In a multitude of life’s processes, cilia and eukaryotic flagella are ubiquitous and indispensable. In the human body, lung and ependymal cilia coordinate the pumping of fluid, but the very same cellular appendages are used by diverse species of protists and algae as microscale analogues of limbs to swim through aqueous environments. In our group, we use a combination of theory, experiment, and computation to investigate the physics of motile cilia and the mechanistic origins of active cell motility.
1. Self-propulsion of microorganisms
Locomotion achieved through the actuation of multiple appendages, is inherently combinatorial. Even simple microorganisms display a fascinating behavioural heterogeneity, transitioning between different swimming modes, or fast and slow dynamics. We use high-resolution spatiotemporal information obtained from quantitative live-cell imaging to characterise and model stereotyped states or gaits, revealing an unprecedented complexity in the non-nervous control of locomotor behaviour in different species of single-celled eukaryotes.
Control of helical navigation by three-dimensional flagellar beating
D. Cortese & K. Y. Wan, Physical Review Letters 126, 088003 (2021) [online] [Exeter News]
* Selected as Editors’ Suggestion
* See also Physics synopsis
Antiphase Synchronization in a Flagellar-Dominance Mutant of Chlamydomonas
K.C. Leptos*, K.Y. Wan*, M. Polin, I. Tuval, A.I. Pesci & R.E. Goldstein, Physical Review Letters 111, 158101 (2013) [online]
2. Genesis and control of motile cilia
Functional exploration of heterotrimeric kinesin-II in IFT and ciliary length control in Chlamydomonas
S. Li, K. Y. Wan, W. Chen, H. Tao, X. Liang, J. Pan, eLife, 9, e58868 (2020) [online]
Reorganisation of complex ciliary flows around regenerating Stentor coeruleus
K. Y. Wan, S. K. Hürlimann, A. M. Fenix, R. M. McGillivary, T. Makushok, E. Burns, J. Y. Sheung, W. F. Marshall, Philosophical Transactions of the Royal Society B 375, 20190167 (2019) [online]
Coordination of eukaryotic cilia and flagella
K.Y. Wan, Essays in Biochemistry 62(6), 829-838 (2018) [online]
Coordinated Beating of Algal Flagella is Mediated by Basal Coupling
K.Y. Wan & R.E. Goldstein, Proceedings of the National Academy of Sciences USA 113, E2784-93 (2016) [online] [Cambridge News] [Fierceroller Blog] [galloping algae]
Cilia often exhibit synchronization phenomena, including phase-locking and metachronal waves. It has long been hypothesised that synchrony arises from fluid dynamical coupling. By controlling the distance of separation between pairs of pipette-held somatic cells of Volvox, we proved that hydrodynamic interactions were sufficient to produce synchrony in ciliary arrays. In contrast, many unicellular organisms rely on a different mechanism – which we have termed intracellular or basal coupling, to orchestrate ciliary coordination. The correct length and placement of cilia are critical to achieve proper function.
3. Stochasticity and behavioural stereotypy
Like the human heartbeat, the Chlamydomonas flagellum is a complex biological oscillator, exhibiting strong rhythmicity, yet also responsiveness to certain environmental or physiological cues. Extracting and digitising flagellar beat patterns and frequencies from long-time, high-speed recordings, we devise novel measures of shape and waveform stochasticity. When complex spatiotemporal dynamics are projected onto a low-dimensional state-space, macroscopic breaking of detailed balance is revealed.
Time-irreversibility and criticality in the motility of a flagellate microorganism
K.Y. Wan & R.E. Goldstein, Physical Review Letters 121, 058103 (2018) [online]
Lag, Lock, Sync, Slip: The Many ‘Phases’ of Coupled Flagella
K.Y. Wan, K.C. Leptos & R.E. Goldstein, Journal of the Royal Society Interface 11, 20131160 (2014) [online]
Rhythmicity, Recurrence, and Recovery of Flagellar Beating
K.Y. Wan & R.E. Goldstein, Physical Review Letters 113, 238103 (2014) [online]
4. Protists and the origin of eukaryotes
We propose a new scenario for eukaryogenesis in which eukaryotes harnessed their larger size, improved complement of ion channels, and novel locomotor organelles to access new biophysical and sensory regimes.
5. Bio-inspired robotics
A minimal robophysical model of quadriflagellate self-propulsion
K. Diaz, T.L. Robinson, Y. Ozkan-Aydin, E. Aydin, D.I. Goldman & K.Y. Wan, biorxiv (2021) [online]
6. Editorials and Commentaries
On the unity and diversity of cilia
K.Y. Wan & Gáspár Jékely, Philosophical Transactions of the Royal Society B 375, 20190148 (2019) [online]
Link to my google scholar profile.