Speaker: Wilson Bennett Lough, UW–Madison
Research, teaching and outreach in Physics
Title: Self-buckling and self-writhing of semi-flexible microorganisms
Multi-flagellated microorganisms can buckle and writhe under their own activity as they swim through a viscous fluid. New equilibrium configurations and steady-state dynamics then emerge which depend on the organism’s mechanical properties and on the oriented distribution of flagella along its surface. Modeling the cell body as a semi-flexible Kirchhoff rod and coupling the mechanics to a dynamically evolving flagellar orientation field, we derive the Euler-Poincarè equations governing dynamics of the system, and rationalize experimental observations of buckling and writhing of
elongated swarmer P. mirabilis cells. A sequence of bifurcations is identified as the body is made more compliant, due to both buckling and torsional instabilities. The results suggest that swarmer cells invest no more resources in maintaining membrane integrity than is necessary to prevent self-buckling.