Evaluation of the role of extracellular DNA and lipoteichoic acid in the structural and functional properties of the matrix of cariogenic biofilm

Abstract

Dental caries is a multifactorial disease, and the major cause is a pathogenic biofilm. Biofilms are microbial communities enmeshed in an extracellular matrix. The Extracellular Matrix (ECM) of cariogenic biofilms contain high quantities of polysaccharides, extracellular DNA (eDNA) and Lipoteichoic Acids (LTA). Streptococcus mutans coordinates the construction of biofilm by producing exoenzymes that are present on the salivary pellicle and on the microbial surfaces. These exoenzymes use dietary sucrose and starch to synthetize exopolysaccharides. The exopolysaccharides help to assembly the ECM, which serves as a framework for microbial cells and confers an optimal environment with acidic niches for the aciduric microorganism to thrive. These acidic niches also lead to tooth demineralization (clinically known as dental caries). Sucrose, starch and elevated acidity influences the release of eDNA and LTA, but how this process favors the ECM assembly needs to be studied. Sucrose and starch induce the expression of S. mutans genes lytTS (linked to eDNA) in biofilms, which can yield a ECM with high amounts of eDNA. In addition, the synthesis of LTA metabolism proteins (encoded by dltABCD and SMU.775) is also induced in S. mutans when sucrose is available in mixed-species biofilms. Therefore, the present hypothesis is that eDNA and LTA, acting in concert with exopolysaccharides, impact the assembly, structural organization and functional properties of ECM during biofilm formation. The aim of this proposal is to elucidate the role of eDNA and LTA in the structural and functional properties of ECM in vitro, using spectroscopic, in situ rheology and fluorescence methods. The study will provide support for new therapeutic agents aimed at steps (and components) leading to ECM assembly, disrupting formation of pathogenic biofilms. (AU)