Genomic characterization of the bivalve pathogen Vibrio europaeus

Abstract

Bivalve hatcheries are essential for aquaculture, ensuring a stable seed supply, but face challenges, particularly mortalities caused by Vibrio species, known as vibriosis. These infections, primarily affecting larval stages, lead to significant economic losses. The pathogenicity of Vibrio depends on virulence factors, host susceptibility, and environmental conditions, making prevention the best strategy. This Thesis focuses on Vibrio europaeus, a recently identified species associated with bivalve mortalities across various life stages and geographic regions. A genomic analysis was conducted on 39 strains from hatcheries worldwide. The V. europaeus pangenome, encompassing both core and accessory genes, revealed a species highly adaptable to its environment through DNA acquisition. Intraspecific variability analysis identified three phylogenetic branches and eight clusters, with Spanish strains showing lower diversity than French strains, indicating localized dispersal. In contrast, French strains were more diverse, and strains from Chile and the USA formed separate clusters, suggesting intercontinental transmission via human activities such as mollusc trade.