The relationship of the streptococcal hemolysin which is recognized on incubation of RBC with streptococcal cells (cell-bound hemolysin, CBH), to RNA hemolysin, a representative of oxygen-stable hemolysin (streptolysin S) has been studied. A number of similarities have been found in the conditions for optimal production of each of these hemolysins, a requirement for cysteine, Mg++, and glucose; maximal production by streptococci in the stationary phase; similar curves of pH-dependence. In both systems, the production of hemolysin was inhibited by certain antibiotics, by ultraviolet irradiation, and by sonic disruption and was absent in the same streptococcal mutant strain. The hemolytic activity of both systems was inhibited by lecithin, trypan blue, and papain. Similarities were also found in relative susceptibilities to the two hemolytic systems of erythrocytes of a number of animal species.

These data support a suggestion advanced in an earlier study that a streptococcal hemolytic moiety, which can be induced by, and carried on, a number of diverse agents to comprise the group of oxygen-stable hemolysins, serves, in its original attachment to a component of the streptococcal cell, to produce the hemolytic effect recognized as the cell-bound hemolysin.

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