3D-SIM super resolution microscopy reveals a bead-like arrangement for FtsZ and the division machinery: implications for triggering cytokinesis

• Published in: PLoS biology 2012-09, Vol.10 (9), p.e1001389-e1001389
• Main Authors: Strauss, Michael P, Liew, Andrew T F, Turnbull, Lynne, Whitchurch, Cynthia B, Monahan, Leigh G, Harry, Elizabeth J
• Format: Article
• Language: English
• Subjects: Bacillus subtilis - cytology; Bacillus subtilis - metabolism; Bacterial Proteins - metabolism; Bacteriology; Biology; Cell division; Cytokinesis; Cytoskeletal Proteins - metabolism; Green Fluorescent Proteins - metabolism; Guanosine triphosphatase; Imaging, Three-Dimensional - methods; Methods; Microbial Viability; Microbiology; Microscope and microscopy; Microscopy - methods; Models, Biological; Movement; Physiological aspects; Polymerization; Protein Transport; Proteins; Recombinant Fusion Proteins - metabolism; Staphylococcus aureus - cytology; Staphylococcus aureus - metabolism; Time-Lapse Imaging
• ISSN: 1545-7885; 1544-9173; 1545-7885
• DOI: 10.1371/journal.pbio.1001389

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.