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SUMMARY:On the interaction of helical structures within bundles of bacteri
 al flagella - Maria Tătulea-Codrean (University of Cambridge)
DTSTART:20180503T120000Z
DTEND:20180503T130000Z
UID:TALK105202@talks.cam.ac.uk
CONTACT:Anne Herrmann
DESCRIPTION:The rapid bundling and unbundling of helical flagellar filamen
 ts is an essential component to the run-and-tumble motion of multi-flagell
 ated bacteria\, but the physical mechanism behind it is not yet fully unde
 rstood. What makes this problem difficult to solve is not only the couplin
 g of elastic and hydrodynamic effects\, but also the way in which the heli
 cal structures manage to fit together.  During a `run'\, all flagella rota
 te counterclockwise and they wrap around  each  other  in  a  right-handed
   sense  to  form  a  tight  helical  bundle. This  is possible despite th
 e intrinsic left-handedness of normal shape flagella\, which indicates tha
 t geometry plays an important role in this process. During a `tumble'\, at
  least one of the flagella changes its rotation direction\, and the associ
 ated flagellum separates from the rest of the bundle under the combined ac
 tion of hydrodynamic and elastic forces. To add to this complexity\, the f
 lagellum is known to transition between different polymorphic shapes. The 
 combination of geometry and mechanics will once again be crucial if we wan
 t to understand how all these different polymorphic shapes interact. In th
 is talk we will present some ongoing work on the geometric constraints tha
 t govern the wrapping of helical structures around each other. We will als
 o discuss the relevance of our results to the helical flagella of Salmonel
 la typhimurium and Escherichia coli\, two of the most commonly studied spe
 cies of bacteria.
LOCATION:MR11\, Centre for Mathematical Sciences\, Wilberforce Road\, Camb
 ridge
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