Physical Aspects Of Chemotaxis And Proliferation Of Dictyostelium Discoideum Amoeba

Abstract

In this dissertation, we explore two aspects of Dictyostelium discoideum life cycle, chemotaxis and proliferation. We use Shannon's information theory to study the physical limits of chemotaxis due to the stochastic process of ligands binding and unbinding to cell receptors (receptor noise). Using microfluidic experiments, we show that cells acquire much more information than the contemporary application of this theory allows. Next, we investigate how cells modify their extracellular environment by secreting enzymes that degrade chemoattractants and show that simple first order degradation leads to the significant improvement of the receptor signal-to-noise ratio of chemical gradients. Finally, we investigate the seemingly solitary vegetative phase of the same cells and find that they synchronize their growth after transferring from suspension culture to substrate. We show that this synchronization can be suppressed using microfluidic flow experiments, indicating that the synchronization is a collective behavior mediated by a diffusible molecule.