Biofilm and complex microbial community formation are fundamental processes in colonisation of the human oral cavity. Defining the mechanisms by which microbes interact with each other will lead to better understanding of how these communities are assembled. Many species of oral bacteria express cell-surface proteins (adhesins) that promote colonisation and infection through host receptor recognition. Streptococcus gordonii is ' a commensal primary coloniser of the oral cavity, and is also implicated as a leading cause of infective endocarditis . S. gordonii expresses a number of cell-surface proteins that enable the bacteria to colonise a variety of sites throughout the human body and to coaggregate with other microorganisms in biofilm community development. These include two Antigen I/ ll-family proteins, 'termed SspA and SspB, that have been implicated in colonisation and pathogenic mechanisms utilised by S. gordonii. The first aim of this study was to determine the molecular basis of interaction between two early colonisers of the oral cavity, S. gordonii and Actinomyces oris. This work identified a novel primary coloniser interaction involving recognition by SspB of cell surface polysaccharide expressed by A. oris. Another adhesin expressed by S. gordonii is CshA, which forms fibrils that extend away from the bacterial cell surface, interacts with fibronectin, and mediates coaggregation with other oral microorganisms in the formation of biofilm communities. However, the molecular mechanisms that underpin these interactions were unknown. The second aim of this study was to obtain detailed structural information about CshA, and to define functional regions relevant to S. gordonii colonisation and pathogenesis. This work showed that CshA had a unique structure with new protein folds, not previously reported for bacterial adhesins, and identified specific functional regions. Better understanding of molecular mechanisms involved in bacterial colonisation will assist development of new clinical interventions for diseases caused by oral microorganisms.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:650102 |
| Date | January 2014 |
| Creators | Back, Catherine R. |
| Publisher | University of Bristol |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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