Transition to bound states for bacteria swimming near surfaces

Das, Debasish; Lauga, Eric

doi:10.1103/physreve.100.043117

Cited by 21 publications

(12 citation statements)

References 47 publications

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“…A similar dependence on N was found by Petroff et al [17] in analysis of Thiovulum majus bacteria that selforganise into 2D clusters rotating counter-clockwise at a solid boundary [41]. Here, the counter-clockwise orientation is imposed by the chirality of the bacterial flagella, and a global torque results from the coupling of the individual spinners.…”

Section: Phase Diagram For the Cluster Dynamicssupporting

confidence: 74%

Spontaneously rotating clusters of active droplets

Hokmabad,

Nishide,

Ramesh

et al. 2021

Preprint

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We report on the emergence of spontaneously rotating clusters in active emulsions. Ensembles of self-propelling droplets sediment and then self-organise into planar, hexagonally ordered clusters which hover over the container bottom while spinning around the plane normal. This effect exists for symmetric and asymmetric arrangements of isotropic droplets and is therefore not caused by torques due to geometric asymmetries. We found, however, that individual droplets exhibit a helical swimming mode in a small window of intermediate activity in a force-free bulk medium. We show that by forming an ordered cluster, the droplets cooperatively suppress their chaotic dynamics and turn the transient instability into a steady rotational state. We analyse the collective rotational dynamics as a function of droplet activity and cluster size and further propose that the stable collective rotation in the cluster is caused by a cooperative coupling between the rotational modes of individual droplets in the cluster.

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Section: Phase Diagram For the Cluster Dynamicssupporting

confidence: 74%

Spontaneously rotating clusters of active droplets

Hokmabad,

Nishide,

Ramesh

et al. 2021

Preprint

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“…The rotational velocity of a cluster linearly decreases with N . A similar trend was reported for Thiovulum majus bacteria that transition to downwards oriented bound states near surfaces [235] and self-organize into 2D clusters rotating on a solid boundary [232]. The clusters only rotate counter-clockwise since each individual, flagellated bacterium generates flow fields with counter-clockwise chirality.…”

Section: Phase Diagram For the Cluster Dynamicssupporting

confidence: 76%

Active Emulsions: Physicochemical Hydrodynamics and Collective Behavior

Babak¹

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Compartmentalization is critical to separate the components of the living system from the environment. It spatially concentrates reactants and chemical networks and confines the genetic material of the cell. In cells, this semi-permeable membrane is responsible for compartmentalisation. It regulates the communication of the cell with the environment enabling the cell to create spatiotemporal chemical gradients that are critical for functioning out of equilibrium.U and characteristic length scale L, the Reynolds number is defined as the ratio of the inertial term, ∼ ρu • ∇u, to the viscous term, ∼ η∇ 2 u, in the Navier-Stokes equation [30]. Hence, Micro-swimmers with or without moving partsArtificial microswimmers that are driven mechanically use moving parts that mimic biological counterparts in performing non-reciprocal movements. The first example of such systems was the linear chains of DNA-linked magnetic colloids that were attached to a red blood cell [42]. The flexible synthetic flagellum was actuated by an external oscillating magnetic field. The manufacturing of such designs is challenging and they are prone to fatigue failure. Intrinsic symmetry breakingIntrinsic symmetry breaking means the asymmetry is imposed on the systems, typically geometrically, and is not a result of dynamical instability. Thus, it is useful for the diffusive regime where P e ≪ 1. The broadly-adopted approach for creating such an asymmetry is to spatially vary the surface activity. Janus particles are well-known Active dropletsThe framework discussed in Section 1.3.1 is applicable to any autophoretic particle which undergoes chemical activity at its surface such as active droplets. Active droplets, in particular, are known as the experimental realization of isotropic autophoretic particles. Estimates from scaling analysis suggest that the dominant driving force for active droplets is provided by Marangoni stresses (see Chapter 3). Thus, active droplets have to induce a self-sustaining fore-aft gradient in interfacial tension to achieve continuous propulsion. This gradient generally originates from a chemical activity at the interface which drives a fluid dynamical advection-diffusion instability. Based on the way the energy for activity is obtained, the experimental systems fall into three distinct categories: i) a chemical reaction taking place inside the droplet, ii) phase separation, and iii) micellar solubilization. i. Internal chemical reactionSince the chemical reaction takes place inside the droplet, this type of active droplet, compared to its counterparts, has a shorter lifetime and thereby shorter cruising range, i.e. the maximum distance the swimmer can self-propel before stopping. The mechanism depends on a specific chemical reaction, therefore, it is challenging to tune, modify, or improve. This limits the applications as well as further studies where for Collective dynamics governed by long-range interactionsLong-range inter-particle interactions in phoretic suspensions include [10] (i) Chemical interactions. The che...

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“…Although it has been observed in generic settings that a helical flagellum does not substantially deform under rotation [14], a more recent investigation by Jabbarzadeh & Fu indicates that both hook as well as flagellum deformability is needed to account for the large hook angles seen in such flicks [15,16], consistent with experimental observations [13]. Even without the added complexity of a cell body, the chirality of a helical filament results in coupling of translation and rotation which can lead to surprisingly rich dynamics under gravity [17], under magnetic actuation [18,19], near surfaces [20,21], in a background flow [22,23] or even double-helical trajectories for double-helical "superhelices" like insect spermatozoa [24,25]. For very soft filaments, other instabilities and dynamics abound [26][27][28] The end result of such flagellar activity is the body trajectory, itself an object of intense scrutiny.…”

Section: Introductionmentioning

confidence: 56%

“…The model of the flagellum will incorporate its geometry and the nontrivial relationship between the motor torque and its dynamics via the flexible hook, to second order in the flagellum amplitude. For this purpose we use the simplest resistive force theory approximation [47,48] as recently used in similar contexts, including the instability of bodies propelled by N flagella or swimming with a flexible flagellum near a wall [20,21,49], and neglecting hydrodynamic interactions with the cell body. Comparisons between this resistive force theory and full hydrodynamic theory have been explored in detail [48,50]; a comparison for this precise context in Ref.…”

Section: B Model Flagellummentioning

confidence: 99%

Helical trajectories of swimming cells with a flexible flagellar hook

Zou,

Lough,

Spagnolie

2021

Preprint

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The flexibility of the bacterial flagellar hook is believed to have substantial consequences for microorganism locomotion. Using a simplified model of a rigid flagellum and a flexible hook, we show that the paths of axisymmetric cell bodies driven by a single flagellum are generically helical. Phase-averaged resistance and mobility tensors are produced to describe the flagellar hydrodynamics, and a helical rod model which retains a coupling between translation and rotation is identified as a distinguished asymptotic limit. A supercritical Hopf bifurcation in the flagellar orientation beyond a critical ratio of flagellar motor torque to hook bending stiffness, which is set by the spontaneous curvature of the flexible hook, the shape of the cell body, and the flagellum geometry, can have a dramatic effect on the cell's trajectory through the fluid. Although the equilibrium hook angle can result in a wide variance in the trajectory's helical pitch, we find a very consistent prediction for the trajectory's helical amplitude using parameters relevant to swimming P. aeruginosa cells.

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Transition to bound states for bacteria swimming near surfaces

Cited by 21 publications

References 47 publications

Spontaneously rotating clusters of active droplets

Spontaneously rotating clusters of active droplets

Active Emulsions: Physicochemical Hydrodynamics and Collective Behavior

Helical trajectories of swimming cells with a flexible flagellar hook

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