Title: From Bacteria to Chromosomes: Hydrodynamic Self-organization of Biological Active Matter

Speaker: David Saintillan, Professor, Department of Mechanical and Aerospace Engineering, UC San Diego

Abstract: The spontaneous emergence of large-scale coherent motions and patterns is a striking feature of many active soft matter systems and often results from long-ranged hydrodynamic interactions driven by internal active forces. In the first part of my talk, I will focus on bacterial suspensions, where hydrodynamic instabilities are known to arise due to the force dipoles exerted by motile microorganisms which couple to their orientations through the flows they generate. Using both models and simulations, I will analyze the interplay between these instabilities and geometrical confinement, where an apparent transition to superfluiditycan be harnessed to drive unidirectional streaming flows.The second part of the talk will address the seemingly very different -yet perhaps related -case of chromosomal dynamics inside the nucleus during cell interphase, where experiments recently revealed coherent motion on large length and time scales. A model of chromatin dynamics as a confined polymer chain acted upon by molecular enzymes exerting force dipoles will be discussed, where hydrodynamic interactions emerge once again as a potential mechanism for coherent motions and large-scale self-organization.

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