Nanowire Arrays as Cell Force Sensors To Investigate Adhesin-Enhanced Holdfast of Single Cell Bacteria and Biofilm Stability

Surface attachment of a planktonic
bacteria, mediated by adhesins
and extracellular polymeric substances (EPS), is a crucial step for
biofilm formation. Some pathogens can modulate cell adhesiveness,
impacting host colonization and virulence. A framework able to quantify
cell-surface interaction forces and their dependence on chemical surface
composition may unveil adhesiveness control mechanisms as new targets
for intervention and disease control. Here we employed InP nanowire
arrays to dissect factors involved in the early stage biofilm formation
of the phytopathogen Xylella fastidiosa. Ex vivo experiments demonstrate single-cell adhesion
forces up to 45 nN, depending on the cell orientation with respect
to the surface. Larger adhesion forces occur at the cell poles; secreted
EPS layers and filaments provide additional mechanical support. Significant
adhesion force enhancements were observed for single cells anchoring
a biofilm and particularly on XadA1 adhesin-coated surfaces, evidencing
molecular mechanisms developed by bacterial pathogens to create a
stronger holdfast to specific host tissues.