Leading cause of cavities, S. mutans, evolved over time
SUMMARY: In a recent study, researchers analyzed how the cavity-causing bacteria S. mutans adapted to humans' diets.
Posted: July 30, 2014
Everyone knows that sugar causes cavities. But even more damaging than that tasty white sweetener is Streptococcus mutans, a natural bacteria that lives in the mouth and is the No. 1 cause of cavities.
Recently, international researchers attempted to find out if S. mutans has changed over time by sequencing its genetic material from past populations. They discovered that S. mutans has increased in genetic alterations over the last several thousand years - a shift that may coincide with large-scale dietary changes.
One of the most prominent dietary shifts is known as the Agricultural Revolution, or Neolithic period, which occurred 10,000 years ago (during the Stone Age) when humans went from being hunters and gatherers to farmers and animal herders. According to dental experts, this is the single most significant development in human history, as our bodies weren't equipped to handle foods produced from cultivating crops and domesticating animals, leading to the most dramatic rise in cavities ever. You can bet that at the start of this time period, new diets coupled with poor oral hygiene produced some mummifying halitosis.
The researchers examined the bacterium in the mouths of 11 individuals from the Bronze Age (around 3,000 B.C. to 1,700) up to the 20th century, from locations in Europe and pre- and postcolonial America. The oldest case was that of an individual who lived around 1,200 B.C. and whose body was found in a burial chamber in the Montanisell Cave in Lleida, Spain, while the most recent one is from the beginning of the 20th century.
The results indicated that in the most recent samples there was more genetic diversity in S. mutans, suggesting a population-based expansion by the bacterium that may have occurred in conjunction human expansion during the Neolithic period. The researchers honed in on dextranase, a virulence factor that prevents tooth decay by eliminating dental plaque.
"The relationship is well known between the increase in frequency of caries and the dietary changes that occurred in the Neolithic, or with the European discovery of America, with the large-scale introduction of sugarcane to Europe, or the Industrial Revolution, but what was not known was whether this change happened jointly with changes at a genetic level [in] this bacterium," the article's main author, Marc Simón, a trainee researcher in the Autonomous University of Barcelona's biodiversity doctorate program, explained in a press release.
This study provided a piece of long-sought-after evidence for the historical relationship between human eating habits and dental cavities. The discovery, published in Proceedings of the Royal Society B, was led by researchers from UAB and the National Laboratory of Genomics for Biodiversity in Mexico.
In short, S. mutans have adapted based on the changes found in dextranase. Researchers point out that knowing how the cavity-causing bacteria reacted in the past may give us an idea of how they will do so in the future, thereby preparing us for reducing cavities and bad breath caused by caries.