Influence of dietary carbohydrates on Streptococcus mutans biofilm structure-architecture

Objectives: To determine the influence of starch and sucrose on the structure and architecture of S. mutans biofilm. Methods: Biofilms of S. mutans UA159 ATCC 700610 were formed on saliva coated hydroxyapatite (HA) discs in batch culture for 72 h in the presence of different concentrations and combinations of sucrose and starch. The biofilms were removed at specific time points and subjected to structural and biochemical analyses. The structural organization and architecture was determined by confocal laser scanning microscopy (CLSM) using computational analysis for both visualization and quantification (COMSTAT). The biomass (dry weight), total protein content and polysaccharide composition (extracellular water-soluble and insoluble polysaccharide) were determined using colorimetric assays. Results: The visualization and quantification of CLSM data showed complex and dynamic 3-D structural changes of the organization of bacteria and polysaccharides during the various stages of the biofilm development. Moreover, the structure-architecture of starch+sucrose-biofilms was markedly distinct from sucrose-grown biofilms; the middle and deeper layers of starch+sucrose-biofilms presented higher polysaccharide to bacteria ratio than sucrose-biofilms (P<0.05). The combinations of starch and sucrose also produced biofilms with more biomass and higher amounts of extracellular polysaccharides than those formed in sucrose alone (P<0.05). Conclusion: The combination of starch and sucrose influenced the 3-D structural organization and biochemical composition of S. mutans biofilms, which may affect the biological and physicochemical properties of dental biofilms.