Your mouth is the house of one of the most diverse ecosystems on the planet. Can you imagine? But Yes, it’s true: there is a thriving ecosystem of more than 500 different species of bacteria living in distinct, structured communities called biofilms. Surprisingly, it doubles after splitting (or dividing) into two, suggests a new study from the Marine Biological Laboratory (MBL) and ADA Forsyth.
Corynebacterium matruchotii is one of the most common bacteria living in dental plaque. Scientists uncovered an interesting mechanism of cell division in C. matruchotii. They found that this filamentous bacterium splits into multiple cells at once after division. This process is known as multiple fission.
The fission depends on the length of the original mother cell. Also, cell growth occurs only at one pole of the mother filament—called “tip extension.”
Scientists observed that C. matruchotii cells divide into up to 14 cells simultaneously.
This study highlights how these bacteria proliferate, compete for resources with other bacteria, and maintain their structural integrity within the intricate environment of dental plaque.
Paper co-author Jessica Mark Welch, senior scientist at ADA Forsyth and adjunct scientist at the MBL, said, “Reefs have coral, forests have trees, and the dental plaque in our mouths has Corynebacterium. The Corynebacterium cells in dental plaque are like a big, bushy tree in the forest; they create a spatial structure that provides the habitat for many other species of bacteria around them.”
“These biofilms are like microscopic rainforests. The bacteria in these biofilms interact as they grow and divide. The unusual C. matruchotii cell cycle enables this species to form these very dense networks at the core of the biofilm.”
This study extends on a 2016 study that used an imaging technique to visualize the spatial structure of dental plaque extracted from healthy donors. The earlier study looked at groups of bacteria in dental plaque, known as “hedgehogs,” because of their shape. It was found that filamentous C. matruchotii bacteria form the main part of the hedgehog structure.
In this new study, scientists determined the biology of C. matruchotii closely. Using time-lapse microscopy, they studied how the filamentous cells grow and imaged bacterial growth dynamics of the miniature ecosystem in real-time.
They observed how these bacteria interact, use the space, and, for C. matruchotii, the impressive way they grow.
Even after brushing, this biofilm comes back. From experiments measuring cell growth in micrometers per hour, scientists estimated that C. matruchotii colonies can grow up to half a millimeter per day.
Other Corynebacterium species live on the skin and in the nasal cavity. These species are shorter and rod-shaped and don’t grow by extending their tips or dividing in multiple ways.
“Something about this very dense, competitive habitat of the dental plaque may have driven the evolution of this way of growing,” said Chimileski.
C. matruchotii don’t have flagella, so they can’t move on their own. Scientists think their unique way of growing and dividing helps them explore their surroundings, much like the way fungi and soil bacteria use networks to spread out.
“If these cells have the ability to move preferentially towards nutrients or towards other species to form beneficial interactions—this could help us understand how the spatial organization of plaque biofilms comes about,” said Chimileski.
“Who would have thought that our familiar mouths would harbor a microbe whose reproductive strategy is virtually unique in the bacterial world,” said co-author Gary Borisy, principal investigator at ADA Forsyth and former director of the Marine Biological Laboratory. “The next challenge is to understand the meaning of this strategy for the health of our mouths and our bodies.”
Journal Reference:
- Chimileski, Scott et al, Tip extension and simultaneous multiple fission in a filamentous bacterium, Proceedings of the National Academy of Sciences (2024). DOI: 10.1073/pnas.2408654121
