Molecular mechanisms of biofilm formation in Staphylococci bacteria: How antibiotic resistant bacteria is evolving to become more resilient to mechanical force loads.

Abstract

Among the arsenal of virulence factors used by Staphylococcus aureus bacteria, adhesins play critical roles participating actively on the formation of biofilms. Combining single molecule force spectroscopy in vitro and in silico, we have discovered the extreme mechanostability of the interaction between pathogenic adhesins and proteins of the human extracellular matrix. Here we describe how Staphylococci adhesins use a catch-bond mechanism to hold tight to their human target peptides under high-force loads, while allowing for thermal dissociation in a low-force regime. Furthermore, we employed bioinformatic tools to retrieve and align nearly 200 proteins of the bacterial adhesin superfamily. Using AI-based protein structure prediction, we modelled, together with their human target, adhesins from methicillin susceptible strains of S. aureus (MSSA) and methicillin resistant strains of S. aureus (MRSA). Using GPU-accelerated NAMD 3, thousands of steered molecular dynamics (SMD) simulations were performed using a wide-sampling paradigm. Our protocol reveled that mechanostability is preserved among all strains with a pattern of higher forces for the MRSA strains. In summary, our work shows that the complex formed by Staphylococci adhesins with proteins of the human extracellular matrix is, by far, the most mechanically stable protein complex know to date, surpassing the mechanostability of the widely employed streptavidin:biotin complex by an order of magnitude. To keep such mechanostable complex, a catch-bond mechanism, where bonds live longer under mechanical load, is used by these adhesins. Additionally, we have recently discovered that the mechanostability of the complex is increasing with the evolution of these bacteria to become resistant to methicillin. With increasing prevalence of multidrug resistant bacterial infections, this new finding could be exploited for the development of antiadhesion strategies as an alternative to antibiotics.