Use this URL to cite or link to this record in EThOS:
Title: Molecular genetic analysis of Bacteroides fragilis virulence factors
Author: Houston, Simon Andrew
Awarding Body: Queen's University of Belfast
Current Institution: Queen's University Belfast
Date of Award: 2008
Availability of Full Text:
Access from EThOS:
B. fragilis is the most commonly isolated Gram-negative anaerobe from human clinical infections, and is the most common cause of anaerobic bacteraemia. The aim of the current study was to analyse potential virulence factors of B. fragilis, by investigating the contribution of three genes putatively involved in capsule biosynthesis, and by examination of fibrinogen binding and degradation. A novel plasmid DNA transformation protocol exploiting the anti restrictive property of Ocr protein was developed which allowed for the transformation of wild-type and mutant B.fragilis NCTC9343 strains. The current study is the first report of successful DNA transformation in strain NCTC9343 by electroporation. B. jfragilis is capable of within-strain variable expression of micro, small, and large capsules. Data presented herein indicate that the putative transcriptional regulator, upcY, is necessary for expression of the micro capsule polysaccharide biosynthesis locus, PS C/8, the putative wzz-like capsular polysaccharide processing gene, Bf1708, is required for micro capsule biosynthesis, and the putative glycosyltransferase, Bj2782, is necessary for large capsule expression. DNA inversion of the Bj2782 promoter was shown to regulate large capsule production in strain NCTC9343. Fibrinogen is the structural protein used in fibrin abscess formation, a pathological host response to B. ji-agilis intra-abdominal infections. Abscess formation is likely to be important in bacterial containment, preventing dissemination of infection and bacteraemia. All clinical isolates of B. ji-agilis tested degraded human fibrinogen. Fibrinoge~ degradation was related to secreted and outer membrane proteases. B.ji-agilis NCTC9343 bound human fibrinogen. A putative fibrinogen binding protein, Bfl705, after gene cloning and expression, was purified from E. coli and shown to bind human fibrinogen. The fibrinogen binding protein and fibrinogenolytic proteases may be important virulence factors in B. fragilis, allowing the bacteria to slow down, or prevent abscess fom1ation, resulting in dissemination of infection.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available