Kinematics and kinetics of Chlamydomonas reinhardtii under imposed flows

Kinematics and kinetics of Chlamydomonas reinhardtii under imposed flows

Jongsma, C.J.

Tam, D.S.W. (mentor)

Mechanical, Maritime and Materials Engineering

Process and Energy

2016-10-18

From the bacteria living on a keyboard to algae surviving in snow, microorganisms can be found virtually everywhere on the planet. Due to their small size, microorganism swim in the low Reynolds number regime, which has important consequences for their swimming strategies. For motility, these organisms commonly use long slender filaments known as cilia or flagella, located at the exterior of the cell. Eukaryotic flagella are active structures with molecular motors distributed along their length. The precise mechanism of self-organization of the beat is still unknown. This study focuses on the changes in kinematics, forces and rate of work when subjecting the eukaryotic microalgae C. reinhardtii to imposed flows. C. reinhardtii cells are clamped using a micropipette and subjected to a periodic flow generated by a piezoelectric element. Video recordings are processed using a custom-made Matlab script that uses Gaussian background modeling and principal component analysis to recover the flagellar waveforms. An accurate boundary element method computational code is used to calculate the forces on the cell body and flagella. When beating in absence of a background flow, we found a viscous rate of work of 69 fW RMS, with a peak of 110 fW, much higher than suggested by existing literature. The rate of work to deform the elastic flagella is 176 fW RMS with peaks of -360/+160 fW. The elastic forces dominate the overall power profiles, so that the instantaneous power is mostly determined by the kinematics rather than the viscous dissipation. Flagella can cease to beat altogether if the applied load is high enough. No such “stalling point” has been found, however the cell did show a truncated stroke with a 30% decreased amplitude and a 10% increased frequency when beating in antiphase with a 3 mm/s flow. This stroke pattern is similar to antiphase beating in the ptx mutant of C. reinhardtii and phase slips in wild-type cells.

eukaryotic flagellum
low Reynolds number
Chlamydomonas reinhardtii
Boundary Element Method
kinematics
rate of work
synchronization

http://resolver.tudelft.nl/uuid:18af44c9-cf28-4ab5-8120-2b40fb6c1f78

Student theses

master thesis

(c) 2016 Jongsma, C.J.