Large-scale orientational order in bacterial colonies during inward growth
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 hot spots. The present results indicate a new mechanism underlying structural order and provide mechanistic insights into the dynamics of bacterial growth on complex surfaces.
The critical experimental data generated or analyzed during this study are provided as supporting video files.Code Availability:The codes utilized previously published open-source software from https://depts.washington.edu/soslab/gro/ and are made available on GitHub (https://github.com/mustafa-basaran/Large_Scale_Orientation_Bacteria).
Article and author information
EMBO Installation Grant (IG 3275)
- Askin Kocabas
BAGEP (young investigator award)
- Askin Kocabas
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
- Pierre Sens, Institut Curie, CNRS UMR168, France
- Received: July 14, 2021
- Accepted: February 24, 2022
- Accepted Manuscript published: March 7, 2022 (version 1)
- Version of Record published: March 29, 2022 (version 2)
© 2022, Basaran et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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Our results reveal that average condylar A-P translations, rotations, as well as their ranges of motion were comparable between stable and unstable groups. However, the unstable group exhibited more heterogeneous muscle synergy patterns and prolonged activation of knee flexors compared to the stable group. In addition, subjects who reported instability events during measurement showed distinct, subject-specific tibiofemoral kinematic patterns in the early/mid-swing phase of gait.
Our findings suggest that accurate movement analysis is sensitive for detecting acute instability events, but might be less robust in identifying general joint instability. Conversely, muscle synergy patterns seem to be able to identify muscular adaptation associated with underlying chronic knee instability.
This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.