Experimental and computational characterization of biofilm formation and deformation

Abstract

Bacterial adhesion to surfaces is one of the crucial phases in biofilm formation. Bacterial attachment is a complex process which can be affected by flow conditions and properties of the substratum material. Experiments on initial attachment were carried out using the oral bacterial species Streptococcus gordonii which is one of the early colonizers of tooth surfaces. There has been a limited study about how early colonizing bacteria like S. gordonii adhere to stainless steel with different surface characteristics. In this study, we will concentrate on understanding the interactions at the interface between bacteria and materials. In natural environments, a conditioning layer (e.g., saliva) would appear on the implant surface before the arrival of bacteria. Therefore, bacterial adhesion on stainless steel coated with saliva was also studied. To understand the physics of bacterial adhesion, an in-house computational model has been developed by implementing a population balance model coupled with Extended Derjaguin Landau Verwey and Overbeek (XDLVO) theory. The effect of microtopography, roughness, and flow on bacterial attachment were examined quantitatively with the computational model. The results from the experimental and computational methods have been qualitatively comparable, and the attachment of bacteria has been altered due to combination of different surface characteristics. Biofilm detachment and deformation is the final stage of a biofilm cycle and it is important to study how biofilms react to physical forces. Biofilm deformation was studied in situ, and in particular, the viscoelastic behavior of the biofilms was assessed using Particle Image Velocimetry techniques. The viscoelastic behavior was studied using the loading and unloading cycle of stress resulting from different flow velocities applied to the surface of the biofilm. The in situ experimental models can be used to study the material properties of biofilms without disrupting the internal structure