<i>Staphylococcus epidermidis</i> can form biofilms on medical devices, resulting in difficult-to-treat infections and poor patient outcomes. The R2ab and amidase domains from Staphylococcal autolysin have a high affinity for binding polystyrene surfaces, and they contribute to the microorganism’s biofilm forming ability. The molecular mechanism of this interaction is poorly understood, however, and a better understanding of protein-surface interactions could lead to improved, biofilm-resistant surfaces. In this work, we have studied how the R2ab and amidase domains interact with both polystyrene surfaces and polystyrene nanoparticles (PSNPs). We find that both domains, when applied to polystyrene plates, stunt Staphylococcal biofilm formation, obstructing bacterial surface attachment. Investigations of protein binding to PSNPs using dynamic light scattering confirm that both domains bind tightly to polystyrene. Circular dichroism and limited proteolysis experiments reveal significant structural changes in both domains in the presence of PSNPs. A closer analysis of the cleaved proteolytic products using mass spectrometry reveals that some aromatic residues have altered accessibility in the presence of nanoparticles. These proteins show parallel behavior on both anionic, carboxyl-functionalized, and neutral, non-functionalized PSNPs. Interestingly, however, BSA, a control protein, does not exhibit any of these behaviors. We hypothesize that the strong interaction between autolysin domains and polystyrene surfaces is mainly driven by aromatic residues in these proteins, and that this interaction is mediated by intrinsic properties like protein shape, hydrophobic burial, and global stability. In the long term, this work will inform new, bio-compatible techniques to eradicate biofilm formation on medical devices.

Staphylococcal autolysin domains bind polystyrene surfaces and can impede biofilm formation

ACS Fall 2021

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