Geometry and dynamical morphology of growing bacterial colonies

TL;DR

This study analyzes the evolving geometry of bacterial colonies during growth, revealing periods of consistent scaling and transient morphological reorganizations, and introduces a time-resolved geometric framework for understanding non-equilibrium biological growth.

Contribution

It provides a novel time-resolved geometric analysis of bacterial colony growth, linking morphological dynamics to underlying non-equilibrium processes.

Findings

Extended intervals of area-perimeter scaling with exponent ~2

Transient boundary reorganizations during growth

Morphological diversity within the same geometric growth regime

Abstract

We study non-equilibrium bacterial colony growth using a geometry-first, time-resolved analysis of morphology. From time-lapse microscopy data, we track the coupled evolution of area, perimeter, and boundary-sensitive shape descriptors along the full growth history. We find that non-equilibrium growth can exhibit extended intervals of compact area--perimeter scaling with exponent $\alpha \approx 2$, consistent with growth governed by a single effective geometric length scale, as well as time-localized breakdowns of this scaling during ongoing growth. These breakdowns coincide with transient boundary reorganization while bulk area growth remains sustained. Our results demonstrate that visually distinct morphologies can arise within the same geometric growth regime, and that departures from single-scale behavior reflect intrinsic dynamical restructuring rather than growth arrest. More broadly, this work establishes time-resolved geometry as a coarse-grained framework for identifying when non-equilibrium growth departs from single-scale geometric constraints in living systems.