Study How the caries-causing bacteria survive in dental plaque

Extracellular polysaccharides play an important role in the survival of the bacteria

Certain bacteria in the mouth can trigger tooth decay. Researchers have now discovered how these bacteria can survive in dental plaque. In survivability so-called extracellular polysaccharides play a major role.

The researchers at the Department of Preventive Dentistry and Oral Microbiology and the Department of Biomedical Engineering at the University of Basel found that extracellular polysaccharides play a key role in the survival of bacteria in plaque. The experts published the results of their study in the English-language journal "PlOS ONE".

Bacteria play an important role in the development of tooth decay. Physicians are now investigating how harmful bacteria in plaque can survive. (Image: Igor Gromoff / fotolia.com)

Cariogenic bacteria convert sugar and starch into acids

So-called cariogenic bacteria attack the enamel. They convert sugar and starch into acids. These acids are able to dissolve calcium out of the enamel. The process triggered by the bacteria can then lead to the development of tooth decay. The harmful bacteria live in biofilms.

How can bacteria survive in a hostile environment??

When the calcium is released, it increases the local concentration of calcium. This leads to a hostile environment for bacteria. The researchers wanted to answer the question in their investigation, why the bacteria despite these conditions at all in the plaque can survive.

Extracellular polysaccharides promote the survival of the bacteria

The dentists had suggested that so-called extracellular polysaccharides (EPS) promote the bacteria's ability to survive. These are substances that form cariogenic bacteria from sugar residues. These bacteria are then applied outside their cells. They form the scaffolding of the biofilm and ensure that the bacteria can anchor themselves in the plaque.

Cariogenic bacteria develop protective mechanisms

The results of the study show that the more calcium the cariogenic bacteria degrade, the higher their tolerance to calcium. In addition, they can better survive in biofilms. The cariogenic bacteria develop mechanisms that provide protection against the existing concentration of calcium.

Extracellular polysaccharides neutralize the toxic content

The scientists also found that extracellular polysaccharides have a large number of so-called calcium binding sites. With these they put the dissolved calcium into the biofilm. The process actually neutralizes the toxic content. In addition, the EPS structure of the biofilm will be strengthened, the researchers explain.

Calcium binding through EPS improves bacterial survival and leads to tooth decay

The binding of calcium by the EPS not only leads to cariogenic bacteria in the enamel can survive, in addition, they also lead to the development of tooth decay. "By binding calcium, they inhibit remineralization of the enamel because it means that there is not enough free calcium in the plaque. This discovery is important in order to better understand calcium regulation in caries, "explains microbiologist and author Monika Astašov-Frauenhoffer in a press release from the University of Basel. (As)