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CNA Seminar/Colloquium/Joint Pitt-CNA Colloquium
Henry Shum
Rudolf Peierls Centre for Theoretical Physics, University of Oxford
Title: Hydrodynamics and elastodynamics of flagellated bacteria

Abstract: Bacteria are ubiquitous on Earth and perform many vital roles in addition to being responsible for a variety of diseases. Locomotion allows the bacterium to explore the environment to find nutrient-rich locations and is also crucial in the formation of large colonies, known as biofilms, on solid surfaces immersed in the fluid. Many bacteria swim by turning corkscrew-shaped flagella. This can be studied computationally by considering hydrodynamic forces acting on the bacterium as the flagellum rotates. Using a boundary element method to solve the Stokes flow equations, it is found that details of the shape of the cell and flagellum affect both swimming efficiency and attraction of the swimmer towards flat no-slip surfaces. For example, simulations show that relatively small changes in cell elongation or flagellum length could make the difference between an affinity for swimming near surfaces and a repulsion. A new model is introduced for considering elastic behaviour in the bacterial hook that links the flagellar filament to the motor in the cell body. This model, based on Kirchhoff rod theory, predicts upper and lower bounds on the hook stiffness for effective swimming as well as the possibility of more complex behaviours such as cell reorientation and dynamic modification of surface accumulation.

Recording: http://mm.math.cmu.edu/recordings/cna/CNA-HenryShum-Jan-31-2012.avi
Recording: http://mm.math.cmu.edu/recordings/cna/CNA-HenryShum-Jan-31-2012.mp4
Date: Tuesday, January 31, 2012
Time: 1:30 pm
Location: Wean Hall 7218
Submitted by:  David Kinderlehrer