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SUMMARY:How E.coli organizes and segregates its chromosome - Kleckner\, N 
 (Harvard University\, USA)
DTSTART:20120903T152000Z
DTEND:20120903T160000Z
UID:TALK39498@talks.cam.ac.uk
CONTACT:Mustapha Amrani
DESCRIPTION:Live cell imaging of the E.coli nucleoid\, illuminated with Hu
 pA-mCherry\, reveals a well-defined helical ellipsoid that is trapped with
 in the cell radially but not longitudinally.  Basic elliposidal shape resu
 lts from longitudinal density bundling while helicity results from interac
 tions between these bundles and the cell periphery.  Unexpectedly\, the nu
 cleoid exhibits two distinct types of cyclic dynamic changes\, both indepe
 ndent of DNA replication:  (1) On time scales of seconds-to-minutes\, long
 itudinal density waves flux through the shape over distances comparable to
  the length of the nucleoid\, resulting in dynamic shape changes. (2) At i
 ntervals of ~20min\, the nucleoid exhibits ~10min pulses of chromosome elo
 ngation.  These pulses\, which are implemented by elongation-biased densit
 y waves\, are temporally and functionally linked to step-wise separation o
 f sister chromosomes. The presented findings support a two-component model
  for sister segregation and the existence of nucleoid stress cycles which\
 , we propose\, function to release the nucleoid from linkages that constra
 in both morphogenetic evolution and separation of sisters.  These cycles c
 ould comprise a primordial cell cycle\, and the same principles could pert
 ain broadly across evolutionary space and time. \n
LOCATION:Seminar Room 1\, Newton Institute
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