Dr. Severine Atis is an experimental physicist in the Institut Pprime at CNRS. Her research spans soft matter, nonequilibrium statistical physics and biophysics. She received her PhD from Sorbonne University in Physics where she worked with reaction wave propagation in disordered media. She joined David Nelson’s group at Harvard University as a postdoctoral scholar where she investigated evolutionary dynamics coupled with hydrodynamic flows in collaboration with Andrew Murray in the Molecular and Cellular Biology department. She then received the University of Chicago Grainger Fellowship in Experimental Physics where she worked on active matter and elastic networks with William Irvine, Sidney Nagel and Heinrich Jaeger.
Thursday April 20th
Growing in flows: from scaling laws to microbial jets
Biological systems can self-organize in complex structures, able to evolve and adapt to widely varying environmental conditions. In this talk, I will illustrate how simple growth dynamics, when coupled with environmental properties, can lead to a diversity of self-organization phenomena in two experimental model systems: reaction waves propagating in disordered flows, and living microorganisms growing on viscous substrates. Resulting from the balance between molecular diffusion and nonlinear chemical kinetics, autocatalytic reactions can generate self-sustained fronts which propagate like progressive waves. I will show that in the presence of a disordered flow, the front fluctuations display scaling laws consistent with the universal behavior predicted by the Kardar-Parisi-Zhang stochastic growth model. Controlled by the mean flow amplitude, the system encompasses three distinct universality classes associated with different front morphologies and dynamical behaviors. I will then focus on mutual interactions between microbial growth and fluid flows. I will show that the metabolic activity of an expanding population of microorganisms can produce strong hydrodynamical flows when grown on top of a viscous medium. These flows in turn affect the growth dynamics and can drive positive feedback phenomena such as accelerated propagation, fragmentation of the initial colony and the formation of growing microbial jets.