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Study: How the tooth decay bacteria survive in the plaque


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

Certain bacteria in the mouth can cause tooth decay. Researchers have now discovered how these bacteria can survive on plaque. So-called extracellular polysaccharides play a major role in survivability.

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

Cariogenic bacteria convert sugar and starch into acids

So-called cariogenic bacteria attack the enamel. To do this, they convert sugar and starch into acids. These acids are able to extract calcium from the tooth enamel. The process triggered by the bacteria can then lead to the development of caries. The harmful bacteria live in biofilms.

How can bacteria survive in a hostile environment?

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

Extracellular polysaccharides promote bacterial survival

Dentists suspected that so-called extracellular polysaccharides (EPS) promote the ability of the bacteria to survive. These are substances that form cariogenic bacteria from sugar residues. These bacteria are then created outside of their cells. They form the scaffolding of the biofilm and ensure that the bacteria can anchor themselves in the dental plaque.

Cariogenic bacteria develop protective mechanisms

The results of the study show that the more calcium the cariogenic bacteria break down, the higher their tolerance to calcium. It also helps them survive better in biofilms. The cariogenic bacteria develop mechanisms that offer 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 incorporate the extracted calcium into the biofilm. The process actually neutralizes the toxic content. In addition, the EPS structure of the biofilm is 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 means that cariogenic bacteria can survive in the tooth enamel, they also lead to the development of caries. “By binding calcium, they inhibit the remineralization of the tooth enamel because it means that there is no longer enough free calcium in the plaque. This discovery is important to better understand calcium regulation in tooth decay, ”explains the microbiologist and author of the Monika Astašov-Frauenhoffer study in a press release from the University of Basel. (as)

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