Date of Award
Doctor of Philosophy (PhD)
Cilia and flagella are subcellular organelles used to generate fluid flow or propel the cell. These long cylindrical structures are composed of cytoskeletal elements activated by the unidirectional motor protein dynein. Cilia and flagella are crucial to a number of physiological functions, yet the specific mechanisms of dynein activation and coordination remain unclear. This work investigates the response of the flagellum of Chlamydomonas reinhardtii to increased mechanical loading achieved by variation of media viscosity, and to structural changes achieved by genetic manipulation. Effects of these perturbations are quantified using high spatiotemporal resolution recordings; the results demonstrate mutation-specific changes to the flagellar waveform. The flagellum may be mathematically modeled as a slender beam in viscous fluid. Two proposed mechanisms of dynein regulation are evaluated by identification of unstable modes and by numerical simulation. The sliding-controlled model of dynein regulation leads to non-propulsive retrograde modes of bend propagation. The geometric clutch model provides a mechanism of anterograde bend propagation and flagellar feedback which promotes bend switching at the base, similar to observed waveforms.
Philip V Bayly
Susan Dutcher, Ruth Okamoto, David Peters, Jin-Yu Shao, Jessica Wagenseil