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The major outer membrane protein OmpU of Vibrio splendidus contributes to host antimicrobial peptide resistance and is required for virulence in the oyster Crassostrea gigas

Authors

  • Marylise Duperthuy,

    1. CNRS, UMR 5119, Laboratoire ‘Ecosystèmes lagunaires’, Université Montpellier 2, 34095 Montpellier, France.
    2. Ifremer and
    3. Université Montpellier 2, Laboratoire ‘Ecosystèmes lagunaires’, 34095 Montpellier, France.
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  • Johan Binesse,

    1. Institut Pasteur, CNRS, URA 2171, Laboratoire ‘Plasticité du génome bactérien’, 75015 Paris, France.
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  • Frédérique Le Roux,

    1. Institut Pasteur, CNRS, URA 2171, Laboratoire ‘Plasticité du génome bactérien’, 75015 Paris, France.
    2. Laboratoire de génétique et pathologie, Ifremer, 17390 La Tremblade, France.
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  • Bernard Romestand,

    1. CNRS, UMR 5119, Laboratoire ‘Ecosystèmes lagunaires’, Université Montpellier 2, 34095 Montpellier, France.
    2. Ifremer and
    3. Université Montpellier 2, Laboratoire ‘Ecosystèmes lagunaires’, 34095 Montpellier, France.
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  • Audrey Caro,

    1. CNRS, UMR 5119, Laboratoire ‘Ecosystèmes lagunaires’, Université Montpellier 2, 34095 Montpellier, France.
    2. Ifremer and
    3. Université Montpellier 2, Laboratoire ‘Ecosystèmes lagunaires’, 34095 Montpellier, France.
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  • Patrice Got,

    1. CNRS, UMR 5119, Laboratoire ‘Ecosystèmes lagunaires’, Université Montpellier 2, 34095 Montpellier, France.
    2. Ifremer and
    3. Université Montpellier 2, Laboratoire ‘Ecosystèmes lagunaires’, 34095 Montpellier, France.
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  • Alain Givaudan,

    1. INRA and
    2. Université Montpellier 2, Laboratoire ‘Ecologie Microbienne des Insectes et Interactions Hôte-Pathogène’, 34095 Montpellier, France.
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  • Didier Mazel,

    1. Institut Pasteur, CNRS, URA 2171, Laboratoire ‘Plasticité du génome bactérien’, 75015 Paris, France.
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  • Evelyne Bachère,

    1. CNRS, UMR 5119, Laboratoire ‘Ecosystèmes lagunaires’, Université Montpellier 2, 34095 Montpellier, France.
    2. Ifremer and
    3. Université Montpellier 2, Laboratoire ‘Ecosystèmes lagunaires’, 34095 Montpellier, France.
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  • Delphine Destoumieux-Garzón

    Corresponding author
    1. CNRS, UMR 5119, Laboratoire ‘Ecosystèmes lagunaires’, Université Montpellier 2, 34095 Montpellier, France.
    2. Ifremer and
    3. Université Montpellier 2, Laboratoire ‘Ecosystèmes lagunaires’, 34095 Montpellier, France.
      E-mail ddestoum@ifremer.fr; Tel. (+33) 467 14 46 25; Fax (+33) 467 14 46 22.
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E-mail ddestoum@ifremer.fr; Tel. (+33) 467 14 46 25; Fax (+33) 467 14 46 22.

Summary

Vibrio splendidus, strain LGP32, is an oyster pathogen associated with the summer mortalities affecting the production of Crassostrea gigas oysters worldwide. Vibrio splendidus LGP32 was shown to resist to up to 10 µM Cg-Def defensin and Cg-BPI bactericidal permeability increasing protein, two antimicrobial peptides/proteins (AMPs) involved in C. gigas immunity. The resistance to both oyster Cg-Def and Cg-BPI and standard AMPs (polymyxin B, protegrin, human BPI) was dependent on the ompU gene. Indeed, upon ompU inactivation, minimal bactericidal concentrations decreased by up to fourfold. AMP resistance was restored upon ectopic expression of ompU. The susceptibility of bacterial membranes to AMP-induced damages was independent of the ompU-mediated AMP resistance. Besides its role in AMP resistance, ompU proved to be essential for the adherence of V. splendidus LGP32 to fibronectin. Interestingly, in vivo, ompU was identified as a major determinant of V. splendidus pathogenicity in oyster experimental infections. Indeed, the V. splendidus-induced oyster mortalities dropped from 56% to 11% upon ompU mutation (Kaplan–Meier survival curves, P < 0.01). Moreover, in co-infection assays, the ompU mutant was out competed by the wild-type strain with competitive indexes in the range of 0.1–0.2. From this study, ompU is required for virulence of V. splendidus. Contributing to AMP resistance, conferring adhesive properties to V. splendidus, and being essential for in vivo fitness, the OmpU porin appears as an essential effector of the C. gigas/V. splendidus interaction.

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