File:E. coli FtsZ.png

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Total internal reflection PALM image of an E. coli BL21(DE3)pLysS cell expressing FtsZ-mEos2

Example of a functional compartment in bacteria.


Representative image of a fixed cell expressing FtsZ-mEos2 in the order of bright-field (A), total internal reflection (TIR) ensemble fluorescence image of the cell prior to TIR photoactivated localization microscopy (PALM) imaging (B), TIR PALM image (C), and contour plot of FtsZ packing density in units of number of FtsZ-mEos2 molecules per PALM pixel (15×15 nm2). The number of FtsZ-mEos2 molecules used to construct the PALM image was 1704. Bars, 500 nm.

The FtsZ protein, a tubulin-like GTPase, plays a pivotal role in prokaryotic cell division. In vivo it localizes to the midcell and assembles into a ring-like structure-the Z-ring. The Z-ring serves as an essential scaffold to recruit all other division proteins and generates contractile force for cytokinesis, but its supramolecular structure remains unknown. Electron microscopy (EM) has been unsuccessful in detecting the Z-ring due to the dense cytoplasm of bacterial cells, and conventional fluorescence light microscopy (FLM) has only provided images with limited spatial resolution (200–300 nm) due to the diffraction of light. Hence, given the small sizes of bacteria cells, identifying the in vivo structure of the Z-ring presents a substantial challenge. Here, we used photoactivated localization microscopy (PALM), a single molecule-based super-resolution imaging technique, to characterize the in vivo structure of the Z-ring in E. coli. We achieved a spatial resolution of ~35 nm and discovered that in addition to the expected ring-like conformation, the Z-ring of E. coli adopts a novel compressed helical conformation with variable helical length and pitch. We measured the thickness of the Z-ring to be ~110 nm and the packing density of FtsZ molecules inside the Z-ring to be greater than what is expected for a single-layered flat ribbon configuration. Our results strongly suggest that the Z-ring is composed of a loose bundle of FtsZ protofilaments that randomly overlap with each other in both longitudinal and radial directions of the cell. Our results provide significant insight into the spatial organization of the Z-ring and open the door for further investigations of structure-function relationships and cell cycle-dependent regulation of the Z-ring.

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Reference

Citation: Fu G, Huang T, Buss J, Coltharp C, Hensel Z, et al. (2010) In Vivo Structure of the E. coli FtsZ-ring Revealed by Photoactivated Localization Microscopy (PALM). PLoS ONE 5(9): e12680.

http://www.ncbi.nlm.nih.gov/pubmed/20856929

http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0012680

doi:10.1371/journal.pone.0012680

Editor: Michael Polymenis, Texas A&M University, United States of America

Received: March 13, 2010; Accepted: August 13, 2010; Published: September 13, 2010

Copyright

© 2010 Fu et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

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current08:04, 9 March 2011Thumbnail for version as of 08:04, 9 March 2011600 × 483 (517 KB)S8600021 (talk | contribs)==Total internal reflection PALM image of an E. coli BL21(DE3)pLysS cell expressing FtsZ-mEos2== Representative image of a fixed cell expressing FtsZ-mEos2 in the order of bright-field (A), total internal reflection (TIR) ensemble fluorescence image of t
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