Title: Cholera toxin phage: structural and functional diversity between <em>Vibrio cholerae</em> biotypes
Abstract: Cholera is a severe form of watery diarrhea caused by <i>Vibrio cholerae</i> toxigenic strains. Typically, the toxigenic variants of <i>V. cholerae</i> harbor a bacteriophage, cholera toxin phage, integrated in their genome. The <i>ctxAB</i> genes from the phage genome encode the cholera toxin, which is responsible for the major clinical symptoms of the disease. Although <i>ctxAB</i> genes are crucial to <i>V. cholerae</i> strains for cholera manifestation, the genetic structure of cholera toxin phage, DNA sequence of its genes, spatial organization in the host genome and its satellite phage content are not homogenous between <i>V. cholerae</i> biotypes—classical and El Tor. Differences in cholera toxin phage and its genes play a significant role in the identification of <i>V. cholerae</i> biotypes and in the understanding of their pathogenic and epidemic potentials. Here, we present an account of the variations of cholera toxin phage and its genes in <i>V. cholerae</i> biotypes as well as their usefulness in the identification of classical and El Tor strains.