Molecular basis of Streptococcus gordonii biofilm formation and eDNA release

Abstract

Streptococcus gordonii is a primary coloniser of the clean tooth surface. It forms part of the dental plaque biofilm, and can influence the way in which this polymicrobial community develops through its interactions with host molecules and other microbes. These interactions and the capacity for S. gordonii to form biofilms are facilitated, in large part, by LPxTG family surface proteins. However, not all such proteins have been fully characterised. In this project, six LPxTG proteins were investigated for their role in S. gordonii adhesion and biofilm formation. This included development of a novel imaging and analysis technique to enable quantification of extracellular DNA (eDNA) strands within biofilms, an important component of biofilm matrix. PalA was found to bind cellular fibronectin, with potential implications for mucosal tissue interactions and the pathogenesis of infective endocarditis. SedA and SndA were both implicated in eDNA stranding during biofilm development. Further studies into the mechanistic basis of eDNA release and assembly implied that SedA and SndA mediated their effects through binding eDNA strands on the surface of S. gordonii. Furthermore, induction of eDNA by competence stimulating peptide (CSP) in S. gordonii biofilms was implied to occur via the Hpp system, in a pathway involving autolysins AtlS and LytF. Taken together, these data provide further insights into the molecular basis of S. gordonii colonisation, and could provide research avenues for future therapeutic development.

Date of Award	19 Mar 2019
Original language	English
Awarding Institution	The University of Bristol
Supervisor	Angela H Nobbs (Supervisor) & Mark A Jepson (Supervisor)