(365b) The Role of Intermolecular and Surface Forces on the Kinetics and Thermodynamics of Bacterial Adhesion

Bacterial fouling causes not only the transmission of infection and disease from one surface to another and humans, but also the reduction in the operational function, sustainability, and efficiency of various types of surfaces and devices. This presentation discusses our recent findings on the effect of substrate hydrophobicity and zeta potential on the dynamics and kinetics of the initial stages of bacterial adhesion. For this purpose, we have relied on bacterial pathogens Staphylococcus aureus and Escherichia coli O157:H7 and substrates of systematically varying surface chemistry. The time-resolved adhesion data have revealed a transformation from an exponential dependence to a square root dependence on time upon changing the substrate from hydrophobic or hydrophilic with a negative zeta potential value to hydrophilic with a negative zeta potential for both pathogens. The dewetting of extracellular polymeric substances (EPS) produced by E. coli O157:H7 has been more noticeable on hydrophobic substrates, compared to that of S. aureus, which is attributed to the more amphiphilic nature of staphylococcal EPS. The interplay between the timescale of EPS dewetting and the inverse of the adhesion rate constant has modulated the distribution of E. coli O157:H7 within microcolonies and the resultant microcolonial morphology on hydrophobic substrates. Observed trends in the formation of bacterial monolayers rather than multilayers and microcolonies rather than isolated and evenly spaced bacterial cells could be explained by a colloidal model considering van der Waals and electrostatic double-layer interactions only after introducing the contribution of elastic energy due to adhesion-induced deformations at intercellular and substrate-cell interfaces. The gained knowledge is significant in the context of identifying surfaces with greater risk of bacterial contamination and guiding the development of novel surfaces and coatings with superior bacterial antifouling characteristics.