Extended Data Fig. 6: Elasticity dependence of the global motion modes in active solids under isotropic lateral confinement.

(a) Oscillation frequency of global motion modes in modelled active solids as a function of k_b (fixing v₀ = 4). Colour of data points indicates the mode of global motion (blue: oscillatory translation; red: oscillatory rotation). Data are presented as mean + /-S.D. (N=100 simulation runs). (b) Temperature dependence of P. mirabilis single-cell speed. P. mirabilis cells in quasi-2D dilute bacterial suspension drops (prepared in the same manner as described in the caption of Extended Data Fig. 4) were tracked in fluorescent microscopy while the environmental temperature was varied from 24 °C to 50 °C with a custom-built temperature-control system (Methods). As shown in the plot the speed of cells only changed slightly in this temperature range (up to ~15%). The mean speed of cells at a specific temperature was computed based on 1-s segments of cell trajectories tracked in a 200-s time window. Data shown in the plot was normalized by the mean speed at temperature 24 °C. Data are presented as mean + /-S.D. (N = 2500). (c,d) Transition of global motion modes in bacterial active solids controlled by temperature. Panel c shows the temperature dependence of oscillation frequency in the bacterial active solid during mode transition. Colour of data points indicates the mode of global motion (blue: oscillatory translation; red: oscillatory rotation). Panel d shows the temporal dynamics of spatially averaged collective velocity during transition from the oscillatory rotation mode to the oscillatory translation mode following the decrease of temperature. The spatially averaged collective velocity was decomposed as Cartesian components (yellow and blue traces; upper part of panel d) and polar-coordinate components (red: tangential or azimuthal component, green: radial component; lower part of panel d). Data in panels c,d were from a representative experiment (>5 replicates).