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Investigations on the Quorum sensing Circuitry in Burkholderia cenocepacia H111


Inhülsen, S. Investigations on the Quorum sensing Circuitry in Burkholderia cenocepacia H111. 2011, University of Zurich, Faculty of Science.

Abstract

Burkholderia cenocepacia is a Gram-negative bacterium which is ubiquitously found in the environment. Three decades ago, B. cenocepacia was identified as the causative agent of severe pulmonary infections in patients with cystic fibrosis (CF). The disease was accompanied by a characteristic bacteraemia that resulted in the early death of CF individuals. Since then, B. cenocepacia has emerged as a problematic opportunistic pathogen in patients with immunodeficiency disorders demonstrating the need for further exploration and elucidation of factors which contribute to B. cenocepacia virulence. It has become clear that the expression of pathogenic traits in B. cenocepacia is at least partly controlled by quorum sensing (QS), a cell density-dependent regulatory process. In the present thesis, the QS regulon of B. cenocepacia H111, which is comprised by the cepIR genes, was mapped and studied in detail. CepIR-regulated functions were identified by a combined transcriptomic, proteomic and phenotypic approach. The results of this analysis provided new insights into the molecular mechanisms of previously identified QS-regulated phenotypes, including biofilm formation, and pathogenicity, and revealed novel information of the complex QS circuitry operating in B. cenocepacia H111. In the second part of this thesis, the products of three QS-activated loci, which were identified in our mapping study, were further characterized. These included the orphan LuxR homologous transcriptional regulator CepR2, the BclACB lectins, and BCAM1869, which is encoded by a gene located within the intergenetic region of the cepR and cepI genes. The results of this work identified CepR2 as an AHL-independent transcriptional regulator. Moreover, CepR2 was shown to stimulate expression of the siderophore pyochelin, while acting as a downstream regulator of the H111 QS network. In the present thesis, the subcellular localization of lectin BclB was determined, and the importance of the BclACB proteins for the structural development of H111 biofilms was investigated. The results obtained suggest that BCAM1869 fine-tunes QS regulation: BCAM1869 represses the producton of AHL signal molecules in B. cenocepacia H111. Furthermore, BCAM1869 seems to interfere with the activity of LuxR-like transcriptional regulators, including the Vibrio fischeri LuxR protein. The results of this work also suggest that BCAM1869 positively influences the activity of CepR2 in B. cenocepacia H111.

Abstract

Burkholderia cenocepacia is a Gram-negative bacterium which is ubiquitously found in the environment. Three decades ago, B. cenocepacia was identified as the causative agent of severe pulmonary infections in patients with cystic fibrosis (CF). The disease was accompanied by a characteristic bacteraemia that resulted in the early death of CF individuals. Since then, B. cenocepacia has emerged as a problematic opportunistic pathogen in patients with immunodeficiency disorders demonstrating the need for further exploration and elucidation of factors which contribute to B. cenocepacia virulence. It has become clear that the expression of pathogenic traits in B. cenocepacia is at least partly controlled by quorum sensing (QS), a cell density-dependent regulatory process. In the present thesis, the QS regulon of B. cenocepacia H111, which is comprised by the cepIR genes, was mapped and studied in detail. CepIR-regulated functions were identified by a combined transcriptomic, proteomic and phenotypic approach. The results of this analysis provided new insights into the molecular mechanisms of previously identified QS-regulated phenotypes, including biofilm formation, and pathogenicity, and revealed novel information of the complex QS circuitry operating in B. cenocepacia H111. In the second part of this thesis, the products of three QS-activated loci, which were identified in our mapping study, were further characterized. These included the orphan LuxR homologous transcriptional regulator CepR2, the BclACB lectins, and BCAM1869, which is encoded by a gene located within the intergenetic region of the cepR and cepI genes. The results of this work identified CepR2 as an AHL-independent transcriptional regulator. Moreover, CepR2 was shown to stimulate expression of the siderophore pyochelin, while acting as a downstream regulator of the H111 QS network. In the present thesis, the subcellular localization of lectin BclB was determined, and the importance of the BclACB proteins for the structural development of H111 biofilms was investigated. The results obtained suggest that BCAM1869 fine-tunes QS regulation: BCAM1869 represses the producton of AHL signal molecules in B. cenocepacia H111. Furthermore, BCAM1869 seems to interfere with the activity of LuxR-like transcriptional regulators, including the Vibrio fischeri LuxR protein. The results of this work also suggest that BCAM1869 positively influences the activity of CepR2 in B. cenocepacia H111.

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Additional indexing

Item Type:Dissertation
Referees:Eberl L
Communities & Collections:07 Faculty of Science > Department of Plant and Microbial Biology
Dewey Decimal Classification:580 Plants (Botany)
Language:English
Date:2011
Deposited On:16 Mar 2012 07:43
Last Modified:05 Apr 2016 15:38
Related URLs:http://opac.nebis.ch/F/?local_base=NEBIS&CON_LNG=GER&func=find-b&find_code=SYS&request=006522435

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