Suspensions of swimming algal cells form intricate mottled patterns that are governed by a complex interplay between light, gravity and fluid dynamics. The patterns (pictured) change with shifting lighting conditions, which could one day be exploited to improve the yields of bioreactors that use algae to produce biofuel.

Rosie Williams and Martin Alan Bees of the University of Glasgow, UK, studied the patterns formed by suspensions of Chlamydomonas augustae cells in response to changes in the orientation and intensity of the light source. As overhead white light grew brighter, dense groups of cells first moved apart, then drew closer together. When the algae were lit from below, brighter light resulted in a shortening and then a levelling off of distances between dense cell groups.

Credit: M. A. BEES

Such pattern changes could be exploited to increase the penetration of light and nutrients to cell suspensions, and to concentrate cells for harvesting.

J. Exp. Biol. 24, 2398–2408 (2011)