title: Comparative genomics of pathogenic lineages of Vibrio nigripulchritudo identifies virulence-associated traits.
abstract: Vibrio nigripulchritudo is an emerging pathogen of farmed shrimp in New Caledonia and other regions in the Indo-Pacific. The molecular determinants of V. nigripulchritudo pathogenicity are unknown; however, molecular epidemiological studies have suggested that pathogenicity is linked to particular lineages. Here, we performed high-throughput sequencing-based comparative genome analysis of 16 V. nigripulchritudo strains to explore the genomic diversity and evolutionary history of pathogen-containing lineages and to identify pathogen-specific genetic elements. Our phylogenetic analysis revealed three pathogen-containing V. nigripulchritudo clades, including two clades previously identified from New Caledonia and one novel clade comprising putatively pathogenic isolates from septicemic shrimp in Madagascar. The similar genetic distance between the three clades indicates that they have diverged from an ancestral population roughly at the same time and recombination analysis indicates that these genomes have, in the past, shared a common gene pool and exchanged genes. As each contemporary lineage is comprised of nearly identical strains, comparative genomics allowed differentiation of genetic elements specific to shrimp pathogenesis of varying severity. Notably, only a large plasmid present in all highly pathogenic (HP) strains encodes a toxin. Although less/non-pathogenic strains contain related plasmids, these are differentiated by a putative toxin locus. Expression of this gene by a non-pathogenic V. nigripulchritudo strain resulted in production of toxic culture supernatant, normally an exclusive feature of HP strains. Thus, this protein, here termed 'nigritoxin', is implicated to an extent that remains to be precisely determined in the toxicity of V. nigripulchritudo.
authors.affiliation: Equipe Émergente Ifremer-UPMC Génomique des Vibrio, Roscoff, France.
authors.forename: David
authors.initials: D
authors.lastname: Goudenège
authors.forename: Yannick
authors.initials: Y
authors.lastname: Labreuche
authors.forename: Evelyne
authors.initials: E
authors.lastname: Krin
authors.forename: Dominique
authors.initials: D
authors.lastname: Ansquer
authors.forename: Sophie
authors.initials: S
authors.lastname: Mangenot
authors.forename: Alexandra
authors.initials: A
authors.lastname: Calteau
authors.forename: Claudine
authors.initials: C
authors.lastname: Médigue
authors.forename: Didier
authors.initials: D
authors.lastname: Mazel
authors.forename: Martin F
authors.initials: MF
authors.lastname: Polz
authors.forename: Frédérique
authors.initials: F
authors.lastname: Le Roux
mesh_terms: D000818:Animals; D001427:Bacterial Toxins / Q000235:genetics / Q000494:pharmacology; D022761:Gene Transfer, Horizontal; D014644:Genetic Variation; D016680:Genome, Bacterial / Q000235:genetics*; D023281:Genomics; D008270:Madagascar; D046529:Microscopy, Electron, Transmission; D009510:New Caledonia; D033561:Penaeidae / Q000187:drug effects / Q000382:microbiology*; D010802:Phylogeny; D010957:Plasmids / Q000235:genetics; D014733:Vibrio / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification / Q000502:physiology / Q000648:ultrastructure; D014774:Virulence / Q000235:genetics*
chemical_list: D001427:Bacterial Toxins