A Theoretical Prediction of Laminar Falling Plumes in Bioconvection of Oxytactic Bacteria in Porous Media

The objective of this paper is to investigate theoretically laminar falling bioconvection plumes in a deep chamber filled with a fluid saturated porous medium. A suspension of motile oxytactic bacteria, such as Bacillus subtilis, which swim up the oxygen gradient, is considered. In a deep chamber, because of the limited diffusivity of oxygen, oxygen concentration is high only in a thin cell-rich upper boundary layer. Since bacteria are heavier than water, the cell-rich upper boundary layer becomes unstable and bioconvection plumes develop. The bioconvection plume carries oxygen and cells from this cell-rich upper boundary layer to the lower region of the chamber.