MPIDS Colloquium: Active and Passive Dewetting in Living Organisms

The dewetting of a fluid from a solid interface, such as the beading of rain droplets on a raincoat, can be seen in many phenomena from our daily lives. I will discuss two systems in which dewetting phe-nomena play a key role in the biology of living cells. I will first discuss the formation of droplets of a liquid phase of the protein TPX2. This fluid dewets from the surface of polymeric microtubules via the passive Rayleigh-Plateau instability to define the birth place of the majority of microtubules in your body. I will then discuss an active form of dewetting as a model for how the soil dwelling bacte-rium Myxococcus xanthus forms protective "fruiting body" droplets in a response to starva-tion. Inspired by recent work on active matter and the physics of liquid crystals, I will discuss experi-ments that reveal how these cells generate nematic order, how defect structure can dictate global be-havior, and how Myxo actively tune the Péclet number of the population to drive a dewetting phase transition and droplet formation.