Scientists in the US are exploring whether it may be possible to influence bacterial behaviour instead of simply trying to destroy bacteria outright.
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 at the University of Minnesota set out to investigate how these bacterial signals shape the oral microbiome and whether interrupting those signals could help prevent harmful plaque build-up while preserving healthy bacteria.
Their findings—published in npj Biofilms and Microbiomes—could eventually influence treatments far beyond dentistry.
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 specialised 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,” A/Prof Mikael Elias said.
“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 colonisers 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 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,” lead author Rakesh Sikdar said.
“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 colonisers.
“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.
