Role of Temperate Bacteriophage 139 in Changing Cholera Toxin Production in Vibrio cholerae Classical Biovar

New data were obtained concerning cell sensitivity of pathogenic strains of cholera vibrions, which belong to the serogroup O1 of classical biovar, to the temperate bacteriophage 139, the native host of which is Vibrio cholerae O139. Molecular–genetic and biochemical studies showed that phage 139 integrated into the chromosome of strains V. cholerae O1 can change their toxigenic properties. A change in the production of cholera toxin (CT) in lysogens is associated both with an increase in the activity of the toxR regulatory gene and with an alteration of the structure of a chromosomal DNA region that contains a copy of the operon ctxAB encoding CT biosynthesis.