True Polyvalence of Pure Bacteriophages. ∗

Abstract

As found in their natural environment, bacteriophages often exhibit lytic activity against a variety of organisms sometimes quite unrelated to each other. This polyvalence is usually due to the presence of several independent phages which can be separated from each other by special procedures. Frequently, however, even such isolated single phages, satisfying all known criteria of purity, may exhibit activity against several more or less closely related species of bacteria. In such cases the characteristics of these bacteriophages usually remain immutable no matter which one of the organisms susceptible to their activity is used for their propagation. 1 Since the active principle in such instances is regenerated equally well on either one of the several susceptible organisms, it is perhaps possible to suppose that the active principle is represented by a very similar if not an identical substance in each case, and that the bacteria in turn have a common element in their composition (“receptor”) rendering them susceptible to it. If this could be proven, the nature of this true polyvalence of pure phages would be satisfactorily explained. We have recently made some observations which bring supporting evidence for such a view.

One of the coli-phages in our collection, used in the various experiments in our laboratory for nearly 6 years and invariably found to be pure according to all accepted criteria, exhibits the same degree of lytic activity against our type strains of B. coli, B. dysenteriae “Shiga”, and B. dysenteriae “Flexner”, irrespective of whether it is propagated with one or another of these organisms. When this phage is subjected to heating, all 3 valencies disappear at the same time. However, if the speed of inactivation by heat is delayed by the addition of glycerin or of saccharose, 2 the Shiga and Flexner valencies disappear slightly in advance of that against B. coli (see protocol).