Item – Theses Canada

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OCLC number
436330118
Link(s) to full text
LAC copy
LAC copy
Author
Malott, Rebecca J.(Rebecca Jean)
Title
Quorum-sensing in Burkholderia cenocepacia and Burkholderia vietnamiensis.
Degree
Ph. D. -- University of Calgary, 2007
Publisher
Ottawa : Library and Archives Canada = Bibliothèque et Archives Canada, [2007]
Description
3 microfiches
Notes
Includes bibliographical references.
Abstract
The 'Burkholderia cepacia' complex (Bcc) is a group of closely related bacterial species that are found throughout the environment and are known for their biotechnological applications. The Bcc is also recognized as emerging opportunistic pathogens. The Bcc utilizes 'N'-acyl-homoserine lactone (AHL)-mediated quorum-sensing systems for regulation of diverse physiological processes, including many that are involved in virulence. The 'cepIR ' system is distributed throughout the Bcc. In addition to ' cepIR', 'B. cenocepacia' strains that possess the cenocepaica island contain 'cciIR' and 'B. vietnamiensis' strains contain 'bviIR'. The main objective of this thesis was to define a role for these additional systems and determine their relationship to 'cepIR'. The 'cciIR' genes were determined to comprise a functional quorum-sensing system. AHL production profiles indicated that the major product of CciI is 'N'-hexanoyl-L-homoserine lactone (HHL). The ' cciI' and 'cciR' genes were found to be co-transcribed. CciR negatively regulates the expression of 'cciIR' and ' cepI'. Transcriptional analysis and AHL production profiles of quorum-sensing mutants established that 'cepIR' and 'cciIR' are arranged in a hierarchy, with CepR being essential for expression of ' cciIR'. The 'cciIR' system was shown to be involved in the regulation of protease production, biofilm formation and swarming motility. An additional LuxR homologue, BCAM0188, was identified and determined to be specific to 'B. cenocepacia' strains. BCAM0188 is potentially a part of the 'B. cenocepacia' quorum-sensing network. In the environmental 'B. vietnamiensis' strain G4 it was determined that BviR positively regulates the expression of 'bviI'. Unlike the 'cepIR' genes in other Bcc species, 'cepIR ' is not auto-regulated in G4. The 'cepIR' and ' bviIR' systems are arranged in a hierarchy, where CepR is required for expression of 'bviI'. The regulatory network in the clinical strain PC259 is similar to G4, except CepR positively regulates 'cepI ' and negatively regulates 'cepR'. AHL production and ' bviI' expression in 'B. vietnamiensis' isolates are variable. Three of seven strains did not express 'bviI'. Molecular investigations indicated that an additional regulatory element may be involved in the regulation of 'bviIR' in certain 'B. vietnamiensis ' strains. These studies provide further understanding of the intricate role quorum-sensing plays in Bcc gene regulation.
ISBN
9780494262443
0494262443