Mutation of Cholera Vibrios

In a previous communication (1931) we showed that colonies obtained from the direct plating of a cholera stool may be variable in their agglutinability to a cholera standard serum and in their lysability to the cholera bacteriophage. Some colonies escape infection by bacteriophage present in the stool, and are lysable by the filtrate of the stool from which they themselves were isolated. From the secondary growths that develop after the action of ' natural' bacteriophage on freshly-isolated vibrios, colonies that differ serologically from the parent strain can be obtained, whereas after the action of laboratory-cultured races of bacteriophage on freshly-isolated vibrios or on laboratory-cultured vibrios, serological mutations cannot be so readily demonstrated. We stressed the importance of the study of mutations of the cholera vibrio soon after its escape from the human body and under the influence of agents such as bacteriophage that act on the cholera vibrio in its natural life. The study of mass cultures on laboratory media and the employment of methods?such as freezing and thawing, passage through laboratory animals, and other similar conditions?which the vibrio