Compaction of isolated Escherichia coli nucleoids: Polymer and H-NS protein synergetics

Anna S. Wegner, Kathelijne Wintraecken, Roberto Spurio, Conrad L. Woldringh, Renko de Vries, Theo Odijk*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

10 Citations (Scopus)


Escherichia coli nucleoids were compacted by the inert polymer polyethylene glycol (PEG) in the presence of the H-NS protein. The protein by itself appears to have little impact on the size of the nucleoids as determined by fluorescent microscopy. However, it has a significant impact on the nucleoidal collapse by PEG. This is quantitatively explained by assuming the H-NS protein enhances the effective diameter of the DNA helix leading to an increase in the depletion forces induced by the PEG. Ultimately, however, the free energy of the nucleoid itself turns out to be independent of the H-NS concentration. This is because the enhancement of the supercoil excluded volume is negligible. The experiments on the nucleoids are corroborated by dynamic light scattering and EMSA analyses performed on DNA plasmids in the presence of PEG and H-NS.

Original languageEnglish
Pages (from-to)129-137
JournalJournal of Structural Biology
Issue number1
Publication statusPublished - 1 Apr 2016


  • Dynamic light scattering
  • EMSA
  • Escherichia coli
  • H-NS protein
  • Nucleoid
  • Polyethylene glycol
  • Polymer physics
  • Supercoiling


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