Phage-resistant and phage-carrying strains of lactic streptococci

Abstract

1. The types of resistance acquired by certain related strains of Str. cremoris as a result of phage action were investigated.2. Some partially resistant forms of Str. cremoris were able to ‘carry’ phage in symbiotic association when subcultured daily in milk for long periods of time.3. The phage ‘carrying’ power of the cultures was of a non-inherent nature. ‘Purification’ of the phage-carrying cultures by plating resulted in the production of phage-free colonies.4. Under certain circumstances, the presence of symbiotic phage in a culture gave a measure of protection against attack by other phage races.