Calcium modulation of growth of Streptococcus mutans

The steady-state growth yield of Streptococcus mutans (in a Teflon chemostat using a chemically defined medium that was treated to lower trace metal contamination and supplemented with high-purity trace metals) was doubled by addition of 0.63 microM calcium. Subsequent increases in calcium concentration to 1.3 microM and 2.5 microM lowered steady-state growth yield below the level with no added calcium, suggesting that calcium has dose-dependent stimulatory and inhibitory effects on S. mutans.