Dependency of Escherichia coli cell-division size, and independency of nucleoid segregation on the mode and level of ftsZ expression

Authors

  • Pilar Palacios,

    1. Departamento de Bioiogía Celular y del Desarrollo, Centro de Investigaciones Biológicas, Cousejo Superior de Investigaciones Científicas, Velázquez 144, 28006 Madrid, Spain
    Search for more papers by this author
  • Miguel Vicente,

    Corresponding author
    1. Departamento de Bioiogía Celular y del Desarrollo, Centro de Investigaciones Biológicas, Cousejo Superior de Investigaciones Científicas, Velázquez 144, 28006 Madrid, Spain
    Search for more papers by this author
  • Manuel Sánchez

    1. Departamento de Bioiogía Celular y del Desarrollo, Centro de Investigaciones Biológicas, Cousejo Superior de Investigaciones Científicas, Velázquez 144, 28006 Madrid, Spain
    Search for more papers by this author

Summary

Expression of ftsZ in strain VIP205 is dissociated from its natural promoters, and is under the control of an inducible tac promoter. This abolishes the oscillation in ftsZ transcription observed in the wild type, allowing different levels of ftsZ expression. We demonstrate that this construction does not affect the expression of other genes, and has no effects on replication or nucleoid segregation. A shift in IPTG from 30 μM, that supports division at wild-type sizes, to lower (6 μM) or higher (100μM) concentrations, indicates that VIP205 cells can divide within a broad range of FtsZ concentrations. Analysis of the morphological parameters during the transition from one IPTG concentration to another suggests that the correct timing of ftsZ expression, and the correct FtsZ concentration, are required for division to occur at normal cell sizes. After a transient division delay during the transition to lower IPTG concentrations, cells in which ftsZ is expressed continuously (yielding 80% of the wild-type FtsZ levels) divide with the same division time as the wild type, but at the expense of becoming 1.5 times larger. A precise control of ftsZ expression is required for normal division, but the existence of additional regulators to maintain the correct timing during the cell cycle cannot be ruled out.

Ancillary