We have measured the spatial distribution of motile Escherichia coli inside spherical water droplets emulsified in oil. At low cell concentrations, the cell density peaks at the water-oil interface; at increasing concentration, the bulk of each droplet fills up uniformly while the surface peak remains. Simulations and theory show that the bulk density results from a `traffic' of cells leaving the surface layer, increasingly due to cell-cell scattering as the surface coverage rises above ∼10%. Our findings show similarities with the physics of a rarefied gas in a spherical cavity with attractive walls.
@article{arxiv.1407.6859,
title = {Filling an emulsion drop with motile bacteria},
author = {I. D. Vladescu and E. J. Marsden and J. Schwarz-Linek and V. A. Martinez and J. Arlt and A. N. Morozov and D. Marenduzzo and M. E. Cates and W. C. K. Poon},
journal= {arXiv preprint arXiv:1407.6859},
year = {2015}
}
Comments
5 pages, 4 figures, Supporting Information (5 pages, 5 figures)