Merits and limits of surface and line tensions to account for  the shape of epithelial cells. By Nicolas Harmand.

Building a physical framework to account for the shape of cells in epithelia is an important challenge to understand various biological processes, such as embryogenesis. The goal of my thesis work is to understand how surface tensions and line tensions shape epithelial cells. We explored the influence of the curvature of the substrate on the shape of these cells, especially the resulting thickness of the epithelial sheet. The model we propose uses differentiated surface tensions for the different interfaces and an apical line tension as ingredients. We combined these measurements with force inference within the tissue using both the shape of cells in the epithelial sheet plane and the shape of the intercellular junctions within the thickness of the epithelium.

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Bacterial biofilms: microbe sweet home. By Nelly Henry.

Bacterial biofilms represent an adherent, dense and predominant way of life in the microbial world. The conditions in these three-dimensional structures give rise to emergent properties whose mechanisms we inspect.
   In particular we are looking for establishing the causal relationships linking the physico-chemical properties of the environment and the biological properties. For this, we rely on creating devices that enable the control of the environmental parameters together with the real-time monitoring of the biofilm biological development, aiming to provide a kinetic description of the processes involved. I will give several examples of this research and make a focus on oxygen distribution in these systems.
     We find that these systems essentially develop according to ecosystemic feed-back loops between biotic and abiotic factors enhanced by the confinement of the cells which generates strong spatiotemporal physicochemical gradients.