A tale of three taxes: photo-gyro-gravitactic bioconvection

Williams, C.R. and Bees, M. (2011) A tale of three taxes: photo-gyro-gravitactic bioconvection. Journal of Experimental Biology, 214, pp. 2398-2408. (doi: 10.1242/​jeb.051094)

Abstract

The term bioconvection encapsulates the intricate patterns in concentration, due to hydrodynamic instabilities, that may arise in suspensions of non-neutrally buoyant, biased swimming microorganisms. The directional bias may be due to light (phototaxis), gravity (gravitaxis), a combination of viscous and gravitational torques (gyrotaxis) or other taxes. The aim of this study is to quantify experimentally the wavelength of the initial pattern to form from an initially well-mixed suspension of unicellular, swimming green algae as a function of concentration and illumination. As this is the first such study, it is necessary to develop a robust and meticulous methodology to achieve this end. The phototactic, gyrotactic and gravitactic alga Chlamydomonas augustae was employed, with various red or white light intensities from above or below, as the three not altogether separable taxes were probed. Whilst bioconvection was found to be unresponsive to changes in red light, intriguing trends were found for pattern wavelength as a function of white light intensity, depending critically on the orientation of the illumination. These trends are explored to help unravel the mechanisms. Furthermore, comparisons are made with theoretical predictions of initial wavelengths from a recent model of photo-gyrotaxis, encouragingly revealing good qualitative agreement.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Bees, Dr Martin
• Authors: Williams, C.R., and Bees, M.
• College/School: College of Science and Engineering > School of Mathematics and Statistics > Mathematics
• Journal Name: Journal of Experimental Biology
• ISSN: 0022-0949
• Copyright Holders: Copyright © 2011 Company of Biologists
• First Published: First published in Journal of Experimental Biology 214: 2398-2408
• Publisher Policy: Reproduced in accordance with the copyright policy of the publisher