Bacterial pathogens with a strong grip

During pathogenesis, bacterial pathogens adhere to host surfaces through specific receptor-ligand bonds that experience strong hydrodynamic forces. It is commonly accepted that such adhesion complexes slip apart more easily under increasing external shear ("slip bonds"). However, it has become clear that mechanical stimulation can also promote cell adhesion through "catch bonds" complexes that, counterintuitively, strengthen under force, similarly to a Chinese finger trap. Until recently microbial catch-bond mechanisms had only been identified and thoroughly characterized at the molecular level for the Escherichia coli FimH adhesion protein. The longer-lived bonds formed by FimH and mannose residues on endothelial cells eventually favor pathogen adhesion, during urinary tract infections. A recent LIBST study published in Nature Communications provides the first direct and quantitative demonstration of a catch-bond in a Gram-positive pathogen, by means of atomic force microscopy. The authors discover that the interaction between staphylococcal surface protein SpsD and fibrinogen, a crucial component of the extracellular matrix, is extremely strong and exhibits a catch binding behavior up to a critical force orders of magnitude higher than previously investigated purified complexes. This provides the pathogen with a mechanism to tightly control its adhesive function during colonization and infection, staphylococci being highly involved in vascular and skin diseases. This work, funded by ERC, improves our understanding of the molecular details behind stress-dependent bacterial adhesion and could pave the way for the development of antiadhesive therapies able to inhibit such phenomena. See also "When bacteria hang on tight".

Published on October 27, 2020