Chlamydomonas Swims with Two “Gears” in a Eukaryotic Version of Run-and-Tumble Locomotion

Abstract

All Together Now (Sometimes) Motile cilia and flagella protrude from the surface of many eukaryotic cells. Understanding how cilia and flagella operate is important for understanding ciliated cells in metazoans, the ecology and behavior of motile microorganisms, and the mechanisms of molecular motors and signal transduction. Using very-high-speed video microscopy, Polin et al. (p. 487 ; see the Perspective by Stocker and Durham ) discovered that the biflagellated cells of the single-cell alga Chlamydomonas rheinhartii switch between synchronous beating, which keeps the cells traveling forward, and asynchronous beating, which allows the organisms to make sharp turns. This random progression occurs in the dark and allows cells to diffuse, and it may underpin directional movement toward light in the same way that the run-and-tumble behavior of prokaryotes allows them to move up chemical gradients.

Batchelor Prize Lecture Fluid dynamics at the scale of the cell

“…I close this section with a brief discussion of additional developments in the study of flagellar synchrony. The initial quantifications of noise in the beating of Chlamydomonas flagella Polin et al 2009) were not well resolved in time, but more recent precision studies ) have begun to reveal that there are important and largely unexplained systematics both within a beat period and on much larger time scales. For example, the noise amplitude peaks within a cycle during the transition between the power and recovery strokes.…”

“…Our initial investigations of this phenomenon Polin et al 2009) dynamics with greater spatio-temporal precision, but also to interpret the resulting time series of beating in the context of emerging models of synchrony. While it is now routine to extract detailed beating waveforms from videos of single cells, it was conceptually simpler first to implement a Poincaré section method to study…”

Fast, high-throughput measurement of collective behaviour in a bacterial population

“…A striking diversity in microbial single-cell behaviour has been observed [2,5,6]. Although cell-tracking provides valuable information, it is often slow and sometimes subject to biaslarge distributions of cell shapes or speeds might not be sampled properly because of faulty image recognition.…”

On the self-propulsion of an -sphere micro-robot

“…For reasonably small values of parameters (say, ε ≃ 0.2 and δ ≃ 0.2) we have max E ∼ 0.1%, hence the efficiency of the micro-robots considered is low. In order to compare the velocities of micro-robots and micro-organisms we use the dimensional variables, in which max V * 0 ∼ ω * L * ε 2 δ; this shows that (for typical stroke frequency of self-swimming micro-organisms, which is about several Hz, see Pedley & Kessler 1987;Vladimirov et al 2004;Pedley 2009;Polin et al 2009) a micro-robot can move itself with the speed ∼10% of its own size per second. This estimation is 20-40 times lower than a similar value for natural micro-swimmers, see Vladimirov et al (2004); it again shows the low efficiency of the micro-robots considered.…”

“…The simplicity of the geometry represents the major advantage in studies of micro-robots (in contrast with the extreme complexity of self-swimming micro-organisms, e.g. Pedley & Kessler (1987), Vladimirov et al (2004), Pedley (2009) and Polin et al (2009)); it allows us to describe the motions of micro-robots in greater depth. In this paper, we generalize the theory of the three-sphere micro-robot of Najafi & Golestanian (2004) and Golestanian & Ajdari (2008) to an N-sphere micro-robot.…”