  Bacteria can adjust the structure of colonies and biofilms to enhance their
survival rate under external stress. Here, we explore the link between
bacterial interaction forces and colony structure. We show that the activity of
extracellular pilus motors enhances local ordering and accelerates fusion
dynamics of bacterial colonies. The radial distribution function of mature
colonies shows local fluid-like order. The degree and dynamics of ordering are
dependent on motor activity. At a larger scale, the fusion dynamics of two
colonies shows liquid-like behavior whereby motor activity strongly affects
tension and viscosity.

Soft Condensed Matter;Biological Physics