How Does Cavity Causing Bacteria Survive?

Researchers from the University of Basel’s Preventative Dentistry and Oral Microbiology Clinic and Department of Biomedical Engineering have found that extracellular polysaccharides play a central role in the survival capabilities of cavity causing bacteria in dental plaque. These bacteria live in biofilm and cause cavities by attacking dental enamel by converting sugar and starch into acids that dissolve out calcium from the enamel. The dissolution of calcium increases the concentration of calcium locally which creates an environment hostile to bacterial life.

The researchers investigated how bacteria manage to survive in dental plaque despite conditions of hostility. They suggested that extracellular polysaccharides (EPS) support the bacteria’s survival capabilities. EPS are substances that build extracellular cariogenic bacteria from sugar residue. These substances create biofilm’s scaffolding and ensure bacteria are able to anchor themselves in  dental plaque. The researchers showed the more that calcium cariogenic bacteria dissolve, the greater their calcium tolerance and survival capability in the biofilm. The team demonstrated that cariogenic bacteria develop mechanisms to help them survive the high concentrations of calcium.

The team showed that extracellular polysaccharides possess a high number of calcium binding sites which can integrate the free calcium into the biofilm. This neutralizes the toxic substance and strengthens the EPS structure of the biofilm. The EPS’ integration of calcium causes cavities in addition to helping cariogenic bacteria to survive in dental enamel. EPS integration of calcium inhibits the remineralization of the enamel since there is not enough free calcium present in the plaque. The researchers feel that this work is important to improve understanding of how calcium regulation occurs in cavities.

Source: Monika Astasov-Frauenhoffer and et. al., Exopolysaccharides regulate calcium flow in cariogenic biofilms, PLOS ONE, vol. 12, issue 10, 2017.

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