Hall 123

Mechanics of motility: from unicellular organisms to tissues

Mohd Suhail Rizvi

Université Grenoble Alpes and CNRS, France

Motility is an essential characteristic of many biological cells. For unicellular organisms, such as bacteria, it is crucial for their survival. For the multicellular organisms it is required for many physiological functions, such as protection against pathogens by the immune cells, and also during embryonic development and in cancer metastasis.

Some of the unicellular organisms propel themselves by cyclic deformation of flagella. The small size of these organisms results in negligible inertial forces and the motion is described using Stokes flow. Recently, immune cells have also been shown to move in fluid by similar mechanism where shape changes provide cell propulsion. This motion which does not require any support from solid substrate has been labelled “amoeboid swimming”. We have developed theoretical models to study the mechanical principles governing the amoeboid and flagellar swimming. Using these models and numerical simulations we have studied the cell swimming under external fields (forces and flows) and the role of hydrodynamic and ligand-receptor based interactions of amoeboid swimmers with substrates on their motility. We have found that the presence of swimmers in a suspension results in its non-Newtonian rheological properties. Unlike force-dipole based rigid swimmers, the suspensions of deformable amoeboid swimmers show a shear-thinning as well as shear-thickening behaviors.

Another example of cell motion is collective cell migration which is essential during animal development and in conditions such as wound healing. I will show an example of the regulation of the collective cell migration in the epithelial tissues during development. The motion of cells in tissues has another layer of complexity which arises from its regulation by the genetic machinery. I will show how the subcellular proteins affect the mechanical properties of the epithelial tissues and their movements.