Dynamic SpoIIIE assembly mediates septal membrane fission during Bacillus subtilis sporulation

Tinya C. Fleming, Jae Yen Shin, Sang Hyuk Lee, Eric Becker, Kerwyn Casey Huang, Carlos Bustamante, Kit Pogliano

Research output: Contribution to journalArticlepeer-review

48 Scopus citations


SpoIIIE is an FtsK-related protein that transports the forespore chromosome across the Bacillus subtilis sporulation septum. We use membrane photobleaching and protoplast assays to demonstrate that SpoIIIE is required for septal membrane fission in the presence of trapped DNA, and that DNA is transported across separate daughter cell membranes, suggesting that SpoIIIE forms a channel that partitions the daughter cell membranes. Our results reveal a close correlation between septal membrane fission and the assembly of a stable SpoIIIE translocation complex at the septal midpoint. Time-lapse epifluorescence, total internal reflection fluorescence (TIRF) microscopy, and live-cell photoactivation localization microscopy (PALM) demonstrate that the SpoIIIE transmembrane domain mediates dynamic localization to active division sites, whereas the assembly of a stable focus also requires the cytoplasmic domain. The transmembrane domain fails to completely separate the membrane, and it assembles unstable foci. TIRF microscopy and biophysical modeling of fluorescence recovery after photobleaching (FRAP) data suggest that this unstable protein transitions between disassembled and assembled oligomeric states. We propose a new model for the role of SpoIIIE assembly in septal membrane fission that has strong implications for how the chromosome terminus crosses the septum.

Original languageEnglish (US)
Pages (from-to)1160-1172
Number of pages13
JournalGenes and Development
Issue number11
StatePublished - Jun 1 2010

All Science Journal Classification (ASJC) codes

  • Genetics
  • Developmental Biology


  • DNA translocase
  • FRAP
  • Membrane fission
  • PALM
  • SpoIIIE


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