1
|
Bhasne K, Jain N, Karnawat R, Arya S, Majumdar A, Singh A, Mukhopadhyay S. Discerning Dynamic Signatures of Membrane-Bound α-Synuclein Using Site-Specific Fluorescence Depolarization Kinetics. J Phys Chem B 2020; 124:708-717. [PMID: 31917569 DOI: 10.1021/acs.jpcb.9b09118] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
α-Synuclein is an intrinsically disordered protein that adopts an α-helical structure upon binding to the negatively charged lipid membrane. Binding-induced conformational change of α-synuclein plays a crucial role in the regulation of synaptic plasticity. In this work, we utilized the fluorescence depolarization kinetics methodology to gain the site-specific dynamical insights into the membrane-bound α-synuclein. We took advantage of the nonoccurrence of Cys in α-synuclein and created single-Cys variants at different sites for us to be able to label it with a thiol-active fluorophore. Our fluorescence depolarization results reveal the presence of three dynamically distinct types of motions of α-synuclein on POPG (1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-(1'-rac-glycerol)) small unilamellar vesicles (SUVs): (i) the (local) wobbling-in-cone motion of the fluorophore on the subnanosecond timescale, (ii) the backbone segmental mobility on the nanosecond timescale, and (iii) a slow depolarization component with a characteristic long rotational correlation time (∼60 ns) that is independent of the residue position. This characteristic timescale could potentially arise due to global tumbling of the protein-membrane complex, the global reorientation of only the protein within the membrane, and/or the translation diffusion of the protein on the curved membrane surface that could result in fluorescence depolarization due to the angular displacement of the transition dipole. In order to discern the molecular origin of the characteristic long rotational correlation time, we then carried our depolarization experiments varying the curvature of the membrane and varying the binding affinity by changing the lipid headgroup. These experiments revealed that the long rotational correlation time primarily arises due to the translational diffusion of α-synuclein on the curved membrane surface with a diffusion coefficient of ∼8.7 × 10-10 m2/s. The site-specific fluorescence depolarization methodology will find broad application in quantifying diffusion of a wide range of membrane-associated proteins involved in functions and diseases.
Collapse
Affiliation(s)
- Karishma Bhasne
- Centre for Protein Science, Design and Engineering , Indian Institute of Science Education and Research (IISER) , Mohali 140306 , India.,Department of Biological Sciences , Indian Institute of Science Education and Research (IISER) , Mohali 140306 , India
| | - Neha Jain
- Department of Biological Sciences , Indian Institute of Science Education and Research (IISER) , Mohali 140306 , India
| | - Rishabh Karnawat
- Department of Biological Sciences , Indian Institute of Science Education and Research (IISER) , Mohali 140306 , India
| | - Shruti Arya
- Centre for Protein Science, Design and Engineering , Indian Institute of Science Education and Research (IISER) , Mohali 140306 , India.,Department of Chemical Sciences , Indian Institute of Science Education and Research (IISER) , Mohali 140306 , India
| | - Anupa Majumdar
- Centre for Protein Science, Design and Engineering , Indian Institute of Science Education and Research (IISER) , Mohali 140306 , India.,Department of Biological Sciences , Indian Institute of Science Education and Research (IISER) , Mohali 140306 , India
| | - Anubhuti Singh
- Department of Chemical Sciences , Indian Institute of Science Education and Research (IISER) , Mohali 140306 , India
| | - Samrat Mukhopadhyay
- Centre for Protein Science, Design and Engineering , Indian Institute of Science Education and Research (IISER) , Mohali 140306 , India.,Department of Biological Sciences , Indian Institute of Science Education and Research (IISER) , Mohali 140306 , India.,Department of Chemical Sciences , Indian Institute of Science Education and Research (IISER) , Mohali 140306 , India
| |
Collapse
|
2
|
Involvement of organic acids and amino acids in ameliorating Ni(II) toxicity induced cell cycle dysregulation in Caulobacter crescentus: a metabolomics analysis. Appl Microbiol Biotechnol 2018; 102:4563-4575. [PMID: 29616314 DOI: 10.1007/s00253-018-8938-0] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2017] [Revised: 03/13/2018] [Accepted: 03/13/2018] [Indexed: 10/17/2022]
Abstract
Nickel (Ni(II)) toxicity is addressed by many different bacteria, but bacterial responses to nickel stress are still unclear. Therefore, we studied the effect of Ni(II) toxicity on cell proliferation of α-proteobacterium Caulobacter crescentus. Next, we showed the mechanism that allows C. crescentus to survive in Ni(II) stress condition. Our results revealed that the growth of C. crescentus is severely affected when the bacterium was exposed to different Ni(II) concentrations, 0.003 mM slightly affected the growth, 0.008 mM reduced the growth by 50%, and growth was completely inhibited at 0.015 mM. It was further shown that Ni(II) toxicity induced mislocalization of major regulatory proteins such as MipZ, FtsZ, ParB, and MreB, resulting in dysregulation of the cell cycle. GC-MS metabolomics analysis of Ni(II) stressed C. crescentus showed an increased level of nine important metabolites including TCA cycle intermediates and amino acids. This indicates that changes in central carbon metabolism and nitrogen metabolism are linked with the disruption of cell division process. Addition of malic acid, citric acid, alanine, proline, and glutamine to 0.015 mM Ni(II)-treated C. crescentus restored its growth. Thus, the present work shows a protective effect of these organic acids and amino acids on Ni(II) toxicity. Metabolic stimulation through the PutA/GlnA pathway, accelerated degradation of CtrA, and Ni-chelation by organic acids or amino acids are some of the possible mechanisms suggested to be involved in enhancing C. crescentus's tolerance. Our results shed light on the mechanism of increased Ni(II) tolerance in C. crescentus which may be useful in bioremediation strategies and synthetic biology applications such as the development of whole cell biosensor.
Collapse
|
3
|
Govindarajan S, Albocher N, Szoke T, Nussbaum-Shochat A, Amster-Choder O. Phenotypic Heterogeneity in Sugar Utilization by E. coli Is Generated by Stochastic Dispersal of the General PTS Protein EI from Polar Clusters. Front Microbiol 2018; 8:2695. [PMID: 29387047 PMCID: PMC5776091 DOI: 10.3389/fmicb.2017.02695] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2017] [Accepted: 12/26/2017] [Indexed: 11/13/2022] Open
Abstract
Although the list of proteins that localize to the bacterial cell poles is constantly growing, little is known about their temporal behavior. EI, a major protein of the phosphotransferase system (PTS) that regulates sugar uptake and metabolism in bacteria, was shown to form clusters at the Escherichia coli cell poles. We monitored the localization of EI clusters, as well as diffuse molecules, in space and time during the lifetime of E. coli cells. We show that EI distribution and cluster dynamics varies among cells in a population, and that the cluster speed inversely correlates with cluster size. In growing cells, EI is not assembled into clusters in almost 40% of the cells, and the clusters in most remaining cells dynamically relocate within the pole region or between the poles. In non-growing cells, the fraction of cells that contain EI clusters is significantly higher, and dispersal of these clusters is often observed shortly after exiting quiescence. Later, during growth, EI clusters stochastically re-form by assembly of pre-existing dispersed molecules at random time points. Using a fluorescent glucose analog, we found that EI function inversely correlates with clustering and with cluster size. Thus, activity is exerted by dispersed EI molecules, whereas the polar clusters serve as a reservoir of molecules ready to act when needed. Taken together our findings highlight the spatiotemporal distribution of EI as a novel layer of regulation that contributes to the population phenotypic heterogeneity with regard to sugar metabolism, seemingly conferring a survival benefit.
Collapse
Affiliation(s)
- Sutharsan Govindarajan
- Department of Microbiology and Molecular Genetics, IMRIC, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Nitsan Albocher
- Department of Microbiology and Molecular Genetics, IMRIC, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Tamar Szoke
- Department of Microbiology and Molecular Genetics, IMRIC, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Anat Nussbaum-Shochat
- Department of Microbiology and Molecular Genetics, IMRIC, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Orna Amster-Choder
- Department of Microbiology and Molecular Genetics, IMRIC, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem, Israel
| |
Collapse
|
4
|
Taylor JA, Panis G, Viollier PH, Marczynski GT. A novel nucleoid-associated protein coordinates chromosome replication and chromosome partition. Nucleic Acids Res 2017; 45:8916-8929. [PMID: 28911105 PMCID: PMC5587793 DOI: 10.1093/nar/gkx596] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2017] [Accepted: 07/05/2017] [Indexed: 11/14/2022] Open
Abstract
We searched for regulators of chromosome replication in the cell cycle model Caulobacter crescentus and found a novel DNA-binding protein (GapR) that selectively aids the initiation of chromosome replication and the initial steps of chromosome partitioning. The protein binds the chromosome origin of replication (Cori) and has higher-affinity binding to mutated Cori-DNA that increases Cori-plasmid replication in vivo. gapR gene expression is essential for normal rapid growth and sufficient GapR levels are required for the correct timing of chromosome replication. Whole genome ChIP-seq identified dynamic DNA-binding distributions for GapR, with the strongest associations at the partitioning (parABS) locus near Cori. Using molecular-genetic and fluorescence microscopy experiments, we showed that GapR also promotes the first steps of chromosome partitioning, the initial separation of the duplicated parS loci following replication from Cori. This separation occurs before the parABS-dependent partitioning phase. Therefore, this early separation, whose mechanisms is not known, coincides with the poorly defined mechanism(s) that establishes chromosome asymmetry: C. crescentus chromosomes are partitioned to distinct cell-poles which develop into replicating and non-replicating cell-types. We propose that GapR coordinates chromosome replication with asymmetry-establishing chromosome separation, noting that both roles are consistent with the phylogenetic restriction of GapR to asymmetrically dividing bacteria.
Collapse
Affiliation(s)
- James A Taylor
- Department of Microbiology and Immunology, McGill University, 3775 University St., Montreal, QC H3A 2B4, Canada
| | - Gaël Panis
- Department of Microbiology and Molecular Medicine, University of Geneva Medical School, 1 rue Michel-Servet, CH-1211 Geneva 4, Switzerland
| | - Patrick H Viollier
- Department of Microbiology and Molecular Medicine, University of Geneva Medical School, 1 rue Michel-Servet, CH-1211 Geneva 4, Switzerland
| | - Gregory T Marczynski
- Department of Microbiology and Immunology, McGill University, 3775 University St., Montreal, QC H3A 2B4, Canada
| |
Collapse
|
5
|
Arias-Cartin R, Dobihal GS, Campos M, Surovtsev IV, Parry B, Jacobs-Wagner C. Replication fork passage drives asymmetric dynamics of a critical nucleoid-associated protein in Caulobacter. EMBO J 2016; 36:301-318. [PMID: 28011580 DOI: 10.15252/embj.201695513] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2016] [Revised: 11/29/2016] [Accepted: 11/30/2016] [Indexed: 01/06/2023] Open
Abstract
In bacteria, chromosome dynamics and gene expression are modulated by nucleoid-associated proteins (NAPs), but little is known about how NAP activity is coupled to cell cycle progression. Using genomic techniques, quantitative cell imaging, and mathematical modeling, our study in Caulobacter crescentus identifies a novel NAP (GapR) whose activity over the cell cycle is shaped by DNA replication. GapR activity is critical for cellular function, as loss of GapR causes severe, pleiotropic defects in growth, cell division, DNA replication, and chromosome segregation. GapR also affects global gene expression with a chromosomal bias from origin to terminus, which is associated with a similar general bias in GapR binding activity along the chromosome. Strikingly, this asymmetric localization cannot be explained by the distribution of GapR binding sites on the chromosome. Instead, we present a mechanistic model in which the spatiotemporal dynamics of GapR are primarily driven by the progression of the replication forks. This model represents a simple mechanism of cell cycle regulation, in which DNA-binding activity is intimately linked to the action of DNA replication.
Collapse
Affiliation(s)
- Rodrigo Arias-Cartin
- Microbial Sciences Institute, Yale University, West Haven, CT, USA.,Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, CT, USA
| | - Genevieve S Dobihal
- Microbial Sciences Institute, Yale University, West Haven, CT, USA.,Howard Hughes Medical Institute, Yale University, New Haven, CT, USA
| | - Manuel Campos
- Microbial Sciences Institute, Yale University, West Haven, CT, USA.,Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, CT, USA.,Howard Hughes Medical Institute, Yale University, New Haven, CT, USA
| | - Ivan V Surovtsev
- Microbial Sciences Institute, Yale University, West Haven, CT, USA.,Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, CT, USA.,Howard Hughes Medical Institute, Yale University, New Haven, CT, USA
| | - Bradley Parry
- Microbial Sciences Institute, Yale University, West Haven, CT, USA.,Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, CT, USA
| | - Christine Jacobs-Wagner
- Microbial Sciences Institute, Yale University, West Haven, CT, USA .,Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, CT, USA.,Howard Hughes Medical Institute, Yale University, New Haven, CT, USA.,Department of Microbial Pathogenesis, Yale Medical School, Yale University, New Haven, CT, USA
| |
Collapse
|
6
|
Wu Y, Sims RC, Zhou A. AFM resolves effects of ethambutol on nanomechanics and nanostructures of single dividing mycobacteria in real-time. Phys Chem Chem Phys 2015; 16:19156-64. [PMID: 24965038 DOI: 10.1039/c4cp01317d] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Dynamic nanomechanics and nanostructures of dividing and anti-mycobacterial drug treated mycobacterium remain to be fully elucidated. Atomic force microscopy (AFM) is a promising nanotechnology tool for characterization of these dynamic alterations, especially at the single cell level. In this work, single dividing mycobacterium JLS (M.JLS) before and after anti-mycobacterial drug (ethambutol, EMB) treatment was in situ quantitatively analyzed, suggesting that nanomechanics would be referred as a sensitive indicator for evaluating efficacy of anti-mycobacterial drugs. Dynamic evidence on the contractile ring and septal furrow of dividing M.JLS implied that inhibition of contractile ring formation would be a crucial process for EMB to disturb M.JLS division. These results could facilitate further explaining the regulation mechanism of the contractile ring as well as nanomechanical roles of the cell wall in the course of mycobacterial division. This work describe a new way for further elucidating the mechanisms of mycobacterial division and anti-mycobacterial drug action, as well as the drug-resistance developing mechanism of pathogenic mycobacteria.
Collapse
Affiliation(s)
- Yangzhe Wu
- Department of Biological Engineering, Utah State University, 4105 Old Main Hill, Logan, Utah 84322-4105, USA.
| | | | | |
Collapse
|
7
|
Positioning of bacterial chemoreceptors. Trends Microbiol 2015; 23:247-56. [PMID: 25843366 DOI: 10.1016/j.tim.2015.03.004] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2015] [Revised: 03/06/2015] [Accepted: 03/06/2015] [Indexed: 11/24/2022]
Abstract
For optimum growth, bacteria must adapt to their environment, and one way that many species do this is by moving towards favourable conditions. To do so requires mechanisms to both physically drive movement and provide directionality to this movement. The pathways that control this directionality comprise chemoreceptors, which, along with an adaptor protein (CheW) and kinase (CheA), form large hexagonal arrays. These arrays can be formed around transmembrane receptors, resulting in arrays embedded in the inner membrane, or they can comprise soluble receptors, forming arrays in the cytoplasm. Across bacterial species, chemoreceptor arrays (both transmembrane and soluble) are localised to a variety of positions within the cell; some species with multiple arrays demonstrate this variety within individual cells. In many cases, the positioning pattern of the arrays is linked to the need for segregation of arrays between daughter cells on division, ensuring the production of chemotactically competent progeny. Multiple mechanisms have evolved to drive this segregation, including stochastic self-assembly, cellular landmarks, and the utilisation of ParA homologues. The variety of mechanisms highlights the importance of chemotaxis to motile species.
Collapse
|
8
|
Li J, Bu P, Chen KY, Shen X. Spatial perturbation with synthetic protein scaffold reveals robustness of asymmetric cell division. ACTA ACUST UNITED AC 2013; 6:134-143. [PMID: 25750689 DOI: 10.4236/jbise.2013.62017] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Asymmetric cell division is an important mechanism for creating diversity in a cellular population. Stem cells commonly perform asymmetric division to generate both a daughter stem cell for self-renewal and a more differentiated daughter cell to populate the tissue. During asymmetric cell division, protein cell fate determinants asymmetrically localize to the opposite poles of a dividing cell to cause distinct cell fate. However, it remains unclear whether cell fate determination is robust to fluctuations and noise during this spatial allocation process. To answer this question, we engineered Caulobacter, a bacterial model for asymmetric division, to express synthetic scaffolds with modular protein interaction domains. These scaffolds perturbed the spatial distribution of the PleC-DivJ-DivK phospho-signaling network without changing their endogenous expression levels. Surprisingly, enforcing symmetrical distribution of these cell fate determinants did not result in symmetric daughter fate or any morphological defects. Further computational analysis suggested that PleC and DivJ form a robust phospho-switch that can tolerate high amount of spatial variation. This insight may shed light on the presence of similar phospho-switches in stem cell asymmetric division regulation. Overall, our study demonstrates that synthetic protein scaffolds can provide a useful tool to probe biological systems for better understanding of their operating principles.
Collapse
Affiliation(s)
- Jiahe Li
- Department of Biomedical Engineering, Cornell University, Ithaca, USA
| | - Pengcheng Bu
- School of Electrical and Computer Engineering, Cornell University, Ithaca, USA
| | - Kai-Yuan Chen
- School of Electrical and Computer Engineering, Cornell University, Ithaca, USA
| | - Xiling Shen
- Department of Biomedical Engineering, Cornell University, Ithaca, USA ; School of Electrical and Computer Engineering, Cornell University, Ithaca, USA
| |
Collapse
|
9
|
Longo G, Rio LM, Roduit C, Trampuz A, Bizzini A, Dietler G, Kasas S. Force volume and stiffness tomography investigation on the dynamics of stiff material under bacterial membranes. J Mol Recognit 2012; 25:278-84. [DOI: 10.1002/jmr.2171] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Giovanni Longo
- Laboratory of Physics of Living Matter; EPFL; Lausanne; Switzerland
| | - Laura Marques Rio
- Infectious Diseases Service, Department of Medicine; University Hospital Lausanne (CHUV); Lausanne; Switzerland
| | - Charles Roduit
- Laboratory of Physics of Living Matter; EPFL; Lausanne; Switzerland
| | - Andrej Trampuz
- Infectious Diseases Service, Department of Medicine; University Hospital Lausanne (CHUV); Lausanne; Switzerland
| | | | - Giovanni Dietler
- Laboratory of Physics of Living Matter; EPFL; Lausanne; Switzerland
| | - Sandor Kasas
- Laboratory of Physics of Living Matter; EPFL; Lausanne; Switzerland
| |
Collapse
|
10
|
Aldridge BB, Fernandez-Suarez M, Heller D, Ambravaneswaran V, Irimia D, Toner M, Fortune SM. Asymmetry and aging of mycobacterial cells lead to variable growth and antibiotic susceptibility. Science 2011; 335:100-4. [PMID: 22174129 DOI: 10.1126/science.1216166] [Citation(s) in RCA: 302] [Impact Index Per Article: 23.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Cells use both deterministic and stochastic mechanisms to generate cell-to-cell heterogeneity, which enables the population to better withstand environmental stress. Here we show that, within a clonal population of mycobacteria, there is deterministic heterogeneity in elongation rate that arises because mycobacteria grow in an unusual, unipolar fashion. Division of the asymmetrically growing mother cell gives rise to daughter cells that differ in elongation rate and size. Because the mycobacterial cell division cycle is governed by time, not cell size, rapidly elongating cells do not divide more frequently than slowly elongating cells. The physiologically distinct subpopulations of cells that arise through asymmetric growth and division are differentially susceptible to clinically important classes of antibiotics.
Collapse
Affiliation(s)
- Bree B Aldridge
- Department of Immunology and Infectious Diseases, Harvard School of Public Health, Boston, MA 02115, USA
| | | | | | | | | | | | | |
Collapse
|
11
|
Ingerson-Mahar M, Gitai Z. A growing family: the expanding universe of the bacterial cytoskeleton. FEMS Microbiol Rev 2011; 36:256-66. [PMID: 22092065 DOI: 10.1111/j.1574-6976.2011.00316.x] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2011] [Revised: 11/02/2011] [Accepted: 11/10/2011] [Indexed: 12/16/2022] Open
Abstract
Cytoskeletal proteins are important mediators of cellular organization in both eukaryotes and bacteria. In the past, cytoskeletal studies have largely focused on three major cytoskeletal families, namely the eukaryotic actin, tubulin, and intermediate filament (IF) proteins and their bacterial homologs MreB, FtsZ, and crescentin. However, mounting evidence suggests that these proteins represent only the tip of the iceberg, as the cellular cytoskeletal network is far more complex. In bacteria, each of MreB, FtsZ, and crescentin represents only one member of large families of diverse homologs. There are also newly identified bacterial cytoskeletal proteins with no eukaryotic homologs, such as WACA proteins and bactofilins. Furthermore, there are universally conserved proteins, such as the metabolic enzyme CtpS, that assemble into filamentous structures that can be repurposed for structural cytoskeletal functions. Recent studies have also identified an increasing number of eukaryotic cytoskeletal proteins that are unrelated to actin, tubulin, and IFs, such that expanding our understanding of cytoskeletal proteins is advancing the understanding of the cell biology of all organisms. Here, we summarize the recent explosion in the identification of new members of the bacterial cytoskeleton and describe a hypothesis for the evolution of the cytoskeleton from self-assembling enzymes.
Collapse
|
12
|
Briegel A, Beeby M, Thanbichler M, Jensen GJ. Activated chemoreceptor arrays remain intact and hexagonally packed. Mol Microbiol 2011; 82:748-57. [PMID: 21992450 PMCID: PMC3641884 DOI: 10.1111/j.1365-2958.2011.07854.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Bacterial chemoreceptors cluster into exquisitively sensitive, tunable, highly ordered, polar arrays. While these arrays serve as paradigms of cell signalling in general, it remains unclear what conformational changes transduce signals from the periplasmic tips, where attractants and repellents bind, to the cytoplasmic signalling domains. Conflicting reports support and contest the hypothesis that activation causes large changes in the packing arrangement of the arrays, up to and including their complete disassembly. Using electron cryotomography, here we show that in Caulobacter crescentus, chemoreceptor arrays in cells grown in different media and immediately after exposure to the attractant galactose all exhibit the same 12 nm hexagonal packing arrangement, array size and other structural parameters. ΔcheB and ΔcheR mutants mimicking attractant- or repellent-bound states prior to adaptation also show the same lattice structure. We conclude that signal transduction and amplification must be accomplished through only small, nanoscale conformational changes.
Collapse
Affiliation(s)
- Ariane Briegel
- Division of Biology, California Institute of Technology, Pasadena, CA 91125, USA
| | | | | | | |
Collapse
|
13
|
Abstract
Visualization of RNA in live cells is a challenging task due to the transient character of most RNA molecules and the lack of adequate methods to label RNA noninvasively. Here, we describe a system for regulated RNA synthesis and visualization of RNA in live Escherichia coli cells based on protein complementation. This method allows for labeling RNA with a relatively small protein complex that becomes fluorescent only when bound to an RNA. This method greatly reduces the high fluorescence background characteristic of methods employing intact fluorescent proteins. A short reporter RNA was shown to localize at the cell periphery in nonrandom patterns.
Collapse
|
14
|
van den Wildenberg SMJL, Bollen YJM, Peterman EJG. How to quantify protein diffusion in the bacterial membrane. Biopolymers 2011; 95:312-21. [PMID: 21240922 DOI: 10.1002/bip.21585] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2010] [Revised: 12/10/2010] [Accepted: 12/10/2010] [Indexed: 01/18/2023]
Abstract
Lateral diffusion of proteins in the plane of a biological membrane is important for many vital processes, including energy conversion, signaling, chemotaxis, cell division, protein insertion, and secretion. In bacteria, all these functions are located in a single membrane. Therefore, quantitative measurements of protein diffusion in bacterial membranes can provide insight into many important processes. Diffusion of membrane proteins in eukaryotes has been studied in detail using various experimental techniques, including fluorescence correlation spectroscopy (FCS), fluorescence recovery after photobleaching (FRAP), and particle tracking using single-molecule fluorescence (SMF) microscopy. In case of bacteria, such experiments are intrinsically difficult due to the small size of the cells. Here, we review these experimental approaches to quantify diffusion in general and their strengths and weaknesses when applied to bacteria. In addition, we propose a method to extract multiple diffusion coefficients from trajectories obtained from SMF data, using cumulative probability distributions (CPDs). We demonstrate the power of this approach by quantifying the heterogeneous diffusion of the bacterial membrane protein TatA, which forms a pore for the translocation of folded proteins. Using computer simulations, we study the effect of cell dimensions and membrane curvature on measured CPDs. We find that at least two mobile populations with distinct diffusion coefficients (of 7 and 169 nm(2) ms(-1) , respectively) are necessary to explain the experimental data. The approach described here should be widely applicable for the quantification of membrane-protein diffusion in living bacteria.
Collapse
|
15
|
Di Talia S, Wang H, Skotheim JM, Rosebrock AP, Futcher B, Cross FR. Daughter-specific transcription factors regulate cell size control in budding yeast. PLoS Biol 2009; 7:e1000221. [PMID: 19841732 PMCID: PMC2756959 DOI: 10.1371/journal.pbio.1000221] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2008] [Accepted: 09/11/2009] [Indexed: 12/31/2022] Open
Abstract
The asymmetric localization of cell fate determinants results in asymmetric cell cycle control in budding yeast. In budding yeast, asymmetric cell division yields a larger mother and a smaller daughter cell, which transcribe different genes due to the daughter-specific transcription factors Ace2 and Ash1. Cell size control at the Start checkpoint has long been considered to be a main regulator of the length of the G1 phase of the cell cycle, resulting in longer G1 in the smaller daughter cells. Our recent data confirmed this concept using quantitative time-lapse microscopy. However, it has been proposed that daughter-specific, Ace2-dependent repression of expression of the G1 cyclin CLN3 had a dominant role in delaying daughters in G1. We wanted to reconcile these two divergent perspectives on the origin of long daughter G1 times. We quantified size control using single-cell time-lapse imaging of fluorescently labeled budding yeast, in the presence or absence of the daughter-specific transcriptional regulators Ace2 and Ash1. Ace2 and Ash1 are not required for efficient size control, but they shift the domain of efficient size control to larger cell size, thus increasing cell size requirement for Start in daughters. Microarray and chromatin immunoprecipitation experiments show that Ace2 and Ash1 are direct transcriptional regulators of the G1 cyclin gene CLN3. Quantification of cell size control in cells expressing titrated levels of Cln3 from ectopic promoters, and from cells with mutated Ace2 and Ash1 sites in the CLN3 promoter, showed that regulation of CLN3 expression by Ace2 and Ash1 can account for the differential regulation of Start in response to cell size in mothers and daughters. We show how daughter-specific transcriptional programs can interact with intrinsic cell size control to differentially regulate Start in mother and daughter cells. This work demonstrates mechanistically how asymmetric localization of cell fate determinants results in cell-type-specific regulation of the cell cycle. Asymmetric cell division is a universal mechanism for generating differentiated cells. The progeny of such divisions can often display differential cell cycle regulation. This study addresses how differential regulation of gene expression in the progeny of a single division can alter cell cycle control. In budding yeast, asymmetric cell division yields a bigger ‘mother’ cell and a smaller ‘daughter’ cell. Regulation of gene expression is also asymmetric because two transcription factors, Ace2 and Ash1, are specifically localized to the daughter. Cell size has long been proposed as important for the regulation of the cell cycle in yeast. Our work shows that Ace2 and Ash1 regulate size control in daughter cells: daughters ‘interpret’ their size as smaller, making size control more stringent and delaying cell cycle commitment relative to mother cells of the same size. This asymmetric interpretation of cell size is associated with differential regulation of the G1 cyclin CLN3 by Ace2 and Ash1, at least in part via direct binding of these factors to the CLN3 promoter. CLN3 is the most upstream regulator of Start, the initiation point of the yeast cell cycle, and differential regulation of CLN3 accounts for most or all asymmetric regulation of Start in budding yeast mother and daughter cells.
Collapse
Affiliation(s)
- Stefano Di Talia
- The Rockefeller University, New York, New York, United States of America
| | - Hongyin Wang
- Department of Molecular Genetics and Microbiology, SUNY at Stony Brook, Stony Brook, New York, United States of America
| | - Jan M. Skotheim
- The Rockefeller University, New York, New York, United States of America
| | - Adam P. Rosebrock
- Department of Molecular Genetics and Microbiology, SUNY at Stony Brook, Stony Brook, New York, United States of America
| | - Bruce Futcher
- Department of Molecular Genetics and Microbiology, SUNY at Stony Brook, Stony Brook, New York, United States of America
| | - Frederick R. Cross
- The Rockefeller University, New York, New York, United States of America
- * E-mail:
| |
Collapse
|
16
|
Russell JH, Keiler KC. Subcellular localization of a bacterial regulatory RNA. Proc Natl Acad Sci U S A 2009; 106:16405-9. [PMID: 19805312 PMCID: PMC2752561 DOI: 10.1073/pnas.0904904106] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2009] [Indexed: 01/22/2023] Open
Abstract
Eukaryotes and bacteria regulate the activity of some proteins by localizing them to discrete subcellular structures, and eukaryotes localize some RNAs for the same purpose. To explore whether bacteria also spatially regulate RNAs, the localization of tmRNA was determined using fluorescence in situ hybridization. tmRNA is a small regulatory RNA that is ubiquitous in bacteria and that interacts with translating ribosomes in a reaction known as trans-translation. In Caulobacter crescentus, tmRNA was localized in a cell-cycle-dependent manner. In G(1)-phase cells, tmRNA was found in regularly spaced foci indicative of a helix-like structure. After initiation of DNA replication, most of the tmRNA was degraded, and the remaining molecules were spread throughout the cytoplasm. Immunofluorescence assays showed that SmpB, a protein that binds tightly to tmRNA, was colocalized with tmRNA in the helix-like pattern. RNase R, the nuclease that degrades tmRNA, was localized in a helix-like pattern that was separate from the SmpB-tmRNA complex. These results suggest a model in which tmRNA-SmpB is localized to sequester tmRNA from RNase R, and localization might also regulate tmRNA-SmpB interactions with ribosomes.
Collapse
Affiliation(s)
- Jay H. Russell
- The Pennsylvania State University, Department of Biochemistry and Molecular Biology, 401 Althouse Lab, University Park, PA 16802
| | - Kenneth C. Keiler
- The Pennsylvania State University, Department of Biochemistry and Molecular Biology, 401 Althouse Lab, University Park, PA 16802
| |
Collapse
|
17
|
Spatiotemporal patterns and transcription kinetics of induced RNA in single bacterial cells. Proc Natl Acad Sci U S A 2009; 106:16399-404. [PMID: 19805311 DOI: 10.1073/pnas.0907495106] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Bacteria have a complex internal organization with specific localization of many proteins and DNA, which dynamically move during the cell cycle and in response to changing environmental stimuli. Much less is known, however, about the localization and movements of RNA molecules. By modifying our previous RNA labeling system, we monitor the expression and localization of a model RNA transcript in live Escherichia coli cells. Our results reveal that the target RNA is not evenly distributed within the cell and localizes laterally along the long cell axis, in a pattern suggesting the existence of ordered helical RNA structures reminiscent of known bacterial cytoskeletal cellular elements.
Collapse
|
18
|
Woo JS, Lim JH, Shin HC, Suh MK, Ku B, Lee KH, Joo K, Robinson H, Lee J, Park SY, Ha NC, Oh BH. Structural studies of a bacterial condensin complex reveal ATP-dependent disruption of intersubunit interactions. Cell 2009; 136:85-96. [PMID: 19135891 DOI: 10.1016/j.cell.2008.10.050] [Citation(s) in RCA: 121] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2008] [Revised: 07/31/2008] [Accepted: 10/28/2008] [Indexed: 12/27/2022]
Abstract
Condensins are key mediators of chromosome condensation across organisms. Like other condensins, the bacterial MukBEF condensin complex consists of an SMC family protein dimer containing two ATPase head domains, MukB, and two interacting subunits, MukE and MukF. We report complete structural views of the intersubunit interactions of this condensin along with ensuing studies that reveal a role for the ATPase activity of MukB. MukE and MukF together form an elongated dimeric frame, and MukF's C-terminal winged-helix domains (C-WHDs) bind MukB heads to constitute closed ring-like structures. Surprisingly, one of the two bound C-WHDs is forced to detach upon ATP-mediated engagement of MukB heads. This detachment reaction depends on the linker segment preceding the C-WHD, and mutations on the linker restrict cell growth. Thus ATP-dependent transient disruption of the MukB-MukF interaction, which creates openings in condensin ring structures, is likely to be a critical feature of the functional mechanism of condensins.
Collapse
Affiliation(s)
- Jae-Sung Woo
- Center for Biomolecular Recognition and Division of Molecular and Life Science, Department of Life Sciences, Pohang University of Science and Technology, Pohang, Kyungbuk, 790-784, Korea
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
19
|
Wu Y, Zhou A. In situ, real-time tracking of cell wall topography and nanomechanics of antimycobacterial drugs treated Mycobacterium JLS using atomic force microscopy. Chem Commun (Camb) 2009:7021-3. [DOI: 10.1039/b914605a] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
20
|
Cell-cell signaling and the Agrobacterium tumefaciens Ti plasmid copy number fluctuations. Plasmid 2008; 60:89-107. [PMID: 18664372 DOI: 10.1016/j.plasmid.2008.05.003] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2008] [Accepted: 05/15/2008] [Indexed: 11/20/2022]
Abstract
The Agrobacterium tumefaciens oncogenic Ti plasmids replicate and segregate to daughter cells via repABC cassettes, in which repA and repB are plasmid partitioning genes and repC encodes the replication initiator protein. repABC cassettes are encountered in a growing number of plasmids and chromosomes of the alpha-proteobacteria, and findings from particular representatives of agrobacteria, rhizobia and Paracoccus have began to shed light on their structure and functions. Amongst repABC replicons, Ti plasmids and particularly the octopine-type Ti have recently stood as model in regulation of repABC basal expression, which acts in plasmid copy number control, but also appear to undergo pronounced up-regulation of repABC, upon interbacterial and host-bacterial signaling. The last results in considerable Ti copy number increase and collective elevation of Ti gene expression. Inhibition of the Ti repABC is in turn conferred by a plant defense compound, which primarily affects Agrobacterium virulence and interferes with cell-density perception. Altogether, the above suggest that the entire Ti gene pool is subjected to the bacterium-eukaryote signaling network, a phenomenon quite unprecedented for replicons thought of as stringently controlled. It remains to be seen whether similar copy number variations characterize related replicons or if they are of even broader significance in plasmid biology.
Collapse
|
21
|
Scheu P, Sdorra S, Liao YF, Wegner M, Basché T, Unden G, Erker W. Polar accumulation of the metabolic sensory histidine kinases DcuS and CitA in Escherichia coli. Microbiology (Reading) 2008; 154:2463-2472. [DOI: 10.1099/mic.0.2008/018614-0] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Affiliation(s)
- Patrick Scheu
- Institute of Microbiology and Wine Research, Johannes Gutenberg University, Mainz, Becherweg 15, 55099 Mainz, Germany
| | - Sven Sdorra
- Institute of Physical Chemistry, Johannes Gutenberg University, Mainz, Welderweg 11, 55099 Mainz, Germany
| | - Yun-Feng Liao
- Institute of Physical Chemistry, Johannes Gutenberg University, Mainz, Welderweg 11, 55099 Mainz, Germany
| | - Maria Wegner
- Institute of Physical Chemistry, Johannes Gutenberg University, Mainz, Welderweg 11, 55099 Mainz, Germany
| | - Thomas Basché
- Institute of Physical Chemistry, Johannes Gutenberg University, Mainz, Welderweg 11, 55099 Mainz, Germany
| | - Gottfried Unden
- Institute of Microbiology and Wine Research, Johannes Gutenberg University, Mainz, Becherweg 15, 55099 Mainz, Germany
| | - Wolfgang Erker
- Institute of Physical Chemistry, Johannes Gutenberg University, Mainz, Welderweg 11, 55099 Mainz, Germany
| |
Collapse
|
22
|
Briegel A, Ding HJ, Li Z, Werner J, Gitai Z, Dias DP, Jensen RB, Jensen GJ. Location and architecture of the Caulobacter crescentus chemoreceptor array. Mol Microbiol 2008; 69:30-41. [PMID: 18363791 DOI: 10.1111/j.1365-2958.2008.06219.x] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A new method for recording both fluorescence and cryo-EM images of small bacterial cells was developed and used to identify chemoreceptor arrays in cryotomograms of intact Caulobacter crescentus cells. We show that in wild-type cells preserved in a near-native state, the chemoreceptors are hexagonally packed with a lattice spacing of 12 nm, just a few tens of nanometers away from the flagellar motor that they control. The arrays were always found on the convex side of the cell, further demonstrating that Caulobacter cells maintain dorsal/ventral as well as anterior/posterior asymmetry. Placing the known crystal structure of a trimer of receptor dimers at each vertex of the lattice accounts well for the density and agrees with other constraints. Based on this model for the arrangement of receptors, there are between one and two thousand receptors per array.
Collapse
Affiliation(s)
- Ariane Briegel
- Division of Biology, California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125, USA
| | | | | | | | | | | | | | | |
Collapse
|
23
|
Thanbichler M, Iniesta AA, Shapiro L. A comprehensive set of plasmids for vanillate- and xylose-inducible gene expression in Caulobacter crescentus. Nucleic Acids Res 2007; 35:e137. [PMID: 17959646 PMCID: PMC2175322 DOI: 10.1093/nar/gkm818] [Citation(s) in RCA: 236] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Caulobacter crescentus is widely used as a powerful model system for the study of prokaryotic cell biology and development. Analysis of this organism is complicated by a limited selection of tools for genetic manipulation and inducible gene expression. This study reports the identification and functional characterization of a vanillate-regulated promoter (Pvan) which meets all requirements for application as a multi-purpose expression system in Caulobacter, thus complementing the established xylose-inducible system (Pxyl). Furthermore, we introduce a newly constructed set of integrating and replicating shuttle vectors that considerably facilitate cell biological and physiological studies in Caulobacter. Based on different narrow and broad-host range replicons, they offer a wide choice of promoters, resistance genes, and fusion partners for the construction of fluorescently or affinity-tagged proteins. Since many of these constructs are also suitable for use in other bacteria, this work provides a comprehensive collection of tools that will enrich many areas of microbiological research.
Collapse
Affiliation(s)
- Martin Thanbichler
- Max Planck Institute for Terrestrial Microbiology, Karl-von-Frisch-Strasse, 35043 Marburg, Germany.
| | | | | |
Collapse
|
24
|
Abstract
Proper placement of the cell division site in some rod-shaped bacteria requires two different negative regulatory systems, nucleoid occlusion and the Min proteins. Caulobacter crescentus lacks these systems, but recent work has uncovered a novel regulator that achieves the same goals.
Collapse
|
25
|
Yao S, Helinski DR, Toukdarian A. Localization of the naturally occurring plasmid ColE1 at the cell pole. J Bacteriol 2006; 189:1946-53. [PMID: 17158664 PMCID: PMC1855736 DOI: 10.1128/jb.01451-06] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The naturally occurring plasmid ColE1 was found to localize as a cluster in one or both of the cell poles of Escherichia coli. In addition to the polar localization of ColE1 in most cells, movement of the plasmid to the midcell position was observed in time-lapse studies. ColE1 could be displaced from its polar location by the p15A replicon, pBAD33, but not by plasmid RK2. The displacement of ColE1 by pBAD33 resulted in an almost random positioning of ColE1 foci in the cell and also in a loss of segregational stability, as evidenced by the large number of cells carrying pBAD33 with no visible ColE1 focus and as confirmed by ColE1 stability studies. The addition of the active partitioning systems of the F plasmid (sopABC) or RK2 (O(B1) incC korB) resulted in movement of the ColE1 replicon from the cell pole to within the nucleoid region. This repositioning did not result in destabilization but did result in an increase in the number of plasmid foci, most likely due to partial declustering. These results are consistent with the importance of par regions to the localization of plasmids to specific regions of the cell and demonstrate both localization and dynamic movement for a naturally occurring plasmid that does not encode a replication initiation protein or a partitioning system that is required for plasmid stability.
Collapse
Affiliation(s)
- Shiyin Yao
- Division of Biological Sciences, University of California at San Diego, La Jolla, CA 92093-0322, USA
| | | | | |
Collapse
|
26
|
Konopka MC, Shkel IA, Cayley S, Record MT, Weisshaar JC. Crowding and confinement effects on protein diffusion in vivo. J Bacteriol 2006; 188:6115-23. [PMID: 16923878 PMCID: PMC1595386 DOI: 10.1128/jb.01982-05] [Citation(s) in RCA: 153] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The first in vivo measurements of a protein diffusion coefficient versus cytoplasmic biopolymer volume fraction are presented. Fluorescence recovery after photobleaching yields the effective diffusion coefficient on a 1-mum-length scale of green fluorescent protein within the cytoplasm of Escherichia coli grown in rich medium. Resuspension into hyperosmotic buffer lacking K+ and nutrients extracts cytoplasmic water, systematically increasing mean biopolymer volume fraction, <phi>, and thus the severity of possible crowding, binding, and confinement effects. For resuspension in isosmotic buffer (osmotic upshift, or Delta, of 0), the mean diffusion coefficient, <D>, in cytoplasm (6.1 +/- 2.4 microm2 s(-1)) is only 0.07 of the in vitro value (87 microm2 s(-1)); the relative dispersion among cells, sigmaD/<D> (standard deviation, sigma(D), relative to the mean), is 0.39. Both <D> and sigmaD/<D> remain remarkably constant over the range of Delta values of 0 to 0.28 osmolal. For a Delta value of > or =0.28 osmolal, formation of visible plasmolysis spaces (VPSs) coincides with the onset of a rapid decrease in <D> by a factor of 380 over the range of Delta values of 0.28 to 0.70 osmolal and a substantial increase in sigmaD/<D>. Individual values of D vary by a factor of 9 x 10(4) but correlate well with f(VPS), the fractional change in cytoplasmic volume on VPS formation. The analysis reveals two levels of dispersion in D among cells: moderate dispersion at low Delta values for cells lacking a VPS, perhaps related to variation in phi or biopolymer organization during the cell cycle, and stronger dispersion at high Delta values related to variation in f(VPS). Crowding effects alone cannot explain the data, nor do these data alone distinguish crowding from possible binding or confinement effects within a cytoplasmic meshwork.
Collapse
Affiliation(s)
- Michael C Konopka
- Department of Chemistry, University of Wisconsin-Madison, Madison, 1101 University Avenue, WI 53706, USA
| | | | | | | | | |
Collapse
|
27
|
Jensen RB. Coordination between chromosome replication, segregation, and cell division in Caulobacter crescentus. J Bacteriol 2006; 188:2244-53. [PMID: 16513754 PMCID: PMC1428140 DOI: 10.1128/jb.188.6.2244-2253.2006] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Progression through the Caulobacter crescentus cell cycle is coupled to a cellular differentiation program. The swarmer cell is replicationally quiescent, and DNA replication initiates at the swarmer-to-stalked cell transition. There is a very short delay between initiation of DNA replication and movement of one of the newly replicated origins to the opposite pole of the cell, indicating the absence of cohesion between the newly replicated origin-proximal parts of the Caulobacter chromosome. The terminus region of the chromosome becomes located at the invaginating septum in predivisional cells, and the completely replicated terminus regions stay associated with each other after chromosome replication is completed, disassociating very late in the cell cycle shortly before the final cell division event. Invagination of the cytoplasmic membrane occurs earlier than separation of the replicated terminus regions and formation of separate nucleoids, which results in trapping of a chromosome on either side of the cell division septum, indicating that there is not a nucleoid exclusion phenotype.
Collapse
Affiliation(s)
- Rasmus B Jensen
- Department of Life Sciences and Chemistry, Roskilde University, Universitetsvej 1, DK-4000 Roskilde, Denmark.
| |
Collapse
|
28
|
Wang SCE, West L, Shapiro L. The bifunctional FtsK protein mediates chromosome partitioning and cell division in Caulobacter. J Bacteriol 2006; 188:1497-508. [PMID: 16452433 PMCID: PMC1367234 DOI: 10.1128/jb.188.4.1497-1508.2006] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Bacterial chromosome partitioning and cell division are tightly connected cellular processes. We show here that the Caulobacter crescentus FtsK protein localizes to the division plane, where it mediates multiple functions involved in chromosome segregation and cytokinesis. The first 258 amino acids of the N terminus are necessary and sufficient for targeting the protein to the division plane. Furthermore, the FtsK N terminus is required to either assemble or maintain FtsZ rings at the division plane. The FtsK C terminus is essential in Caulobacter and is involved in maintaining accurate chromosome partitioning. In addition, the C-terminal region of FtsK is required for the localization of the topoisomerase IV ParC subunit to the replisome to facilitate chromosomal decatenation prior to cell division. These results suggest that the interdependence between chromosome partitioning and cell division in Caulobacter is mediated, in part, by the FtsK protein.
Collapse
Affiliation(s)
- Sherry C E Wang
- Department of Developmental Biology, Stanford University School of Medicine, Beckman Center, B300, 279 Campus Dr., Stanford, California 94304-5329, USA
| | | | | |
Collapse
|
29
|
Lawler ML, Larson DE, Hinz AJ, Klein D, Brun YV. Dissection of functional domains of the polar localization factor PodJ in Caulobacter crescentus. Mol Microbiol 2006; 59:301-16. [PMID: 16359336 DOI: 10.1111/j.1365-2958.2005.04935.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The polar organelle development protein, PodJ, is important for proper establishment of polarity in Caulobacter crescentus. podJ null mutants are unable to form holdfast or pili, have reduced swarming motility, and have difficulty ejecting the flagellum during the swarmer to stalked cell transition. In this study, we create a series of truncation mutants to investigate functional domains of PodJ. We show that PodJ has a transmembrane domain between amino acids 600 and 670. We identify a periplasmic region important for pili production and a cytoplasmic region required for holdfast formation and swarming motility, and establish that PleC localization is not required for holdfast formation and motility in soft agar. Analysis of the mutants reveals that the last 54 amino acids of the protein negatively regulate processing of the full-length form of the protein, PodJ(L), to a shorter form, PodJ(S). Finally, we identify a cytoplasmic region of PodJ involved in targeting it to the flagellar pole, and a periplasmic region required for localization of PleC.
Collapse
Affiliation(s)
- Melanie L Lawler
- Department of Biology, Indiana University, 1001 E. Third Street, Bloomington, IN 47405-7005, USA
| | | | | | | | | |
Collapse
|
30
|
Ranganath RM. Asymmetric cell divisions in flowering plants - one mother, "two-many" daughters. PLANT BIOLOGY (STUTTGART, GERMANY) 2005; 7:425-48. [PMID: 16163608 DOI: 10.1055/s-2005-865899] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Plant development shows a fascinating range of asymmetric cell divisions. Over the years, however, cellular differentiation has been interpreted mostly in terms of a mother cell dividing mitotically to produce two daughter cells of different fates. This popular view has masked the significance of an entirely different cell fate specification pathway, where the mother cell first becomes a coenocyte and then cellularizes to simultaneously produce more than two specialized daughter cells. The "one mother - two different daughters" pathways rely on spindle-assisted mechanisms, such as translocation of the nucleus/spindle to a specific cellular site and orientation of the spindle, which are coordinated with cell-specific allocation of cell fate determinants and cytokinesis. By contrast, during "coenocyte-cellularization" pathways, the spindle-assisted mechanisms are irrelevant since cell fate specification emerges only after the nuclear divisions are complete, and the number of specialized daughter cells produced depends on the developmental context. The key events, such as the formation of a coenocyte and migration of the nuclei to specific cellular locations, are coordinated with cellularization by unique types of cell wall formation. Both one mother - two different daughters and the coenocyte-cellularization pathways are used by higher plants in precise spatial and time windows during development. In both the pathways, epigenetic regulation of gene expression is crucial not only for cell fate specification but also for its maintenance through cell lineage. In this review, the focus is on the coenocyte-cellularization pathways in the context of our current understanding of the asymmetric cell divisions. Instances where cell differentiation does not involve an asymmetric division are also discussed to provide a comprehensive account of cell differentiation.
Collapse
Affiliation(s)
- R M Ranganath
- Cytogenetics and Developmental Biology Laboratory, Department of Botany, Bangalore University, India.
| |
Collapse
|
31
|
Sciochetti SA, Ohta N, Newton A. The role of polar localization in the function of an essential Caulobacter crescentus tyrosine kinase. Mol Microbiol 2005; 56:1467-80. [PMID: 15916599 DOI: 10.1111/j.1365-2958.2005.04652.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
DivL is an essential tyrosine kinase in Caulobacter crescentus that controls an early step in the cell division cycle. We show here that DivL dynamically localizes to the stalk-distal cell pole and less frequently to the stalked cell pole during the S-phase. The kinase is subsequently released from the cell poles late in division and remains dispersed in the newly divided progeny stalk and swarmer cells. Mutational analysis of DivL in a DivL-GFP fusion protein demonstrated that the extreme C-terminus and residues in the conserved four-helix bundle, which is the phosphorylation-dimerization domain, are important for localization. We speculate that the four-helix bundle of the core catalytic domain may serve as a recognition site for the "localization machinery". Unexpectedly, a DivL protein with mutations in the C-terminal localization sequence, and an intact catalytic domain, efficiently complemented a divL null mutation. Thus, subcellular localization of DivL is not essential to its function in cell division regulation. Regulation of cell division by DivL does, however, depend on its localization in the cell membrane.
Collapse
|
32
|
Abstract
Despite decades of study, the exquisite temporal and spatial organization of bacterial chromosomes has only recently been appreciated. The direct visualization of specific chromosomal loci has revealed that bacteria condense, move and position their chromosomes in a reproducible fashion. The realization that bacterial chromosomes are actively translocated through the cell suggests the existence of specific mechanisms that direct this process. Here, we review bacterial chromosome dynamics and our understanding of the mechanisms that direct and coordinate them.
Collapse
Affiliation(s)
- Zemer Gitai
- Department of Developmental Biology, Beckman Center, School of Medicine, Stanford University, Stanford, CA 94305, USA.
| | | | | |
Collapse
|
33
|
Abstract
Recent advances have demonstrated that bacterial cells have an exquisitely organized and dynamic subcellular architecture. Like their eukaryotic counterparts, bacteria employ a full complement of cytoskeletal proteins, localize proteins and DNA to specific subcellular addresses at specific times, and use intercellular signaling to coordinate multicellular events. The striking conceptual and molecular similarities between prokaryotic and eukaryotic cell biology thus make bacteria powerful model systems for studying fundamental cellular questions.
Collapse
Affiliation(s)
- Zemer Gitai
- Department of Developmental Biology, Beckman Center, School of Medicine, Stanford University, Stanford, CA 94305, USA.
| |
Collapse
|
34
|
Abstract
The actin cytoskeleton is important for cell polarity and morphogenesis in eukaryotic organisms. A recent article describes an unexpected requirement for the actin-like protein MreB in the polarization of the bacterium Caulobacter crescentus. More surprisingly, the formation of a filamentous MreB structure that traverses the length of the cell is sufficient for randomized polar localization of cell-fate proteins. In this article, we discuss the significance of these findings and the possible mechanisms by which an actin-like cytoskeleton could mediate cell polarity in bacteria.
Collapse
Affiliation(s)
- Rong Li
- Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA.
| | | |
Collapse
|
35
|
Ben-Yehuda S, Fujita M, Liu XS, Gorbatyuk B, Skoko D, Yan J, Marko JF, Liu JS, Eichenberger P, Rudner DZ, Losick R. Defining a Centromere-like Element in Bacillus subtilis by Identifying the Binding Sites for the Chromosome-Anchoring Protein RacA. Mol Cell 2005; 17:773-82. [PMID: 15780934 DOI: 10.1016/j.molcel.2005.02.023] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2004] [Revised: 01/16/2005] [Accepted: 02/16/2005] [Indexed: 10/25/2022]
Abstract
Chromosome segregation during sporulation in Bacillus subtilis involves the anchoring of sister chromosomes to opposite ends of the cell. Anchoring is mediated by RacA, which acts as a bridge between a centromere-like element in the vicinity of the origin of replication and the cell pole. To define this element we mapped RacA binding sites by performing chromatin immunoprecipitation in conjunction with gene microarray analysis. RacA preferentially bound to 25 regions spread over 612 kb across the origin portion of the chromosome. Computational and biochemical analysis identified a GC-rich, inverted 14 bp repeat as the recognition sequence. Experiments with single molecules of DNA demonstrated that RacA can condense nonspecific DNA dramatically against appreciable forces to form a highly stable protein-DNA complex. We propose that interactions between DNA bound RacA molecules cause the centromere-like element to fold up into a higher order complex that fastens the chromosome to the cell pole.
Collapse
Affiliation(s)
- Sigal Ben-Yehuda
- Department of Molecular and Cellular Biology, Harvard University, 16 Divinity Avenue, Cambridge, Massachusetts 02138, USA
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
36
|
Abstract
Whereas most prokaryotes rely on binary fission for propagation, many species use alternative mechanisms, which include multiple offspring formation and budding, to reproduce. In some bacterial species, these eccentric reproductive strategies are essential for propagation, whereas in others the programmes are used conditionally. Although there are tantalizing images and morphological descriptions of these atypical developmental processes, none of these reproductive structures are characterized at the molecular genetic level. Now, with newly available analytical techniques, model systems to study these alternative reproductive programmes are being developed.
Collapse
Affiliation(s)
- Esther R Angert
- Department of Microbiology, Cornell University, 260A Wing Hall, Ithaca, New York 14853-5701, USA.
| |
Collapse
|
37
|
Gitai Z, Dye NA, Reisenauer A, Wachi M, Shapiro L. MreB Actin-Mediated Segregation of a Specific Region of a Bacterial Chromosome. Cell 2005; 120:329-41. [PMID: 15707892 DOI: 10.1016/j.cell.2005.01.007] [Citation(s) in RCA: 282] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2004] [Revised: 12/22/2004] [Accepted: 01/06/2005] [Indexed: 10/25/2022]
Abstract
Faithful chromosome segregation is an essential component of cell division in all organisms. The eukaryotic mitotic machinery uses the cytoskeleton to move specific chromosomal regions. To investigate the potential role of the actin-like MreB protein in bacterial chromosome segregation, we first demonstrate that MreB is the direct target of the small molecule A22. We then demonstrate that A22 completely blocks the movement of newly replicated loci near the origin of replication but has no qualitative or quantitative effect on the segregation of other loci if added after origin segregation. MreB selectively interacts, directly or indirectly, with origin-proximal regions of the chromosome, arguing that the origin-proximal region segregates via an MreB-dependent mechanism not used by the rest of the chromosome.
Collapse
Affiliation(s)
- Zemer Gitai
- Department of Developmental Biology, Beckman Center, School of Medicine, Stanford University, California 94305, USA.
| | | | | | | | | |
Collapse
|
38
|
Abstract
Cell cycle progression in Caulobacter is governed by a multilayered regulatory network linking chromosome replication with polar morphogenesis and cell division. Temporal and spatial regulation have emerged as the central themes, with the abundance, activity and subcellular location of key structural and regulatory proteins changing over the course of the cell cycle. An additional layer of complexity was recently uncovered, showing that each segment of the chromosome is located at a specific cellular position both during and after the completion of DNA replication, raising the possibility that this positioning contributes to temporal and spatial control of gene expression.
Collapse
Affiliation(s)
- Patrick H Viollier
- Department of Molecular Biology and Microbiology, Case Western Reserve University School of Medicine, 10900 Euclid Avenue, Cleveland, Ohio 44106, USA.
| | | |
Collapse
|
39
|
Entcheva-Dimitrov P, Spormann AM. Dynamics and control of biofilms of the oligotrophic bacterium Caulobacter crescentus. J Bacteriol 2005; 186:8254-66. [PMID: 15576774 PMCID: PMC532430 DOI: 10.1128/jb.186.24.8254-8266.2004] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Caulobacter crescentus is an oligotrophic alpha-proteobacterium with a complex cell cycle involving sessile-stalked and piliated, flagellated swarmer cells. Because the natural lifestyle of C. crescentus intrinsically involves a surface-associated, sessile state, we investigated the dynamics and control of C. crescentus biofilms developing on glass surfaces in a hydrodynamic system. In contrast to biofilms of the well-studied Pseudomonas aeruginosa, Escherichia coli, and Vibrio cholerae, C. crescentus CB15 cells form biphasic biofilms, consisting predominantly of a cell monolayer biofilm and a biofilm containing densely packed, mushroom-shaped structures. Based on comparisons between the C. crescentus strain CB15 wild type and its holdfast (hfsA; DeltaCC0095), pili (DeltapilA-cpaF::Omegaaac3), motility (motA), flagellum (flgH) mutants, and a double mutant lacking holdfast and flagellum (hfsA; flgH), a model for biofilm formation in C. crescentus is proposed. For both biofilm forms, the holdfast structure at the tip of a stalked cell is crucial for mediating the initial attachment. Swimming motility by means of the single polar flagellum enhances initial attachment and enables progeny swarmer cells to escape from the monolayer biofilm. The flagellum structure also contributes to maintaining the mushroom structure. Type IV pili enhance but are not absolutely required for the initial adhesion phase. However, pili are essential for forming and maintaining the well-defined three-dimensional mushroom-shaped biofilm. The involvement of pili in mushroom architecture is a novel function for type IV pili in C. crescentus. These unique biofilm features demonstrate a spatial diversification of the C. crescentus population into a sessile, "stem cell"-like subpopulation (monolayer biofilm), which generates progeny cells capable of exploring the aqueous, oligotrophic environment by swimming motility and a subpopulation accumulating in large mushroom structures.
Collapse
|
40
|
Deich J, Judd EM, McAdams HH, Moerner WE. Visualization of the movement of single histidine kinase molecules in live Caulobacter cells. Proc Natl Acad Sci U S A 2004; 101:15921-6. [PMID: 15522969 PMCID: PMC528753 DOI: 10.1073/pnas.0404200101] [Citation(s) in RCA: 105] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2004] [Indexed: 01/26/2023] Open
Abstract
The bacterium Caulobacter crescentus divides asymmetrically as part of its normal life cycle. This asymmetry is regulated in part by the membrane-bound histidine kinase PleC, which localizes to one pole of the cell at specific times in the cell cycle. Here, we track single copies of PleC labeled with enhanced yellow fluorescent protein (EYFP) in the membrane of live Caulobacter cells over a time scale of seconds. In addition to the expected molecules immobilized at one cell pole, we observed molecules moving throughout the cell membrane. By tracking the positions of these molecules for several seconds, we determined a diffusion coefficient (D) of 12 +/- 2 x 10(-3) microm(2)/s for the mobile copies of PleC not bound at the cell pole. This D value is maintained across all cell cycle stages. We observe a reduced D at poles containing localized PleC-EYFP; otherwise D is independent of the position of the diffusing molecule within the bacterium. We did not detect any directional bias in the motion of the PleC-EYFP molecules, implying that the molecules are not being actively transported.
Collapse
Affiliation(s)
- J Deich
- Department of Chemistry, Stanford University, Stanford, CA 94305, USA
| | | | | | | |
Collapse
|
41
|
McGrath PT, Viollier P, McAdams HH. Setting the pace: mechanisms tying Caulobacter cell-cycle progression to macroscopic cellular events. Curr Opin Microbiol 2004; 7:192-7. [PMID: 15063858 DOI: 10.1016/j.mib.2004.02.012] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The bacterium Caulobacter crescentus divides asymmetrically, producing daughter cells with differing polar structures, different cell fates and asymmetric regulation of the initiation of chromosome replication. Complex intracellular signaling is required to keep the organelle developmental processes at the cell poles synchronized with other cell cycle events. Two recently characterized switch mechanisms controlling cell cycle progress are triggered by relatively large-scale developmental events in the cell: the progress of the DNA replication fork and the physical compartmentalization of the cell that occurs well before division. These mechanisms invoke rapid, precisely timed and even spatially differentiated regulatory responses at important points in the cell cycle.
Collapse
Affiliation(s)
- Patrick T McGrath
- Department of Developmental Biology, Stanford University School of Medicine, B300 Beckman Center, Stanford, CA 94305, USA
| | | | | |
Collapse
|
42
|
Wang SC, Shapiro L. The topoisomerase IV ParC subunit colocalizes with the Caulobacter replisome and is required for polar localization of replication origins. Proc Natl Acad Sci U S A 2004; 101:9251-6. [PMID: 15178756 PMCID: PMC438962 DOI: 10.1073/pnas.0402567101] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The process of bacterial DNA replication generates chromosomal topological constraints that are further confounded by simultaneous transcription. Topoisomerases play a key role in ensuring orderly replication and partition of DNA in the face of a continuously changing DNA tertiary structure. In addition to topological constraints, the cellular position of the replication origin is strictly controlled during the cell cycle. In Caulobacter crescentus, the origin of DNA replication is located at the cell pole. Upon initiation of DNA replication, one copy of the duplicated origin sequence rapidly appears at the opposite cell pole. To determine whether the maintenance of DNA topology contributes to the dynamic positioning of a specific DNA region within the cell, we examined origin localization in cells that express temperature-sensitive forms of either the ParC or ParE subunit of topoisomerase (Topo) IV. We found that in the absence of active Topo IV, replication initiation can occur but a significant percent of replication origins are either no longer moved to or maintained at the cell poles. During the replication process, the ParC subunit colocalizes with the replisome, whereas the ParE subunit is dispersed throughout the cell. However, an active ParE subunit is required for ParC localization to the replisome as it moves from the cell pole to the division plane during chromosome replication. We propose that the maintenance of DNA topology throughout the cell cycle contributes to the dynamic positioning of the origin sequence within the cell.
Collapse
Affiliation(s)
- Sherry C Wang
- Department of Developmental Biology, and Cancer Biology Program, Stanford University School of Medicine, Beckman Center B300, 279 Campus Drive, Stanford, CA 94305, USA
| | | |
Collapse
|
43
|
Viollier PH, Thanbichler M, McGrath PT, West L, Meewan M, McAdams HH, Shapiro L. Rapid and sequential movement of individual chromosomal loci to specific subcellular locations during bacterial DNA replication. Proc Natl Acad Sci U S A 2004; 101:9257-62. [PMID: 15178755 PMCID: PMC438963 DOI: 10.1073/pnas.0402606101] [Citation(s) in RCA: 325] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The chromosomal origin and terminus of replication are precisely localized in bacterial cells. We examined the cellular position of 112 individual loci that are dispersed over the circular Caulobacter crescentus chromosome and found that in living cells each locus has a specific subcellular address and that these loci are arrayed in linear order along the long axis of the cell. Time-lapse microscopy of the location of the chromosomal origin and 10 selected loci in the origin-proximal half of the chromosome showed that during DNA replication, as the replisome sequentially copies each locus, the newly replicated DNA segments are moved in chronological order to their final subcellular destination in the nascent half of the predivisional cell. Thus, the remarkable organization of the chromosome is being established while DNA replication is still in progress. The fact that the movement of these 10 loci is, like that of the origin, directed and rapid, and occurs at a similar rate, suggests that the same molecular machinery serves to partition and place many, if not most, chromosomal loci at defined subcellular sites.
Collapse
Affiliation(s)
- Patrick H Viollier
- Department of Developmental Biology, Beckman Center, Stanford University School of Medicine, Stanford, CA 94305, USA
| | | | | | | | | | | | | |
Collapse
|
44
|
Gitai Z, Dye N, Shapiro L. An actin-like gene can determine cell polarity in bacteria. Proc Natl Acad Sci U S A 2004; 101:8643-8. [PMID: 15159537 PMCID: PMC423248 DOI: 10.1073/pnas.0402638101] [Citation(s) in RCA: 246] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Achieving proper polarity is essential for cellular function. In bacteria, cell polarity has been observed by using both morphological and molecular markers; however, no general regulators of bacterial cell polarity have been identified. Here we investigate the effect on cell polarity of two cytoskeletal elements previously implicated in cell shape determination. We find that the actin-like MreB protein mediates global cell polarity in Caulobacter crescentus, although the intermediate filament-like CreS protein influences cell shape without affecting cell polarity. MreB is organized in an axial spiral that is dynamically rearranged during the cell cycle, and MreB dynamics may be critical for the determination of cell polarity. By examining depletion and overexpression strains, we demonstrate that MreB is required both for the polar localization of the chromosomal origin sequence and the dynamic localization of regulatory proteins to the correct cell pole. We propose that the molecular polarity inherent in an actin-like filament is translated into a mechanism for directing global cell polarity.
Collapse
Affiliation(s)
- Zemer Gitai
- Department of Developmental Biology, Stanford University, Stanford, CA 94305, USA
| | | | | |
Collapse
|
45
|
Holtzendorff J, Hung D, Brende P, Reisenauer A, Viollier PH, McAdams HH, Shapiro L. Oscillating global regulators control the genetic circuit driving a bacterial cell cycle. Science 2004; 304:983-7. [PMID: 15087506 DOI: 10.1126/science.1095191] [Citation(s) in RCA: 168] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
A newly identified cell-cycle master regulator protein, GcrA, together with the CtrA master regulator, are key components of a genetic circuit that drives cell-cycle progression and asymmetric polar morphogenesis in Caulobacter crescentus. The circuit drives out-of-phase temporal and spatial oscillation of GcrA and CtrA concentrations, producing time- and space-dependent transcriptional regulation of modular functions that implement cell-cycle processes. The CtrA/GcrA regulatory circuit controls expression of polar differentiation factors and the timing of DNA replication. CtrA functions as a silencer of the replication origin and GcrA as an activator of components of the replisome and the segregation machinery.
Collapse
Affiliation(s)
- Julia Holtzendorff
- Department of Developmental Biology, School of Medicine, Beckman Center, Stanford University, Stanford, CA 94305, USA
| | | | | | | | | | | | | |
Collapse
|
46
|
Abstract
It is now clear that bacterial chromosomes rapidly separate in a manner independent of cell elongation, suggesting the existence of a mitotic apparatus in bacteria. Recent studies of bacterial cells reveal filamentous structures similar to the eukaryotic cytoskeleton, proteins that mediate polar chromosome anchoring during Bacillus subtilis sporulation, and SMC interacting proteins that are involved in chromosome condensation. A picture is thereby developing of how bacterial chromosomes are organized within the cell, how they are separated following duplication, and how these processes are coordinated with the cell cycle.
Collapse
Affiliation(s)
- Kit Pogliano
- Division of Biological Sciences, 9500 Gilman Drive, University of California-San Diego, La Jolla, CA 92093-0349, USA.
| | | | | |
Collapse
|
47
|
Frenkiel-Krispin D, Ben-Avraham I, Englander J, Shimoni E, Wolf SG, Minsky A. Nucleoid restructuring in stationary-state bacteria. Mol Microbiol 2004; 51:395-405. [PMID: 14756781 DOI: 10.1046/j.1365-2958.2003.03855.x] [Citation(s) in RCA: 107] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The textbook view of the bacterial cytoplasm as an unstructured environment has been overturned recently by studies that highlighted the extent to which non-random organization and coherent motion of intracellular components are central for bacterial life-sustaining activities. Because such a dynamic order critically depends on continuous consumption of energy, it cannot be perpetuated in starved, and hence energy-depleted, stationary-state bacteria. Here, we show that, at the onset of the stationary state, bacterial chromatin undergoes a massive reorganization into ordered toroidal structures through a process that is dictated by the intrinsic properties of DNA and by the ubiquitous starvation-induced DNA-binding protein Dps. As starvation proceeds, the toroidal morphology acts as a structural template that promotes the formation of DNA-Dps crystalline assemblies through epitaxial growth. Within the resulting condensed assemblies, DNA is effectively protected by means of structural sequestration. We thus conclude that the transition from bacterial active growth to stationary phase entails a co-ordinated process, in which the energy-dependent dynamic order of the chromatin is sequentially substituted with an equilibrium crystalline order.
Collapse
|
48
|
Ausmees N, Jacobs-Wagner C. Spatial and temporal control of differentiation and cell cycle progression in Caulobacter crescentus. Annu Rev Microbiol 2004; 57:225-47. [PMID: 14527278 DOI: 10.1146/annurev.micro.57.030502.091006] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The dimorphic and intrinsically asymmetric bacterium Caulobacter crescentus has become an important model organism to study the bacterial cell cycle, cell polarity, and polar differentiation. A multifaceted regulatory network orchestrates the precise coordination between the development of polar organelles and the cell cycle. One master response regulator, CtrA, directly controls the initiation of chromosome replication as well as several aspects of polar morphogenesis and cell division. CtrA activity is temporally and spatially regulated by multiple partially redundant control mechanisms, such as transcription, phosphorylation, and targeted proteolysis. A multicomponent signal transduction network upstream CtrA, containing histidine kinases CckA, PleC, DivJ, and DivL and the essential response regulator DivK, contributes to the control of CtrA activity in response to cell cycle and developmental cues. An intriguing feature of this signaling network is the dynamic cell cycle-dependent polar localization of its components, which is believed to have a novel regulatory function.
Collapse
Affiliation(s)
- Nora Ausmees
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, Connecticut 06520-8103, USA.
| | | |
Collapse
|
49
|
Abstract
Here, we review recent progress that yields fundamental new insight into the molecular mechanisms behind plasmid and chromosome segregation in prokaryotic cells. In particular, we describe how prokaryotic actin homologs form mitotic machineries that segregate DNA before cell division. Thus, the ParM protein of plasmid R1 forms F actin-like filaments that separate and move plasmid DNA from mid-cell to the cell poles. Evidence from three different laboratories indicate that the morphogenetic MreB protein may be involved in segregation of the bacterial chromosome.
Collapse
Affiliation(s)
- Kenn Gerdes
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Odense, DK-5230 Odense M, Denmark.
| | | | | | | | | |
Collapse
|
50
|
Viollier PH, Shapiro L. A lytic transglycosylase homologue, PleA, is required for the assembly of pili and the flagellum at the Caulobacter crescentus cell pole. Mol Microbiol 2003; 49:331-45. [PMID: 12828633 DOI: 10.1046/j.1365-2958.2003.03576.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Two distinct protein complexes, the flagellum and the pilus biogenesis machinery, are asymmetrically assembled at one pole of the Caulobacter predivisional cell. Cell division yields dissimilar daughter cells: a stalked cell and a swarmer cell that assembles several pili at the flagellated cell pole. Strains bearing mutations in the pleA gene are pililess and non-flagellated. The PleA protein contains a region that is similar to a peptidoglycan-hydrolytic active site, and a point mutation at this site in PleA results in the loss of flagellum and pili biogenesis. PleA was found to be required for the insertion of the outer membrane pilus secretion channel at the cell pole and for the accumulation of the PilA pilin subunit. PleA is also required for the assembly of substructures of the flagellar basal body hook complex that are located in or traverse the peptidoglycan layer. These results argue that PleA facilitates the assembly of envelope-spanning structures at the cell pole. In support of this, PleA was found to be present only during a short interval in the cell cycle that coincides with the assembly of the flagellum and the pilus secretion apparatus.
Collapse
Affiliation(s)
- Patrick H Viollier
- Department of Developmental Biology, Stanford University School of Medicine, Beckman Center, B343, 279 Campus Drive, Stanford, CA 94305, USA.
| | | |
Collapse
|