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Original Article

Genomic structure and rearrangement of the lysogenic bacteriophage pre-CTXΦ in four non-toxigenic strains of Vibrio cholerae serogroups O1 and O139

  • LI Xu ,
  • ZHAO Lin ,
  • FAN Fenxia ,
  • LI Zhe ,
  • LU Xin ,
  • PANG Bo ,
  • KAN Biao
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  • State Key Laboratory of Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, 102206, China

Received date: 2019-02-07

  Online published: 2019-08-25

Abstract

The lysogenic phage CTXΦ of Vibrio cholerae can carry and transfer the cholera toxin gene ctxAB from toxigenic strains to non-toxigenic strains. CTXΦ also has a precursor, pre-CTXΦ,which does not carry ctxAB gene. In this study, we sequenced the genomes of four nontoxigenic serogroups O1 and O139 strains carrying pre-CTXΦ with the next generation sequencing. Both short-reading and long-reading sequencing were conducted to facilitate the assembly of long repeats. pre-CTXΦ prophage sequences were extracted from the genomes of these strains. The genes of CTXΦ receptor TcpA and the receptor-binding protein pIII in CTXΦ genome was subjected to sequence alignment, phylogenic tree construction and possible domains for protein-protein interactions. The tandem repeats of the different pre-CTXΦ alleles and their novel arrangement in the genomes were identified, and the precursor genome of classical type CTXΦ was also found. The arrangements of the pre-CTXΦ alleles in these strains were significantly different from the pandemic O1 El Tor strains. New sequences of the TcpA and the pIII were found in some strains. TcpA-pIII sequence correspondence analysis indicated the complicated interactions of the different sequence types of both proteins during the infection of pre-CTXΦ alleles. In addition, we have discovered a new type of pre-CTXΦ on small chromosome of VC702. The rstR-4 gene in VC702 has been disrupted by an insertion of a transposon which was firstly found in Klebsiella pneumoniae. Our study revealed new sequence types and arrangement of the pre-CTXΦ alleles and new evidence for better understanding the horizontal transfer of CTXΦ/pre-CTXΦ among the strains.

Cite this article

LI Xu , ZHAO Lin , FAN Fenxia , LI Zhe , LU Xin , PANG Bo , KAN Biao . Genomic structure and rearrangement of the lysogenic bacteriophage pre-CTXΦ in four non-toxigenic strains of Vibrio cholerae serogroups O1 and O139[J]. Journal of Microbes and Infections, 2019 , 14(4) : 216 -224 . DOI: 10.3969/j.issn.1673-6184.2019.04.004

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