Osmotic Pressure: Resisting or Promoting DNA Ejection from Phage?

Meerim Jeembaeva, Martin Castelnovo, Frida Larsson, Alex Evilevitch

Research output: Contribution to journalArticlepeer-review


Recent in vitro experiments have shown that DNA ejection from bacteriophage can be partially stopped by surrounding osmotic pressure when ejected DNA is digested by DNase I in the course of ejection. In this work, we argue by a combination of experimental techniques (osmotic suppression without DNase I monitored by UV absorbance, pulse-field electrophoresis, and cryo-transmission electron microscopy visualization) and simple scaling modeling that intact genome (i.e., undigested) ejection in a crowded environment is, on the contrary, enhanced or eventually complete with the help of a pulling force resulting from DNA condensation induced by the osmotic stress itself. This demonstrates that in vivo, the osmotically stressed cell cytoplasm will promote phage DNA ejection rather than resist it. The further addition of DNA-binding proteins under crowding conditions is shown to enhance the extent of ejection. We also found some optimal crowding conditions for which DNA content remaining in the capsid upon ejection is maximum, which correlates well with the optimal conditions of maximum DNA packaging efficiency into viral capsids observed almost 20 years ago. Biological consequences of this finding are discussed.

Original languageEnglish (US)
Pages (from-to)310-323
Number of pages14
JournalJournal of Molecular Biology
Issue number2
StatePublished - Aug 29 2008
Externally publishedYes


  • DNA-binding proteins
  • PEG
  • dextran
  • osmotic suppression
  • phage ejection

ASJC Scopus subject areas

  • Biophysics
  • Structural Biology
  • Molecular Biology


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