Evolution and Diversity of Pathogenic Vibrio Species of Importance in Aquaculture

: (Alternative Format Thesis)

Abstract

The advent of whole-genome sequencing (WGS) has provided powerful insights into bacterial evolution, and greatly facilitated the surveillance and management of human and animal pathogens. The application of this technology to aquaculture will become more critical as the industry continues to grow. In this thesis, I describe and analyse novel WGS datasets for 4 pathogenic Vibrio species of importance to aquaculture: specifically V. anguillarum, its close relative V. ordalii, V. aestuarianus (a pathogen of oysters) and representatives of the V. splendidus species complex.
In chapters 2 and 3, I describe the genomic diversity within the population of V. anguillarum. I identify thirty-seven lineages within the population, six of which have been sequenced multiple times and likely represent important lineages to the aquaculture industry. In addition, I uncover multiple novel large recombination events that have shaped the evolution of specific lineages. Lastly, I explore lipopolysaccharide and exopolysaccharide biosynthesis genomic islands that are linked to serotype switching events.
In chapter 4, I examine strains of V. aestuarianus and the V. splendidus species complex isolated from outbreaks of oyster mortality across Ireland. This revealed that V. aestuarianus isolates detected in Ireland were closely related to two clades previously described in France. Isolates from the V. splendidus species complex were highly dissimilar, with the exception of a small clonal group that was observed in 2009.
Lastly, chapter 5 combines genomic datasets from previous chapters to study gene content variation in the V. anguillarum species complex which comprises of V. anguillarum, V. aestuarianus and V. ordalii. This included an evaluation of the application of the pangenome concept to RNA loci and intergenic regions. In addition, this chapter showed that an isolate thought to be intermediate to V. ordalii and V. anguillarum likely represents a pool of more diverse V. anguillarum strains.

Date of Award	17 Jan 2022
Original language	English
Awarding Institution	University of Bath
Sponsors	Raoul & Catherine Hughes
Supervisor	Edward Feil (Supervisor) & Jaime Martinez-Urtaza (Supervisor)