TY - JOUR TI - Large-scale orientational order in bacterial colonies during inward growth AU - Basaran, Mustafa AU - Yaman, Y Ilker AU - YĆ¼ce, Tevfik Can AU - Vetter, Roman AU - Kocabas, Askin A2 - Sens, Pierre A2 - Walczak, Aleksandra M A2 - Shankar, Suraj VL - 11 PY - 2022 DA - 2022/03/07 SP - e72187 C1 - eLife 2022;11:e72187 DO - 10.7554/eLife.72187 UR - https://doi.org/10.7554/eLife.72187 AB - During colony growth, complex interactions regulate the bacterial orientation, leading to the formation of large-scale ordered structures, including topological defects, microdomains, and branches. These structures may benefit bacterial strains, providing invasive advantages during colonization. Active matter dynamics of growing colonies drives the emergence of these ordered structures. However, additional biomechanical factors also play a significant role during this process. Here, we show that the velocity profile of growing colonies creates strong radial orientation during inward growth when crowded populations invade a closed area. During this process, growth geometry sets virtual confinement and dictates the velocity profile. Herein, flow-induced alignment and torque balance on the rod-shaped bacteria result in a new stable orientational equilibrium in the radial direction. Our analysis revealed that the dynamics of these radially oriented structures, also known as aster defects, depend on bacterial length and can promote the survival of the longest bacteria around localized nutritional hotspots. The present results indicate a new mechanism underlying structural order and provide mechanistic insights into the dynamics of bacterial growth on complex surfaces. KW - active matter KW - bacterial alignment KW - nemato-hydrodynamics JF - eLife SN - 2050-084X PB - eLife Sciences Publications, Ltd ER -