Bacterial Adhesion-force Sensing in Oral Biofilms

Abstract

Streptococcus mutans is a major contributor to dental caries which affects yearly 3.9 billion people globally, costing >$290 billion/y. This thesis investigated bacterial adhesion-force sensing by this oral pathogen in mono-species S. mutans biofilms and in multi-species biofilms comprising S. mutans amongst others. Chapter 1 started with a review on how substratum heterogeneity and bacterial adhesion-force sensing may influence heterogeneous microenvironments in biofilms. In Chapter 2 a novel method of re-scaling of signal intensity distributions in optical coherence tomography-images was developed, allowing quantitative comparison of biofilm densities in different images. Chapter 3 investigated how bacterial adhesion-force sensing by the important oral pathogen S. mutans plays a role in mono-species S. mutans biofilms. In Chapter 4, it was determined whether and how salivary-conditioning-film adsorption and the multi-species nature of oral biofilms influence adhesion-force sensing and associated gene expression by S. mutans. In Chapter 5 S. mutans biofilms were grown at the border between hydrophobic silicone rubber and hydrophilic glass to further advance our understanding of the influence of surface heterogeneity on adhesion-force sensing and development of phenotypically heterogeneous micro-environments in biofilms. In the general discussion of this thesis (Chapter 6), an overview is given of the variety of different surfaces on which oral biofilm grows in the human oral cavity. Also, the wide range of hydrophobicities they represent is highlighted and the clinical relevance of adhesion-force sensing and surface adaptation is discussed. Future studies to further advance the results of this PhD thesis are given.