Date of Award

2009

Degree Type

Thesis

Degree Name

Master of Science (MSc)

Department

Molecular Science

First Advisor

Debora Barnett Foster

Second Advisor

Céline Lévesque

Abstract

Enterohemorrhagic Eschericia coli (EHEC) 0157:H7 must be able to survive the acid stress of gastric passage. Previous studies show that adhesion of EHEC 0157:H7 to human epithelial cells is increased if EHEC was pre-exposed to acid. Whole genome array analysis of EHEC reveals that the putative fimbrial gene yadK is significantly upregulated after EHEC exposure to acid treatments. In this study, a YadK deficient mutant (△yadK) in EHEC 0157:H7 wild-type (WT) strain 85-170 was constructed and phenotyped. The results of this study demonstrate that △yadK exposed to acid stress showed no acid-induced increase in bacteria-host cell adhesion observed in similarly acid-induced wild type cells. This study concludes that YadK plays a role in acid-induced host adhesion of EHEC 0157:H7. It also indicates that acid stress, which is a part of the host’s natural assault to resist invasion, may regulate factors responsible for enhanced bacteria-host attachment, resulting in increased EHEC virulence.


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