ESPCI web site
PMMH’s weekly seminar is held every Friday at 11 am (map)
Stéphane Perrard
Etienne Reyssat
Virgile Thiévenaz
PMMH
BARRE CASSAN
BAT A 1ER ETAGE CASE 18
7 QUAI SAINT BERNARD
75005 PARIS
France
Tel : (33) 1 40 79 45 22
Séminaire PMMH : Raphaël Jeanneret, LPENS
Light-induced phase separation and pattern formation by phototactic micro-algae
Excess of light can be hazardous and lethal for photosynthetic organisms. When intensity is too high, the motile micro-algae Chlamydomonas reinhardtii therefore reorient itself to swim away from the incident light (negative phototaxis). We recently discovered that a collection of such migrating cells can be unstable, whereby small spatial fluctuations in cell density can trigger the local densification of the system and the formation of dynamic branching patterns, whose features depend on the global cell density, the intensity of light, the viscosity of the medium or the concentration of extra-cellular calcium. Mutants with deficient eyespots (organelle for light detection) still perform negative phototaxis but do not exhibit branching patterns. In this talk I will show how this new kind of instability can be understood from the strong coupling between cell density and light fields through both negative phototaxis and light scattering by the individual cells. I will present our results on the quantitative characterization of the patterns as well as the analytical model we developed in order to rationalise our observations. We believe our findings will help to better understand phototaxis by micro-organisms and provide a new route to decipher the complex interplay between photosynthesis, photoprotection and phototaxis.
The audience is composed of people with rather heterogeneous backgrounds including specialists in solids, fluids, granular flows, statistical physics... so the idea is to keep your talk understandable by people not necessarily working in your field... The seminar time slot runs from 11am to noon so the best is to make the talk last around 45 minutes to leave some time for discussion.
- Séminaires ESPCI-ENS de biophysique
- Séminaires du Département de Physique de l’ENS
- Séminaires du Laboratoire d’Hydrodynamique de l’X
- Séminaire de Mécanique d’Orsay (page web FAST)
- Séminaire de Mécanique d’Orsay (page web LIMSI)
- Séminaire de Mécanique des Fluides de l’Institut Jean le Rond d’Alembert
- Séminaires du laboratoire MSC, Paris VII
- Séminaires Gulliver
Link to cofee seminar (internal, every Thursday)
