A steering mechanism for phototaxis in
            <i>Chlamydomonas</i>

Bennett, Rachel R.; Golestanian, Ramin

doi:10.1098/rsif.2014.1164

Cited by 89 publications

(84 citation statements)

References 48 publications

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“…This unicellular green alga actively redirects its swimming motion through occasional desynchronization of its two cilia (19), although it is still debated whether this effect is of mechanical (20) (23) show that the alga's reorientation dynamics can lead to localization in shear flow (24,25), with potentially profound implications in marine ecology. In contrast to taxis in multiflagellate organisms (2,5,18,26,27), the navigation strategies of uniflagellate cells are less well understood. For instance, it was discovered only recently that uniflagellate marine bacteria, such as Vibrio alginolyticus and Pseudoalteromonas haloplanktis, use a buckling instability in their lone flagellum to change their swimming direction (28).…”

mentioning

confidence: 99%

Bimodal rheotactic behavior reflects flagellar beat asymmetry in human sperm cells

Bukatin

Kukhtevich

Stoop

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

101

125

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Rheotaxis, the directed response to fluid velocity gradients, has been shown to facilitate stable upstream swimming of mammalian sperm cells along solid surfaces, suggesting a robust physical mechanism for long-distance navigation during fertilization. However, the dynamics by which a human sperm orients itself relative to an ambient flow is poorly understood. Here, we combine microfluidic experiments with mathematical modeling and 3D flagellar beat reconstruction to quantify the response of individual sperm cells in time-varying flow fields. Single-cell tracking reveals two kinematically distinct swimming states that entail opposite turning behaviors under flow reversal. We constrain an effective 2D model for the turning dynamics through systematic large-scale parameter scans, and find good quantitative agreement with experiments at different shear rates and viscosities. Using a 3D reconstruction algorithm to identify the flagellar beat patterns causing left or right turning, we present comprehensive 3D data demonstrating the rolling dynamics of freely swimming sperm cells around their longitudinal axis. Contrary to current beliefs, this 3D analysis uncovers ambidextrous flagellar waveforms and shows that the cell's turning direction is not defined by the rolling direction. Instead, the different rheotactic turning behaviors are linked to a broken mirror symmetry in the midpiece section, likely arising from a buckling instability. These results challenge current theoretical models of sperm locomotion.sperm swimming | rheotaxis | fluid dynamics | microfluidics | simulations T axis, the directed kinematic response to external signals, is a defining feature of living things that affects their reproduction, foraging, migration, and survival strategies (1-4). Higher organisms rely on sophisticated networks of finely tuned sensory mechanisms to move efficiently in the presence of chemical or physical stimuli. However, various fundamental forms of taxis are already manifest at the unicellular level, ranging from chemotaxis in bacteria (5) and phototaxis in unicellular green algae (2) to the mechanical response (durotaxis) of fibroblasts (6) and rheotaxis (7, 8) in spermatozoa (3, 9-12). Over the last few decades, much progress has been made in deciphering chemotactic, phototactic, and durotactic pathways in prokaryotic and eukaryotic model systems. In contrast, comparatively little is known about the physical mechanisms that enable flow gradient sensing in sperm cells (3, 9-13). Recent studies (3, 12) suggest that mammalian sperm use rheotaxis for long-distance navigation, but it remains unclear how shear flows alter flagellar beat patterns in the vicinity of surfaces and, in particular, how such changes in the beat dynamics affect the steering process. Answering these questions will be essential for evaluating the importance of chemical (14) and physical (4) signals during mammalian fertilization (15-17).A necessary requirement for any form of directed kinematic response is the ability to change the direction of loco...

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mentioning

confidence: 99%

Bimodal rheotactic behavior reflects flagellar beat asymmetry in human sperm cells

Bukatin

Kukhtevich

Stoop

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

101

125

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“…a single rotating flagellum [33]) which does not allow the cell to actively steer towards any controlled direction (nonetheless our data seems to show that the stochastic reorientation process is enhanced by some type of cell activity) as opposed to most algae that are also aided by dedicated eyespots for detecting light (e.g. C. reinhardtii [60], Euglena gracilis [61]) Instead, the phototactic drifts experienced by Micromonas sp. population originates from subtle directional asymmetries in run lengths.…”

Section: Discussionmentioning

confidence: 95%

Phototaxis of the dominant marine pico-eukaryoteMicromonas sp.: from population to single cell

Henshaw

Jeanneret

Polin

2019

Preprint

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Micromonas commoda (previously Micromonas pusilla, a unicellular photosynthetic picoeukaryote globally dominant in marine ecosystems, has previously been qualified as being strongly phototactic. To date, no detailed quantitative or qualitative description of this behaviour has been reported, nor have thorough studies of its motility been undertaken. This primary producer has only been qualitatively described as utilizing run-and-tumble motion, but such motility strategy is incompatible with its morphology comprising only one propelling flagellum. Moreover, it is still unclear as to how Micromonas sp. detects a light direction due to the lack of a dedicated eyespot; the organism is essentially blind. Here we first perform population-scale phototactic experiments to show that this organism actively responds to a wide range of light wavelengths and intensities. These population responses are well accounted for within a simple drift-diffusion framework. Based on single-cell tracking experiments, we then detail thoroughly Micromonas sp.'s motility which resembles run-and-reverse styles of motion commonly observed in marine prokaryotes and that we name stop-run or reverse. The associated peculiar microscopic changes upon photo-stimulation are finally described and integrating those into jump-diffusion simulations appears to produce phototactic drifts that are quantitatively compatible with those obtained experimentally at the population level.

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“…which in turn, is equivalent to a single separable first order differential equation that upon solving yields the following transcendental equation. [12] where Rint and αint denote initial conditions of R and α at time t = 0 respectively. This system of equations involving α has two fixed points R o , α o,± = v0/κ0, ±π/2 corresponding to closed circular trajectories in the R-θ plane, and can also be seen as the set of solutions whereθ =φ in eqs.…”

Section: Overdamped Dynamicsmentioning

confidence: 99%

“…Tactic responses are also known for many other physical stimuli such as variation in the intensity of light (phototaxis) (11)(12)(13)(14)(15)(16)(17)(18), external magnetic (magnetotaxis) (19)(20)(21)(22) or gravitational field strengths (gravitaxis) (23)(24)(25)(26), temperature (thermotaxis) (27,28), viscosity (viscotaxis) (29), orientation of the solvent flow field (rheotaxis) (30)(31)(32) and even topographical gradients that may be present in distorted solids or environments (topotaxis) (33)(34)(35).…”

mentioning

confidence: 99%

Rototaxis: Localization of active motion under rotation

Zheng

Löwen

2020

Phys. Rev. Research

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The ability to navigate in complex, inhomogeneous environments is fundamental to survival at all length scales, giving rise to the rapid development of various subfields in bio-locomotion such as the well established concept of chemotaxis. In this work, we extend this existing notion of taxis to rotating environments and introduce the idea of "roto-taxis" to bio-locomotion. In particular, we explore both overdamped and inertial dynamics of a model synthetic self-propelled particle in the presence of constant global rotation, focusing on the particle's ability to localize near a rotation center as a survival strategy. We find that in the overdamped regime, the swimmer is in general able to generate a self restoring active torque that enables it to remain on stable epicyclical-like trajectories. On the other hand, for underdamped motion with inertial effects, the intricate competition between self-propulsion and inertial forces, in conjunction with the rototactic torque leads to complex dynamical behavior with nontrivial phase space of initial conditions which we reveal by numerical simulations. Our results are relevant for a wide range of setups, from vibrated granular matter on turntables to microorganisms or animals swimming near swirls or vortices.biological movement | chemotaxis| microswimmers | active matter

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A steering mechanism for phototaxis in Chlamydomonas

Cited by 89 publications

References 48 publications

Bimodal rheotactic behavior reflects flagellar beat asymmetry in human sperm cells

Bimodal rheotactic behavior reflects flagellar beat asymmetry in human sperm cells

Phototaxis of the dominant marine pico-eukaryoteMicromonas sp.: from population to single cell

Rototaxis: Localization of active motion under rotation

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