Vibrio splendidus O-antigen structure: A trade-off between virulence to oysters and resistance to grazers

A major debate in evolutionary biology is whether virulence is maintained as an adaptive trait and/or evolves to non‐virulence. In the environment, virulence traits of non‐obligatory parasites are subjected to diverse selective pressures and trade‐offs. Here we focus on a population of Vibrio splendidus that displays moderate virulence for oysters. A MARTX (Multifunctional‐autoprocessing repeats‐in‐toxin) and a type‐six secretion system (T6SS) were found to be necessary for virulence toward oysters, while a region (wbe) involved in O‐antigen synthesis is necessary for resistance to predation against amoebae. Gene inactivation within the wbe region had major consequences on the O‐antigen structure, conferring lower immunogenicity, competitive advantage and increased virulence in oyster experimental infections. Therefore, O‐antigen structures that favor resistance to environmental predators result in an increased activation of the oyster immune system and a reduced virulence in that host. These trade‐offs likely contribute to maintaining O‐antigen diversity in the marine environment by favoring genomic plasticity of the wbe region. The results of this study indicate an evolution of V. splendidus toward moderate virulence as a compromise between fitness in the oyster as a host, and resistance to its predators in the environment.

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Table S1 Genes specific to moderately virulent strains of V. splendidus Pop#23. Genes listed below are present in the genomes of 3T8_11, 4D1_8 and 4G4_4 but absent from the 4G1_8 genome.
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Table S2 Bacterial strains
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Table S3 Plasmids
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Table S4 Oligonucleotides
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Figure S1 The rtxACHBDE cluster in V. splendidus #23
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Figure S2 Growth curves of mutants versus wild type strains in LB NaCl medium.
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Figure S3 Genetic organization of the T6SS cluster in V. splendidus #23.
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Figure S4 Strains of V. splendidus #23 are cytotoxic towards hemocytes.
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Figure S5 Lipid A inferred structure does not differ between strains 4G1_8 and 4G4_4.
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Publisher's official version
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How to cite
Oyanedel Daniel, Labreuche Yannick, Bruto Maxime, Amraoui Hajar, Robino Etienne, Haffner Philippe, Rubio Tristan, Charrière Guillaume, Le Roux Frederique, Destoumieux-Garzón Delphine (2020). Vibrio splendidus O-antigen structure: A trade-off between virulence to oysters and resistance to grazers. Environmental Microbiology. 22 (10). 4264-4278.,

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