Figure 1.

(a1–a4) Schematic diagrams of side views of the experimental geometry used for AFM pulling measurements of T4P. Cells of a pilT mutant of P. aeruginosa PAO1 (ellipses) are adhered near the end of the tip on the AFM cantilevers, and T4P were pulled away from an underlying surface. Four of the different possible scenarios for contact between the T4P and the surface are indicated: (a1) a single contact point, (a2) an adsorbed segment, (a3) multiple contacts along the length of a single T4P, and (a4) multiple T4P. (b) Single force peaks in typical AFM force-separation curves measured for pulling on single T4P from a mica surface (upper curve) and from a gold surface (lower curve) using a sharp AFM tip. Both curves were measured for T4P on the P. aeruginosa PAO1 pilT mutant. The solid curves correspond to the best fit of each force peak to the WLC model (Eq. 1). The best-fit values of the persistence length L_p are indicated on the plots. (c) Multiple force peaks in typical AFM force-separation curves measured for the pulling of T4P on a P. aeruginosa PAO1 pilT mutant strain from a mica surface using a sharp AFM tip. The solid curves correspond to best fits of individual force peaks to the WLC model. The best-fit values of the persistence length L_p are indicated on the plots. To see this figure in color, go online.