Figure 4.

Experimental validation of the GV geometry-buckling relationship. (a) Hydrostatic collapse pressure curves for stripped GVs isolated from cyanobacterium Anabaena flos-aquae (AnaS), with (orange) and without (blue) precollapse hydrostatic pressure treatment at 200 kPa. Dashed lines indicate the pressure and corresponding OD₅₀₀ for samples that were collected for cryo-EM and nonlinear ultrasound imaging analysis. (b) Representative cryo-EM images of AnaS used to measure lengths and diameters of GVs from the control sample (left) and after incubation at a hydrostatic pressure of 200 (middle) and 220 kPa (right). Scale bars, 100 nm. (c and d) Length (c) and diameter (d) distributions of the intact GV fraction after exposure to the indicated hydrostatic pressure. Center line indicates median, the box limits denote the interquartile range and the whiskers absolute range. Each dot represents an individual measurement. Asterisks indicate statistical significance by one-way ANOVA tests (∗∗∗∗p < 0.0001); ns, no significance. (e) Nonlinear ultrasound signals from AnaS (n = 4) as a function of acoustic pressure from samples with (orange) and without (blue) precollapse hydrostatic pressure treatment at 200 kPa. Asterisks represent statistical significance by unpaired t-tests (^∗∗∗∗p < 0.0001, ^∗∗∗p < 0.001, ^∗∗p < 0.01, ^∗p < 0.05). Error bars represent mean ± SEM, where not seen, are hidden by symbols. To see this figure in color, go online.