Effects of fluid shear stress on oral biofilm formation and composition and the transcriptional response of <i>Streptococcus gordonii</i>

Biofilms are subjected to many environmental pressures that can influence community structure and physiology. In the oral cavity, and many other environments, biofilms are exposed to forces generated by fluid flow; however, our understanding of how oral biofilms respond to these forces remains limited. In this study, we developed a linear rocker model of fluid flow to study the impact of shear forces on Streptococcus gordonii and dental plaque-derived multispecies biofilms. We observed that as shear forces increased, S. gordonii biofilm biomass decreased. Reduced biomass was largely independent of overall bacterial growth. Transcriptome analysis of S. gordonii biofilms exposed to moderate levels of shear stress uncovered numerous genes with differential expression under shear. We also evaluated an ex vivo plaque biofilm exposed to fluid shear forces. Like S. gordonii, the plaque biofilm displayed decreased biomass as shear forces increased. Examination of plaque community composition revealed decreased diversity and compositional changes in the plaque biofilm exposed to shear. These studies help to elucidate the impact of fluid shear on oral bacteria and may be extended to other bacterial biofilm systems.