Abstract
Cilia-driven motility and fluid transport are ubiquitous in nature and essential for many biological processes, including swimming of eukaryotic unicellular organisms, mucus transport in airway apparatus or fluid flow in the brain. The-biflagellated micro-swimmer Chlamydomonas reinhardtii is a model organism to study the dynamics of flagellar synchronization. Hydrodynamic interactions, intracellular mechanical coupling or cell body rocking is believed to play a crucial role in the synchronization of flagellar beating in green algae. Here, we use freely swimming intact flagellar apparatus isolated from a wall-less strain of Chlamydomonas to investigate wave dynamics. Our analysis on phase coordinates shows that when the frequency difference between the flagella is high (10–41% of the mean), neither mechanical coupling via basal body nor hydrodynamics interactions are strong enough to synchronize two flagella, indicating that the beating frequency is perhaps controlled internally by the cell. We also examined the validity of resistive force theory for a flagellar apparatus swimming freely in the vicinity of a substrate and found quantitative agreement between the experimental data and simulations with a drag anisotropy of ratio 2. Finally, using a simplified wave form, we investigated the influence of phase and frequency differences, intrinsic curvature and wave amplitude on the swimming trajectory of flagellar apparatus. Our analysis shows that by controlling the phase or frequency differences between two flagella, steering can occur.
Highlights
Cilia and flagella are hair-like organelles, which protrude from the surface of many eukaryotic cells and play a fundamental role in signal processing,[1] sensing,[2,3] propulsion of microorganisms[4,5,6] and micro-scale fluid transport[7,8] at a low Reynolds number regime
We have used high-speed imaging, quantitative image processing, and mode analysis to study the wave dynamics of flagellar apparatus isolated from wall-less strain of C. reinhardtii
In contrast to the results reported in ref. 35 and 36, all of the isolated apparatus in our experiments (N = 10) had an intrinsic frequency mismatch of Df = 3.73 Æ 1.84 Hz (B10–41% of the mean) and it was not possible with our data to investigate the synchronization dynamics in swimmers with no or very small frequency differences
Summary
Cilia and flagella are hair-like organelles, which protrude from the surface of many eukaryotic cells and play a fundamental role in signal processing,[1] sensing,[2,3] propulsion of microorganisms[4,5,6] and micro-scale fluid transport[7,8] at a low Reynolds number regime. Constrains at the basal region and along the contour length of the axoneme convert sliding to bending deformations.[9,10,11] The coordinated beating activity of flagella is crucial for efficient swimming of many ciliated cells in an ambient fluid. Using a low-dimensional stochastic model of hydrodynamically coupled oscillators, namely the stochastic Adler equation,[21] they capture the dynamics of phase slips and the statistics of phase-locked intervals. In this stochastic model, noise amplitude is set by the intrinsic fluctuations
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