title: Escherichia coli Chromosomal Loci Segregate from Midcell with Universal Dynamics.
abstract: The structure of the Escherichia coli chromosome is inherently dynamic over the duration of the cell cycle. Genetic loci undergo both stochastic motion around their initial positions and directed motion to opposite poles of the rod-shaped cell during segregation. We developed a quantitative method to characterize cell-cycle dynamics of the E. coli chromosome to probe the chromosomal steady-state mobility and segregation process. By tracking fluorescently labeled chromosomal loci in thousands of cells throughout the entire cell cycle, our method allows for the statistical analysis of locus position and motion, the step-size distribution for movement during segregation, and the locus drift velocity. The robust statistics of our detailed analysis of the wild-type E. coli nucleoid allow us to observe loci moving toward midcell before segregation occurs, consistent with a replication factory model. Then, as segregation initiates, we perform a detailed characterization of the average segregation velocity of loci. Contrary to origin-centric models of segregation, which predict distinct dynamics for oriC-proximal versus oriC-distal loci, we find that the dynamics of loci were universal and independent of genetic position.
authors.affiliation: Departments of Physics, Bioengineering, and Microbiology, University of Washington, Seattle, Washington.
authors.forename: Julie A
authors.initials: JA
authors.lastname: Cass
authors.affiliation: Departments of Physics, Bioengineering, and Microbiology, University of Washington, Seattle, Washington.
authors.forename: Nathan J
authors.initials: NJ
authors.lastname: Kuwada
authors.affiliation: Departments of Physics, Bioengineering, and Microbiology, University of Washington, Seattle, Washington.
authors.forename: Beth
authors.initials: B
authors.lastname: Traxler
authors.affiliation: Departments of Physics, Bioengineering, and Microbiology, University of Washington, Seattle, Washington. Electronic address: pwiggins@uw.edu.
authors.forename: Paul A
authors.initials: PA
authors.lastname: Wiggins
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000235:genetics / Q000378:metabolism; D002874:Chromosome Mapping; D020090:Chromosome Segregation; D002876:Chromosomes, Bacterial / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D004058:Diffusion; D004926:Escherichia coli / Q000235:genetics* / Q000502:physiology*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D056426:Genetic Loci; D008856:Microscopy, Fluorescence; D009038:Motion; D009154:Mutation
chemical_list: D001425:Bacterial Outer Membrane Proteins; C062011:DNA replication terminus site-binding protein, E coli; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C089746:SeqA protein, E coli