Active-matter droplets: patterns of an active filament by Romain Leroux

Known as the cytoskeleton, networks of active biopolymers dynamically shape the cell membrane. Described by active matter physics, the cytoskeleton has gained the attention of both theorists and experimentalists who developed filament-motor model systems that exhibit remarkable self-organizations.  

Here, we encapsulate a microtubule-kinesin based active matter in microfluidic water-in-oil droplets. Microtubule bundles spontaneously migrate at the water-oil interface and form an active extensile filament whose movements of folding show a periodical pattern. We aim at studying this system to understand the dynamics of a growing filament confined into a sphere, the influence of varying parameters - such as confinement, amount of matter or energy - on its movement and the robustness of this pattern.

Membrane potential in bacteria by Frédéric Joubert

The membrane potential of living cells is a key element in the exchange and communication between cells. It is essential in excitable cells such as neurons and contractile cells. However, its role in bacteria has only recently been investigated. It has been implicated in cell division, bacterial movement, antibiotic resistance and possibly bacterial communication. Spontaneous variations in potential have also been observed in isolated cells or in biofilms/microcolonies, but this phenomenon is not well understood. 

In this talk, I will give a brief reminder of what a membrane potential is, what technical approaches are used to measure it, what is known about it in bacteria, and what questions we are trying to address. I will also present some preliminary data showing how monitoring membrane potential in bacteria can provide insight into the physiological state of the bacteria.