AUTHOR=Coyle Nicola M. , Bartie Kerry L. , Bayliss Sion C. , Bekaert Michaël , Adams Alexandra , McMillan Stuart , Verner-Jeffreys David W. , Desbois Andrew P. , Feil Edward J. 

TITLE=A Hopeful Sea-Monster: A Very Large Homologous Recombination Event Impacting the Core Genome of the Marine Pathogen Vibrio anguillarum

JOURNAL=Frontiers in Microbiology

VOLUME=11

YEAR=2020

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2020.01430

DOI=10.3389/fmicb.2020.01430

ISSN=1664-302X

ABSTRACT=<p><italic>Vibrio anguillarum</italic> is the causative agent of vibriosis in many species important to aquaculture. We generated whole genome sequence (WGS) data on a diverse collection of 64 <italic>V. anguillarum</italic> strains, which we supplemented with 41 publicly available genomes to produce a combined dataset of 105 strains. These WGS data resolved six major lineages (L1-L6), and the additional use of multilocus sequence analysis (MLSA) clarified the association of L1 with serotype O1 and <italic>Salmonidae</italic> hosts (salmon/trout), and L2 with serotypes O2a/O2b/O2c and <italic>Gadidae</italic> hosts (cod). Our analysis also revealed a large-scale homologous replacement of 526-kb of core genome in an L2 strain from a con-specific donor. Although the strains affected by this recombination event are exclusively associated with <italic>Gadidae</italic>, we find no clear genetic evidence that it has played a causal role in host specialism. Whilst it is established that <italic>Vibrio</italic> species freely recombine, to our knowledge this is the first report of a contiguous recombinational replacement of this magnitude in any <italic>Vibrio</italic> genome. We also note a smaller accessory region of high single nucleotide polymorphism (SNP) density and gene content variation that contains lipopolysaccharide biosynthesis genes which may play a role in determining serotype.</p>