Amoeboid swimming - crawling in a fluid

December 4, 2013
Credit: © LIPhy, CNRS/UJF Grenoble Cell shape deformations during a swimming cycle.

Researchers from CNRS, Inserm, and Université Joseph Fourier - Grenoble have developed a particularly simple model that reproduces the swimming mechanism of amoebas. They show that, by changing shape, these single cell organisms propel themselves forward in a viscous fluid at the same speed as when they crawl on a solid substrate. This work has recently been published in the journal Physical Review Letters.

The way microorganisms swim is fundamentally different to that of fish since, at their scale, viscosity effects dominate and make fins totally inefficient. Various strategies are employed. The majority of such organisms propel themselves forward by beating their flagella or cilia while others, such as amoebas, deform their bodies in the same way as they would for crawling. However the efficiency of this method of propulsion remains poorly understood.

Physicists from the Laboratoire Interdisciplinaire de Physique (LIPhy, CNRS/Université Joseph Fourier Grenoble), Oslo University and the Institut Albert Bonniot (Inserm/Université Joseph Fourier – Grenoble) have elucidated the key elements of this method of locomotion by analyzing a simplified theoretical model.

They determined the necessary morphological deformations and the speed of propulsion and showed that incompressibility of the is essential.

To conduct this study, the researchers modeled the cell using an inextensible fluid membrane (in other words, able to deform while maintaining its membrane area) containing a viscous fluid and located within a . Surface deformations in this model are uniquely due to forces perpendicular to the surface of the membrane. Among all the possible deformations, the physicists favored those that maintain symmetry of revolution around the axis of movement. Cell deformations induce stresses in the external fluid, which, in return, exerts a force on the cell. To simulate a swimming motion, the researchers considered elementary movements during which the forces exerted on the surface remain constant. These forces alter the shape of the cell and calculations show that motion depends solely on these shapes and not on the speed of movement.

Swimming is thus uniquely determined by the succession of shapes adopted by the cell and the distance covered only depends on the geometry of the surfaces. The model described reproduces certain swimming cycles observed in nature. It will certainly improve our knowledge of cell mobility and make it possible to envisage novel types of artificial micro-swimmers.

Explore further: Researchers explain the flagellar synchronisation of swimming algae

More information: Amoeboid Swimming: A Generic Self-Propulsion of Cells in Fluids by Means of Membrane Deformations, A. Farutin, S. Rafaï, D. K. Dysthe, A. Duperray, P. Peyla and C. Misbah. Published on the 27 November 2013 in Physical Review Letters.

Related Stories

High-angle helix helps bacteria swim

August 13, 2013

(Phys.org) —A high-angle helix helps microorganisms like sperm and bacteria swim through mucus and other viscoelastic fluids, according to a new study by researchers from Brown University and the University of Wisconsin. ...

Microswimmers hit the wall (w/ video)

January 8, 2013

(Phys.org)—New research reveals what happens when swimming cells such as spermatozoa and algae hit a solid wall, and has implications for applications in diagnostics and biofuel production.

New tool enables biomechanical studies of individual cells

October 3, 2013

More than 40 years ago, the foundation for optical tweezers was laid when Arthur Ashkin demonstrated that near the focus of a laser beam, momentum transfer between light and dielectric particles creates gradient forces large ...

Recommended for you

Study shows how to get sprayed metal coatings to stick

November 21, 2017

When bonding two pieces of metal, either the metals must melt a bit where they meet or some molten metal must be introduced between the pieces. A solid bond then forms when the metal solidifies again. But researchers at MIT ...

Imaging technique unlocks the secrets of 17th century artists

November 21, 2017

The secrets of 17th century artists can now be revealed, thanks to 21st century signal processing. Using modern high-speed scanners and the advanced signal processing techniques, researchers at the Georgia Institute of Technology ...

Physicists design $100 handheld muon detector

November 20, 2017

At any given moment, the Earth's atmosphere is showered with high-energy cosmic rays that have been blasted from supernovae and other astrophysical phenomena far beyond the Solar System. When cosmic rays collide with the ...

A curious quirk brings organic diode lasers one step closer

November 20, 2017

Since their invention in 1962, semiconductor diode lasers have revolutionized communications and made possible information storage and retrieval in CDs, DVDs and Blu-ray devices. These diode lasers use inorganic semiconductors ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.