title: CTX genetic element encodes a site-specific recombination system and an intestinal colonization factor.
abstract: In Vibrio cholerae, the genes encoding cholera toxin (ctxAB) are located on a segment of DNA (termed the "core" region) that is flanked by two or more copies of a repeated sequence called RS1. Together these DNA units comprise the CTX genetic element. Evidence presented here suggests that RS1 sequences encode a site-specific recombination system, which allows integration of a suicide plasmid carrying RS1 into an 18-base-pair sequence (attRS1) located on the chromosome of nontoxigenic V. cholerae strains. Strains of V. cholerae with large deletions removing attRS1 and the entire CTX genetic element no longer undergo site-specific recombination with the RS1 sequence. Additionally, these deletion strains show a defect in intestinal colonization. Recombination experiments localize the gene responsible for enhancing colonization to a portion of the core region of the CTX element. The identified gene encodes a peptide that is highly similar in amino acid sequence to the flexible pilin of Aeromonas hydrophila. These results have important implications in the construction of stable, live attenuated cholera vaccines.
authors: Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, MA 02115.
authors: G D
authors: GD
authors: Pearson
authors: A
authors: A
authors: Woods
authors: S L
authors: SL
authors: Chiang
authors: J J
authors: JJ
authors: Mekalanos
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015139:Blotting, Southern; D002772:Cholera Toxin / Q000235:genetics*; D002876:Chromosomes, Bacterial; D003001:Cloning, Molecular; D003227:Conjugation, Genetic; D004269:DNA, Bacterial / Q000235:genetics / Q000302:isolation & purification; D004926:Escherichia coli / Q000235:genetics; D017353:Gene Deletion; D005838:Genotype; D007422:Intestines / Q000382:microbiology*; D051379:Mice; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides; D010957:Plasmids; D016133:Polymerase Chain Reaction / Q000379:methods; D011995:Recombination, Genetic; D012091:Repetitive Sequences, Nucleic Acid; D015183:Restriction Mapping; D017386:Sequence Homology, Amino Acid; D014734:Vibrio cholerae / Q000235:genetics* / Q000472:pathogenicity*
chemical_list: D004269:DNA, Bacterial; D009838:Oligodeoxyribonucleotides; D002772:Cholera Toxin