Physics (Internal)

"On Growth and Form of Range Expansions at Liquid Interfaces"

This event is part of the Biophysics Seminars. 12:30PM.

Transport phenomena shape and constantly reorganize materials at every scale. In presence of hydrodynamical flows, the Lagrangian advection of individual particles strongly influences their dispersion, segregation and clustering. Range expansions of living cells resting on liquid substrates is of great importance in understanding the organization of microorganism populations. However, combining growth dynamics of an expanding assembly of cells with hydrodynamics leads to challenging problems, which involve the coupling of nonlinear dynamics, stochasticity and transport. In this talk, I will present laboratory experiments, combined with numerical modelling, focused on the collective dynamics of genetically labelled microorganisms undergoing division and competition in the presence of a variety of flows. We have created an extremely viscous medium that allows us to grow cells on a controlled liquid interface over macroscopic scales. I will show that an expanding population of microorganisms can itself generate a radial flow, leading to an accelerated propagation and fragmentation of the initial colony. I will show how the dynamics and morphology of these microbial populations is affected by the fluid dynamics triggered by this metabolically generated flow. I will conclude by discussing the potential influence of transport and mixing on evolutionary dynamics, and how the control of cell assemblies on liquid interfaces can lead to a wide range of phenomena at the intersection between cellular biology and physics.