1
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Köhler R, Kaganovitch E, Murray SM. High-throughput imaging and quantitative analysis uncovers the nature of plasmid positioning by ParABS. eLife 2022; 11:78743. [PMID: 36374535 PMCID: PMC9662831 DOI: 10.7554/elife.78743] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2022] [Accepted: 10/23/2022] [Indexed: 11/16/2022] Open
Abstract
The faithful segregation and inheritance of bacterial chromosomes and low-copy number plasmids requires dedicated partitioning systems. The most common of these, ParABS, consists of ParA, a DNA-binding ATPase and ParB, a protein that binds to centromeric-like parS sequences on the DNA cargo. The resulting nucleoprotein complexes are believed to move up a self-generated gradient of nucleoid-associated ParA. However, it remains unclear how this leads to the observed cargo positioning and dynamics. In particular, the evaluation of models of plasmid positioning has been hindered by the lack of quantitative measurements of plasmid dynamics. Here, we use high-throughput imaging, analysis and modelling to determine the dynamical nature of these systems. We find that F plasmid is actively brought to specific subcellular home positions within the cell with dynamics akin to an over-damped spring. We develop a unified stochastic model that quantitatively explains this behaviour and predicts that cells with the lowest plasmid concentration transition to oscillatory dynamics. We confirm this prediction for F plasmid as well as a distantly-related ParABS system. Our results indicate that ParABS regularly positions plasmids across the nucleoid but operates just below the threshold of an oscillatory instability, which according to our model, minimises ATP consumption. Our work also clarifies how various plasmid dynamics are achievable in a single unified stochastic model. Overall, this work uncovers the dynamical nature of plasmid positioning by ParABS and provides insights relevant for chromosome-based systems.
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Affiliation(s)
- Robin Köhler
- Max Planck Institute for Terrestrial Microbiology and LOEWE Centre for Synthetic Microbiology (SYNMIKRO), Marburg, Germany
| | - Eugen Kaganovitch
- Max Planck Institute for Terrestrial Microbiology and LOEWE Centre for Synthetic Microbiology (SYNMIKRO), Marburg, Germany
| | - Seán M Murray
- Max Planck Institute for Terrestrial Microbiology and LOEWE Centre for Synthetic Microbiology (SYNMIKRO), Marburg, Germany
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2
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Mancini L, Crozat E, Javer A, Lagomarsino MC, Cicuta P. Dynamics of Bacterial Chromosomes by Locus Tracking in Fluorescence Microscopy. Methods Mol Biol 2022; 2476:155-170. [PMID: 35635703 DOI: 10.1007/978-1-0716-2221-6_12] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
In the last two decades, it has been shown that bacterial chromosomes have remarkable spatial organization at various scales, and they display well-defined movements during the cell cycle, for example to reliably segregate daughter chromosomes. More recently, various labs have begun investigating also the short time dynamics (displacements during time intervals of 0.1 s-100 s), which should be related to the molecular structure. Probing these dynamics is analogous to "microrheology" approaches that have been applied successfully to study mechanical response of complex fluids. These studies of chromosome fluctuation dynamics have revealed differences of fluctuation amplitude across the chromosome, and different characters of motion depending on the time window of interest. Different fluctuation amplitudes have also been observed for the same chromosomal loci under antibiotic treatments, with magnitudes that are correlated to changes in intracellular density and thus crowding. We describe how to carry out tracking experiments of single loci and how to analyze locus motility. We point out the importance of considering in the analysis the number of GFP molecules per fluorescent locus, as well as the nature of the protein they are fused to, and also how to measure intracellular density.
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Affiliation(s)
- Leonardo Mancini
- Department of Physics, Cavendish Laboratory, University of Cambridge, Cambridge, UK
| | - Estelle Crozat
- Centre de Biologie Intégrative de Toulouse, Laboratoire de Microbiologie et de Génétique Moléculaires, Université de Toulouse, CNRS, UPS, Toulouse, France
- Department of Physics, Cavendish Laboratory, University of Cambridge, Cambridge, UK
| | - Avelino Javer
- Institute of Biomedical Engineering, Department of Engineering Science, University of Oxford, Oxford, UK
- Department of Physics, Cavendish Laboratory, University of Cambridge, Cambridge, UK
| | - Marco Cosentino Lagomarsino
- IFOM, FIRC Institute of Molecular Oncology, Milan, Italy
- Physics Department, University of Milan, and INFN, Milan, Italy
| | - Pietro Cicuta
- Department of Physics, Cavendish Laboratory, University of Cambridge, Cambridge, UK.
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3
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Polson JM, Zhu Q. Free energy and segregation dynamics of two channel-confined polymers of different lengths. Phys Rev E 2021; 103:012501. [PMID: 33601524 DOI: 10.1103/physreve.103.012501] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2020] [Accepted: 01/04/2021] [Indexed: 12/14/2022]
Abstract
Polymers confined to a narrow channel are subject to strong entropic forces that tend to drive the molecules apart. In this study, we use Monte Carlo computer simulations to study the segregation behavior of two flexible hard-sphere polymers under confinement in a cylindrical channel. We focus on the effects of using polymers of different lengths. We measure the variation of the conformational free energy, F, with the center-of-mass separation distance, λ. The simulations reveal four different separation regimes, characterized by different scaling properties of the free energy with respect to the polymer lengths and the channel diameter, D. We propose a regime map in which the state of the system is determined by the values of the quantities N_{2}/N_{1} and λ/(N_{1}+N_{2})D^{-β}, where N_{1} and N_{2} are the polymer lengths, and where β≈0.64. The observed scaling behavior of F(λ) in each regime is in reasonable agreement with predictions using a simple theoretical model. In addition, we use MC dynamics simulations to study the segregation dynamics of initially overlapping polymers by measurement of the incremental mean first-passage time with respect to λ. For systems characterized by a wide range of λ in which a short polymer is nested within a longer one, the segregation dynamics are close to that expected for two noninteracting one-dimensional random walkers undergoing unbiased diffusion. When the free-energy gradient is large, segregation is rapid and characterized by out-of-equilibrium effects.
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Affiliation(s)
- James M Polson
- Department of Physics, University of Prince Edward Island, 550 University Avenue, Charlottetown, Prince Edward Island C1A 4P3, Canada
| | - Qinxin Zhu
- Department of Physics, University of Prince Edward Island, 550 University Avenue, Charlottetown, Prince Edward Island C1A 4P3, Canada
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4
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Post-replicative pairing of sister ter regions in Escherichia coli involves multiple activities of MatP. Nat Commun 2020; 11:3796. [PMID: 32732900 PMCID: PMC7394560 DOI: 10.1038/s41467-020-17606-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2019] [Accepted: 07/03/2020] [Indexed: 02/07/2023] Open
Abstract
The ter region of the bacterial chromosome, where replication terminates, is the last to be segregated before cell division in Escherichia coli. Delayed segregation is controlled by the MatP protein, which binds to specific sites (matS) within ter, and interacts with other proteins such as ZapB. Here, we investigate the role of MatP by combining short-time mobility analyses of the ter locus with biochemical approaches. We find that ter mobility is similar to that of a non ter locus, except when sister ter loci are paired after replication. This effect depends on MatP, the persistence of catenanes, and ZapB. We characterise MatP/DNA complexes and conclude that MatP binds DNA as a tetramer, but bridging matS sites in a DNA-rich environment remains infrequent. We propose that tetramerisation of MatP links matS sites with ZapB and/or with non-specific DNA to promote optimal pairing of sister ter regions until cell division. Protein, MatP, binds to and delays segregation of the ter region of the bacterial chromosome before cell division. Here, the authors show that MatP displays multiple activities to promote optimal pairing of sister ter regions until cell division.
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5
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Kisner JR, Kuwada NJ. Nucleoid-mediated positioning and transport in bacteria. Curr Genet 2019; 66:279-291. [PMID: 31691024 DOI: 10.1007/s00294-019-01041-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2019] [Revised: 10/21/2019] [Accepted: 10/23/2019] [Indexed: 12/28/2022]
Abstract
Precise management of the spatiotemporal position of subcellular components is critical to a number of essential processes in the bacterial cell. The bacterial nucleoid is a highly structured yet dynamic object that undergoes significant reorganization during the relatively short cell cycle, e.g. during gene expression, chromosome replication, and segregation. Although the nucleoid takes up a large fraction of the volume of the cell, the mobility of macromolecules within these dense regions is relatively high and recent results suggest that the nucleoid plays an integral role of dynamic localization in a host of seemingly disparate cellular processes. Here, we review a number of recent reports of nucleoid-mediated positioning and transport in the model bacteria Escherichia coli. These results viewed as a whole suggest that the dynamic, cellular-scale structure of the nucleoid may be a key driver of positioning and transport within the cell. This model of a global, default positioning and transport system may help resolve many unanswered questions about the mechanisms of partitioning and segregation in bacteria.
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Affiliation(s)
- Jessica R Kisner
- Department of Physics, Central Washington University, Ellensburg, WA, 98926, USA
| | - Nathan J Kuwada
- Department of Physics, Central Washington University, Ellensburg, WA, 98926, USA.
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6
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Hofmann A, Mäkelä J, Sherratt DJ, Heermann D, Murray SM. Self-organised segregation of bacterial chromosomal origins. eLife 2019; 8:e46564. [PMID: 31397672 PMCID: PMC6701925 DOI: 10.7554/elife.46564] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2019] [Accepted: 08/09/2019] [Indexed: 01/12/2023] Open
Abstract
The chromosomal replication origin region (ori) of characterised bacteria is dynamically positioned throughout the cell cycle. In slowly growing Escherichia coli, ori is maintained at mid-cell from birth until its replication, after which newly replicated sister oris move to opposite quarter positions. Here, we provide an explanation for ori positioning based on the self-organisation of the Structural Maintenance of Chromosomes complex, MukBEF, which forms dynamically positioned clusters on the chromosome. We propose that a non-trivial feedback between the self-organising gradient of MukBEF complexes and the oris leads to accurate ori positioning. We find excellent agreement with quantitative experimental measurements and confirm key predictions. Specifically, we show that oris exhibit biased motion towards MukBEF clusters, rather than mid-cell. Our findings suggest that MukBEF and oris act together as a self-organising system in chromosome organisation-segregation and introduces protein self-organisation as an important consideration for future studies of chromosome dynamics.
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Affiliation(s)
- Andreas Hofmann
- Institute for Theoretical PhysicsHeidelberg UniversityHeidelbergGermany
| | - Jarno Mäkelä
- Department of BiochemistryUniversity of OxfordOxfordUnited Kingdom
| | - David J Sherratt
- Department of BiochemistryUniversity of OxfordOxfordUnited Kingdom
| | - Dieter Heermann
- Institute for Theoretical PhysicsHeidelberg UniversityHeidelbergGermany
| | - Seán M Murray
- Max Planck Institute for Terrestrial Microbiology, LOEWE Centre for Synthetic Microbiology (SYNMIKRO)MarburgGermany
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7
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Wu F, Swain P, Kuijpers L, Zheng X, Felter K, Guurink M, Solari J, Jun S, Shimizu TS, Chaudhuri D, Mulder B, Dekker C. Cell Boundary Confinement Sets the Size and Position of the E. coli Chromosome. Curr Biol 2019; 29:2131-2144.e4. [PMID: 31155353 PMCID: PMC7050463 DOI: 10.1016/j.cub.2019.05.015] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2019] [Revised: 04/27/2019] [Accepted: 05/03/2019] [Indexed: 11/28/2022]
Abstract
Although the spatiotemporal structure of the genome is crucial to its biological function, many basic questions remain unanswered on the morphology and segregation of chromosomes. Here, we experimentally show in Escherichia coli that spatial confinement plays a dominant role in determining both the chromosome size and position. In non-dividing cells with lengths increased to 10 times normal, single chromosomes are observed to expand > 4-fold in size. Chromosomes show pronounced internal dynamics but exhibit a robust positioning where single nucleoids reside robustly at mid-cell, whereas two nucleoids self-organize at 1/4 and 3/4 positions. The cell-size-dependent expansion of the nucleoid is only modestly influenced by deletions of nucleoid-associated proteins, whereas osmotic manipulation experiments reveal a prominent role of molecular crowding. Molecular dynamics simulations with model chromosomes and crowders recapitulate the observed phenomena and highlight the role of entropic effects caused by confinement and molecular crowding in the spatial organization of the chromosome.
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Affiliation(s)
- Fabai Wu
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Van der Maasweg 9, 2629 HZ, Delft, the Netherlands; Division of Geological and Planetary Sciences, California Institute of Technology, 1200 E California Blvd, Pasadena, CA 91125, USA
| | - Pinaki Swain
- Indian Institute of Technology Hyderabad, Kandi, Sangareddy 502285, Telangana, India
| | - Louis Kuijpers
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Van der Maasweg 9, 2629 HZ, Delft, the Netherlands
| | - Xuan Zheng
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Van der Maasweg 9, 2629 HZ, Delft, the Netherlands
| | - Kevin Felter
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Van der Maasweg 9, 2629 HZ, Delft, the Netherlands
| | - Margot Guurink
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Van der Maasweg 9, 2629 HZ, Delft, the Netherlands
| | - Jacopo Solari
- Institute AMOLF, Science Park 104, 1098 XG, Amsterdam, the Netherlands
| | - Suckjoon Jun
- Department of Physics, University of California San Diego, 9500 Gilman Dr. La Jolla, CA 92093, USA; Section of Molecular Biology, Division of Biological Sciences, University of California San Diego, 9500 Gilman Dr. La Jolla, CA 92093, USA
| | - Thomas S Shimizu
- Institute AMOLF, Science Park 104, 1098 XG, Amsterdam, the Netherlands
| | - Debasish Chaudhuri
- Institute of Physics, Sachivalaya Marg, Bhubaneswar 751005, India; Homi Bhabha National Institute, Anushaktinagar, Mumbai 400094, India
| | - Bela Mulder
- Institute AMOLF, Science Park 104, 1098 XG, Amsterdam, the Netherlands; Laboratory of Cell Biology, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, the Netherlands.
| | - Cees Dekker
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Van der Maasweg 9, 2629 HZ, Delft, the Netherlands.
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8
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Swain P, Mulder BM, Chaudhuri D. Confinement and crowding control the morphology and dynamics of a model bacterial chromosome. SOFT MATTER 2019; 15:2677-2687. [PMID: 30830139 DOI: 10.1039/c8sm02092b] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Motivated by recent experiments probing the shape, size and dynamics of bacterial chromosomes in growing cells, we consider a polymer model consisting of a circular backbone to which side-loops are attached, confined to a cylindrical cell. Such a model chromosome spontaneously adopts a helical shape, which is further compacted by molecular crowders to occupy a nucleoid-like sub-volume of the cell. With increasing cell length, the longitudinal size of the chromosome increases in a non-linear fashion until finally saturating, its morphology gradually opening up while displaying a changing number of helical turns. For shorter cells, the chromosome extension varies non-monotonically with cell size, which we show is associated with a radial to longitudinal spatial reordering of the crowders. Confinement and crowders constrain chain dynamics leading to anomalous diffusion. While the scaling exponent for the mean squared displacement of center of mass grows and saturates with cell length, that of individual loci displays a broad distribution with a sharp maximum.
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Affiliation(s)
- Pinaki Swain
- Indian Institute of Technology Hyderabad, Kandi, Sangareddy 502285, Telangana, India
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9
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Inferring Active Noise Characteristics from the Paired Observations of Anomalous Diffusion. Polymers (Basel) 2018; 11:polym11010002. [PMID: 30959986 PMCID: PMC6401841 DOI: 10.3390/polym11010002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2018] [Revised: 12/17/2018] [Accepted: 12/17/2018] [Indexed: 11/24/2022] Open
Abstract
Anomalous diffusion has been most often argued in terms of a position fluctuation of a tracer. We here propose the other fluctuating observable, i.e., momentum transfer defined as the time integral of applied force to hold a tracer’s position. Being a conjugated variable, the momentum transfer is thought of as generating the anomalous diffusion paired with the position’s one. By putting together the paired anomalous diffusions, we aim to extract useful information in complex systems, which can be applied to experiments like tagged monomer observations in chromatin. The polymer being in the equilibrium, the mean square displacement (or variance) of position displacement or momentum transfer exhibits the sub- or superdiffusion, respectively, in which the sum of the anomalous diffusion indices is conserved quite generally, but the nonequilibrium media that generate the active noise may manifest the derivations from the equilibrium relation. We discuss the deviations that reflect the characteristics of the active noise.
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10
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Dewachter L, Verstraeten N, Fauvart M, Michiels J. An integrative view of cell cycle control in Escherichia coli. FEMS Microbiol Rev 2018; 42:116-136. [PMID: 29365084 DOI: 10.1093/femsre/fuy005] [Citation(s) in RCA: 46] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2017] [Accepted: 01/19/2018] [Indexed: 11/14/2022] Open
Abstract
Bacterial proliferation depends on the cells' capability to proceed through consecutive rounds of the cell cycle. The cell cycle consists of a series of events during which cells grow, copy their genome, partition the duplicated DNA into different cell halves and, ultimately, divide to produce two newly formed daughter cells. Cell cycle control is of the utmost importance to maintain the correct order of events and safeguard the integrity of the cell and its genomic information. This review covers insights into the regulation of individual key cell cycle events in Escherichia coli. The control of initiation of DNA replication, chromosome segregation and cell division is discussed. Furthermore, we highlight connections between these processes. Although detailed mechanistic insight into these connections is largely still emerging, it is clear that the different processes of the bacterial cell cycle are coordinated to one another. This careful coordination of events ensures that every daughter cell ends up with one complete and intact copy of the genome, which is vital for bacterial survival.
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Affiliation(s)
- Liselot Dewachter
- Centre of Microbial and Plant Genetics, KU Leuven-University of Leuven, B-3001 Leuven, Belgium.,VIB Center for Microbiology, B-3001 Leuven, Belgium
| | - Natalie Verstraeten
- Centre of Microbial and Plant Genetics, KU Leuven-University of Leuven, B-3001 Leuven, Belgium.,VIB Center for Microbiology, B-3001 Leuven, Belgium
| | - Maarten Fauvart
- Centre of Microbial and Plant Genetics, KU Leuven-University of Leuven, B-3001 Leuven, Belgium.,VIB Center for Microbiology, B-3001 Leuven, Belgium.,Department of Life Sciences and Imaging, Smart Electronics Unit, imec, B-3001 Leuven, Belgium
| | - Jan Michiels
- Centre of Microbial and Plant Genetics, KU Leuven-University of Leuven, B-3001 Leuven, Belgium.,VIB Center for Microbiology, B-3001 Leuven, Belgium
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11
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Polson JM, Kerry DRM. Segregation of polymers under cylindrical confinement: effects of polymer topology and crowding. SOFT MATTER 2018; 14:6360-6373. [PMID: 30028460 DOI: 10.1039/c8sm01062e] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Monte Carlo computer simulations are used to study the segregation behaviour of two polymers under cylindrical confinement. Using a multiple-histogram method, the conformational free energy, F, of the polymers was measured as a function of the centre-of-mass separation distance, λ. We examined the scaling of the free energy functions with the polymer length, the length and diameter of the confining cylinder, the polymer topology (i.e. linear vs. ring polymers), and the packing fraction and size of mobile crowding agents. In the absence of crowders, the observed scaling of F(λ) is similar to that predicted using a simple model employing the de Gennes blob model and the approximation that the free energy of overlapping chains in a tube is equal to that of two isolated chains each in a tube of half the cross-sectional area. Simulations were used to test the latter approximation and reveal that it yields poor quantitative predictions. This, along with generic finite-size effects, likely gives rise to the discrepancies between the predicted and measured values of scaling exponents for F(λ). For segregation in the presence of crowding agents, the free energy barrier generally decreases with increasing crowder packing fraction, thus reducing the entropic forces driving segregation. However, for fixed packing fraction, the barrier increases as the crowder/monomer size ratio decreases.
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Affiliation(s)
- James M Polson
- Department of Physics, University of Prince Edward Island, 550 University Ave., Charlottetown, Prince Edward Island C1A 4P3, Canada.
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12
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Gherardi M, Calabrese L, Tamm M, Cosentino Lagomarsino M. Model of chromosomal loci dynamics in bacteria as fractional diffusion with intermittent transport. Phys Rev E 2017; 96:042402. [PMID: 29347533 DOI: 10.1103/physreve.96.042402] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2017] [Indexed: 06/07/2023]
Abstract
The short-time dynamics of bacterial chromosomal loci is a mixture of subdiffusive and active motion, in the form of rapid relocations with near-ballistic dynamics. While previous work has shown that such rapid motions are ubiquitous, we still have little grasp on their physical nature, and no positive model is available that describes them. Here, we propose a minimal theoretical model for loci movements as a fractional Brownian motion subject to a constant but intermittent driving force, and compare simulations and analytical calculations to data from high-resolution dynamic tracking in E. coli. This analysis yields the characteristic time scales for intermittency. Finally, we discuss the possible shortcomings of this model, and show that an increase in the effective local noise felt by the chromosome associates to the active relocations.
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Affiliation(s)
- Marco Gherardi
- Sorbonne Universités, UPMC Univ Paris 06, 75005 Paris, France
- Physics Department, University of Milan, Via Celoria 16, 20133 Milano, Italy
| | - Ludovico Calabrese
- Physics Department, University of Milan, Via Celoria 16, 20133 Milano, Italy
| | - Mikhail Tamm
- Physics Department, University of Moscow, 119991 Moscow, Russia
- Department of Applied Mathematics, Higher School of Economics, 101000 Moscow, Russia
| | - Marco Cosentino Lagomarsino
- Sorbonne Universités, UPMC Univ Paris 06, 75005 Paris, France
- CNRS, UMR 7238, Paris, France
- IFOM, FIRC Institute of Molecular Oncology, 20139 Milan, Italy
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13
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Cass JA, Kuwada NJ, Traxler B, Wiggins PA. Escherichia coli Chromosomal Loci Segregate from Midcell with Universal Dynamics. Biophys J 2017; 110:2597-2609. [PMID: 27332118 DOI: 10.1016/j.bpj.2016.04.046] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Revised: 03/31/2016] [Accepted: 04/28/2016] [Indexed: 12/31/2022] Open
Abstract
The structure of the Escherichia coli chromosome is inherently dynamic over the duration of the cell cycle. Genetic loci undergo both stochastic motion around their initial positions and directed motion to opposite poles of the rod-shaped cell during segregation. We developed a quantitative method to characterize cell-cycle dynamics of the E. coli chromosome to probe the chromosomal steady-state mobility and segregation process. By tracking fluorescently labeled chromosomal loci in thousands of cells throughout the entire cell cycle, our method allows for the statistical analysis of locus position and motion, the step-size distribution for movement during segregation, and the locus drift velocity. The robust statistics of our detailed analysis of the wild-type E. coli nucleoid allow us to observe loci moving toward midcell before segregation occurs, consistent with a replication factory model. Then, as segregation initiates, we perform a detailed characterization of the average segregation velocity of loci. Contrary to origin-centric models of segregation, which predict distinct dynamics for oriC-proximal versus oriC-distal loci, we find that the dynamics of loci were universal and independent of genetic position.
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Affiliation(s)
- Julie A Cass
- Departments of Physics, Bioengineering, and Microbiology, University of Washington, Seattle, Washington
| | - Nathan J Kuwada
- Departments of Physics, Bioengineering, and Microbiology, University of Washington, Seattle, Washington
| | - Beth Traxler
- Departments of Physics, Bioengineering, and Microbiology, University of Washington, Seattle, Washington
| | - Paul A Wiggins
- Departments of Physics, Bioengineering, and Microbiology, University of Washington, Seattle, Washington.
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14
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Saito T, Sakaue T. Complementary mode analyses between sub- and superdiffusion. Phys Rev E 2017; 95:042143. [PMID: 28505743 DOI: 10.1103/physreve.95.042143] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2016] [Indexed: 06/07/2023]
Abstract
Several subdiffusive stochastic processes in nature, e.g., the motion of a tagged monomer in polymers, the height fluctuation of interfaces, particle dynamics in single-file diffusion, etc., can be described rigorously or approximately by the superposition of various modes whose relaxation times are broadly distributed. In this paper, we propose a mode analysis generating superdiffusion, which is paired with or complementary to subdiffusion. The key point in our discussion lies in the identification of a pair of conjugated variables, which undergo sub- and superdiffusion, respectively. We provide a simple interpretation for the sub- and superdiffusion duality for these variables using the language of polymer physics. The analysis also suggests the usefulness of looking at the force fluctuation in experiments, where a polymer is driven by a constant velocity.
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Affiliation(s)
- Takuya Saito
- Earthquake Research Institute, University of Tokyo, Tokyo 113-0032, Japan
| | - Takahiro Sakaue
- Department of Physics, Kyushu University, Fukuoka 819-0395, Japan
- JST, PRESTO, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan
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15
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Mangiameli SM, Veit BT, Merrikh H, Wiggins PA. The Replisomes Remain Spatially Proximal throughout the Cell Cycle in Bacteria. PLoS Genet 2017; 13:e1006582. [PMID: 28114307 PMCID: PMC5293282 DOI: 10.1371/journal.pgen.1006582] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2016] [Revised: 02/06/2017] [Accepted: 01/13/2017] [Indexed: 11/23/2022] Open
Abstract
The positioning of the DNA replication machinery (replisome) has been the subject of several studies. Two conflicting models for replisome localization have been proposed: In the Factory Model, sister replisomes remain spatially co-localized as the replicating DNA is translocated through a stationary replication factory. In the Track Model, sister replisomes translocate independently along a stationary DNA track and the replisomes are spatially separated for the majority of the cell cycle. Here, we used time-lapse imaging to observe and quantify the position of fluorescently labeled processivity-clamp (DnaN) complexes throughout the cell cycle in two highly-divergent bacterial model organisms: Bacillus subtilis and Escherichia coli. Because DnaN is a core component of the replication machinery, its localization patterns should be an appropriate proxy for replisome positioning in general. We present automated statistical analysis of DnaN positioning in large populations, which is essential due to the high degree of cell-to-cell variation. We find that both bacteria show remarkably similar DnaN positioning, where any potential separation of the two replication forks remains below the diffraction limit throughout the majority of the replication cycle. Additionally, the localization pattern of several other core replisome components is consistent with that of DnaN. These data altogether indicate that the two replication forks remain spatially co-localized and mostly function in close proximity throughout the replication cycle. The conservation of the observed localization patterns in these highly divergent species suggests that the subcellular positioning of the replisome is a functionally critical feature of DNA replication. Cell proliferation depends on efficient replication of the genome. Bacteria typically have a single origin of replication on a circular chromosome. After replication initiation, two replisomes assemble at the origin and each copy one of the two arms of the chromosome until they reach the terminus. There have been conflicting reports about the subcellular positioning and putative co-localization of the two replication forks during this process. It has remained controversial whether the two replisomes remain relatively close to each other with the DNA being pulled through, or separate as they translocate along the DNA like a track. Existing studies have relied heavily on snapshot images and these experiments cannot unambiguously distinguish between these two models: i.e. two resolvable forks versus two pairs of co-localized forks. The ability of replication to re-initiate before cell division in bacterial cells further complicates the interpretation of these types of imaging studies. In this paper, we use a combination of snapshot imaging, time-lapse imaging, and quantitative analysis to measure the fraction of time forks are co-localized during each cell cycle. We find that the forks are co-localized for the majority (80%) of the replication cycle in two highly-divergent model organisms: B. subtilis and E. coli. Our observations are consistent with proximal localization of the two forks, but also some transient separations of sister forks during replication. The conserved behavior of sub-cellular positioning of the replisomes in these two highly divergent species implies a potential functional relevance of this feature.
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Affiliation(s)
- Sarah M. Mangiameli
- Department of Physics, University of Washington, Seattle, Washington, United States of America
| | - Brian T. Veit
- Department of Physics, University of Washington, Seattle, Washington, United States of America
| | - Houra Merrikh
- Department of Microbiology, University of Washington, Seattle, Washington, United States of America
- Department of Genome Sciences, University of Washington, Seattle, Washington, United States of America
- * E-mail: (HM); (PAW)
| | - Paul A. Wiggins
- Department of Physics, University of Washington, Seattle, Washington, United States of America
- Department of Microbiology, University of Washington, Seattle, Washington, United States of America
- Department of Bioengineering, University of Washington, Seattle, Washington, United States of America
- * E-mail: (HM); (PAW)
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16
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Mangiameli SM, Merrikh CN, Wiggins PA, Merrikh H. Transcription leads to pervasive replisome instability in bacteria. eLife 2017; 6. [PMID: 28092263 PMCID: PMC5305214 DOI: 10.7554/elife.19848] [Citation(s) in RCA: 53] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2016] [Accepted: 01/15/2017] [Indexed: 12/19/2022] Open
Abstract
The canonical model of DNA replication describes a highly-processive and largely continuous process by which the genome is duplicated. This continuous model is based upon in vitro reconstitution and in vivo ensemble experiments. Here, we characterize the replisome-complex stoichiometry and dynamics with single-molecule resolution in bacterial cells. Strikingly, the stoichiometries of the replicative helicase, DNA polymerase, and clamp loader complexes are consistent with the presence of only one active replisome in a significant fraction of cells (>40%). Furthermore, many of the observed complexes have short lifetimes (<8 min), suggesting that replisome disassembly is quite prevalent, possibly occurring several times per cell cycle. The instability of the replisome complex is conflict-induced: transcription inhibition stabilizes these complexes, restoring the second replisome in many of the cells. Our results suggest that, in contrast to the canonical model, DNA replication is a largely discontinuous process in vivo due to pervasive replication-transcription conflicts. DOI:http://dx.doi.org/10.7554/eLife.19848.001
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Affiliation(s)
| | | | - Paul A Wiggins
- Department of Physics, University of Washington, Seattle, United States.,Department of Microbiology, University of Washington, Seattle, United States.,Department of Bioengineering, University of Washington, Seattle, United States
| | - Houra Merrikh
- Department of Microbiology, University of Washington, Seattle, United States.,Department of Genome Sciences, University of Washington, Seattle, United States
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17
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Mangiameli SM, Merrikh CN, Wiggins PA, Merrikh H. Transcription leads to pervasive replisome instability in bacteria. eLife 2017; 6. [PMID: 28092263 DOI: 10.7554/elife.19848.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2016] [Accepted: 01/15/2017] [Indexed: 05/21/2023] Open
Abstract
The canonical model of DNA replication describes a highly-processive and largely continuous process by which the genome is duplicated. This continuous model is based upon in vitro reconstitution and in vivo ensemble experiments. Here, we characterize the replisome-complex stoichiometry and dynamics with single-molecule resolution in bacterial cells. Strikingly, the stoichiometries of the replicative helicase, DNA polymerase, and clamp loader complexes are consistent with the presence of only one active replisome in a significant fraction of cells (>40%). Furthermore, many of the observed complexes have short lifetimes (<8 min), suggesting that replisome disassembly is quite prevalent, possibly occurring several times per cell cycle. The instability of the replisome complex is conflict-induced: transcription inhibition stabilizes these complexes, restoring the second replisome in many of the cells. Our results suggest that, in contrast to the canonical model, DNA replication is a largely discontinuous process in vivo due to pervasive replication-transcription conflicts.
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Affiliation(s)
| | | | - Paul A Wiggins
- Department of Physics, University of Washington, Seattle, United States
- Department of Microbiology, University of Washington, Seattle, United States
- Department of Bioengineering, University of Washington, Seattle, United States
| | - Houra Merrikh
- Department of Microbiology, University of Washington, Seattle, United States
- Department of Genome Sciences, University of Washington, Seattle, United States
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18
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Cass JA, Stylianidou S, Kuwada NJ, Traxler B, Wiggins PA. Probing bacterial cell biology using image cytometry. Mol Microbiol 2016; 103:818-828. [PMID: 27935200 DOI: 10.1111/mmi.13591] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/28/2016] [Indexed: 01/01/2023]
Abstract
Advances in automated fluorescence microscopy have made snapshot and time-lapse imaging of bacterial cells commonplace, yet fundamental challenges remain in analysis. The vast quantity of data collected in high-throughput experiments requires a fast and reliable automated method to analyze fluorescence intensity and localization, cell morphology and proliferation as well as other descriptors. Inspired by effective yet tractable methods of population-level analysis using flow cytometry, we have developed a framework and tools for facilitating analogous analyses in image cytometry. These tools can both visualize and gate (generate subpopulations) more than 70 cell descriptors, including cell size, age and fluorescence. The method is well suited to multi-well imaging, analysis of bacterial cultures with high cell density (thousands of cells per frame) and complete cell cycle imaging. We give a brief description of the analysis of four distinct applications to emphasize the broad applicability of the tool.
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Affiliation(s)
- Julie A Cass
- Department of Physics, University of Washington, Seattle, WA, 98195, USA
| | - Stella Stylianidou
- Department of Physics, University of Washington, Seattle, WA, 98195, USA
| | - Nathan J Kuwada
- Department of Physics, Central Washington University, Ellensburg, WA, 98926, USA
| | - Beth Traxler
- Department of Microbiology, University of Washington, Seattle, WA, 98195, USA
| | - Paul A Wiggins
- Department of Physics, University of Washington, Seattle, WA, 98195, USA.,Department of Microbiology, University of Washington, Seattle, WA, 98195, USA.,Department of Bioengineering, University of Washington, Seattle, WA, 98195, USA
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19
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Surovtsev IV, Campos M, Jacobs-Wagner C. DNA-relay mechanism is sufficient to explain ParA-dependent intracellular transport and patterning of single and multiple cargos. Proc Natl Acad Sci U S A 2016; 113:E7268-E7276. [PMID: 27799522 PMCID: PMC5135302 DOI: 10.1073/pnas.1616118113] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Spatial ordering of macromolecular components inside cells is important for cellular physiology and replication. In bacteria, ParA/B systems are known to generate various intracellular patterns that underlie the transport and partitioning of low-copy-number cargos such as plasmids. ParA/B systems consist of ParA, an ATPase that dimerizes and binds DNA upon ATP binding, and ParB, a protein that binds the cargo and stimulates ParA ATPase activity. Inside cells, ParA is asymmetrically distributed, forming a propagating wave that is followed by the ParB-rich cargo. These correlated dynamics lead to cargo oscillation or equidistant spacing over the nucleoid depending on whether the cargo is in single or multiple copies. Currently, there is no model that explains how these different spatial patterns arise and relate to each other. Here, we test a simple DNA-relay model that has no imposed asymmetry and that only considers the ParA/ParB biochemistry and the known fluctuating and elastic dynamics of chromosomal loci. Stochastic simulations with experimentally derived parameters demonstrate that this model is sufficient to reproduce the signature patterns of ParA/B systems: the propagating ParA gradient correlated with the cargo dynamics, the single-cargo oscillatory motion, and the multicargo equidistant patterning. Stochasticity of ATP hydrolysis breaks the initial symmetry in ParA distribution, resulting in imbalance of elastic force acting on the cargo. Our results may apply beyond ParA/B systems as they reveal how a minimal system of two players, one binding to DNA and the other modulating this binding, can transform directionally random DNA fluctuations into directed motion and intracellular patterning.
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Affiliation(s)
- Ivan V Surovtsev
- Microbial Sciences Institute, Yale University, West Haven, CT 06517
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, CT 06516
- Howard Hughes Medical Institute, Yale University, New Haven, CT 06516
| | - Manuel Campos
- Microbial Sciences Institute, Yale University, West Haven, CT 06517
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, CT 06516
- Howard Hughes Medical Institute, Yale University, New Haven, CT 06516
| | - Christine Jacobs-Wagner
- Microbial Sciences Institute, Yale University, West Haven, CT 06517;
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, CT 06516
- Howard Hughes Medical Institute, Yale University, New Haven, CT 06516
- Department of Microbial Pathogenesis, Yale Medical School, New Haven, CT 06516
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20
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Stylianidou S, Brennan C, Nissen SB, Kuwada NJ, Wiggins PA. SuperSegger: robust image segmentation, analysis and lineage tracking of bacterial cells. Mol Microbiol 2016; 102:690-700. [PMID: 27569113 DOI: 10.1111/mmi.13486] [Citation(s) in RCA: 108] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/19/2016] [Indexed: 11/29/2022]
Abstract
Many quantitative cell biology questions require fast yet reliable automated image segmentation to identify and link cells from frame-to-frame, and characterize the cell morphology and fluorescence. We present SuperSegger, an automated MATLAB-based image processing package well-suited to quantitative analysis of high-throughput live-cell fluorescence microscopy of bacterial cells. SuperSegger incorporates machine-learning algorithms to optimize cellular boundaries and automated error resolution to reliably link cells from frame-to-frame. Unlike existing packages, it can reliably segment microcolonies with many cells, facilitating the analysis of cell-cycle dynamics in bacteria as well as cell-contact mediated phenomena. This package has a range of built-in capabilities for characterizing bacterial cells, including the identification of cell division events, mother, daughter and neighbouring cells, and computing statistics on cellular fluorescence, the location and intensity of fluorescent foci. SuperSegger provides a variety of postprocessing data visualization tools for single cell and population level analysis, such as histograms, kymographs, frame mosaics, movies and consensus images. Finally, we demonstrate the power of the package by analyzing lag phase growth with single cell resolution.
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Affiliation(s)
- Stella Stylianidou
- Department of Physics, University of Washington, Seattle, WA, 98195, USA
| | - Connor Brennan
- Department of Physics, University of Washington, Seattle, WA, 98195, USA
| | - Silas B Nissen
- Department of StemPhys, Niels Bohr Institute, University of Copenhagen, Copenhagen, 2100, Denmark
| | - Nathan J Kuwada
- Department of Physics, Central Washington University, Ellensburg, WA, 98926, USA
| | - Paul A Wiggins
- Department of Physics, University of Washington, Seattle, WA, 98195, USA.,Department of Bioengineering, University of Washington, Seattle, WA, 98195, USA.,Department of Microbiology, University of Washington, Seattle, WA, 98195, USA
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21
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Moolman MC, Tiruvadi Krishnan S, Kerssemakers JWJ, de Leeuw R, Lorent V, Sherratt DJ, Dekker NH. The progression of replication forks at natural replication barriers in live bacteria. Nucleic Acids Res 2016; 44:6262-73. [PMID: 27166373 PMCID: PMC5291258 DOI: 10.1093/nar/gkw397] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2015] [Revised: 04/27/2016] [Accepted: 04/28/2016] [Indexed: 01/07/2023] Open
Abstract
Protein-DNA complexes are one of the principal barriers the replisome encounters during replication. One such barrier is the Tus-ter complex, which is a direction dependent barrier for replication fork progression. The details concerning the dynamics of the replisome when encountering these Tus-ter barriers in the cell are poorly understood. By performing quantitative fluorescence microscopy with microfuidics, we investigate the effect on the replisome when encountering these barriers in live Escherichia coli cells. We make use of an E. coli variant that includes only an ectopic origin of replication that is positioned such that one of the two replisomes encounters a Tus-ter barrier before the other replisome. This enables us to single out the effect of encountering a Tus-ter roadblock on an individual replisome. We demonstrate that the replisome remains stably bound after encountering a Tus-ter complex from the non-permissive direction. Furthermore, the replisome is only transiently blocked, and continues replication beyond the barrier. Additionally, we demonstrate that these barriers affect sister chromosome segregation by visualizing specific chromosomal loci in the presence and absence of the Tus protein. These observations demonstrate the resilience of the replication fork to natural barriers and the sensitivity of chromosome alignment to fork progression.
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Affiliation(s)
- M Charl Moolman
- Department of Bionanoscience, Kavli Institute of Nanoscience, Faculty of Applied Sciences, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands
| | - Sriram Tiruvadi Krishnan
- Department of Bionanoscience, Kavli Institute of Nanoscience, Faculty of Applied Sciences, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands
| | - Jacob W J Kerssemakers
- Department of Bionanoscience, Kavli Institute of Nanoscience, Faculty of Applied Sciences, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands
| | - Roy de Leeuw
- Department of Bionanoscience, Kavli Institute of Nanoscience, Faculty of Applied Sciences, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands
| | - Vincent Lorent
- Université Paris 13, Sorbonne Paris Cité, Laboratoire de Physique des Lasers, CNRS, (UMR 7538), F-93430 Villetaneuse, France
| | - David J Sherratt
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK
| | - Nynke H Dekker
- Department of Bionanoscience, Kavli Institute of Nanoscience, Faculty of Applied Sciences, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands
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22
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Javer A, Lagomarsino MC, Cicuta P. Bacterial Chromosome Dynamics by Locus Tracking in Fluorescence Microscopy. Methods Mol Biol 2016; 1431:161-173. [PMID: 27283309 DOI: 10.1007/978-1-4939-3631-1_13] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Bacterial chromosomes have been shown in the last two decades to have remarkable spatial organization at various scales, and also well-defined movements during the cell cycle, for example, to reliably segregate daughter chromosomes. More recently, various labs have begun investigating the short-time dynamics (displacements during time intervals of 0.1-100 s), which one hopes to link to structure, in analogy to "microrheology" approaches applied successfully to study mechanical response of complex fluids. These studies of chromosome fluctuation dynamics have revealed differences of fluctuation amplitude across the chromosome, and different characters of motion depending on the time window of interest. The highly nontrivial motion at the shortest experimentally accessible times is still not fully understood in terms of physical models of DNA and cytosol. We describe how to carry out tracking experiments of single locus and how to analyze locus motility. We point out the importance of considering in the analysis the number of GFP molecules per fluorescent locus.
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Affiliation(s)
- Avelino Javer
- Cavendish Laboratory, University of Cambridge, Room 237, J.J. Thomson Avenue, Cambridge, CB3 0HE, UK
| | | | - Pietro Cicuta
- Cavendish Laboratory, University of Cambridge, Room 237, J.J. Thomson Avenue, Cambridge, CB3 0HE, UK.
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23
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Vandebroek H, Vanderzande C. Dynamics of a polymer in an active and viscoelastic bath. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2015; 92:060601. [PMID: 26764617 DOI: 10.1103/physreve.92.060601] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2015] [Indexed: 06/05/2023]
Abstract
We study the dynamics of an ideal polymer chain in a viscoelastic medium and in the presence of active forces. The motion of the center of mass and of individual monomers is calculated. On time scales that are comparable to the persistence time of the active forces, monomers can move superdiffusively, while on larger time scales subdiffusive behavior occurs. The difference between this subdiffusion and that in the absence of active forces is quantified. We show that the polymer swells in response to active processes and determine how this swelling depends on the viscoelastic properties of the environment. Our results are compared to recent experiments on the motion of chromosomal loci in bacteria.
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Affiliation(s)
- Hans Vandebroek
- Faculty of Sciences, Hasselt University, 3590 Diepenbeek, Belgium
| | - Carlo Vanderzande
- Faculty of Sciences, Hasselt University, 3590 Diepenbeek, Belgium
- Instituut Theoretische Fysica, Katholieke Universiteit Leuven, 3001 Heverlee, Belgium
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24
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Lampo TJ, Kuwada NJ, Wiggins PA, Spakowitz AJ. Physical modeling of chromosome segregation in escherichia coli reveals impact of force and DNA relaxation. Biophys J 2015; 108:146-53. [PMID: 25564861 DOI: 10.1016/j.bpj.2014.10.074] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2014] [Revised: 10/15/2014] [Accepted: 10/23/2014] [Indexed: 12/20/2022] Open
Abstract
The physical mechanism by which Escherichia coli segregates copies of its chromosome for partitioning into daughter cells is unknown, partly due to the difficulty in interpreting the complex dynamic behavior during segregation. Analysis of previous chromosome segregation measurements in E. coli demonstrates that the origin of replication exhibits processive motion with a mean displacement that scales as t(0.32). In this work, we develop a model for segregation of chromosomal DNA as a Rouse polymer in a viscoelastic medium with a force applied to a single monomer. Our model demonstrates that the observed power-law scaling of the mean displacement and the behavior of the velocity autocorrelation function is captured by accounting for the relaxation of the polymer chain and the viscoelastic environment. We show that the ratio of the mean displacement to the variance of the displacement during segregation events is a critical metric that eliminates the compounding effects of polymer and medium dynamics and provides the segregation force. We calculate the force of oriC segregation in E. coli to be ∼0.49 pN.
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Affiliation(s)
- Thomas J Lampo
- Department of Chemical Engineering, Stanford University, Stanford, California
| | - Nathan J Kuwada
- Departments of Physics and Bioengineering, University of Washington, Seattle, Washington
| | - Paul A Wiggins
- Departments of Physics and Bioengineering, University of Washington, Seattle, Washington
| | - Andrew J Spakowitz
- Department of Chemical Engineering, Stanford University, Stanford, California; Biophysics Program, Stanford University, Stanford, California; Department of Materials Science & Engineering, Stanford University, Stanford, California; Department of Applied Physics, Stanford University, Stanford, California.
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25
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Saito T, Sakaue T. Driven anomalous diffusion: An example from polymer stretching. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2015; 92:012601. [PMID: 26274194 DOI: 10.1103/physreve.92.012601] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/24/2015] [Indexed: 06/04/2023]
Abstract
The way tension propagates along a chain is a key to govern many anomalous dynamics in macromolecular systems. After introducing the weak and the strong force regimes of the tension propagation, we focus on the latter, in which the dynamical fluctuations of a segment in a long polymer during its stretching process is investigated. We show that the response, i.e., average drift, is anomalous, which is characterized by the nonlinear memory kernel, and its relation to the fluctuation is nontrivial. These features are discussed on the basis of the generalized Langevin equation, in which the role of the temporal change in spring constant due to the stress hardening is pinpointed. We carried out the molecular dynamics simulation, which supports our theory.
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Affiliation(s)
- Takuya Saito
- Fukui Institute for Fundamental Chemistry, Kyoto University, Kyoto 606-8103, Japan
| | - Takahiro Sakaue
- Department of Physics, Kyushu University 33, Fukuoka 812-8581, Japan
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26
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High-throughput cell-cycle imaging opens new doors for discovery. Curr Genet 2015; 61:513-6. [DOI: 10.1007/s00294-015-0493-y] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2015] [Accepted: 05/07/2015] [Indexed: 10/23/2022]
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27
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Liu J. The ghost in the machine: is the bacterial chromosome a phantom chain? Biophys J 2015; 108:20-1. [PMID: 25564847 DOI: 10.1016/j.bpj.2014.11.3451] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2014] [Accepted: 11/18/2014] [Indexed: 11/26/2022] Open
Affiliation(s)
- Jian Liu
- Biochemistry and Biophysics Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland.
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28
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Stylianidou S, Kuwada NJ, Wiggins PA. Cytoplasmic dynamics reveals two modes of nucleoid-dependent mobility. Biophys J 2014; 107:2684-92. [PMID: 25468347 DOI: 10.1016/j.bpj.2014.10.030] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2014] [Revised: 10/13/2014] [Accepted: 10/15/2014] [Indexed: 11/19/2022] Open
Abstract
It has been proposed that forces resulting from the physical exclusion of macromolecules from the bacterial nucleoid play a central role in organizing the bacterial cell, yet this proposal has not been quantitatively tested. To investigate this hypothesis, we mapped the generic motion of large protein complexes in the bacterial cytoplasm through quantitative analysis of thousands of complete cell-cycle trajectories of fluorescently tagged ectopic MS2-mRNA complexes. We find the motion of these complexes in the cytoplasm is strongly dependent on their spatial position along the long axis of the cell, and that their dynamics are consistent with a quantitative model that requires only nucleoid exclusion and membrane confinement. This analysis also reveals that the nucleoid increases the mobility of MS2-mRNA complexes, resulting in a fourfold increase in diffusion coefficients between regions of the lowest and highest nucleoid density. These data provide strong quantitative support for two modes of nucleoid action: the widely accepted mechanism of nucleoid exclusion in organizing the cell and a newly proposed mode, in which the nucleoid facilitates rapid motion throughout the cytoplasm.
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Affiliation(s)
| | - Nathan J Kuwada
- Department of Physics, University of Washington, Seattle, Washington; Department of Bioengineering, University of Washington, Seattle, Washington
| | - Paul A Wiggins
- Department of Physics, University of Washington, Seattle, Washington; Department of Bioengineering, University of Washington, Seattle, Washington; Department of Microbiology, University of Washington, Seattle, Washington.
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29
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Polson JM, Montgomery LG. Polymer segregation under confinement: Free energy calculations and segregation dynamics simulations. J Chem Phys 2014; 141:164902. [DOI: 10.1063/1.4898714] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- James M. Polson
- Department of Physics, University of Prince Edward Island, 550 University Ave., Charlottetown, Prince Edward Island C1A 4P3, Canada
| | - Logan G. Montgomery
- Department of Physics, University of Prince Edward Island, 550 University Ave., Charlottetown, Prince Edward Island C1A 4P3, Canada
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30
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Persistent super-diffusive motion of Escherichia coli chromosomal loci. Nat Commun 2014; 5:3854. [DOI: 10.1038/ncomms4854] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2013] [Accepted: 04/10/2014] [Indexed: 01/15/2023] Open
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31
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Lim HC, Surovtsev IV, Beltran BG, Huang F, Bewersdorf J, Jacobs-Wagner C. Evidence for a DNA-relay mechanism in ParABS-mediated chromosome segregation. eLife 2014; 3:e02758. [PMID: 24859756 PMCID: PMC4067530 DOI: 10.7554/elife.02758] [Citation(s) in RCA: 154] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2014] [Accepted: 05/16/2014] [Indexed: 12/12/2022] Open
Abstract
The widely conserved ParABS system plays a major role in bacterial chromosome segregation. How the components of this system work together to generate translocation force and directional motion remains uncertain. Here, we combine biochemical approaches, quantitative imaging and mathematical modeling to examine the mechanism by which ParA drives the translocation of the ParB/parS partition complex in Caulobacter crescentus. Our experiments, together with simulations grounded on experimentally-determined biochemical and cellular parameters, suggest a novel 'DNA-relay' mechanism in which the chromosome plays a mechanical function. In this model, DNA-bound ParA-ATP dimers serve as transient tethers that harness the elastic dynamics of the chromosome to relay the partition complex from one DNA region to another across a ParA-ATP dimer gradient. Since ParA-like proteins are implicated in the partitioning of various cytoplasmic cargos, the conservation of their DNA-binding activity suggests that the DNA-relay mechanism may be a general form of intracellular transport in bacteria.DOI: http://dx.doi.org/10.7554/eLife.02758.001.
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Affiliation(s)
- Hoong Chuin Lim
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, United States Microbial Diversity Institute, Yale University, West Haven, United States
| | - Ivan Vladimirovich Surovtsev
- Microbial Diversity Institute, Yale University, West Haven, United States Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, United States Howard Hughes Medical Institute, Yale University, New Haven, United States
| | - Bruno Gabriel Beltran
- Department of Mathematics, Louisiana State University, Baton Rouge, United States Howard Hughes Medical Institute, Yale University, New Haven, United States
| | - Fang Huang
- Department of Cell Biology, Yale School of Medicine, New Haven, United States
| | - Jörg Bewersdorf
- Department of Cell Biology, Yale School of Medicine, New Haven, United States Department of Biomedical Engineering, Yale University, New Haven, United States
| | - Christine Jacobs-Wagner
- Microbial Diversity Institute, Yale University, West Haven, United States Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, United States Howard Hughes Medical Institute, Yale University, New Haven, United States Department of Microbial Pathogenesis, Yale School of Medicine, New Haven, United States
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RecA bundles mediate homology pairing between distant sisters during DNA break repair. Nature 2013; 506:249-53. [PMID: 24362571 PMCID: PMC3925069 DOI: 10.1038/nature12868] [Citation(s) in RCA: 123] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2013] [Accepted: 11/05/2013] [Indexed: 11/08/2022]
Abstract
DNA double-strand break (DSB) repair by homologous recombination has evolved to maintain genetic integrity in all organisms. Although many reactions that occur during homologous recombination are known, it is unclear where, when and how they occur in cells. Here, by using conventional and super-resolution microscopy, we describe the progression of DSB repair in live Escherichia coli. Specifically, we investigate whether homologous recombination can occur efficiently between distant sister loci that have segregated to opposite halves of an E. coli cell. We show that a site-specific DSB in one sister can be repaired efficiently using distant sister homology. After RecBCD processing of the DSB, RecA is recruited to the cut locus, where it nucleates into a bundle that contains many more RecA molecules than can associate with the two single-stranded DNA regions that form at the DSB. Mature bundles extend along the long axis of the cell, in the space between the bulk nucleoid and the inner membrane. Bundle formation is followed by pairing, in which the two ends of the cut locus relocate at the periphery of the nucleoid and together move rapidly towards the homology of the uncut sister. After sister locus pairing, RecA bundles disassemble and proteins that act late in homologous recombination are recruited to give viable recombinants 1-2-generation-time equivalents after formation of the initial DSB. Mutated RecA proteins that do not form bundles are defective in sister pairing and in DSB-induced repair. This work reveals an unanticipated role of RecA bundles in channelling the movement of the DNA DSB ends, thereby facilitating the long-range homology search that occurs before the strand invasion and transfer reactions.
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Junier I, Boccard F, Espéli O. Polymer modeling of the E. coli genome reveals the involvement of locus positioning and macrodomain structuring for the control of chromosome conformation and segregation. Nucleic Acids Res 2013; 42:1461-73. [PMID: 24194594 PMCID: PMC3919569 DOI: 10.1093/nar/gkt1005] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The mechanisms that control chromosome conformation and segregation in bacteria have not yet been elucidated. In Escherichia coli, the mere presence of an active process remains an open question. Here, we investigate the conformation and segregation pattern of the E. coli genome by performing numerical simulations on a polymer model of the chromosome. We analyze the roles of the intrinsic structuring of chromosomes and the forced localization of specific loci, which are observed in vivo. Specifically, we examine the segregation pattern of a chromosome that is divided into four structured macrodomains (MDs) and two non-structured regions. We find that strong osmotic-like organizational forces, which stem from the differential condensation levels of the chromosome regions, dictate the cellular disposition of the chromosome. Strikingly, the comparison of our in silico results with fluorescent imaging of the chromosome choreography in vivo reveals that in the presence of MDs the targeting of the origin and terminus regions to specific positions are sufficient to generate a segregation pattern that is indistinguishable from experimentally observed patterns.
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Affiliation(s)
- Ivan Junier
- Centre for Genomic Regulation (CRG), Dr. Aiguader 88, 08003 Barcelona, Spain, Universitat Pompeu Fabra (UPF), 08003 Barcelona, Spain, CGM-CNRS, Université Paris-Sud, 1 Avenue de la Terrasse, 91198 Gif sur Yvette, France and CIRB - Collège de France, 11 Place Marcelin Berthelot, 75231 Paris Cedex 05, France
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