A quantitative study of calcium binding and aggregation in selected oral bacteria

Area of Science:

• Oral microbiology
• Biochemistry
• Dental research

Background:

• Calcium is crucial for oral health and bacterial interactions.
• Understanding calcium binding in oral bacteria is key to plaque formation and demineralization processes.

Purpose of the Study:

• To quantify calcium binding capacities and affinities in oral bacteria.
• To investigate the influence of extracellular polysaccharide, pH, and aggregation on calcium binding.
• To explore the role of calcium in bacterial association and plaque development.

Main Methods:

• Micro-equilibrium dialysis was used to measure calcium binding.
• Calcium binding capacities and affinities were determined for three oral bacterial species.
• The effects of pH, extracellular polysaccharide, and cell aggregation were analyzed.

Main Results:

• Calcium binding capacities varied among bacterial species (e.g., 41.5 +/- 5.4 mumol/g for S. downei at pH 7.0).
• Binding capacity decreased significantly at lower pH (e.g., 21.4 +/- 0.8 mumol/g for S. downei at pH 5.0).
• Calcium-facilitated bacterial association was observed in streptococci, with different mechanisms for calcium uptake and desorption.

Conclusions:

• Oral bacteria exhibit significant calcium binding, with pH being a critical factor.
• Calcium plays a role in bacterial aggregation and may influence plaque formation.
• Plaque calcium can act as a reservoir, potentially impacting demineralization during pH drops.