Bacteria in your mouth multiply in a very unique way

One of the most diverse ecosystems on the planet might be closer than you realize – right inside your mouth. This bustling environment hosts over 500 species of bacteria, which form structured communities known as biofilms. 

Almost all of these bacteria reproduce through binary fission, where a single mother cell divides into two daughter cells.

However, new research from the Marine Biological Laboratory (MBL) and ADA Forsyth reveals an extraordinary mode of cell division in Corynebacterium matruchotii, a common bacterium found in dental plaque. 

Multiplying mouth bacteria

Unlike typical bacteria, C. matruchotii undergoes multiple fission, a rare process where a single cell divides into multiple cells simultaneously. The study, published in the journal Proceedings of the National Academy of Sciences, uncovers this unique division mechanism.

The research team discovered that C. matruchotii can produce up to 14 new cells at once, depending on the size of the original cell. Notably, these bacteria only extend growth from one end of the filament – a process known as “tip extension.”

Microbial community of dental plaque 

Within the dental plaque biofilm, C. matruchotii acts as a structural scaffold. Dental plaque is just one of many microbial communities within the broader human microbiome, a complex environment of microorganisms living harmoniously within a healthy body. 

The research provides insight into how these bacteria proliferate, compete for resources, and maintain structural integrity within dental plaque.

“Just as coral forms reefs and trees create forests, Corynebacterium in dental plaque forms a dense, bushy structure that supports a variety of other bacterial species,” explained Jessica Mark Welch, a senior scientist at ADA Forsyth and adjunct scientist at MBL.

“These biofilms are like miniature rainforests. Bacteria interact dynamically as they grow and divide. We believe that C. matruchotii’s unique cell cycle helps it establish dense networks at the core of the biofilm,” added lead author Scott Chimileski, a research scientist at MBL.

Growth strategy of mouth bacteria 

The study builds on a 2016 research paper that utilized an imaging technique known as CLASI-FISH (combinatorial labeling and spectral imaging fluorescent in situ hybridization) to visualize the spatial organization of dental plaque. 

The earlier study revealed that filamentous C. matruchotii cells form the backbone of structures resembling “hedgehogs” within the plaque.

The current research delves deeper into the biology of C. matruchotii, using time-lapse microscopy to observe how these filamentous cells grow. 

Rather than providing a static image of this microbial environment, the scientists captured real-time dynamics of bacterial growth, interactions, and the remarkable growth strategy of C. matruchotii.

Fundamental biology of mouth bacteria

“To understand how various bacteria collaborate in the plaque biofilm, we need to grasp the fundamental biology of these microorganisms that reside exclusively in the human mouth,” Welch said.

Despite regular brushing, dental plaque reappears, which led the scientists to estimate that C. matruchotii colonies can grow up to half a millimeter per day. 

Although other Corynebacterium species are found in different parts of the human body, such as the skin and nasal cavity, these species do not exhibit the same elongation or multiple fission behavior.

“This unique growth strategy might have evolved due to the competitive nature of the dental plaque environment,” Chimileski suggested.

Broader implications of the study

C. matruchotii lacks flagella, which means it cannot move actively. Researchers speculate that its distinctive elongation and cell division strategies might serve as a means to explore its environment, similar to how fungal mycelia or soil-dwelling Streptomyces bacteria operate.

“If these cells can move towards nutrients or interact with other species to form beneficial relationships, it could help us understand how the spatial organization of plaque biofilms develops,” Chimileski said.

Study co-author Gary Borisy, a principal investigator at ADA Forsyth and former director of the MBL, noted that it is remarkable that our mouths harbor a microbe with such a unique reproductive strategy. “The next step is to explore how this strategy impacts oral and overall health.”

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