On the dynamics of C. <i>reinhardtii </i>subject to external periodic flows

Abstract

Synchronization of oscillators is an ubiquitous phenomenon that involves mechanical systems, like pendulum clocks, but also biological systems, like peacemaker cells in the heart or neural activity in the brain. If we consider biological systems at the microscale, namely at the scale of cells, we find that processes like locomotion and fluid transport often exploit synchronization of mechanical oscillators called flagella orcilia. These oscillators at the microscale are whip-like structures extending from the cell body. They are present in a number of micro-organisms like sperm cells, Paramecium or the algae C. reinhardtii. In human, cilia are found in the lungs, the respiratory tract and the middle ear. Cilia are activated in a coordinated way to effectively carry out their function, such as draining mucus. The mechanism behind this cilia coordination is still debated. It is not clear how very simple organisms lacking any feedback system have developed complex oscillatory patterns involving coordination among a multitude of cilia or flagella. There is high interest in understanding the fundamental principles ruling ciliary dynamics, since they would impact medical and engineering applications. The purpose of this thesis is to investigate the mechanisms regulating the synchronization of cilia and flagella.