The Heat Inactivation of Bacteriophages. 20

Abstract

In testing the therapeutic value of the lysed cultures of B. diphtherias it became necessary to destroy the slight amount of toxin present with bacteriophage in some of the filtrates. Since bacteriophage is comparatively resistant to heat it was thought that simple exposure to heat may destroy the toxin without destroying the phage present in the lysates. This, however, we were not able to accomplish. Exposure to heat sufficient to destroy all the toxin caused almost complete destruction of the phage. In a study of the mechanism of inactivation of phages by alcohol we concluded that the effect of alcohol was not due to the direct destruction of the active agent, but to the denaturation of the protein vehicle on which the lytic agent was adsorbed. 1 Suspecting that somewhat similar relation may exist in the inactivation of phages by heat, we attempted 2 series of experiments.

In the first we made use of our earlier finding that the addition of polyvalent cations to the medium containing phage protected it from inactivation by alcohol. 2 We found that the addition of enough CaCl₂, for instance, to bring its concentration between 0.002 m and 0.015 m, some degree of protection against heat inactivation may be secured. Optimum concentration of CaCl₂ differs with each phage, and it thus becomes necessary to find a suitable concentration for each phage and even for each batch of the same phage, a laborious and time-consuming procedure.

In later experiments we used another method suggested by Spiro that glycerin, carbohydrates, urea, urethan, etc., prevent denaturation of proteins during coagulation. 3