Improved Chemotaxis by Repeated Stimulation

Chemotaxis, the chemically directed cell motion, is exhibited by several cell types in various contexts. Here, we study chemotaxis in the social amoeba Dictyostelium discoideum, which secretes and relays cyclic adenosine monophosphate (cAMP) during starvation. The resulting waves of cAMP that travel through the cell population result in aggregation and, eventually, lead to spore formation.

Using a microfluidic environment, we exposed Dictyostelium cells to multiple periodic pulses of cAMP of different periods, constructed tracks of single cells by edge detection and binarization algorithms of DIC microscopy images.

We found that the average chemotactic response of cells increased as a function of the number of waves. Our results are consistent with a previously formulated model that displays perfect adaptation in a uniform chemoattractant field, exhibits memory of the direction of the source upon gradient reversal, and enhances chemotaxis when the background concentration of the chemoattractant is raised.

Our findings suggest that the increased chemotactic response results in improved aggregation and may be a mechanism that improves the survivability of Dictyostelium under challenging conditions.