Ciliary contact interactions dominate surface scattering of swimming eukaryotes

Abstract

Interactions between swimming cells and surfaces are essential to many microbiological processes, from bacterial biofilm formation to human fertilization. However, in spite of their fundamental importance, relatively little is known about the physical mechanisms that govern the scattering of flagellated or ciliated cells from solid surfaces. A more detailed understanding of these interactions promises not only new biological insights into structure and dynamics of flagella and cilia, but may also lead to new microfluidic techniques for controlling cell motility and microbial locomotion, with potential applications ranging from diagnostic tools to therapeutic protein synthesis and photosynthetic biofuel production. Due to fundamental differences in physiology and swimming strategies, it is an open question whether microfluidic transport and rectification schemes that have recently been demonstrated for pusher-type microswimmers such as bacteria and sperm cells, can be transferred to puller-type algae and other motile eukaryotes, as it is not known whether long-range hydrodynamic or short-range mechanical forces dominate the surface interactions of these microorganisms. Here, using high-speed microscopic imaging, we present direct experimental evidence that the surface scattering of both mammalian sperm cells and unicellular green algae is primarily governed by direct ciliary contact interactions. Building on this insight, we predict and verify experimentally the existence of optimal microfluidic ratchets that maximize rectification of initially uniform Chlamydomonas reinhardtii suspensions. Since mechano-elastic properties of cilia are conserved across eukaryotic species, we expect that our results apply to a wide range of swimming microorganisms.

Preprint as accepted for publication in PNAS, for published journal version (open access) and Supporting Information see http://dx.doi.org/10.1073/pnas.1210548110

References in corpus (5)

• Artificial Brownian motors: Controlling transport on the nanoscale
• Hydrodynamic attraction of swimming microorganisms by surfaces
• Fluid dynamics and noise in bacterial cell-cell and cell-surface scattering
• Direct measurement of the flow field around swimming microorganisms
• Rectification of Swimming Bacteria and Self Driven Particle Systems by Arrays of Asymmetric Barriers

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• Green Algae as Model Organisms for Biological Fluid Dynamics
• Rheotaxis facilitates upstream navigation of mammalian sperm cells
• Geometric capture and escape of a microswimmer colliding with an obstacle
• Minimal continuum theories of structure formation in dense active fluids
• Can the self-propulsion of anisotropic microswimmers be described by using forces and torques?
• Giant adsorption of microswimmers: duality of shape asymmetry and wall curvature
• Disrupting the wall accumulation of human sperm cells by artificial corrugation
• Spermatozoa scattering by a microchannel feature: an elastohydrodynamic model