Bacteria solve the problem of crowding by moving slowly

Abstract

In systems as diverse as migrating mammals to road traffic, crowding acts to inhibit efficient collective movement. Bacteria, however, are observed to move in very dense groups containing billions of individuals without causing the gridlock common to other systems. Here we combine experiments, cell tracking and individual-based modelling to study the pathogen Pseudomonas aeruginosa as it collectively migrates across surfaces using grappling-hook like pili. We show that the fast moving cells of a hyperpilated mutant are overtaken and outcompeted by the slower moving wild-type at high cell densities. Using theory developed to study liquid crystals, we demonstrate that this effect is mediated by the physics of topological defects, points where cells with different orientations meet one another. Our analyses reveal that when comet-like defects collide with one another, the fast-moving mutant cells rotate vertically and become trapped. By moving more slowly, wild-type cells avoid this trapping mechanism, allowing them to collectively migrate faster. Our work suggests that the physics of liquid crystals has played a pivotal role in the evolution of collective bacterial motility by exerting a strong selection for cells that exercise restraint in their movement.

arXiv comment48 pages, 4 figures, 10 extended data figures

References in corpus (9)

• Meso-scale turbulence in living fluids
• Fluid dynamics of bacterial turbulence
• Topological defect launches 3D mound in the active nematic sheet of neural progenitors
• Defect dynamics in active nematics
• Topological defects promote layer formation in Myxococcus xanthus colonies
• Defect-mediated morphologies in growing cell colonies
• Emergent states in dense systems of active rods: from swarming to turbulence
• Verticalization of bacterial biofilms
• Emergence of active nematics in bacterial biofilms

Cited by in corpus (29)

• Topological active matter
• Design of nematic liquid crystals to control microscale dynamics
• Vesicle shape transformations driven by confined active filaments
• Mechanical basis and topological routes to cell elimination
• Introduction to topological defects: from liquid crystals to particle physics
• Microbes in porous environments: From active interactions to emergent feedback
• Trade-offs in phenotypic noise synchronize emergent topology to actively enhance transport in microbial environments
• Polar Fluctuations Lead to Extensile Nematic Behavior in Confluent Tissues
• Controlling topological defects and contractile flow in confined nematic cell population
• Learning developmental mode dynamics from single-cell trajectories
• Motile topological defects hinder dynamical arrest in dense liquids of active ellipsoids
• Tilt-induced polar order and topological defects in growing bacterial populations
• Fluctuation-induced dynamics of nematic topological defects
• Symmetry-breaking, motion and bistability of active drops through polarization-surface coupling
• High-resolution three-dimensional imaging of topological textures in single-diamond networks
• Configurational temperature in active matter. II. Quantifying the deviation from thermal equilibrium
• Activity pulses induce spontaneous flow reversals in viscoelastic environments
• Active topological defect absorption by a curvature singularity
• Microbial transport and dispersion in heterogeneous flows created by pillar arrays
• Machine learning topological defects in confluent tissues
• Distinct impacts of polar and nematic self-propulsion on active unjamming
• Hermitian and non-Hermitian topology in active matter
• Elasticity tunes mechanical stress localization around active topological defects
• Active-parameter polydispersity in the 2d ABP Yukawa model
• Topological signatures of collective dynamics and turbulent-like energy cascades in apolar active granular
• Quadrupolar active stress induces exotic phases of defect motion in active nematics
• Self-organised structures in mixed active-passive suspensions due to hydrodynamic interactions
• Self-sustained oscillations of active viscoelastic matter
• Nematic order condensation and topological defects in inertial active nematics