A key challenge for microbes is to locate nutrient hotspots amid nutrient deserts ill-suitable for growth. A prime example of such heterogeneous environments is the ocean, where heterotrophic marine bacteria act as gatekeepers of marine carbon storage by remineralizing sinking particles of organic matter. We'll discuss several challenges and trade-offs involved in the search behavior. Specifically, I describe our work studying risk-reward trade-offs in search behavior of marine bacteria, which leads to a behavioral dichotomy in swimming endurance under carbon starvation: several species rapidly cease motility within hours after starvation to conserve resources, while other species convert biomass into energy to fuel motility and keep searching for several days. Then I describe experiments that demonstrate how the chemotaxis pathway - used to navigate nutrient gradients - can amplify molecular noise to enhance their exploratory behavior even in areas without gradients. Finally, I will also explain how the interactions within chemosensory arrays - large signal-processing protein complexes - are tuned close to a critical point, on the border between order and chaos, and that this helps to leverage a sensory trade-off between response amplitude and speed.

Bio: Johannes Keegstra is a senior researcher based in the Environmental Microfluidics Group of Prof. Roman Stocker at ETH Zurich. He performed his PhD research in biophysics at the AMOLF research institute in Amsterdam, and before that studied physics in Delft and philosophy in Leiden. His work focusses microbes living in complex environments, linking molecular mechanisms to bacterial behaviour that affect biogeochemical cycles.

See for more information about Johannes Keegstra and Martina Dalbello.

Register in advance for this Zoom meeting: https://univienna.zoom.us/meeting/register/rMD4y-AlScesxGeJzka-zQ