Optimization of the cellular response and searching strategy in bacterial chemotaxis

Thierry Emonet (Yale)

Abstract

In low nutrient environment, Escherichia coli bacteria sample the space for food by performing a random walk that consists of straight runs interrupted by random changes of direction called tumbles. When a cell senses that it is moving up a gradient of nutrient, it elongates the duration of the corresponding run therefore biasing the random walk towards the source of food. The control of the motion is achieved by the chemotaxis system, one of the simplest information processing pathways in biology. The input to the chemotaxis pathway is the temporal change of attractant (or repellent) molecules in the medium; the output is the duration of the runs. We studied the relationship between the architecture of the chemotaxis network and the stochastic dynamics of adaptation at the single cell and population level. Our analysis reveals a network design that exploits the relationship between fluctuations and relaxation time, to simultaneously optimize the searching strategy in the absence of nutrients and the cellular response to gradients of attractant.

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