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PLoS One. 2012;7(4):e35412. doi: 10.1371/journal.pone.0035412. Epub 2012 Apr 18.

Modeling E. coli tumbles by rotational diffusion. Implications for chemotaxis.

Author information

1
Laboratoire Physico-chimie Curie - UMR 168, Institut Curie, Centre de Recherche - CNRS - UPMC, Paris, France.

Abstract

The bacterium Escherichia coli in suspension in a liquid medium swims by a succession of runs and tumbles, effectively describing a random walk. The tumbles randomize incompletely, i.e. with a directional persistence, the orientation taken by the bacterium. Here, we model these tumbles by an active rotational diffusion process characterized by a diffusion coefficient and a diffusion time. In homogeneous media, this description accounts well for the experimental reorientations. In shallow gradients of nutrients, tumbles are still described by a unique rotational diffusion coefficient. Together with an increase in the run length, these tumbles significantly contribute to the net chemotactic drift via a modulation of their duration as a function of the direction of the preceding run. Finally, we discuss the limits of this model in propagating concentration waves characterized by steep gradients. In that case, the effective rotational diffusion coefficient itself varies with the direction of the preceding run. We propose that this effect is related to the number of flagella involved in the reorientation process.

PMID:
22530021
PMCID:
PMC3329434
DOI:
10.1371/journal.pone.0035412
[Indexed for MEDLINE]
Free PMC Article

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