Single-cell force spectroscopy of pili-mediated adhesion

Abstract

Although bacterial pili are known to mediate cell adhesion to a variety of substrates, the molecular interactions behind this process are poorly understood. We report the direct measurement of the forces guiding pili-mediated adhesion, focusing on the medically important probiotic bacterium Lactobacillus rhamnosus GG (LGG). Using non-invasive single-cell force spectroscopy (SCFS), we quantify the adhesion forces between individual bacteria and biotic (mucin, intestinal cells) or abiotic (hydrophobic monolayers) surfaces. On hydrophobic surfaces, bacterial pili strengthen adhesion through remarkable nanospring properties, which - presumably - enable the bacteria to resist high shear forces under physiological conditions. On mucin, nanosprings are more frequent and adhesion forces larger, reflecting the influence of specific pili-mucin bonds. Interestingly, these mechanical responses are no longer observed on human intestinal Caco-2 cells. Rather, force curves exhibit constant force plateaus with extended ruptures reflecting the extraction of membrane nanotethers. These single-cell analyses provide novel insights into the molecular mechanisms by which piliated bacteria colonize surfaces (nanosprings, nanotethers), and offer exciting avenues in nanomedicine for understanding and controlling the adhesion of microbial cells (probiotics, pathogens).

Mechanical Strength and Inhibition of the Staphylococcus aureus Collagen-Binding Protein Cna

“…This mechanical resilience results from strategically located intramolecular isopeptide bonds (29). AFM demonstrated that pili from the probiotic Lactobacillus rhamnosus GG bacterium exhibit nanospring properties (37). The pilus spring constant measured at high force (>500 pN) was 15 pN nm −1 and was thus similar to the Cna value.…”

Atomic Force Microscopy in Microbiology: New Structural and Functional Insights into the Microbial Cell Surface

“…Variations in the loading rate and contact time enabled researchers to assess the kinetic dissociation and association constants of the bonds. Using SCFS, Sullan et al (108) investigated the forces guiding pili-mediated adhesion in probiotic L . rhamnosus GG (LGG) bacteria.…”

Nanoscale imaging and force probing of biomolecular systems using atomic force microscopy: from single molecules to living cells

“…With this method, the forces driving pili-mediated adhesion between individual bacteria and different types of surfaces (biotic surfaces and abiotic surfaces) were measured. 131 The results revealed that adhesion forces strongly depended on the nature of the target substrate. Besides, the adhesion involved two different mechanical responses.…”

“…Besides, the nanoscale forces engaged in the physiological processes of yeasts, including yeast flocculation 137 and yeast-macrophage adhesion, 138 have been investigated, improving our understanding of yeast adhesions. All together, these studies [128][129][130][131][132][133][134][135][136][137][138] allow directly quantifying adhesion interactions between individual microbial cells, opening up new avenues for understanding how cell surfaces respond to mechanical forces and how these responses are used to guide cell surface interactions.…”