Science / Technology - Colloquium
Wednesday, January 30, 2008
4:00 PM-5:00 PM
Olin Hall
107
Many bacteria swim by rotating flagella. The swimming cell is an ideal candidate for a physicist's approximation: it is very nearly a prolate spheroid (the cell body) pushed by a simple helical propeller (the flagellum). Moreover, since the motion occurs at low Reynolds number it can be solved analytically. Unfortunately, most bacteria, including common pathogens such as Escherichia coli and Salmonella, have several flagella that operate simultaneously. This slightly more complicated problem - propulsion by several interacting flagella - has not been solved satisfactorily, either analytically or numerically.
I will summarize the simple physics of swimming cells and of the flagellar rotary motor, and point out as-yet-unresolved issues involving interacting flagella, such as the unknown mechanism that causes flagella to bundle. From high-speed video of fluorescently labeled bacteria, we have attempted a complete force-balance accounting of swimming cells. We find that, contrary to physical intuition, adding flagella does not allow a cell to swim faster. In light of this conclusion, I will offer some ideas as to the purpose of having multiple flagella.
Cost: FREE
Sponsored by: WPI Physics Department, Dr. Stephan Koehler
Suggested Audiences: College
E-mail:
sak@wpi.edu
Phone: 508-831-5090
Last Modified: January 22, 2008 at 2:06 PM
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