Format

Send to

Choose Destination
PLoS One. 2017 Oct 12;12(10):e0186256. doi: 10.1371/journal.pone.0186256. eCollection 2017.

Exopolysaccharides regulate calcium flow in cariogenic biofilms.

Author information

1
Department of Preventive Dentistry and Oral Microbiology, University Center for Dental Medicine, University of Basel, Basel, Switzerland.
2
Department of Environmental Health Sciences, Arnold School of Public Health, Columbia, South Carolina, United States.
3
Center of Biomechanics & Biocalorimetry, c/o Department Biomedical Engineering (DBE), University of Basel, Allschwil, Switzerland.

Abstract

Caries-associated biofilms induce loss of calcium from tooth surfaces in the presence of dietary carbohydrates. Exopolysaccharides (EPS) provide a matrix scaffold and an abundance of primary binding sites within biofilms. The role of EPS in binding calcium in cariogenic biofilms is only partially understood. Thus, the aim of the present study is to investigate the relationship between the calcium dissolution rates and calcium tolerance of caries-associated bacteria and yeast as well as to examine the properties of EPS to quantify its binding affinity for dissolved calcium. Calcium dissolution was measured by dissolution zones on Pikovskaya's agar. Calcium tolerance was assessed by isothermal microcalorimetry (IMC) by adding CaCl2 to the bacterial cultures. Acid-base titration and Fourier transform infrared (FTIR) spectroscopy were used to identify possible functional groups responsible for calcium binding, which was assessed by isothermal titration calorimetry (ITC). Lactobacillus spp. and mutans streptococci demonstrated calcium dissolution in the presence of different carbohydrates. All strains that demonstrated high dissolution rates also revealed higher rates of calcium tolerance by IMC. In addition, acidic functional groups were predominantly identified as possible binding sites for calcium ions by acid-base titration and FTIR. Finally, ITC revealed EPS to have a higher binding affinity for calcium compared, for example, to lactic acid. In conclusion, this study illustrates the role of EPS in terms of the calcium tolerance of cariogenic microbiota by determining the ability of EPS to control free calcium concentrations within the biofilms as a self-regulating mode of action in the pathogenesis of dental caries.

PMID:
29023506
PMCID:
PMC5638444
DOI:
10.1371/journal.pone.0186256
[Indexed for MEDLINE]
Free PMC Article

Supplemental Content

Full text links

Icon for Public Library of Science Icon for PubMed Central
Loading ...
Support Center