 2025 in npj Biofilms and Microbiomes suggests that may be possible. Scientists studying dental plaque found that interfering with the chemical signals bacteria use to communicate can change which species thrive, potentially shifting the community toward bacteria associated with better oral health.
How Bacteria Communicate in the Mouth
The human mouth is home to roughly 700 species of bacteria. These microbes do not simply grow alongside one another. Many exchange chemical signals through a process called quorum sensing.
Quorum sensing allows bacteria to detect how many neighboring cells are present and coordinate group behaviors. Some oral bacteria communicate using molecules known as N-acyl homoserine lactones (AHLs).
Researchers from the College of Biological Sciences and the School of Dentistry examined how these signals shape dental plaque. Their goal was to determine whether bacterial communication could be manipulated to help maintain a healthier oral microbiome.
The oral microbiome refers to the community of microorganisms living in the mouth. When that community becomes unbalanced, potentially harmful bacteria can become more dominant and contribute to conditions such as periodontal disease.
Chemical Signals Can Cross the Gumline
The researchers found that bacteria within dental plaque produced AHL signals in aerobic environments (such as above the gumline), where oxygen is available.
Those chemical messages could also be detected by bacteria living in anaerobic environments (beneath the gumline), where oxygen levels are much lower.
This connection was important because conditions below the gumline can favor bacteria associated with periodontal disease.
The team also used specialized enzymes called lactonases to remove AHL signals. Lactonases break down these communication molecules, effectively interfering with the bacterial conversation.
When researchers disrupted AHL signaling, the dental plaque community shifted toward species more strongly associated with oral health.
Their findings suggest that carefully chosen enzymes might someday be used to alter the makeup of dental plaque and help maintain a healthier balance of microorganisms.
Dental Plaque Behaves Like an Ecosystem
“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.”
In other words, dental plaque changes over time rather than appearing all at once. Early communities may contain relatively harmless bacteria, while more complex communities can eventually include species strongly associated with gum disease.
The researchers hope that interfering with bacterial communication could make it possible to guide plaque toward an earlier, healthier state rather than attempting to eliminate the entire microbial population.
Oxygen Changes How Bacterial Signals Behave
One of the most important findings was that the effects of bacterial communication depended heavily on oxygen levels.
“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.”
That difference suggests that the same chemical signals can influence microbial communities in very different ways depending on where they occur in the mouth.
Above the gumline, where oxygen is more plentiful, disrupting AHL signaling favored bacteria linked with better oral health. Beneath the gumline, adding those signals encouraged later colonizing species associated with disease.
A Different Strategy for Preventing Gum Disease
The researchers now want to investigate how bacterial communication varies throughout the mouth and among people at different stages of periodontal disease.
Rather than broadly attacking oral bacteria with antimicrobial treatments, the long term goal is to find ways to influence the balance of the microbial community itself.
“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.
The approach could eventually have implications beyond dentistry. Similar microbial imbalances, often called microbiome dysbiosis, occur elsewhere in the body and have been associated with a range of health problems, including certain types of cancer.
Researchers hope that learning how to manipulate bacterial communication could eventually provide a foundation for therapies designed to steer microbial communities toward healthier states rather than simply destroying them.
The research was funded by the National Institutes of Health.