Understanding the link between single cell and population scale responses of Escherichia coli in differing ligand gradients.

Edgington MP, Tindall MJ - Comput Struct Biotechnol J (2015)

Related In: Results  -  Collection

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f0055: A plot summarising the accumulation of simulated E. coli cells toward gradients of MeAsp and serine with differing peak concentrations. Results displayed here represent a summary of those in Fig. 10 with cells considered to accumulate to MeAsp if they end with x < 1 and to serine where they finish with x > 1. Circles represent the data points drawn from Fig. 10 with the colour indicating the MeAsp gradient scaling factor where ω = 1 (blue), ω = 5 (red) and ω = 10 (green). Since the ABM is stochastic, lines are used to display the general trend of the data. In particular a Hill function is fitted to each set of data using a simple least-squares fit giving values of K = 2.71 × 10− 3 and n = 3.166 for ω = 1; K = 1.25 × 10− 3 and n = 3.605 for ω = 5; and K = 1.28 × 10− 3 and n = 3.180 for ω = 10. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
Mentions: It can be seen in Fig. 10 that there are a number of conditions on ω and υ which result in different numbers of cells being attracted to each gradient. Using these ABM simulations we may count the number of cells accumulating toward each attractant. For simplicity we consider a cell to be attracted to MeAsp if the final location is such that x < 0. If x > 0 we say the cell was attracted to the serine gradient. In order to more clearly elucidate how the relationship between ω and υ affects the accumulation of cells about the two different ligands we consider the total number of cells attracted to MeAsp versus serine, as summarised in Fig. 11.

Bottom Line: We then study the response of cells in the presence of two different chemoattractants.In doing so we demonstrate that the population scale response depends not on the absolute concentration of each chemoattractant but on the sensitivity of the chemoreceptors to their respective concentrations.Our results show the clear link between single cell features and the overall environment in which cells reside.

View Article: PubMed Central - PubMed

Affiliation: Department of Mathematics & Statistics, University of Reading, Whiteknights, PO Box 220, Reading RG6 6AX, UK.

ABSTRACT
We formulate an agent-based population model of Escherichia coli cells which incorporates a description of the chemotaxis signalling cascade at the single cell scale. The model is used to gain insight into the link between the signalling cascade dynamics and the overall population response to differing chemoattractant gradients. Firstly, we consider how the observed variation in total (phosphorylated and unphosphorylated) signalling protein concentration affects the ability of cells to accumulate in differing chemoattractant gradients. Results reveal that a variation in total cell protein concentration between cells may be a mechanism for the survival of cell colonies across a wide range of differing environments. We then study the response of cells in the presence of two different chemoattractants. In doing so we demonstrate that the population scale response depends not on the absolute concentration of each chemoattractant but on the sensitivity of the chemoreceptors to their respective concentrations. Our results show the clear link between single cell features and the overall environment in which cells reside.

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