Bioconvection patterns in swimming microorganism cultures as an example of Rayleigh-Taylor instability

Abstract

RATHER definite spatial patterns are observed in cultures of swimming microorganisms which are heavier than water and which tend to propel themselves toward the upper surface in response to some external stimulus; for example, gravity, light and chemicals. These patterns are characterised by falling fingers containing the organisms and are maintained by return upward swimming of the organisms. The patterns have been termed ‘bioconvection’ patterns¹ and have been known since 1848²; they are found in bacterial, flagellate^3,4, plankton⁵ and ciliate⁶ cultures.