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: 8.68). 11/2010; 3(3). DOI: 10.1101/cshperspect.a006809
Source: PubMed


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.

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Available from: Clare L Kirkpatrick, Oct 04, 2015
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    • "The ‘old’ pole is inherited from the mother cell while the ‘new’ pole arises from the FtsZ-generated division septum. Related to this asymmetry, in many bacteria there is preferential localization of certain structures to a single pole, including flagella, pili, and secretion systems [4]. Importantly, the proper assembly and distribution of these polar functionalities are critical for these bacteria to interact with one another and with their environment. "
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    ABSTRACT: The α-Proteobacterium Agrobacterium tumefaciens has proteins homologous to known regulators that govern cell division and development in Caulobacter crescentus, many of which are also conserved among diverse α-Proteobacteria. In light of recent work demonstrating similarity between the division cycle of C. crescentus and that of A. tumefaciens, the functional conservation for this presumptive control pathway was examined. In C. crescentus the CtrA response regulator serves as the master regulator of cell cycle progression and cell division. CtrA activity is controlled by an integrated pair of multi-component phosphorelays: PleC/DivJ-DivK and CckA-ChpT-CtrA. Although several of the conserved orthologues appear to be essential in A. tumefaciens, deletions in pleC or divK were isolated and resulted in cell division defects, diminished swimming motility, and a decrease in biofilm formation. A. tumefaciens also has two additional pleC/divJ homologue sensor kinases called pdhS1 and pdhS2, absent in C. crescentus. Deletion of pdhS1 phenocopied the ΔpleC and ΔdivK mutants. Cells lacking pdhS2 morphologically resembled wild-type bacteria, but were decreased in swimming motility and elevated for biofilm formation, suggesting that pdhS2 may serve to regulate the motile to non-motile switch in A. tumefaciens. Genetic analysis suggests that the PleC/DivJ-DivK and CckA-ChpT-CtrA phosphorelays in A. tumefaciens are vertically-integrated, as in C. crescentus. A gain-of-function mutation in CckA (Y674D) was identified as a spontaneous suppressor of the ΔpleC motility phenotype. Thus, although the core architecture of the A. tumefaciens pathway resembles that of C. crescentus there are specific differences including additional regulators, divergent pathway architecture, and distinct target functions.
    PLoS ONE 02/2013; 8(2):e56682. DOI:10.1371/journal.pone.0056682 · 3.23 Impact Factor
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    • "Consequently, many proteins exhibit distinct patterns of subcellular localization, some of which arise due to active mechanisms (Shapiro et al. 2009). For example, in rod-shaped bacteria, numerous proteins are localized to a cell pole, where they form complexes critical for processes such as chromosome segregation , motility, and chemotaxis (for review, see Gerdes et al. 2010; Sourjik and Armitage 2010; Kirkpatrick and Viollier 2011). At least in some species, the sets of protein complexes found at the two cell poles (the old and new pole, respectively) differ, generating asymmetry between the two ends of the cell (Shapiro et al. 2009). "
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