Selection of Vibrio crassostreae relies on a plasmid expressing a type 6 secretion system cytotoxic for host immune cells

Summary Pacific oyster mortality syndrome affects juveniles of Crassostrea gigas oysters and threatens the sustainability of commercial and natural stocks of this species. Vibrio crassostreae (V. crassostreae) has been repeatedly isolated from diseased animals, and the majority of the strains have b...

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Bibliographic Details
Published in:Environmental microbiology 2020-10, Vol.22 (10), p.4198-4211
Main Authors: Piel, Damien, Bruto, Maxime, James, Adèle, Labreuche, Yannick, Lambert, Christophe, Janicot, Adrian, Chenivesse, Sabine, Petton, Bruno, Wegner, K. Mathias, Stoudmann, Candice, Blokesch, Melanie, Le Roux, Frédérique
Format: Article
Language:English
Subjects:
Animal diseases
Animals
Aquaculture
Bacteria
Biodiversity and Ecology
Blood cells
Chromosomes
Clams
Crassostrea - immunology
Crassostrea - microbiology
Crassostrea gigas
Cytotoxicity
Environmental Sciences
Farms
Genes
Hemocytes - immunology
Immune system
Juveniles
Lethality
Life Sciences
Marine molluscs
Microbiology and Parasitology
Mollusks
Oysters
Pathogenicity
Pathogens
Phylogeny
Plasmids
Secretion
Stocks
Sustainability
Toxicity
Transcription
Type VI Secretion Systems - genetics
Vibrio
Vibrio - genetics
Vibrio - pathogenicity
Virulence
Virulence factors
Virulence Factors - genetics
Waterborne diseases
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Summary:Summary Pacific oyster mortality syndrome affects juveniles of Crassostrea gigas oysters and threatens the sustainability of commercial and natural stocks of this species. Vibrio crassostreae (V. crassostreae) has been repeatedly isolated from diseased animals, and the majority of the strains have been demonstrated to be virulent for oysters. In this study, we showed that oyster farms exhibited a high prevalence of a virulence plasmid carried by V. crassostreae, while oysters, at an adult stage, were reservoirs of this virulent population. The pathogenicity of V. crassostreae depends on a novel transcriptional regulator, which activates the bidirectional promoter of a type 6 secretion system (T6SS) genes cluster. Both the T6SS and a second chromosomal virulence factor, r5.7, are necessary for virulence but act independently to cause haemocyte (oyster immune cell) cytotoxicity. A phylogenetically closely related T6SS was identified in V. aestuarianus and V. tapetis, which infect adult oysters and clams respectively. We propose that haemocyte cytotoxicity is a lethality trait shared by a broad range of mollusc pathogens, and we speculate that T6SS was involved in parallel evolution of pathogen for molluscs.
ISSN:1462-2912
1462-2920
DOI:10.1111/1462-2920.14776