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Biophys J. 2015 Jan 6;108(1):146-53. doi: 10.1016/j.bpj.2014.10.074.

Physical modeling of chromosome segregation in escherichia coli reveals impact of force and DNA relaxation.

Author information

1
Department of Chemical Engineering, Stanford University, Stanford, California.
2
Departments of Physics and Bioengineering, University of Washington, Seattle, Washington.
3
Department of Chemical Engineering, Stanford University, Stanford, California; Biophysics Program, Stanford University, Stanford, California; Department of Materials Science & Engineering, Stanford University, Stanford, California; Department of Applied Physics, Stanford University, Stanford, California. Electronic address: ajspakow@stanford.edu.

Abstract

The physical mechanism by which Escherichia coli segregates copies of its chromosome for partitioning into daughter cells is unknown, partly due to the difficulty in interpreting the complex dynamic behavior during segregation. Analysis of previous chromosome segregation measurements in E. coli demonstrates that the origin of replication exhibits processive motion with a mean displacement that scales as t(0.32). In this work, we develop a model for segregation of chromosomal DNA as a Rouse polymer in a viscoelastic medium with a force applied to a single monomer. Our model demonstrates that the observed power-law scaling of the mean displacement and the behavior of the velocity autocorrelation function is captured by accounting for the relaxation of the polymer chain and the viscoelastic environment. We show that the ratio of the mean displacement to the variance of the displacement during segregation events is a critical metric that eliminates the compounding effects of polymer and medium dynamics and provides the segregation force. We calculate the force of oriC segregation in E. coli to be ∼0.49 pN.

PMID:
25564861
PMCID:
PMC4286603
DOI:
10.1016/j.bpj.2014.10.074
[Indexed for MEDLINE]
Free PMC Article

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