The Lysis of Pneumococcus by Saponin

Abstract

Pneumococci are not dissolved by saponin when tested in plain broth culture. Treatment with cholesterol renders them susceptible to complete and rapid lysis by saponin; Cholesterol exerts a direct action, independent of bacterial reproduction. The bacteria must be in contact with cholesterol for a definite time prior to addition of saponin, to obtain lysis. Excess saponin inhibits sensitization by cholesterol. Conversely, excess cholesterol inhibits lysis by saponin. Animal fluids, e.g., blood, or ascitic and pleural fluids, act similarly to cholesterol. Evidence is presented to show that the activity of these fluids is due to their cholesterol content. When cholesterol is esterified it loses its affinity for saponin, and becomes incapable of sensitizing pneumococci to saponin. The theory is advanced that the lysis is due to a union of saponin with the cholesterol assimilated by the bacteria during sensitization. The parallelism between saponin bacteriolysis and saponin hemolysis is noted.