Batchelor Prize Lecture Fluid dynamics at the scale of the cell

Abstract

The world of cellular biology provides us with many fascinating fluid dynamical phenomena that lie at the heart of physiology, development, evolution and ecology. Advances in imaging, micromanipulation and microfluidics over the past decade have made possible high-precision measurements of such flows, providing tests of microhydrodynamic theories and revealing a wealth of new phenomena calling out for explanation. Here I summarize progress in four areas within the field of 'active matter': cytoplasmic streaming in plant cells, synchronization of eukaryotic flagella, interactions between swimming cells and surfaces and collective behaviour in suspensions of microswimmers. Throughout, I emphasize open problems in which fluid dynamical methods are key ingredients in an interdisciplinary approach to the mysteries of life.

The walkoff effect: cargo distribution implies motor type in bidirectional microtubule bundles

“…While targeted delivery is vital for the correct cell function, there is an emerging evidence that the cellular cytoplasm undergo mixing by fluid flows [80]. These flows contribute to organization of microtubule network, and consistently with our model require kinesin function [81].…”

Active diffusion and advection in theDrosophilaooplasm result from the interplay of the actin and microtubule cytoskeletons

“…Not surprisingly, streaming is more efficient than thermal diffusion in transporting large organelles (e.g. vesicles) over long distances 46 . However, recent studies in cells, which probably lack microtubule-dependent streaming, outlined the important role of active diffusion mechanisms, that at least in mouse oocytes are seemingly dependent on a recently discovered cytoplasmic F-actin cytoskeleton 10,26,27,47 .…”

Motility and Phototaxis ofGonium, the Simplest Differentiated Colonial Alga

“…We finally consider helical trajectories produced by unbalanced swimmers (ξ = 0), and include in the computation angular modulation of the peripheral flagella force (5). A typical trajectory is illustrated in Fig.…”

“…III C would be a considerable analytical task, because the light variation perceived by each eyespot would depend on the three Euler angles and their time derivatives. Instead, we performed a series of direct numerical studies of phototactic reorientation using the computational model previously introduced, combining in the flagella force the azimuthal modulation (5) and the phototactic response (7). Typical trajectories, obtained for various imbalance parameter ξ (and hence pitch angle χ), are illustrated in Fig.…”

“…In a modern biological view [3], this significance arises from a number of specific features of these algae, including the fact that they are an extant family (obviating the need to study fossils), are readily obtainable in nature, have been studied from a variety of perspectives (biochemical, developmental, genetic), and have had significant ecological studies. From a fluid dynamical perspective [4], their relatively large size and easy culturing conditions allow for precise studies of their motility, the flows they create with their flagella, and interactions between organisms, while their high degree of symmetry simplifies theoretical descriptions of those same phenomena [5].…”