Poles apart: prokaryotic polar organelles and their spatial regulation.

Department of Microbiology and Molecular Medicine, Centre Médicale Universitaire, Faculty of Medicine, University of Geneva, Switzerland.
Cold Spring Harbor perspectives in biology (Impact Factor: 8.23). 11/2010; 3(3). DOI: 10.1101/cshperspect.a006809
Source: PubMed

ABSTRACT While polar organelles hold the key to understanding the fundamentals of cell polarity and cell biological principles in general, they have served in the past merely for taxonomical purposes. Here, we highlight recent efforts in unraveling the molecular basis of polar organelle positioning in bacterial cells. Specifically, we detail the role of members of the Ras-like GTPase superfamily and coiled-coil-rich scaffolding proteins in modulating bacterial cell polarity and in recruiting effector proteins to polar sites. Such roles are well established for eukaryotic cells, but not for bacterial cells that are generally considered diffusion-limited. Studies on spatial regulation of protein positioning in bacterial cells, though still in their infancy, will undoubtedly experience a surge of interest, as comprehensive localization screens have yielded an extensive list of (polarly) localized proteins, potentially reflecting subcellular sites of functional specialization predicted for organelles.

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Placement of motility structures at the poles of rod‐shaped bacteria is a common engineering problem with a variety of potential solutions. While investigating the mechanisms for positioning of the single polar flagellum of Pseudomonas aeruginosa, Cowles and colleagues discovered a new membrane‐bound three‐component system related to TonB–ExbB–ExbD that they named ‘Poc’ for polar organelle co‐ordinator, which controls polar localization of both the flagellum and type IV pili. The Poc complex itself is not found at the poles, and is required for increased expression of pilus genes upon surface association, suggesting a new paradigm of localization control.
    Molecular Microbiology 10/2013; · 5.03 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: It is now well appreciated that bacterial cells are highly organized, which is far from the initial concept that they are merely bags of randomly distributed macromolecules and chemicals. Central to their spatial organization is the precise positioning of certain proteins in subcellular domains of the cell. In particular, the cell poles - the ends of rod-shaped cells - constitute important platforms for cellular regulation that underlie processes as essential as cell cycle progression, cellular differentiation, virulence, chemotaxis and growth of appendages. Thus, understanding how the polar localization of specific proteins is achieved and regulated is a crucial question in bacterial cell biology. Often, polarly localized proteins are recruited to the poles through their interaction with other proteins or protein complexes that were already located there, in a so-called diffusion-and-capture mechanism. Bacteria are also starting to reveal their secrets on how the initial pole 'recognition' can occur and how this event can be regulated to generate dynamic, reproducible patterns in time (for example, during the cell cycle) and space (for example, at a specific cell pole). Here, we review the major mechanisms that have been described in the literature, with an emphasis on the self-organizing principles. We also present regulation strategies adopted by bacterial cells to obtain complex spatiotemporal patterns of protein localization.
    Journal of Cell Science 12/2013; · 5.33 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Burkholderia glumae is a motile plant pathogenic bacterium that has multiple polar flagella and one LuxR/LuxI-type quorum sensing (QS) system, TofR/TofI. A QS-dependent transcriptional regulator, QsmR, activates flagellar master regulator flhDC genes. FlhDC subsequently activates flagellar gene expression in B. glumae at 37°C. Here, we confirm that the interplay between QS and temperature is critical for normal polar flagellar morphogenesis in B. glumae. In the wild-type bacterium, flagellar gene expression and flagellar number were greater at 28°C compared to 37°C. The QS-dependent flhC gene was significantly expressed at 28°C in two QS-defective (tofI::Ω and qsmR::Ω) mutants. Thus, flagella were present in both tofI::Ω and qsmR::Ω mutants at 28°C, but were absent at 37°C. Most tofI::Ω and qsmR::Ω mutant cells possessed polar or nonpolar flagella at 28°C. Nonpolarly flagellated cells processing flagella around cell surface of both tofI::Ω and qsmR::Ω mutants exhibited tumbling and spinning movements. The flhF gene encoding GTPase involved in regulating the correct placement of flagella in other bacteria was expressed in QS mutants in a FlhDC-dependent manner at 28°C. However, FlhF was mislocalized in QS mutants, and was associated with nonpolar flagellar formation in QS mutants at 28°C. These results indicate that QS-independent expression of flagellar genes at 28°C allows flagellar biogenesis, but is not sufficient for normal polar flagellar morphogenesis in B. glumae. Our findings demonstrate that QS functions together with temperature to control flagellar morphogenesis in B. glumae.
    PLoS ONE 01/2014; 9(1):e84831. · 3.53 Impact Factor

Full-text (2 Sources)

Available from
May 31, 2014