Modeling cells as pressurized elastic shells

Animal cells and bacteria are enveloped and sealed by lipid membranes and mechanically protected by cortical polymer networks. Cells typically actively maintain a small (eukaryotic cells) or large (prokaryotic cells) positive osmotic pressure against their environment. Volume and shape regulation impact the mechanical properties of cells. The mechanical properties of cells can be probed by exerting external force and measuring cell response. To interpret micro-mechanical optical trapping experiments with suspended rounded eukaryotic cells, we developed finite element simulations and modeled cells as pressurized elastic shells. During deformation, competition between osmotic pressure resulting from compression of the cytosol and the elastic stretching of the actin cortex determines the cell response. The finite element simulations suggest that (eukaryotic) cell deformations are essentially isovolumetric.