Hou, Yingqi; (2025) A single-cell force spectroscopy analysis of the effects of capsule phenotype and surface proteins on Streptococcus pneumoniae adhesion. Doctoral thesis (Ph.D), UCL (University College London).

Text Yingqi-Hou_thesis_final_2025.pdf - Accepted Version Access restricted to UCL open access staff until 1 October 2026. Download (20MB)

Abstract

Streptococcus pneumoniae is the leading cause of pneumonia, meningitis, and bacteraemia worldwide. Adhesion to the epithelial host cells is a critical step of pathogenesis. Traditionally, bacterial adhesion to substrate is qualitatively assessed by microbiology adhesion assays. With the development of single cell force spectroscopy (SCFS), the biophysical details of the adhesion can be accurately measured. In this thesis, I investigated the role of the polysaccharide capsule and two surface adhesins, PspC and PsrP, in the bacteria’s adhesion to lung epithelial cells and collagen by traditional adhesion assays and AFM respectively. Results on the dynamics of adhesion suggested that adhesion might be a multiphasic process and the adhesion profiles at short contact times (<5 seconds) could be very different from that at long contact times (~1 hour). The capsule might limit surface accessibility of adhesins as well as provide structure support for adhesins. PspC has been found to involved in adhesion and our results showed that pspC mutation reduced the nonspecific and specific interactions between S. pneumoniae and lung epithelial cells compared to the wildtype. PspC may contribute to the medium- and long-ranged interactions (>3000nm) between S. pneumoniae and lung epithelial cells. The thesis also offered one of the first set of evidence on the roles of PspC and PsrP in the adhesion to collagen, the most abundant ECM protein.

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