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Research has been conducted on the CTXphi, a filamentous bacteriophage whose genome encodes cholera toxin produced by Vibrio cholerae. The characterization of the viron production capacities and genetic structures of the classical prophage arrays has been conducted and the results are discussed.

Results suggest that lysogenic filamentous bacteriophage which encodes cholera toxin enters its host with the help of a pilus and TolQRA. Data indicate Escherichia coli and other bacteria also take this course sugesting that this feature is conserved among bacterial species.

Results demonstrate the transcriptional induction patterns of the Vibrio cholerae tcpA and ctxA genes during infection using a recombinase gene. Data indicate that ctxA gene induction is dependent upon tcpA expression and other virus regulators and the induction process exhibits differences during infection and growth conditions.

Results demonstrate that the new CTX Calcutta prophage is capable of giving rise to infectious cholera virus and it is differentiated from the other already existing prophage in the nucleotide sequences of the repressor genes.

The resistance of the non-O1 serogroup Vibrio cholerae O139 to trimethoprim, sulfamethoxazole and streptomycin is mediated by the SXT transposon that does not encode a colonization factor. The transposon is a 62-kb element that can be transferred to V. cholerae O1 and Escherichia coli strains. It integrates into V. cholerae by a recA-independent site specific mechanism. The crossing of a large internal deletion of SXT to the Bengal-2 chromosome produces a Bengal-2.SXT(super S) strain that is antibiotic-sensitive. These variants are useful as live attenuated vaccines against the O139 serogroup.

Vibrio cholerae, the causative agent of cholera, requires two coordinately regulated factors for full virulence: cholera toxin (CT), a potent enterotoxin, and toxin-coregulated pili (TCP), surface organelles required for intestinal colonization. The structural genes for CT are shown here to be encoded by a filamentous bacteriophage (designated CTXψ, which is related to coliphage M13. The CTXψ genome chromosomally integrated or replicated as a plasmid. CTXψ used TCP as its receptor and infected V. cholerae cells within the gastrointestinal tracts of mice more efficiently than under laboratory conditions. Thus, the emergence of toxidenic V. cholerae involves horizontal gene transfer that may depend on in vivo gene expression., Bacterial virulence factors such as toxins are often encoded by accessory genetic elements (bacteriophages, plasmids, chromosomal islands, and transposons) (1). These genetic elements are thought to move horizontally as well [...]

Immunoblot analyses of the different forms of Vibrio cholerae serogroup O139 antigen reveal the presence of three electrophoretic forms of the antigen, a fast moving form resembling O139 lipopolysaccharide and two slow moving forms that resemble the capsular polysaccharide related to the O-antigen. The loss of immunoreactivity of the O-antigen capsule and the LPS, upon insertion of a single transposon, reveals that the biosynthesis of both molecules involves a common set of genes. Serum resistance and colonization in mice small intestine of the O139 strain are influenced by the LPS O side chains and the O-antigen capsule.