Fig. 2.

(A) Schematic (not drawn to scale) illustrating the nanoindentation of the AFM cantilever through the bacterial surface biopolymers. In the schematic, (δ) represents the indentation distance, F represents the loading force and R is the radius of the AFM tip, and the inset depicts the common structure of a Gram-negative bacterial cell envelope. OM and IM represent the bacterial outer and inner membranes respectively. (B) Shows how the 25 points were distributed onto the surface of a representative cell far from cell edges for force measurements. (C) A representative force-indentation curve depicting the portion of the curve (solid circled line) that was fitted to the Hertz model of contact mechanics (red line). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)