Extended Data Fig. 4: Tuning single-cell speed of P. mirabilis via violet-light illumination.

To obtain this plot, cells were extracted from the P. mirabilis-based bacterial active solids that were undergoing either global oscillatory translation or global oscillatory rotation; the extracted cells were mixed with 0.02% Tween 20 and deposited on 0.6% LB agar surface, forming a quasi-2D dilute bacterial suspension drop. P. mirabilis cells in the prepared quasi-2D dilute bacterial suspension drop were continuously illuminated by 406 nm violet light starting from T = 0 s while being tracked in phase-contrast microscopy (Methods); note that for single-cell tracking, a 20x objective lens was used. The speed of an individual cell at a specific time T was computed based on its trajectory tracked from (T-0.5) s to (T + 0.5) s; the single-cell speeds computed from (T-25) s to (T + 25) s were then averaged and taken to be the mean cell speed at T. Data shown in the plot was normalized by the mean speed at T = 0 s (that is, the free-swimming speed of cells without blue light illumination; V₀ = 26.7 ± 6.9 µm/s; mean±S.D., N = 2500). Data are presented as mean + /-S.D. (N = 2500).