Calcium ions play a critical role in calcification of Corynebacterium matruchotii

Dental calculus is a hardened deposit composed of calcium phosphate precipitated within dental plaque. While the involvement of dental calculus in the progression of periodontal disease is well established, many aspects of its formation process remain poorly understood. In this study, we focused on Corynebacterium matruchotii, a key bacterium involved in dental calculus formation, and investigated the role of calcium ions in calcification, as well as the associated internal and external changes in the bacterium through long-term observation. In the absence of calcium ions, no intracellular calcification was observed, and the lipid bilayer with the formation of holes in bacterial body was evident. In contrast, in the presence of calcium ions, lipid bilayer remained intact, and intracellular needle- and plate- like crystals were formed. Furthermore, calcified C. matruchotii showed increased flocculation compared to non-calcified C. matruchotii. These results indicate that the influx of calcium ions is essential for intracellular calcification. Calcium ions entry appears to reinforce the integrity of the lipid bilayer, providing a stable intracellular environment conductive to calcification. Moreover, calcified C. matruchotii may contribute to the nucleation of dental calculus by forming aggregates composed of both bacterial components and calcified material.