[ Research interests ]

Flagellar synchronization by mechanical control

The eukaryotic flagellum is a best-seller of nature: These slender cell appendages propel sperm and many other microswimmers, including disease-causing protists. In mammalian airways or the oviduct, collections of flagella beat in synchrony to pump fluids efficiently. We use theory and experiment to elucidate a mechanism of synchronization in the model organism Chlamydomonas, a green algal cell that swims with two flagella like a breaststroke swimmer. Our analysis shows how synchronization arises by a coupling of swimming and flagellar beating and characterizes an exemplary
force–velocity relationship of the flagellar beat.

Collaboration: Howard lab

Mechanosensing and the emergence of cytoskeletal order 

Tissue cells actively adhere to neighboring cells (or an in vitro substrate) and extert cytoskeletal forces, thus probing their mechanical environment. Substrate stiffness can guide cytoskeletal reorganization, driving the parallel alignment of actin bundles (nematic order) and the formation of acto-myosin crystals (so-called myofibrils) in developing muscle cells. To understand the emergence of cytoskeletal order, we develop minimal descriptions of interacting cytoskeletal force generators. We envision a hierarchy of different actin order that underlies the formation of force-generating myofibrils in muscle cells and thus theoretically address the ultimate question: How to build and regenerate muscle? 

Collaboration: Discher lab

Flagellar propulsion 

Flagella are higly conserved cell apdendages that are powered by molecular motors and can beat regularly like a whip. Many microswimmers including sperm cells and algae propel themselves using flagella; in our lungs, epithelial cells use flagella to transport mucus. We study the mechanics of flagellar bending waves and resulting low Reynolds number flows to understand flagellar self-propelsion in two model systems: sperm cells and the flagellated green algae Chlamydomonas. In the past, high-precision measurements of a wiggling motion accompanying sperm swimming allowed us to callibrate its hydrodynamics. From this, we predicted sperm swimming across scales and explained how sperm cells swim in cirlces. This collaboration with the Howard lab at MPI CBG will be continued to study Chlamydomonas swimming.

Collaboration: Howard lab

Pathfinding of microswimmers 

Purposeful motion requires an orchestrated interplay of motility and sensation. We studied this interplay in the exemplary context of sperm chemotaxis, a process that guides sperm cells on their journey towards the egg. We characterized a navigation strategy along circular and helical paths that is enjoyed by sperm and other microswimmers, but that differs fundamentally from bacterial chemotaxis. This novel navigation strategy is remarkably efficient and robust and reflects perfect adaptation to a noisy environment. Current research aims at understanding quantitativlely the chemotactic signaling system of sperm cells, and to identify general design principles underlying its amazing sensitivity.

Collaboration: Kaupp lab