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By Ismaël Duchesne , Simon Rainville and Tigran Galstian

DSCG liquid crystal’s viscosity: Insight into the motility of bacteria in an anisotropic liquid environment. By Ismaël Duchesne , Simon Rainville and Tigran Galstian. In this talk Anisotropic medium: DSCG liquid crystal

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By Ismaël Duchesne , Simon Rainville and Tigran Galstian

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  1. DSCG liquid crystal’s viscosity: Insight into the motility of bacteria in an anisotropic liquid environment By Ismaël Duchesne, Simon Rainville and TigranGalstian • In this talk • Anisotropic medium: DSCG liquid crystal • Isotropic and anisotropic motility of flagellarbacteria (E. coli) • Speed and orientation of bacteria in DSCG solution • Viscosity of DSCG solution

  2. DSCG liquid crystal’s viscosity: Insight into the motility of bacteria in an anisotropic liquid environment • Anisotropic liquid environment: • Physical properties depend on the direction (as birefringence) • Flagellar bacteria: • Bacteria that may swims in aqueous medium by rotating theirs flagella • Why anisotropic motility: • Many biological tissues and media may be anisotropic (biofilms, enriched chitin soils...) • Difficult task: only few studies

  3. Anisotropic medium: nematic liquid crystal (LC) Temperature

  4. Lyotropic LC: cromolyn sodium salt (DSCG) Yu. A. Nastishin and al., Physical Review E, November 2004.

  5. Isotropic motility of bacteria: runs and tumbles Random walk source: Wikipedia

  6. Anisotropic motility of flagellar bacteria (E. coli)

  7. Experiments: montages Chamber and light-guided dark-field microscopy Microscope

  8. Results: bacterial motility Speed Orientation variation • Purely isotropic phase: as if there were no DSCG • Pretransitional phase: sticky effect • Anisotropic phase: decrease of speed and runs in the direction of the director

  9. Results: viscosity measurements(from diffusion of 0,2-2µm microspheres) Viscosity Axial ratio • Purely isotropic phase:little viscosity increase • Pretransitional phase: exponential viscosity increase • Anisotropic phase:anisotropic viscosity

  10. Can we explain the anisotropic motility with the anisotropic viscosity? Isotropic Anisotropic Beads diffusion Swimming bacteria

  11. Conclusion • Bacteria behave very differently in anisotropic media • Viscosity doesn't explain everything (active motility important) • “New” pretransitional phase • Viscosity increase (aggregation – threshold) • Sticky effect • New possibilities for controlling motion of microorganisms

  12. Acknowledgements • Dr Simon Rainville • phDstudents • Guillaume Paradis • Ismael Duchesne • Dr TigranGalstian • phDstudents • Karen Allahverdyan

  13. Viscosity dependency to the beads size

  14. Propulsive force of bacteria

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