Date of Completion


Embargo Period



Aeromonas, symbiosis, pathogenicity, genomics, physiology

Major Advisor

Joerg Graf

Associate Advisor

J. Peter Gogarten

Associate Advisor

Daniel Gage

Field of Study



Doctor of Philosophy

Open Access

Campus Access


Aeromonas veronii is a bacterium capable of multi-host associations with varying outcomes. Abundant in the aquatic environment, A. veronii also forms beneficial or commensal digestive-tract symbioses with several organisms and is implicated in diseases that afflict humans and aquatic animals. The study of A. veronii provides a unique opportunity to investigate a group of bacteria that play disparate roles in a broad spectrum of host organisms. A key underlying question behind these multi-host associations asks what genetic attributes allow for this versatility and variable manipulation of hosts. Whole genome comparisons provide a comprehensive assessment of the presence of genes of interest among strains of a species that ostensibly occupy different niches. One important determinant in host colonization is symbiont nutrient utilization. This study investigated the importance of three metabolic pathways found to be upregulated by A. veronii in the leech gut: amino sugar catabolism, the glyoxylate cycle and the arginine deiminase pathway. We also find that the presence of a catabolic pathway for sialic acid is found predominantly in leech isolates. Another feature of interest in A. veronii is the type III secretion system (T3SS), which has been characterized in both pathogenic and beneficial associations. We show the distribution of T3SS genes among aeromonads and its significant role in virulence, particularly in fish. Genome comparisons provide a framework in which to investigate the physiological relevance of candidate genes. Combined with genetic tools and model hosts, we can further resolve the requirements for A. veronii to successfully proliferate in symbiotic associations.