L’Institut Philippe Meyer de l’Ecole Normale Supérieure a le plaisir d’annoncer que le Prix Philippe Meyer de Physique 2024 est attribué au Prof. BEN GOOD (Stanford Univerity) pour ses avancées majeures sur l’évolution des communautés microbiennes et l’interaction entre l’évolution et l’écologie.

Le jury international du prix était composé de :
– Professeur Jean-François Joanny (Président)
– Professeur David Nelson
– Professeur Ben Simons
– Professeur Haim Sompolinski

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Cérémonie de remise du prix Philippe Meyer

Vendredi 4 avril 2025

Ecole Normale Supérieure, Salle Emile Borel, 29 rue d’Ulm, Paris 5^e.

Programme

14:00 – Introduction

14:15 – Benjamin Good, lauréat du Prix Philippe Meyer 2024
Statistical physics of evolving microbial communities
Underneath the fascinating biology, evolution is controlled by a stochastic dynamical process that describes how mutations arise and spread through a population. Although the rules of this process are simple, it can be surprisingly difficult to predict how they combine to determine the genetic and phenotypic structure of a population. In this talk, I will show how theoretical approaches from statistical physics, along with experimental data from rapidly evolving microorganisms, can enhance our quantitative understanding of this process. Specific attention will be devoted to microbial communities, where the interactions between ecology and evolution raise a unique set of challenges. I will discuss our recent efforts to predict the coupled ecological and evolutionary dynamics that emerge in minimal models of resource competition, and their connections to empirical data from laboratory evolution experiments and mammalian gut microbiomes. We will see that several counterintuitive behaviors arise in the high-diversity limit that characterizes many natural microbial populations, and that “large-N” approaches can be useful for understanding these self-organized dynamical states.

15:15 – Pause café

15:45 – David Nelson (Harvard University)
Active Antagonism:  Reproducing Microorganisms and Fluid Flows
The growth and evolution of microbial populations is often subject to advection by fluid flows in spatially extended environments, with immediate consequences for spatial population genetics in marine ecology, planktonic diversity and fixation times.  We review recent progress made in understanding this rich problem in the simplified setting of two competing genetic microbial strains subjected to fluid flows. We first review microbial range expansion experiments on liquid substrates and then move on to discuss antagonism, i.e., two killer microorganism strains, each secreting toxins that impede the growth of their competitors (competitive exclusion), both with and without stationary fluid flows.   Recent experiments that reveal the presence of a genetic line tension are described.    Coupled reaction-diffusion equations that include advection by simple steady cellular flows composed of characteristic flow motifs in two dimensions reveal how local flow shear and compressibility effects can interact with selective advantage to have a dramatic influence on genetic competition and fixation in spatially distributed populations.   We analyze a variety of 1d and 2d flow geometries including sources, sinks, vortices and saddles, and show how simple analytical models of the dynamics of the genetic interface can be used to shed light on the nucleation, coexistence and flow-driven instabilities of genetic drops.

16:30 – Jean-François Joanny (Collège de France)
Active Nematic Turbulence
In the limit of high activity, most active systems reach a state of spatio-temporal chaos which has been termed active turbulence. The aim of this talk is to describe our recent results on active turbulence in a single component nematic system in the limit where there are no nematic defects. We first discuss the flow instability of a homogeneous nematic states showing that it can be a supercritical or a sub-criticial bifurcation. We then show using large scale numerical simulations that there exist two turbulent states; a large scale fluctuating turbulent state and an arrested state. We show that the arrested state which is obtained for extensile rod-like nematics has a well defined labyrinth pattern of the nematic field and of the flow field. The slowing down of the fluctuations is due to a topological frustration of the labyrinth structure.

In collaboration with I. Lavi, R. Alert, J. Casademunt

17:15 – Fin