Mapping of a gene in Vibrio cholerae that determines the antigenic structure of cholera toxin

In Ouchterlony-type immunodiffusion gels, the cholera toxin produced by the classical Vibrio cholerae strain 569B was indistinguishable from the cholera toxin of the Eltor strain RJ1. However, the cholera toxin produced by both of these strains was incompletely cross-reactive with the cholera toxin produced by the Eltor strain 3083-2. The allele of the gene responsible for the 569B and RJ1 type of toxin was designated vct-1, and the allele responsible for the 3083-2 type of toxin was designated vct-2. The vct-1 allele was transferred from RJ1 donors to 3083-2 recipients by conjugation. The vct locus was found to be between met and trp on the V. cholerae linkage map.