Wild-type cells implement the S-S mode periodically. (A) Kymograph of the instantaneous magnitude of the traction stresses, (upper part), and axial tension, Tx (lower part), for a representative wild-type cell (the cell shown in Fig. 2 corresponds to t = 100 s until t = 180 s). and cell contours are displayed every 20 s. The dots superimposed on the front cell edge indicate the phases of the cycle. Black circles show pseudopod protrusion and front TA formation. Black arrows show TA loss and back cell edge retraction. The inclined red and black lines indicate the instantaneous position of the front and back cell edges. (B) Phase-average traction stress maps in the cell-based reference frame for the cell shown in A. Each column corresponds to a different phase. The first, second, and third rows show the magnitude of the total, axial, and lateral traction stresses, respectively, for each phase. The color patches indicate the magnitude of the traction stresses, and the arrows denote their direction. The white contours depict the average cell shape. The cell’s front (F) and back (B) are indicated. For each phase, the mean duration (T), speed (V), axial and lateral force (Fx and Fy), and ratio of axial to lateral force (Fx/Fy) are displayed. (C) Box plots of the period of the oscillations of: the cell length, Tλ(t); strain energy, ; and the position of the minimum and maximum Tx at the cell’s front and back with respect to its centroid, TF and TB (n = 8). Circles represent outliers, and the box plots’ notched sections show the 95% confidence interval around the median. (D) Box plots of the relative time duration of each mode implemented by wild-type cells (n = 8). Red asterisks denote a distribution whose median is not 0 (P < 0.05).
