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Mathematical Biology seminar
Greg Huber
U Mass
"Chirality transformations on bacterial flagella"
March 5 (Friday)
3:05pm in LCB 215
Chemotaxis in many bacterial species is made possible by the
remarkable dynamics of their multiple, rotating, helical
flagella. They bundle and de-bundle as their rotary motors
episodically change rotational direction. When the flagella are
bundled, the bacterium moves linearly, but the dissolution of the
bundle leads to a tumbling event that effectively randomizes the
cell's orientation. The motor reversal that initiates the tumbling not
only torques the flagella oppositely, but also reverse the chirality
of the filament, turning a left-handed helix into a right-handed
helix. Hotani has performed careful experiments on helical flagella in
external flows and he observed that regions within the filament
periodically flip to the opposite chirality, and that those domains
propagate stably downstream. I'll present a dynamical model for this
phenomenon based on the existence of two competing locally stable
states of opposite chirality whose interaction with the flow is
through the torque they produce. The model displays a number of the
key features seen in the experiments.
For more information contact J. Keener, 1-6089
E-mail:
keener@math.utah.edu
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