Studies on a smooth phage resistant variant of Brucella abortus II. Mechanism of phage resistance.

The properties of a smooth phage resistant variant of Brucella abortus were studied in an attempt to determine the mechanism of phage resistance. This strain was fully capable of adsorbing phage but penetration, and hence replication, did not occur. No evidence of lysogeny or a phage carrier state could be obtained and gross chemical differences between the resistant strain and its phage susceptible parent were not detected. The phage resistant variant showed increased resistance to lysis from without, either by phage or by lysozyme, in the presence of chelating agents. It was concluded that resistance was the result of a modification in cell wall structure conferring resistance to lysozyme-like enzymes, thus preventing penetration of phage.