Hochschulschrift:
Dissertation, Technische Universität Carolo-Wilhelmina zu Braunschweig, 2022
Anmerkungen:
Zusammenfassung in deutscher und englischer Sprache
Beschreibung:
Whole genome sequencing and subsequent comparative genomic analysis of pathogenic bacteria greatly furthers the understanding of their evolution, epidemiology, virulence and antibiotic resistance. This work presents genomic studies of two entirely different bacterial pathogens. The main part of the thesis covers the analysis of 73 complete and high quality genomes of the genus Piscirickettsia, currently all classified into the species P. salmonis. The second part of the thesis examines 21 Myroides genomes. The fish pathogen Piscirickettsia salmonis, a member of the Gammaproteobacteria, is the causative agent of the multi-systemic infection piscirickettsiosis. The disease can lead to high mortalities in different salmonids and causes considerable commercial losses in the salmon farming industry. It is especially problematic in Chile, while being considered controllable in other salmon producing countries. The pathogen was first isolated and described over thirty years ago, but many fundamental aspects of its biology are still only poorly understood. In this work, the sequencing of more than fifty isolates established a comprehensive data set, that allowed for a detailed comparative genomic analysis aiming to describe diversification, virulence and antibiotic resistance of the bacterium and identify the underlying mechanisms. Genomic distances and neglectable homologous recombination indicate that two previously recognized, not geographically separated, genogroups from Chile and a third group containing non-Chilean isolates represent genetically distinct lineages that should be recognized as separate species. Furthermore, a comprehensive phylogenetic analysis of available 16S rRNA gene sequences reveals the existence of additional species and a global distribution of the genus Piscirickettsia. Unlike closely related bacteria, P. salmonis genomes contain more than one copy of the gene cluster encoding the main virulence factor, the Icm/Dot type IVB secretion system. Although it had first been assumed that in P. ...