Bacteriolysis of Streptococcus mutans BHT by lysozyme and inorganic anions normally present in human saliva

Liberation of DNA from Streptococcus mutans BHT was elicited by hen egg-white lysozyme in the presence of low concentrations of additive inorganic anions. Significant lysis was observed at salt molarities within normal salivary concentrations. Lysis increased with anion concentration until apparent saturation plateau levels were attained. Thiocyanate and bicarbonate anions were more effective than chloride and fluoride anions at all salt molarities tested. The order of anion potency in the liberation of DNA was SCN^- > HCO^-₃ > Cl^- > F^-, although differences between SCN^- and HCO^-₃ as well as between Cl^- and F^- could be minimized by varying the relative enzyme, anion and bacterial-cell concentration. Although DNA was not released at low anion concentrations when the apparent amount of lysozyme bound per cell was high, liberation did occur at low lysozyme concentrations. After release of cell-bound lysozyme in low-molarity bicarbonate solutions, strain BHT retained approx. 10 times as much enzyme from reaction mixtures with high enzyme concentrations as from those with low. The results suggest that physiologic concentrations of various anions present in saliva may be sufficient to trigger lysis of oral microorganisms by lysozyme.