title: Structural variation of the superintegron in the toxigenic Vibrio cholerae O1 El Tor.
abstract: OBJECTIVE
  To understand the genetic structures and variations of the superintegron (SI) in Vibrio cholerae isolated in the seventh cholera pandemic.
  
  
  METHODS
  Polymerase chain reaction scanning and fragment sequencing were used. Sixty toxigenic V. cholerae O1 El Tor strains isolated between 1961 and 2008 were analyzed.
  
  
  RESULTS
  Some variations were found, including insertions, replacements, and deletions. Most of the deletions were probably the result of recombination between V. cholerae repeat sequences. The majority of the variations clustered together. The SIs of the strains isolated in the 1960s and 1970s showed more diversity, whereas SI cassette variations in strains isolated in the 1990s and after were lower, with ∼24 kb signature sequence deletion. This indicates the predominant SI in the host during the epidemic in the 1990s and after. The insertion cassettes suggested the mobilization from the SIs of other V. cholerae serogroups and Vibrio mimicus.
  
  
  CONCLUSIONS
  The study revealed that structural variations of SIs were obvious in the strains isolated in epidemics in different decades, whereas the divergence was based on syntenic structure of SIs in these El Tor strains. Also, the continuing cassette flows in the SIs of the host strains during the seventh cholera pandemics were displayed.
authors.affiliation: State Key Laboratory for Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing 102206, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Gao
authors.forename: Bo
authors.initials: B
authors.lastname: Pang
authors.forename: Hai Yin
authors.initials: HY
authors.lastname: Wang
authors.forename: Hai Jian
authors.initials: HJ
authors.lastname: Zhou
authors.forename: Zhi Gang
authors.initials: ZG
authors.lastname: Cui
authors.forename: Biao
authors.initials: B
authors.lastname: Kan
mesh_terms: D002771:Cholera / Q000453:epidemiology / Q000382:microbiology; D002876:Chromosomes, Bacterial / Q000235:genetics* / Q000648:ultrastructure; D016000:Cluster Analysis; D004269:DNA, Bacterial / Q000235:genetics*; D016521:Electrophoresis, Gel, Pulsed-Field; D017353:Gene Deletion; D051456:Gene Flow; D014644:Genetic Variation; D006801:Humans; D032023:Integrons / Q000235:genetics; D016254:Mutagenesis, Insertional; D016366:Open Reading Frames / Q000235:genetics; D016133:Polymerase Chain Reaction; D020080:Tandem Repeat Sequences; D041241:Vibrio cholerae O1 / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification / Q000648:ultrastructure
chemical_list: D004269:DNA, Bacterial