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Title: Investigating the Type IV pili of Clostridium difficile and Clostridium sordellii
Author: Couchman, Edward
ISNI:       0000 0004 6346 9287
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2016
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Type IV pili (T4P) are the only type of bacterial pili known to be produced by both Gram-negative and Gram-positive organisms. Though the main pilus shaft consists primarily of only one protein (the major pilin), T4P are unusual in their complexity, requiring multiple (10 or more) different protein components for assembly. Like most types of pili, T4P often function as virulence factors. In particular, T4P frequently operate as adhesins, enabling bacteria on which they are present to stick to each other (to form a biofilm or suchlike) or to adhere directly to host cells. Many T4P systems are able to retract, in which case the T4P may mediate flagella-independent motility. Most research into T4P has historically been performed on Gram-negative organisms, with T4P-encoding genes only being identified in Gram-positive organisms more recently. In particular, all sequenced species of the genus Clostridium are known to encode T4P, but only minimal investigation of these systems has been performed to date. In this study, the T4P of Clostridium difficile were investigated. C. difficile is an important pathogen, being the leading cause of antibiotic-associated diarrhoea in the developed world and thus a considerable burden on Western healthcare systems. By investigating the T4P of this species it was hoped to further elucidate its mechanisms of pathogenicity. Data is presented demonstrating the control of T4P expression by cyclic-di-GMP, and identifying which genes are essential for T4P production in C. difficile. Additionally, a genomic analysis of the related pathogen Clostridium sordellii was performed, using the first high quality genome sequence produced for this species. Genes encoding T4P were identified, analysed and investigated. Furthermore, plasmids carrying the genes encoding the species’ key virulence factors (Lethal Toxin, TcsL, and in some cases haemorrhagic toxin, TcsH) were identified. These plasmids appear to be unstable, a fact with significant implications for diagnosis of C. sordellii disease.
Supervisor: Fairweather, Neil Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral