Filament depolymerization during bacterial mitosis

Edward J. Banigan, Michael A. Gelbart, Zemer Gitai, Ned S. Wingreen, Andrea J. Liu

Research output: Chapter in Book/Report/Conference proceedingChapter


Chromosome segregation is fundamental to all cells, but the force-generating mechanisms underlying chromosome translocation in bacteria remain mysterious. Caulobacter crescentus utilizes a depolymerization-driven process in which a ParA protein structure elongates from the new cell pole, binds to a ParB-decorated chromosome, and then retracts via disassembly, pulling the chromosome across the cell. This poses the question of how a depolymerizing structure can robustly pull the chromosome that disassembles it. Brownian dynamics simulations is performed with a simple, physically consistent model of the ParABS system. The simulations suggest that the mechanism of translocation is “self-diffusiophoretic”: by disassembling ParA, ParB generates a ParA concentration gradient so that the ParA concentration is higher in front of the chromosome than behind it. Since the chromosome is attracted to ParA via ParB, it moves up the ParA gradient and across the cell. It is found that translocation is most robust when ParB binds side-on to ParA filaments. In this case, robust translocation occurs over a wide parameter range and is controlled by a single dimensionless quantity: the product of the rate of ParA disassembly and a characteristic relaxation time of the chromosome. This time scale measures the time it takes for the chromosome to recover its average shape after it is has been pulled. Our results suggest explanations for observed phenomena such as segregation failure, filament-length-dependent translocation velocity, and chromosomal compaction.

Original languageEnglish (US)
Title of host publicationTrends in Biophysics
Subtitle of host publicationFrom Cell Dynamics Toward Multicellular Growth Phenomena
PublisherApple Academic Press
Number of pages24
ISBN (Electronic)9781466584105
ISBN (Print)9781926895369
StatePublished - Jan 1 2013

All Science Journal Classification (ASJC) codes

  • General Biochemistry, Genetics and Molecular Biology
  • General Physics and Astronomy


  • Caulobacter crescentus
  • Chromosome segregation
  • Detachment force
  • ParA filament
  • Translocation velocity


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