Mechanical & Materials Engineering, Department of


First Advisor

Timothy Wei

Second Advisor

Sangjin Ryu

Third Advisor

Sidy Ndao

Date of this Version

Fall 2016


Sherman, Erica, "Fluid Dynamic factors as a cause and effect of biofilm formation of Staphylococcus aureus biofilms." (2016)


Staphylococcus aureus bacteria are able to form biofilms and distinctive tower structures that facilitate their ability to tolerate treatment and to spread within the human body. The formation of towers, which break off, get carried downstream and serve to initiate biofilms in other parts of the body are of particular interest here. It is known that flow conditions play a role in the development, dispersion and propagation of biofilms. The influence of flow on tower formation and what factors lead to tower formation is not at all understood The hypothesis being examined is that tower structures form within a specific range of shear stresses and that there is an as yet ill-defined fluid dynamic phenomenon that occurs hours before a tower forms. In this study, a range of shear stresses is examined that brackets 0.6 dynes/cm2, the nominal shear stress where towers seem most likely to form. The biofilm structure is known to be a temporally and spatially heterogeneous structure, which must be taken into account when considering the tower formation frequency and the local flow environment. How this structure differs as a function of applied shear, the experimental stage of biofilm development, and the likelihood of tower formation is analyzed. This work includes µPTV measurements and cell density data indicating variations in flow and biofilm evolution as a function of the applied shear. Causal relations between flow and biofilm development will be discussed as well as the presentation of specific biofilm development terms as predictive measures of tower formation.