The evolution of the pan-genome of Shiga-toxin (Stx) producing Escherichia coli and the Stx₂ bacteriophage
Date
2013
Authors
Laing, Chad R.
University of Lethbridge. Faculty of Arts and Science
Journal Title
Journal ISSN
Volume Title
Publisher
Lethbridge, Alta. : University of Lethbridge, Dept. of Biological Sciences
Abstract
Human infections with Shiga-toxin (Stx)-producing E. coli (STEC) vary in severity of illness.
The pan-genome of a bacterial species contains a shared, essential core genome, and
a variably distributed accessory genome. While single nucleotide changes likely influence
virulence in STEC, horizontal gene transfer (HGT) on elements such as bacteriophage are
thought to be most important. My thesis objectives were to: 1) develop tools for the pangenomic
analyses of bacterial genomes; 2) describe the phylogeny of STEC and; 3) determine
if the evolution of the Stx2-bacteriophage parallels that of its bacterial host. For this
thesis, the software program Panseq was created and used to identify pan-genomic differences
among STEC. Whole-genome phylogenies showed all serotypes as discrete clusters,
with O157:H7 having three distinct lineages and grouping separately from all other STEC.
Finally, the phylogenies of Stx2-bacteriophage and their bacterial hosts were largely concordant,
with occasional instances of HGT having led to novel pathogen emergence.
Description
xvi, 206 leaves : ill. (some col.) ; 29 cm
Keywords
Escherichia coli O157:H7 -- Research , Bacterial genomes -- Research , Bacteriophages -- Research , Verocytotoxins -- Research , Escherichia coli infections , Dissertations, Academic