Chlamydomonas Phototaxis: turn and what?

Phototaxis is one of the main categories of motility regulation by microorganisms. Arguably, it is particularly important for motile micro algae, due to their photosynthetic activity. One of the organisms where it has been studied the most is our beloved micro alga Chlamydomonas reinhardtii. Currently, we have a pretty good idea of the mechanism leading the cells to reorient towards/away from the light, but not much is known about what happens after they’ve reoriented…. In our recent paper we start looking into this, with surprising results.

Julia going back

We had the great pleasure to host for two months Julia Dolger, PhD student from the group of Anders Andersen and Thomas Kiorboe at the Technical University of Denmark. She’s been working very hard during her short stay here on a joint project looking at microbial predator/prey systems, and we had lots of interesting discussions! Good luck to her for the final part of her PhD and let’s keep in touch!

Phase Defects


Does a stronger interaction always make for a more stable system? Certainly not for synchronising oscillators, as we show in a paper just accepted in Physical Review Fluids. There we study the behaviour of a strip of colloidal rotors as the system is lifted from a no-slip surface. As the hydrodynamic coupling strengthens, the system develop recurring phase defects which worsen its synchronisation. Our simulations show that defects result from a competition between short-range and long-range coupling. The paper is currently accessible through the ArXiv.

Update: The paper has been published (open access) and is now available here.

Colloidal Entrainment

figure2Particle entrainment by Raphaël, just accepted on Nat Com!

What happens to passive microparticles within a suspension of microorganisms? If the particles are small, they can be entrained over large distances by the micro swimmers. These interactions are rare, but their magnitude is large and -as it turns out- they end up dominating particle dynamics, which now resembles a jump-diffusion process. This is presented and discussed in details in a new work led by Raphaël, just accepted on Nature Communications. A preprint of the article (well.. a previous version) is currently available on the Arxiv.

Update. The article is now available here.