From organized internal traffic to collective navigation of bacterial swarms

Ariel, Gil; Shklarsh, Adi; Kalisman, Oren; Ingham, Colin J.; Ben‐Jacob, Eshel

doi:10.1088/1367-2630/15/12/125019

Cited by 31 publications

(28 citation statements)

References 38 publications

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“…Spreading and survival of populations of bacteria often depend on their ability to behave collectively: cells aggregate into swarms to seek and migrate towards nutrient-rich regions [1,2], organise into biofilms resistant to antibiotics [3,4], respond to starvation by building fruiting bodies [5,6] or opt for cannibalism [7]. In such organisations, the surrounding environment often plays a major role, through its chemical composition [2,3] or geometrical constraints [4,8]. A complex and fascinating issue is how the various chemical or mechanical interactions between the microorganisms and their environment can guide the intricate dynamics of populations.…”

Section: Introductionmentioning

confidence: 99%

Directed collective motion of bacteria under channel confinement

2016

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Dense suspensions of swimming bacteria are known to exhibit collective behaviour arising from the interplay of steric and hydrodynamic interactions. Unconfined suspensions exhibit transient, recurring vortices and jets, whereas those confined in circular domains may exhibit order in the form of a spiral vortex. Here we show that confinement into a long and narrow macroscopic 'racetrack' geometry stabilises bacterial motion to form a steady unidirectional circulation. This motion is reproduced in simulations of discrete swimmers that reveal the crucial role that bacteria-driven fluid flows play in the dynamics. In particular, cells close to the channel wall produce strong flows which advect cells in the bulk against their swimming direction. We examine in detail the transition from a disordered state to persistent directed motion as a function of the channel width, and show that the width at the crossover point is comparable to the typical correlation length of swirls seen in the unbounded system. Our results shed light on the mechanisms driving the collective behaviour of bacteria and other active matter systems, and stress the importance of the ubiquitous boundaries found in natural habitats.

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Section: Introductionmentioning

confidence: 99%

Directed collective motion of bacteria under channel confinement

2016

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“…This assumption is motivated by experimental observations 20 (see Fig 1) where cells within oncostreams display a length to width ratio of 2.7:1. Using 21 ellipsoid shape is common in the study of bacteria, for instance viscoelastic ellipsoids 22 have been used in [26] or self-propelled spheres in [23] (see also [2,5,9,21,28,35]). We 23 were particularly interested in studying the dynamics in a regime of high cellular density 24 where cells are always in contact with each other.…”

Section: Introductionmentioning

confidence: 99%

“…R 3 , we cannot define anymore the local coordinate y ij since ω ⊥ i is now an hyperplane. However, we can still define x ij = x j − x i , ω i and we will use the second formulation for r ij (2). Some elementary computations show that:…”

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confidence: 99%

Self-organization in brain tumors: how cell morphology and cell density influence glioma pattern formation

Jamous

Comba

Löwenstein

et al. 2019

Preprint

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AbstractModeling cancer cells is essential to better understand the dynamic nature of brain tumors and glioma cells, including their invasion of normal brain. Our goal is to study how the morphology of the glioma cell influences the formation of patterns of collective behavior such as flocks (cells moving in the same direction) or streams (cells moving in opposite direction) referred to as oncostream. We have observed experimentally that the presence of oncostreams correlates with tumor progression. We propose an original agent-based model that considers each cell as an ellipsoid. We show that stretching cells from round to ellipsoid increases stream formation.A systematic numerical investigation of the model was implemented in ℝ2. We deduce a phase diagram identifying key regimes for the dynamics (e.g. formation of flocks, streams, scattering). Moreover, we study the effect of cellular density and show that, in contrast to classical models of flocking, increasing cellular density reduces the formation of flocks. We observe similar patterns in ℝ3 with the noticeable difference that stream formation is more ubiquitous compared to flock formation.Author summarySelf-organization is the formation of large-scale multicellular patterns that result exclusively from the interactions amongst constituent single cells. To establish the existence of self-organization in brain tumors we used agent-based modeling based on data extracted from static and dynamic genetically engineered mouse glioma models. Implementation of our model in ℝ2 identifies the dynamics that lead to formation of flocks (cells moving in a single direction), streams (cells moving in two directions), and cells moving as swarms or scattering. Increasing cellular density reduced formation of flocks and increased the formation of streams both in ℝ2 and in ℝ3. These results demonstrate the detailed mechanism leading to self-organization in brain tumors. As increasing density of oncostreams correlates with tumor malignancy, we establish a pathophysiological link between self-organization of glioma tumors and glioma malignancy. We propose the dismantling of oncostreams as a new therapeutic approach to the treatment of brain tumors.

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“…The bacteria also react to chemical gradients to control their short-time run lengths through rotating the flagellar 16,17 . Theoretical work such as the Vicsek Model 18,19 is based on the assumption of collisions and alignments of single bacterium with its neighbors in short-range. To consider hydrodynamic interactions between motile cells in the context of large-scale collective dynamics 5,[20][21][22][23][24] , some physical models treated the swarm fluid as a continuum entangling the bacteria phase and fluid together 20,24 , in which the bacterial community are treated as discrete individual self-propelled particles surrounded by an incompressible and inseparable fluid 20,25 .…”

Section: Introductionmentioning

confidence: 99%

Single Nanoparticle Tracking Reveals Efficient Long-Distance Undercurrent Transport above Swarming Bacteria

Feng

Zhang²,

Wen

et al. 2019

Preprint

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Flagellated bacteria move collectively in a swirling pattern on agar surfaces immersed in a thin layer of viscous "swarm fluid", but the role of this fluid in mediating the cooperation of the bacterial population is not well understood. Herein, we use gold nanorods (AuNRs) as single particle tracers to explore the spatiotemporal structure of the swarm fluid. We observed that individual AuNRs are transported in a plane of ~2 µm above the motile cells. They can travel for long distances (~800 μm) in a 2D plane at high speed without interferences from bacterial movements. The particles are apparently lifted up and transported by collective mixing of the small vortices around bacteria during localized clustering and de-clustering of the motile cells, exhibiting superdiffusive and non-Gaussian characteristics with alternating large-step jumps and confined lingering. Their motions are consistent with the Lévy walk (LW) model, revealing efficient transport flows above swarms. These flows provide obstacle-free highways for long-range material transportations, shed light on how swarming bacteria perform population-level communications, and reveal the essential role of the fluid phase on the emergence of large-scale synergy. This approach is promising for probing complex fluid dynamics and transports in other collective systems.

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From organized internal traffic to collective navigation of bacterial swarms

Cited by 31 publications

References 38 publications

Directed collective motion of bacteria under channel confinement

Directed collective motion of bacteria under channel confinement

Self-organization in brain tumors: how cell morphology and cell density influence glioma pattern formation

Single Nanoparticle Tracking Reveals Efficient Long-Distance Undercurrent Transport above Swarming Bacteria

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