Every year, over 1.5 million Americans are affected by a healthcare related infection. The source of many of these infections is an implanted medical device, where bacteria can colonize to form biofilms. During the earliest stages of biofilm formation, proteins and other molecules on the bacterial surface spontaneously adsorb to the medical device, but the molecular determinants of this process are unclear. Autolysin (AtlE) is an extracellular protein from <i>S. epidermidis</i> that has been implicated in bacterial attachment during biofilm formation. AtlE has multiple domains, each of which may be important for surface binding. Here, we use NMR spectroscopy to identify the structure-function-surface relationships in bacterial attachment. Fibrinogen- and fibronectin-coated nanoparticles are engineered to model inorganic surfaces coated with human blood proteins. Then, NMR, light scattering, and conventional spectroscopies are used to understand the interaction between AtlE and these model surfaces. Focusing on the AtlE amidase (Ami) and R2ab domains, we have determined that both domains contain dynamic regions, making them good candidates for surface attachment. Both proteins readily coat fibrinogen-functionalized nanoparticles, and binding kinetics are slow on the NMR timescale. Additionally, we have carried out titrations with fibrinogen and fibronectin, and these titrations suggest a potential surface of interaction for R2ab and Ami. When both R2ab and Ami are mixed together, they can compete for the same surface, revealing a complex interplay involving both thermodynamic and kinetic control. Moreover, surface binding of Ami may be modulated by solution conditions, as this domain exhibits altered dynamics when the extracellular zinc concentration is elevated. Together, our results show how protein biophysics and surface chemistry can be leveraged to understand the complexities of biofilm formation.

How staphylococcal autolysin interacts with surfaces during biofilm formation

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.