The role of mechanical forces in the planar-to-bulk transition in growing Escherichia coli microcolonies

Matthew A. A. Grant*, Bartlomiej Waclaw, Rosalind J. Allen, Pietro Cicuta

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

Mechanical forces are obviously important in the assembly of three-dimensional multicellular structures, but their detailed role is often unclear. We have used growing microcolonies of the bacterium Escherichia coli to investigate the role of mechanical forces in the transition from two-dimensional growth (on the interface between a hard surface and a soft agarose pad) to three-dimensional growth (invasion of the agarose). We measure the position within the colony where the invasion transition happens, the cell density within the colony and the colony size at the transition as functions of the concentration of the agarose. We use a phenomenological theory, combined with individual-based computer simulations, to show how mechanical forces acting between the bacterial cells, and between the bacteria and the surrounding matrix, lead to the complex phenomena observed in our experiments-in particular the observation that agarose concentration non-trivially affects the colony size at transition. Matching these approaches leads to a prediction for how the friction between the bacteria and the agarose should vary with agarose concentration. Our experimental conditions mimic numerous clinical and environmental scenarios in which bacteria invade soft matrices, as well as shedding more general light on the transition between two-and three-dimensional growth in multicellular assemblies.

Original languageEnglish
Article number20140400
Number of pages15
JournalJournal of the Royal Society. Interface
Issue number97
Publication statusPublished - 6 Aug 2014

Keywords / Materials (for Non-textual outputs)

  • bacterial microcolony
  • bacterial biofilm
  • mechanics
  • cell growth


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