Figure 7.

Scaling of the merging dynamics. (A) Ratio γ of the short and long axis of the ellipse as a function of time for the coalescence of differently sized colonies. The legend shows the numbers of cells in the individual colonies. By fitting an exponential function (black lines) one can extract the relaxation time τ_relax as a function of the cell number N. (B) The black dots show the relaxation times resulting from the exponential fit of the axis ratio as a function of the cell number. While τ_relax increases with time, we tested different scalings: τ_relax ∝ N^1/3(green), τ_relax ∝ N^2/3 (red) and τ_relax ∝ N¹ (blue). The extracted values for τ_relax seem to agree best with τ_relax ∝ N^2/3. This suggest that the relaxation time is proportional to the surface area of the colonies. (C) Bridge heights h as a function of time for different number of cells inside the colony. The legend shows the numbers of cells in the individual colonies. (D) Rescaled bridge height: the height of the bridge is rescaled by h_∞ = 1.4 · N^1/3 μm and time by the relaxation time τ_relax = 15.1 · N^2/3 s. The relaxation time is obtained from 1 – γ (t) (see (A) and (B)). The rescaling for the height h_∞ corresponds to the diameter of a spherical colony which is reached at times much larger than the relaxation time τ_relax (see figure S4 in the supplementary information). After rescaling all curves collapse.