Fig. 4.

Fraction of colony surfing events $p=N_{\text{surf}}/N$, out of $N=\mathrm{\hspace{0.17em}8}$ runs for each data point, for $2-\mathrm{\mu }\text{L}$ drops (initial $\text{OD}=\mathrm{\hspace{0.17em}0.27}$) of a motile (SSB 1071) and nonmotile (OMG 954) strain at different gel inclinations. The two strains show no statistically significant difference. The uncertainty of the tilt angle measurement is estimated to $\mathrm{\Delta }\alpha =\pm {0.05}^{\circ }$.