More than 500 species of bacteria thrive in our mouths. But one type seems to play by its own rules.

The cells of most bacteria reproduce by splitting in two. Corynebacterium matruchotii takes a different approach. It divides into as many as 14 cells at once. That unique tactic might help it reclaim more space in the mouth after each toothbrushing.

“When we brush our teeth, we brush the bacteria away. But by the next day, it’s back,” says Gary Borisy. “We think it just crawls up by rapidly expanding into fresh territory.” Borisy is a microbiologist who worked on the study. He’s based at the American Dental Association Forsyth Institute. That’s in Cambridge, Mass.

C. matruchotii is one of the most common bacteria in our mouths. Near the gum line, it makes its home in dental plaque. That’s a type of biofilm — a slimy bunch of bacteria that can stick to hard surfaces in moist places.

In fact, this microbe acts sort of like a framework for more bacteria to grow, research had shown. Those bacteria then set up shop within tiny structures of dental plaque.     

It was microbiologist Scott Chimileski who noticed something odd about how C. matruchotii divides. He works at the Marine Biological Laboratory in Woods Hole, Mass.

He was part of a team looking at dental plaque from four healthy volunteers. Using a microscope, Chimileski spotted C. matruchotii cells splitting into many copies of itself very quickly.

“Once he presented the finding,” Borisy says, “we thought, ‘oh my God! This is absolutely amazing.’” Their team shared its surprising findings September 3 in the Proceedings of the National Academy of Sciences.

This video shows one fiber-like Corynebacterium matruchotii bacterial cell dividing into many daughter cells — each of which itself immediately and rapidly divides. This strategy may allow C. matruchotii to quickly spread through the human mouth.

These bacteria make quick splits

Here’s how C. matruchotii’s super-efficient division works.

A threadlike mother cell grows longer from one end before dividing into smaller bits. These bits are known as daughter cells. Depending on length, a mother cell could split into between three and 14 daughters. Each daughter cell starts growing right away in a rare process called multiple fission.

No other known bacterium divides into as many cells that immediately start growing and dividing. The scientists calculate that C. matruchotii colonies could grow almost half a millimeter (2 one-hundredths of an inch) per day.

The team next plans to study how this microbe forms a biofilm to which other bacteria in the mouth bind. What they learn could offer lessons for better oral health.