Sperm as microswimmers – navigation and sensing at the physical limit

Kaupp, U. Benjamin; Álvarez, Luis J.

doi:10.1140/epjst/e2016-60097-1

Cited by 29 publications

(31 citation statements)

References 106 publications

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“…The flagellar beat of sperm and the steering response is controlled by changes in [Ca 2+ ] i 38 . The female sex hormone progesterone evokes robust Ca 2+ entry into human sperm by activating the CatSper Ca 2+ channel 39 , 40 .…”

Section: Resultsmentioning

confidence: 99%

Human sperm steer with second harmonics of the flagellar beat

et al. 2017

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Sperm are propelled by bending waves traveling along their flagellum. For steering in gradients of sensory cues, sperm adjust the flagellar waveform. Symmetric and asymmetric waveforms result in straight and curved swimming paths, respectively. Two mechanisms causing spatially asymmetric waveforms have been proposed: an average flagellar curvature and buckling. We image flagella of human sperm tethered with the head to a surface. The waveform is characterized by a fundamental beat frequency and its second harmonic. The superposition of harmonics breaks the beat symmetry temporally rather than spatially. As a result, sperm rotate around the tethering point. The rotation velocity is determined by the second-harmonic amplitude and phase. Stimulation with the female sex hormone progesterone enhances the second-harmonic contribution and, thereby, modulates sperm rotation. Higher beat frequency components exist in other flagellated cells; therefore, this steering mechanism might be widespread and could inspire the design of synthetic microswimmers.

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Section: Resultsmentioning

confidence: 99%

Human sperm steer with second harmonics of the flagellar beat

et al. 2017

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“…2(a)]. These results have significant implications for understanding beat emergence [36,37] and motor coordination in eukaryotic cilia and flagella [38][39][40].…”

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confidence: 87%

Time Irreversibility and Criticality in the Motility of a Flagellate Microorganism

Wan

Goldstein

2018

Phys. Rev. Lett.

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Active living organisms exhibit behavioral variability, partitioning between fast and slow dynamics. Such variability may be key to generating rapid responses in a heterogeneous, unpredictable environment wherein cellular activity effects continual exchanges of energy fluxes. We demonstrate a novel, noninvasive strategy for revealing nonequilibrium control of swimming-specifically, in an octoflagellate microalga. These organisms exhibit surprising features of flagellar excitability and mechanosensitivity, which characterize a novel, time-irreversible "run-stop-shock" motility comprising forward runs, knee-jerk shocks with dramatic beat reversal, and long stops during which cells are quiescent yet continue to exhibit submicron flagellar vibrations. Entropy production, associated with flux cycles arising in a reaction graph representation of the gait-switching dynamics, provides a direct measure of detailed balance violation in this primitive alga.

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“…9(b). Thus, sperm, E. coli and salmonella are pushers, because they have active propelling flagella in the rear, and a passive head in the front (for details, see minireview [38] by L. Alvarez & U.B. Kaupp for sperm).…”

Section: Hydrodynamic Interactions Of Microswimmers With Surfaces 31mentioning

confidence: 99%

Microswimmers near surfaces

Elgeti

Gompper

2016

Eur. Phys. J. Spec. Top.

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Abstract. Both, in their natural environment and in a controlled experimental setup, microswimmers regularly interact with surfaces. These surfaces provide a steric boundary, both for the swimming motion and the hydrodynamic flow pattern. These effects typically imply a strong accumulation of microswimmers near surfaces. While some generic features can be derived, details of the swimmer shape and propulsion mechanism matter, which give rise to a broad range of adhesion phenomena and have to be taken into account to predict the surface accumulation for a given swimmer. We show in this minireview how numerical simulations and analytic theory can be used to predict the accumulation statistics for different systems, with an emphasis on swimmer shape, hydrodynamics interactions, and type of noisy dynamics.

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Sperm as microswimmers – navigation and sensing at the physical limit

Cited by 29 publications

References 106 publications

Human sperm steer with second harmonics of the flagellar beat

Human sperm steer with second harmonics of the flagellar beat

Time Irreversibility and Criticality in the Motility of a Flagellate Microorganism

Microswimmers near surfaces

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