Characterisation of two key virulence factors in Escherichia coli O157:H7

McQuitty, Claire (2015) Characterisation of two key virulence factors in Escherichia coli O157:H7. MSc(R) thesis, University of Glasgow.

Abstract

Enterohaemorrhagic Escherichia coli (EHEC) are a subset of pathogenic E. coli which can cause diarrhoeal disease, with the majority of infections due to serovar O157:H7. Successful infection by EHEC is determined by the expression of two key virulence factors, flagella and the type three secretion system (T3SS), a bacterially encoded needle-like filament. Flagella are responsible for directional and targeted swimming of the bacteria as well as for initiating bacteria: host cell attachment. A subsequent switch to T3SS expression promotes enhanced binding via the transmission of bacterial proteins (termed effectors) into the host cell. Once in the host cell these effectors act to manipulate host cell pathways and further facilitate infection.

This thesis sets out to explore these two important virulence factors; firstly by exploring the regulation of flagella rotation, and thus motility, in a series of Acetaldehyde coA dehydrogenase (AdhE) deletion mutants; and secondly by assessing the potential of a novel fluorescent reporter molecule, LOV, in imaging the expression, translocation and host cell localisation of T3SS injected effector proteins.

Findings from this study show that the LOV domain can be used to fluorescently tag the bacterial effector, Tir, and monitor it’s expression, translocation through the T3SS and localisation within the host cell, in real-time. This opens up exciting new possibilities in using LOV to fluorescently monitor the localisation of bacterial effector proteins within the host cell and thus give information on potential cellular partners and mechanism of action. Additionally, exploration of flagella rotation regulation, through the isolation and genomic sequencing of a set of AdhE deletion mutants, suggested a role for AdhE in bacterial motility via indirect acetylation of the chemotaxis protein CheY.

A better understanding of both of these virulence factors will render us more capable in our ability to carry out treatment and prevention of EHEC mediated disease.

• Item Type: Thesis (MSc(R))
• Qualification Level: Masters
• Keywords: Enterohaemorrhagic Escherichia coli, EHEC, Type three secretion systen, T3SS, Light, oxygen or voltage sensor, LOV
• Subjects: Q Science > QR Microbiology
• Colleges/Schools: College of Medical Veterinary and Life Sciences > School of Infection & Immunity > Bacteriology
• Supervisor's Name: Roe, Dr Andrew
• Date of Award: 2015
• Depositing User: Miss Claire McQuitty
• Unique ID: glathesis:2015-6943
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 09 Feb 2016 10:18
• Last Modified: 17 Feb 2016 09:11
• URI: https://theses.gla.ac.uk/id/eprint/6943