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Cholera is acquired by ingesting food or water contaminated with the bacterium Vibrio cholerae. The genome contains a variety of potentially mobile genetic elements including plasmids, bacteriophages, and pathogenicity islands (PAIs), which are reviewed in this chapter. The chapter describes recent exciting and provocative discoveries that the PAIs in epidemic V. cholerae can be acquired by horizontal gene transfer by bacteriophages. The genes encoding the most important virulence factors, cholera enterotoxin (CT) and the toxin-coregulated pilus (TCP), are not usually present in V. cholerae strains that are commonly isolated from the environment. All epidemic strains of V. cholerae contain ctxAB genes, which encode CT. The major protein forming the pilus structure (TcpA) is encoded by the tcpA gene and is 20.5 kDa in size. The determination of the genomic sequence of V. cholerae will undoubtedly reveal additional virulence factors, PAIs, and other mobile virulence elements. The recent findings described in the chapter should lead to future studies that will help us understand the emergence, pathogenesis, and spread of cholera, a disease which still surprises and challenges us after a century of study.
Schematic map of the CTXΦ genome integrated in the V. cholerae chromosome.
Schematic map of the VPIΦ genome integrated in the V. cholerae chromosome.
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