Nanomechanics of the molecular complexes between SpsD/SpsL staphylococcal adhesins and elastin

Staphylococcus pseudintermedius is a commensal pathogen having the capacity to develop biofilms. Bacterial adhesion to the host extracellular matrix (mainly dogs but humans too) is known to be mediated by the SpsD and SpsL adhesins. Considering the emergence of zoonosis cases for S. pseudintermedius and the increasing occurrence of methicillin-resistant strains, it is now crucial to unravel the mechanisms by which the pathogen adheres to-, and in turn infect, its hosts. In this context, we studied the strength and dynamics of interaction between SpsD/SpsL and elastin, a key matrix protein critical to the elasticity and resilience of many vertebrate tissues. To this end, we used atomic force microscopy, which allows to quantify the mechanical strength of single receptor-ligand complexes. We observed a bimodal distribution of the forces and rupture lengths with an inverse correlation between both parameters. These so-called low and high force regimes suggest two different binding mechanisms. We also found that both SpsD- and SpsL-elastin interactions are mechanically activated. Weak binding dominates at low stress, whereas strong binding is favored at high stress. We suggest that the ultrastrong Sps-elastin interaction could result from a variation of the “dock, lock and latch” mechanism whereas the low adhesion force results from a weaker binding mechanism. Our results offer promise for the design of novel anti-adhesion strategies thereby helping in the prevention of biofilm formation and infection.