Seminar: Collective functionality in active fluids: Distribution of resources, rheosensing, and ultra-fast hydrodynamic communication


  • Date: May 14, 2018
  • Time: 02:00 PM - 03:00 PM (Local Time Germany)
  • Speaker: Dr. Arnold Mathijssen
  • Stanford University, USA
  • Location: Max-Planck-Institut für Dynamik und Selbstorganisation (MPIDS)
  • Room: SR 0.77
  • Host: MPIDS/DCF
  • Contact: corinna.maass@ds.mpg.dd
The biophysical relationships between physiological sensors and actuators were fundamental to the development of early life forms, as responding promptly to external stimuli opens communicative pathways that are key to survival. We study cooperation in ‘active fluids’, live suspensions that operate far from equilibrium, where long-ranged hydrodynamic interactions allow for shared functionality across length scales. First, we consider the probability of nutrient capture by swimming cells, which feeds back into activity. Moreover, self-organisation in bacterial biofilms is demonstrated to drive coherent solvent currents towards the substrate that also replenish resources. Second, we consider the protist Spirostomum ambiguum, a ciliate that can contract its body within milliseconds. These rapid contractions generate vortex flows that trigger other cells, which facilitates the collective transduction of hydrodynamic signals across a colony moving hundreds of times faster than swimming. By combining a novel rheosensing assay, high-speed PIV experiments and percolation theory we determine the critical cell density required to sustain these signal waves. As contractions release toxins from membrane-bound extrusomes, synchronised discharges could facilitate the repulsion of large-scale predators cooperatively.
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