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Free SepF interferes with recruitment of late cell division proteins

Yongqiang Gao1, Michaela Wenzel1, Martijs J Jonker2

  • 1Swammerdam Institute for Life Sciences, University of Amsterdam, O|2 Building, De Boelelaan 1108, 1081 HZ, Amsterdam, The Netherlands.

Scientific Reports
|December 7, 2017
PubMed

Insights

Overproducing the cell division protein SepF in Bacillus subtilis blocks septum synthesis by interfering with late division proteins, not Z-ring assembly. This SepF imbalance disrupts bacterial cytokinesis.

Area of Science:

  • Bacterial cell division
  • Microbial genetics
  • Cytokinesis mechanisms

Background:

  • SepF is a conserved protein essential for bacterial cell division, aligning FtsZ polymers for Z-ring formation.
  • SepF also functions as a membrane anchor for the Z-ring, crucial for initiating cytokinesis.
  • Previous studies showed SepF overexpression blocks cell division in Mycobacterium smegmatis, but the mechanism remained unclear.

Purpose of the Study:

  • To investigate the mechanism by which SepF overproduction affects bacterial cell division in Bacillus subtilis.
  • To determine if SepF overexpression impacts Z-ring assembly or later stages of septum synthesis.
  • To elucidate the interaction of SepF with other cell division proteins and regulatory systems.

Main Methods:

  • Comparative analysis of SepF overproduction effects in Bacillus subtilis versus Mycobacterium smegmatis.
  • Transposon mutagenesis to identify genetic suppressors of SepF overproduction phenotypes.
  • Localization studies of the WalK protein in SepF overexpressing cells.
  • Transcriptome analysis to assess the impact on gene expression, particularly the WalRK system.
  • Protein-protein interaction studies investigating SepF, FtsZ, EzrA, and FtsA binding.

Main Results:

  • SepF overproduction in Bacillus subtilis disrupts late division protein assembly, not initial Z-ring formation.
  • SepF overproduction impairs WalK localization but does not reduce overall WalRK two-component system activity.
  • SepF competes with EzrA and FtsA for FtsZ binding, suggesting a direct role in regulating FtsZ polymerization dynamics.
  • Increased FtsZ expression, induced by WalRK activation, counteracts the cell division defect caused by SepF overproduction.

Conclusions:

  • An imbalance in early cell division proteins, such as SepF, can impede the recruitment and function of late division proteins necessary for septum synthesis.
  • SepF's interaction with FtsZ is critical for its role in cell division, and excess SepF disrupts this balance.
  • Understanding SepF's regulatory role provides insights into the complex coordination required for bacterial cytokinesis.

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