Surface Chemistry Influence on Orientations, Contact Area, and Deformation of Adhering E. coli Cells

Motivated by the significant role of cell adhesion in biofilm formation, we investigated the impact of surface chemistry starting at the single-cell level. We employed flagella-free Escherichia coli (E. coli) to examine how interactions between the negatively charged cell body and engineered cationic, hydrophobic, and anionic surfaces influenced cell orientation. Cationic surfaces resulted in diverse adhered cell orientations due to rapid electrostatic attractions of cells tumbling in shear flow as they approached the surface. In contrast, hydrophobic and anionic surfaces produced greater cell alignment with the plane of the surface and with the flow direction. Increases in wall shear rate had no impact on the orientation of cells on the cationic surface which were firmly bound; however, increased flow over anionic and hydrophobic surfaces produced reversible alignment changes. These findings suggest mechanisms by which surface chemistry may play a role in the evolving structure and function of microbial communities. Additionally, in studies of bacterial cell adhesion to surfaces, we introduced a novel technique to measure the cell-substrate contact region, gap separation, and curvature near the contact zone. This method provided insights into the undersides of adhered bacterial cells, revealing that the small contact areas of end-adhered cells may pose limitations for antimicrobial surfaces designed for direct bactericidal contact.