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Diversity and distribution of cholix toxin, a novel ADP-ribosylating factor from Vibrio cholerae

Authors

  • Alexandra E. Purdy,

    1. Marine Biology Research Division and
    2. Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California, San Diego, 8750 Biological Grade, La Jolla, CA 92093-0202, USA.
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    • Present addresses: Division of Infectious Diseases, Children's Hospital Boston, 300 Longwood Ave., Boston, MA 02115, USA;

  • Deborah Balch,

    1. Marine Biology Research Division and
    2. Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California, San Diego, 8750 Biological Grade, La Jolla, CA 92093-0202, USA.
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    • Verenium Corporation, 4955 Directors Place, San Diego, CA 92121, USA.

  • Marcial Leonardo Lizárraga-Partida,

    1. Centro de Investigación Científica y de Educación Superior de Ensenada (CICESE), km. 107 Carr, Tijuana-Ensenada, 22860 B.C. México.
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  • Mohammad Sirajul Islam,

    1. International Center for Diarrhoeal Disease Research, Bangladesh, Dhaka, Bangladesh.
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  • Jaime Martinez-Urtaza,

    1. Instituto de Acuicultura, Universidad de Santiago de Compostela, Santiago de Compostela, Spain.
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  • Anwar Huq,

    1. Maryland Pathogen Research Institute and
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  • Rita R. Colwell,

    1. 7Center for Bioinformatics and Computational Biology, University of Maryland, College Park, MD 20742, USA.
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  • Douglas H. Bartlett

    Corresponding author
    1. Marine Biology Research Division and
    2. Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California, San Diego, 8750 Biological Grade, La Jolla, CA 92093-0202, USA.
      E-mail dbartlett@ucsd.edu; Tel. (+1) 858 534 5233; Fax (+1) 858 534 7313.
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  • GenBank accession numbers: chxA (GU299548–GU299630); topA (GU299537–GU299547); ftsZ (GU299631–GU299641); mreB (GU299642–GU299652); pyrH (GU299653–GU299662); recA (GU299663–GU299673).

E-mail dbartlett@ucsd.edu; Tel. (+1) 858 534 5233; Fax (+1) 858 534 7313.

Summary

Non-toxigenic non-O1, non-O139 Vibrio cholerae strains isolated from both environmental and clinical settings carry a suite of virulence factors aside from cholera toxin. Among V. cholerae strains isolated from coastal waters of southern California, this includes cholix toxin, an ADP-ribosylating factor that is capable of halting protein synthesis in eukaryotic cells. The prevalence of the gene encoding cholix toxin, chxA, was assessed among a collection of 155 diverse V. cholerae strains originating from both clinical and environmental settings in Bangladesh and Mexico and other countries around the globe. The chxA gene was present in 47% of 83 non-O1, non-O139 strains and 16% of 72 O1/O139 strains screened as part of this study. A total of 86 chxA gene sequences were obtained, and phylogenetic analysis revealed that they fall into two distinct clades. These two clades were also observed in the phylogenies of several housekeeping genes, suggesting that the divergence observed in chxA extends to other regions of the V. cholerae genome, and most likely has arisen from vertical descent rather than horizontal transfer. Our results clearly indicate that ChxA is a major toxin of V. cholerae with a worldwide distribution that is preferentially associated with non-pandemic strains.

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