Like all living things, bacteria adapt to survive. Over time, bacteria have been developing resistance to common antibiotics and disinfectants, which poses a growing problem for healthcare and sanitation. However, many species of bacteria are beneficial and even essential for human health. What if there was a way to change the behavior of bacteria in the body to prevent illness and poor health outcomes?
Bacteria are very "talkative." Constant streams of communication, known as quorum sensing, occur between and among the 700 species of bacteria that live in a human mouth. A number of them communicate via special molecules called N-acyl homoserine lactones (AHLs).
A team in the College of Biological Sciences and the School of Dentistry wanted to better understand how bacteria in the mouth communicate, and whether this communication could be "hacked" to prevent the formulation of plaque and maintain a healthy oral biome. The research, newly published in the journal npj Biofilms and Microbiomes, has startling implications for the future of medicine.
The team found:
- Bacteria in dental plaque produce AHLs signals in aerobic environments (such as above the gumline), and these messages can be received by bacteria in anaerobic environments (beneath the gumline).
- Removing AHL signals (with specialized enzymes called lactonases) enriched positive health-associated dental plaque species.
- The results suggest that the use of different enzymes could modify the dental plaque community and potentially be used to maintain a healthy microbial population.
"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."
"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 step for researchers is to study how bacterial messaging occurs in different parts of the mouth, and in patients with varying 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. Eventually, the team hopes this method can be the foundation for therapeutics that can be used throughout the body, where microbiome dysbiosis causes issues, including in certain types of cancer.
Funding was provided by the National Institutes of Health.
