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Title: Glycosylation of Staphylococcus aureus surface proteins
Author: McAulay, Kathrine
ISNI:       0000 0004 2719 8918
Awarding Body: University of Sheffield
Current Institution: University of Sheffield
Date of Award: 2011
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Staphylococcus aureus is a major human pathogen, causing a wide spectrum of superficial and systemic infections. With the advent of methicillin resistant Staphylococcus aureus (M RSA) and the increasing spread of antibiotic resistance it has become clear that novel approaches must be taken to control S. aureus. Glycosylation, the modification of proteins with carbohydrate moieties, was long considered a process confined to eukaryotes; however, the last 3 decades have seen increasing awareness and characterisation of glycosylation systems in bacteria, including many pathogens In this study S. aureus strains were found to express several glycoproteins, covalently anchored to the cell wall peptidoglycan, including Cif A, Pis and putatively SdrC, SdrD and Clfb. CIf A glycosylation was readily detected and the glycosyltransferase enzymes responsible for Cif A modification (GtfA and GtID) were found to be encoded in a separate chromosomal location from cl(A. MALDI-MS/MS and GC-MS experiments revealed the presence of hexose and terminal HexNAc residues, consistent with an observed affinity for concanavalin A (ConA) and wheatgerm agglutinin (WGA) lectins. ConA affinity was then utilised to localise CIf A on the surface of S. aureus cells using a lectin-fluorophore conjugate, revealing a punctate presence of glycosylated protein around the cell wall. Glycosylation of CIf A was found to have no effect on fibrinogen (Fg) binding, however a role has been revealed in infection in a murine model of septic arthritis. A strain deficient in c/fA was highly attenuated in this model, whereas a strain deficient in both c/fA and gtfAB resulted in infection similar to the wild type. This data suggests a role for glycosylation in anti-virulence and thus has provided a novel insight into the nature of the host-pathogen interaction. Also, glycosylated CIf A was found to react with human sera at a significantly higher level than recombinant protein. The results highlight potential new avenues concerning immunological approaches to the control of S. aureus.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available