title: 3D-SIM super resolution microscopy reveals a bead-like arrangement for FtsZ and the division machinery: implications for triggering cytokinesis.
abstract: FtsZ is a tubulin-like GTPase that is the major cytoskeletal protein in bacterial cell division. It polymerizes into a ring, called the Z ring, at the division site and acts as a scaffold to recruit other division proteins to this site as well as providing a contractile force for cytokinesis. To understand how FtsZ performs these functions, the in vivo architecture of the Z ring needs to be established, as well as how this structure constricts to enable cytokinesis. Conventional wide-field fluorescence microscopy depicts the Z ring as a continuous structure of uniform density. Here we use a form of super resolution microscopy, known as 3D-structured illumination microscopy (3D-SIM), to examine the architecture of the Z ring in cells of two Gram-positive organisms that have different cell shapes: the rod-shaped Bacillus subtilis and the coccoid Staphylococcus aureus. We show that in both organisms the Z ring is composed of a heterogeneous distribution of FtsZ. In addition, gaps of fluorescence were evident, which suggest that it is a discontinuous structure. Time-lapse studies using an advanced form of fast live 3D-SIM (Blaze) support a model of FtsZ localization within the Z ring that is dynamic and remains distributed in a heterogeneous manner. However, FtsZ dynamics alone do not trigger the constriction of the Z ring to allow cytokinesis. Lastly, we visualize other components of the divisome and show that they also adopt a bead-like localization pattern at the future division site. Our data lead us to propose that FtsZ guides the divisome to adopt a similar localization pattern to ensure Z ring constriction only proceeds following the assembly of a mature divisome.
authors.affiliation: The ithree institute, University of Technology Sydney, Sydney, New South Wales, Australia.
authors.forename: Michael P
authors.initials: MP
authors.lastname: Strauss
authors.forename: Andrew T F
authors.initials: AT
authors.lastname: Liew
authors.forename: Lynne
authors.initials: L
authors.lastname: Turnbull
authors.forename: Cynthia B
authors.initials: CB
authors.lastname: Whitchurch
authors.forename: Leigh G
authors.initials: LG
authors.lastname: Monahan
authors.forename: Elizabeth J
authors.initials: EJ
authors.lastname: Harry
mesh_terms: D001412:Bacillus subtilis / Q000166:cytology* / Q000378:metabolism; D001426:Bacterial Proteins / Q000378:metabolism*; D048749:Cytokinesis; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D049452:Green Fluorescent Proteins / Q000378:metabolism; D021621:Imaging, Three-Dimensional / Q000379:methods*; D050296:Microbial Viability; D008853:Microscopy / Q000379:methods*; D008954:Models, Biological; D009068:Movement; D021381:Protein Transport; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013211:Staphylococcus aureus / Q000166:cytology* / Q000378:metabolism; D059008:Time-Lapse Imaging
chemical_list: D001426:Bacterial Proteins; D003598:Cytoskeletal Proteins; C071525:FtsZ protein, Bacteria; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins