Figure 5.

Spatiotemporal mapping of the traction stresses exerted by wild-type and MyoII mutant cells. (A) Phase-averaged traction stresses and cell shape corresponding to the four stereotypical stages defined in Figure 3 for wild-type (first column, N = 31), mlcE⁻ (second column, N = 14), and mhcA⁻ (third column, N = 27) cells. The contour maps show the average traction stress field, measured in a reference frame rotated to coincide with the instantaneous principal axes of the cells and scaled with their half-length, L(t)/2. The colors indicate the magnitude of the stresses in pN per unit area and the arrows indicate their direction. The white contours show the average shape of the cells in this reference frame. The front (F) of the cell corresponds to x > 0 and the back (B) corresponds to x < 0. (B) Components of the traction stresses parallel and perpendicular to the major axis of the cell averaged over the entire motility cycle. An estimation of the average stresses in Pa (= pN/μm²) can be obtained by dividing the values of traction stresses shown in this figure (in pN) by the squared average of L(t)/2 (in square micrometers). Average values for the length of each cell line during each phase of the motility cycle are given in Table 1.