| The directed motion of eukaryotic cells in a chemoattractant gradient depends both on the steepness of the gradient and on the average concentration surrounding the cell. Ueda and Shibata (2006) theoretically predicted that the stochastic nature of chemical processes was the limiting factor of chemotaxis accuracy. Both the effect of the background concentration and of the gradient were taken into account by defining a signal to noise ratio (SNR), which compared the amplitude of the stochastic fluctuations in the chemotactic pathway to the amplitude of the ideal chemotactic signal. In our experiments, we use microfluidic tools to expose Dictyostelium discoideum cells to stationary spatial gradients of the chemoattractant cyclic adenosine 3',5' monophosphate (cAMP). We quantify chemotactic motion using a Langevin equation, and show how using the SNR accurately describes all data from our experiments, as well as data previously published in the literature. |
|