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Propulsion and Evolution of Algae

Propulsion and Evolution of Algae. R E Goldstein DAMTP Cambridge. ?. The Size-Complexity Relation. Amoebas, Ciliates, Brown Seaweeds Green Algae and Plants Red Seaweeds Fungi Animals. Bell & Mooers (1997) Bonner (2004). Volvox. Phil. Trans . Roy. Soc. 22 , 509-518 (1700). (1758).

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Propulsion and Evolution of Algae

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  1. Propulsion and Evolution of Algae R E Goldstein DAMTP Cambridge

  2. ? The Size-Complexity Relation Amoebas, Ciliates, Brown Seaweeds Green Algae and Plants Red Seaweeds Fungi Animals Bell & Mooers (1997) Bonner (2004)

  3. Volvox Phil. Trans. Roy. Soc. 22, 509-518 (1700) (1758)

  4. Chlamydomonas reinhardtii Eudorina elegans Gonium pectorale A Family Portrait Pleodorina californica Volvox carteri Volvox aureus somatic cells daughter colonies Germ-soma differentiation Altruism, apoptosis

  5. Metabolic requirements scale with surface somatic cells Diffusion to an absorbing sphere Currents PO42- and O2 estimates yield bottleneck radius ~50-200 mm (~Pleodorina, start of germ-soma differentiation) Organism radius R The Diffusional Bottleneck

  6. Advection & Diffusion If a fluid has a typical velocity U, varying on a length scale L, with a molecular species of diffusion constant D. Then there are two times: We define the Péclet number as the ratio: If U=10 mm/s, L=10 mm, Pe ~ 10-1 At the scale of an individual cell, diffusion dominates advection. The opposite holds for multicellularity…

  7. Microscopy & Micromanipulation micro- manipulator micro- manipulator motorized microscope stage

  8. Stirring by Volvox carteri 1 mm Tools of the trade – micropipette preparation Pseudo-darkfield (4x objective, Ph4 ring)

  9. A Closer View Fluorescence

  10. Fluid Velocities During Life Cycle Division Pre-Hatch Daughter Hatch This is “Life at High Péclet Numbers”

  11. Metabolite Exchange

  12. Flagella Beating/Symmetry (2000 frames/s background subtraction)

  13. Noisy Synchronization • Experimental methods: • Micropipette manipulation • with a rotating stage • for precise alignment • Up to 2000 frames/sec • Long time series • (50,000 beats or more) • Can impose external • fluid flow Frame-subtraction Cell body Micropipette

  14. R. Kamiya and E. Hasegawa [Exp. Cell. Res. (‘87)] • (cell models – demembranated) • intrinsically different frequencies of two flagella • U. Rüffer and W. Nultsch [Cell Motil. (‘87,’90,’91,’98)] • short observations (50-100 beats at a time, 1-2 sec.) • truly heroic – hand drawing from videos • synchronization, small phase shift, occasional “slips” Historical Background Key issue: control of phototaxis “Phase oscillator” model used in e.g. circadian rhythms, etc. strokes of flagella natural frequencies amplitudes “phases” or angles Without coupling, the phase difference simply grows in time So, is this seen?

  15. A Phase Slip

  16. Dynamics of Phase Slips (Both Directions!)

  17. Drifts and Slips are Controlled by the Cell Power spectrum frequency (arb)

  18. “Random” Swimming of Chlamydomonas reinhardtii Red light illumination – no phototactic cues 45 s. track – note many changes of direction Volume explored is ~1 mm3 very far from chamber walls

  19. Chlamy w/single flagellum, rotating near a surface Geometry of Turning ~100o Probability (angle) Turning angle (degrees) 90 Angular velocity Angle per beat - Frequency difference - Angular change “Drift” duration-

  20. Walzing Volvox: Orbiting “Bound State”

  21. Dual Views Dominant physics: downward gravitational force on the colony, producing recirculating flows. Fluid flow produced by a point force near a wall: solved exactly by J.R. Blake (1971)

  22. The Minuet Bound State Side view Chamber bottom Numerical solution of a model: Based on hovering, negatively buoyant, bottom-heavy swimmers. Bottom-heaviness confers stability.

  23. Our Team Marco Polin Idan Tuval Kyriacos Leptos Knut Drescher Sujoy Ganguly Cristian Solari Timothy J. Pedley Takuji Ishikawa Jerry P. Gollub www.damtp.cam.ac.uk/user/gold

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