Effect of calcium on reactions between a salivary agglutinin and a serotype c strain of Streptococcus mutans.

Using a serotype c strain of Streptococcus mutans we found that the agglutinating activity could be quantitatively absorbed, and desorbed from the micro-organisms by a phosphate buffer. The desorbed agglutinin was found to be inactive in the absence of calcium. Calcium alone did not induce aggregation. At 0.1 mM calcium most of the activity was regained. Other cations could not substitute for calcium. On a molecular basis the ratio between calcium and agglutinin or bacteria is high, in the order of 10(7) and 10(4) respectively.