1
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Sposini V, Nampoothiri S, Chechkin A, Orlandini E, Seno F, Baldovin F. Being Heterogeneous Is Advantageous: Extreme Brownian Non-Gaussian Searches. PHYSICAL REVIEW LETTERS 2024; 132:117101. [PMID: 38563912 DOI: 10.1103/physrevlett.132.117101] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2023] [Revised: 11/15/2023] [Accepted: 02/01/2024] [Indexed: 04/04/2024]
Abstract
Redundancy in biology may be explained by the need to optimize extreme searching processes, where one or few among many particles are requested to reach the target like in human fertilization. We show that non-Gaussian rare fluctuations in Brownian diffusion dominates such searches, introducing drastic corrections to the known Gaussian behavior. Our demonstration entails different physical systems and pinpoints the relevance of diversity within redundancy to boost fast targeting. We sketch an experimental context to test our results: polydisperse systems.
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Affiliation(s)
- Vittoria Sposini
- Faculty of Physics, University of Vienna, Kolingasse 14-16, 1090 Vienna, Austria
| | - Sankaran Nampoothiri
- Department of Physics, Gandhi Institute of Technology and Management (GITAM) University, Bengaluru 561203, India
| | - Aleksei Chechkin
- Faculty of Pure and Applied Mathematics, Hugo Steinhaus Center, Wroclaw University of Science and Technology, Wyspianskiego Str. 27, 50-370 Wroclaw, Poland
- Institute for Physics & Astronomy, University of Potsdam, 14476 Potsdam-Golm, Germany
- Akhiezer Institute for Theoretical Physics, 61108 Kharkov, Ukraine
| | - Enzo Orlandini
- Dipartimento di Fisica e Astronomia 'G. Galilei' - DFA, Sezione INFN, Università di Padova, Via Marzolo 8, 35131 Padova (PD), Italy
| | - Flavio Seno
- Dipartimento di Fisica e Astronomia 'G. Galilei' - DFA, Sezione INFN, Università di Padova, Via Marzolo 8, 35131 Padova (PD), Italy
| | - Fulvio Baldovin
- Dipartimento di Fisica e Astronomia 'G. Galilei' - DFA, Sezione INFN, Università di Padova, Via Marzolo 8, 35131 Padova (PD), Italy
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2
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Sposini V, Nampoothiri S, Chechkin A, Orlandini E, Seno F, Baldovin F. Being heterogeneous is disadvantageous: Brownian non-Gaussian searches. Phys Rev E 2024; 109:034120. [PMID: 38632764 DOI: 10.1103/physreve.109.034120] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2023] [Accepted: 02/01/2024] [Indexed: 04/19/2024]
Abstract
Diffusing diffusivity models, polymers in the grand canonical ensemble and polydisperse, and continuous-time random walks all exhibit stages of non-Gaussian diffusion. Is non-Gaussian targeting more efficient than Gaussian? We address this question, central to, e.g., diffusion-limited reactions and some biological processes, through a general approach that makes use of Jensen's inequality and that encompasses all these systems. In terms of customary mean first-passage time, we show that Gaussian searches are more effective than non-Gaussian ones. A companion paper argues that non-Gaussianity becomes instead highly more efficient in applications where only a small fraction of tracers is required to reach the target.
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Affiliation(s)
- Vittoria Sposini
- Faculty of Physics, University of Vienna, Kolingasse 14-16, 1090 Vienna, Austria
| | - Sankaran Nampoothiri
- Department of Physics, Gandhi Institute of Technology and Management (GITAM) University, Bengaluru 561203, India
| | - Aleksei Chechkin
- Faculty of Pure and Applied Mathematics, Hugo Steinhaus Center, Wroclaw University of Science and Technology, Wyspianskiego Street 27, 50-370 Wroclaw, Poland
- Institute for Physics and Astronomy, University of Potsdam, 14476 Potsdam-Golm, Germany
- Akhiezer Institute for Theoretical Physics, 61108 Kharkov, Ukraine
| | - Enzo Orlandini
- Dipartimento di Fisica e Astronomia 'G. Galilei' - DFA, Sezione INFN, Università di Padova, Via Marzolo 8, 35131 Padova (PD), Italy
| | - Flavio Seno
- Dipartimento di Fisica e Astronomia 'G. Galilei' - DFA, Sezione INFN, Università di Padova, Via Marzolo 8, 35131 Padova (PD), Italy
| | - Fulvio Baldovin
- Dipartimento di Fisica e Astronomia 'G. Galilei' - DFA, Sezione INFN, Università di Padova, Via Marzolo 8, 35131 Padova (PD), Italy
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3
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Waigh TA, Korabel N. Heterogeneous anomalous transport in cellular and molecular biology. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2023; 86:126601. [PMID: 37863075 DOI: 10.1088/1361-6633/ad058f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2022] [Accepted: 10/20/2023] [Indexed: 10/22/2023]
Abstract
It is well established that a wide variety of phenomena in cellular and molecular biology involve anomalous transport e.g. the statistics for the motility of cells and molecules are fractional and do not conform to the archetypes of simple diffusion or ballistic transport. Recent research demonstrates that anomalous transport is in many cases heterogeneous in both time and space. Thus single anomalous exponents and single generalised diffusion coefficients are unable to satisfactorily describe many crucial phenomena in cellular and molecular biology. We consider advances in the field ofheterogeneous anomalous transport(HAT) highlighting: experimental techniques (single molecule methods, microscopy, image analysis, fluorescence correlation spectroscopy, inelastic neutron scattering, and nuclear magnetic resonance), theoretical tools for data analysis (robust statistical methods such as first passage probabilities, survival analysis, different varieties of mean square displacements, etc), analytic theory and generative theoretical models based on simulations. Special emphasis is made on high throughput analysis techniques based on machine learning and neural networks. Furthermore, we consider anomalous transport in the context of microrheology and the heterogeneous viscoelasticity of complex fluids. HAT in the wavefronts of reaction-diffusion systems is also considered since it plays an important role in morphogenesis and signalling. In addition, we present specific examples from cellular biology including embryonic cells, leucocytes, cancer cells, bacterial cells, bacterial biofilms, and eukaryotic microorganisms. Case studies from molecular biology include DNA, membranes, endosomal transport, endoplasmic reticula, mucins, globular proteins, and amyloids.
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Affiliation(s)
- Thomas Andrew Waigh
- Biological Physics, School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, United Kingdom
| | - Nickolay Korabel
- Department of Mathematics, The University of Manchester, Manchester M13 9PL, United Kingdom
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4
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Simon F, Tinevez JY, van Teeffelen S. ExTrack characterizes transition kinetics and diffusion in noisy single-particle tracks. J Cell Biol 2023; 222:e202208059. [PMID: 36880553 PMCID: PMC9997658 DOI: 10.1083/jcb.202208059] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2022] [Revised: 12/01/2022] [Accepted: 01/27/2023] [Indexed: 03/08/2023] Open
Abstract
Single-particle tracking microscopy is a powerful technique to investigate how proteins dynamically interact with their environment in live cells. However, the analysis of tracks is confounded by noisy molecule localization, short tracks, and rapid transitions between different motion states, notably between immobile and diffusive states. Here, we propose a probabilistic method termed ExTrack that uses the full spatio-temporal information of tracks to extract global model parameters, to calculate state probabilities at every time point, to reveal distributions of state durations, and to refine the positions of bound molecules. ExTrack works for a wide range of diffusion coefficients and transition rates, even if experimental data deviate from model assumptions. We demonstrate its capacity by applying it to slowly diffusing and rapidly transitioning bacterial envelope proteins. ExTrack greatly increases the regime of computationally analyzable noisy single-particle tracks. The ExTrack package is available in ImageJ and Python.
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Affiliation(s)
- François Simon
- Département de Microbiologie, Infectiologie, et Immunologie, Faculté de Médecine, Université de Montréal, Montréal, Quebec, Canada
- Microbial Morphogenesis and Growth Lab, Institut Pasteur, Université de Paris Cité, Paris, France
| | - Jean-Yves Tinevez
- Image Analysis Hub, Institut Pasteur, Université de Paris Cité, Paris, France
| | - Sven van Teeffelen
- Département de Microbiologie, Infectiologie, et Immunologie, Faculté de Médecine, Université de Montréal, Montréal, Quebec, Canada
- Microbial Morphogenesis and Growth Lab, Institut Pasteur, Université de Paris Cité, Paris, France
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5
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Simon F, Tinevez JY, van Teeffelen S. ExTrack characterizes transition kinetics and diffusion in noisy single-particle tracks. J Cell Biol 2023; 222:e202208059. [PMID: 36880553 PMCID: PMC9997658 DOI: 10.1083/jcb.202208059 10.1101/2022.07.13.499913] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2022] [Revised: 12/01/2022] [Accepted: 01/27/2023] [Indexed: 03/23/2024] Open
Abstract
Single-particle tracking microscopy is a powerful technique to investigate how proteins dynamically interact with their environment in live cells. However, the analysis of tracks is confounded by noisy molecule localization, short tracks, and rapid transitions between different motion states, notably between immobile and diffusive states. Here, we propose a probabilistic method termed ExTrack that uses the full spatio-temporal information of tracks to extract global model parameters, to calculate state probabilities at every time point, to reveal distributions of state durations, and to refine the positions of bound molecules. ExTrack works for a wide range of diffusion coefficients and transition rates, even if experimental data deviate from model assumptions. We demonstrate its capacity by applying it to slowly diffusing and rapidly transitioning bacterial envelope proteins. ExTrack greatly increases the regime of computationally analyzable noisy single-particle tracks. The ExTrack package is available in ImageJ and Python.
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Affiliation(s)
- François Simon
- Département de Microbiologie, Infectiologie, et Immunologie, Faculté de Médecine, Université de Montréal, Montréal, Quebec, Canada
- Microbial Morphogenesis and Growth Lab, Institut Pasteur, Université de Paris Cité, Paris, France
| | - Jean-Yves Tinevez
- Image Analysis Hub, Institut Pasteur, Université de Paris Cité, Paris, France
| | - Sven van Teeffelen
- Département de Microbiologie, Infectiologie, et Immunologie, Faculté de Médecine, Université de Montréal, Montréal, Quebec, Canada
- Microbial Morphogenesis and Growth Lab, Institut Pasteur, Université de Paris Cité, Paris, France
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6
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Corci B, Hooiveld O, Dolga AM, Åberg C. Extending the analogy between intracellular motion in mammalian cells and glassy dynamics. SOFT MATTER 2023; 19:2529-2538. [PMID: 36939775 DOI: 10.1039/d2sm01672a] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
How molecules, organelles, and foreign objects move within living cells has been studied in organisms ranging from bacteria to human cells. In mammalian cells, in particular, cellular vesicles move across the cell using motor proteins that carry the vesicle down the cytoskeleton to their destination. We have recently noted several similarities between the motion of such vesicles and that in disordered, "glassy", systems, but the generality of this observation remains unclear. Here we follow the motion of mitochondria, the organelles responsible for cell energy production, in mammalian cells over timescales from 50 ms to 70 s. Qualitative observations show that single mitochondria remain within a spatially limited region for extended periods of time, before moving longer distances relatively quickly. The displacement distribution is roughly Gaussian for shorter distances (≲0.05 μm) but exhibits exponentially decaying tails at longer distances (up to 0.40 μm). This behaviour is well-described by a model developed to describe the motion in glassy systems. These observations are extended to in total 3 different objects (mitochondria, lysosomes and nano-sized beads enclosed in vesicles), 3 different mammalian cell types (HEK 293, HeLa, and HT22), from 2 different organisms (human and mouse). Further evidence that supports glass-like characteristics of the motion is a difference between the time it takes to move a longer distance for the first time and subsequent times, as well as a weak ergodicity breaking of the motion. Overall, we demonstrate the ubiquity of glass-like motion in mammalian cells, providing a different perspective on intracellular motion.
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Affiliation(s)
- Beatrice Corci
- Groningen Research Institute of Pharmacy, University of Groningen, Antonius Deusinglaan 1, 9713 AV Groningen, The Netherlands.
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Oscar Hooiveld
- Groningen Research Institute of Pharmacy, University of Groningen, Antonius Deusinglaan 1, 9713 AV Groningen, The Netherlands.
| | - Amalia M Dolga
- Groningen Research Institute of Pharmacy, University of Groningen, Antonius Deusinglaan 1, 9713 AV Groningen, The Netherlands.
| | - Christoffer Åberg
- Groningen Research Institute of Pharmacy, University of Groningen, Antonius Deusinglaan 1, 9713 AV Groningen, The Netherlands.
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7
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Nampoothiri S, Orlandini E, Seno F, Baldovin F. Polymers critical point originates Brownian non-Gaussian diffusion. Phys Rev E 2022; 104:L062501. [PMID: 35030826 DOI: 10.1103/physreve.104.l062501] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2021] [Accepted: 12/11/2021] [Indexed: 01/04/2023]
Abstract
We demonstrate that size fluctuations close to polymers critical point originate the non-Gaussian diffusion of their center of mass. Static universal exponents γ and ν-depending on the polymer topology, on the dimension of the embedding space, and on equilibrium phase-concur to determine the potential divergency of a dynamic response, epitomized by the center-of-mass kurtosis. Prospects in experiments and stochastic modeling brought about by this result are briefly outlined.
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Affiliation(s)
- Sankaran Nampoothiri
- Dipartimento di Fisica e Astronomia "G. Galilei"-DFA, Sezione INFN, Università di Padova, Via Marzolo 8, 35131 Padova (PD), Italy
| | - Enzo Orlandini
- Dipartimento di Fisica e Astronomia "G. Galilei"-DFA, Sezione INFN, Università di Padova, Via Marzolo 8, 35131 Padova (PD), Italy
| | - Flavio Seno
- Dipartimento di Fisica e Astronomia "G. Galilei"-DFA, Sezione INFN, Università di Padova, Via Marzolo 8, 35131 Padova (PD), Italy
| | - Fulvio Baldovin
- Dipartimento di Fisica e Astronomia "G. Galilei"-DFA, Sezione INFN, Università di Padova, Via Marzolo 8, 35131 Padova (PD), Italy
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8
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Emergent hydrodynamics in a strongly interacting dipolar spin ensemble. Nature 2021; 597:45-50. [PMID: 34471276 DOI: 10.1038/s41586-021-03763-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2020] [Accepted: 06/23/2021] [Indexed: 11/08/2022]
Abstract
Conventional wisdom holds that macroscopic classical phenomena naturally emerge from microscopic quantum laws1-7. However, despite this mantra, building direct connections between these two descriptions has remained an enduring scientific challenge. In particular, it is difficult to quantitatively predict the emergent 'classical' properties of a system (for example, diffusivity, viscosity and compressibility) from a generic microscopic quantum Hamiltonian7-14. Here we introduce a hybrid solid-state spin platform, where the underlying disordered, dipolar quantum Hamiltonian gives rise to the emergence of unconventional spin diffusion at nanometre length scales. In particular, the combination of positional disorder and on-site random fields leads to diffusive dynamics that are Fickian yet non-Gaussian15-20. Finally, by tuning the underlying parameters within the spin Hamiltonian via a combination of static and driven fields, we demonstrate direct control over the emergent spin diffusion coefficient. Our work enables the investigation of hydrodynamics in many-body quantum spin systems.
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9
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Dynamics of Proteins and Macromolecular Machines in Escherichia coli. EcoSal Plus 2021; 9:eESP00112020. [PMID: 34060908 DOI: 10.1128/ecosalplus.esp-0011-2020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Proteins are major contributors to the composition and the functions in the cell. They often assemble into larger structures, macromolecular machines, to carry out intricate essential functions. Although huge progress in understanding how macromolecular machines function has been made by reconstituting them in vitro, the role of the intracellular environment is still emerging. The development of fluorescence microscopy techniques in the last 2 decades has allowed us to obtain an increased understanding of proteins and macromolecular machines in cells. Here, we describe how proteins move by diffusion, how they search for their targets, and how they are affected by the intracellular environment. We also describe how proteins assemble into macromolecular machines and provide examples of how frequent subunit turnover is used for them to function and to respond to changes in the intracellular conditions. This review emphasizes the constant movement of molecules in cells, the stochastic nature of reactions, and the dynamic nature of macromolecular machines.
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10
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Åberg C, Poolman B. Glass-like characteristics of intracellular motion in human cells. Biophys J 2021; 120:2355-2366. [PMID: 33887228 DOI: 10.1016/j.bpj.2021.04.011] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2020] [Revised: 03/29/2021] [Accepted: 04/09/2021] [Indexed: 10/21/2022] Open
Abstract
The motion in the cytosol of microorganisms such as bacteria and yeast has been observed to undergo a dramatic slowing down upon cell energy depletion. These observations have been interpreted as the motion being "glassy," but whether this notion is useful also for active, motor-protein-driven transport in eukaryotic cells is less clear. Here, we use fluorescence microscopy of beads in human (HeLa) cells to probe the motion of membrane-surrounded structures that are carried along the cytoskeleton by motor proteins. Evaluating several hallmarks of glassy dynamics, we show that at short length scales, the motion is heterogeneous, is nonergodic, is well described by a model for the displacement distribution in glassy systems, and exhibits a decoupling of the exchange and persistence times. Overall, these results suggest that the short length scale behavior of objects that can be transported actively by motor proteins in human cells shares features with the motion in glassy systems.
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Affiliation(s)
- Christoffer Åberg
- Groningen Research Institute of Pharmacy, University of Groningen, Groningen, the Netherlands; Department of Biochemistry, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Groningen, the Netherlands.
| | - Bert Poolman
- Department of Biochemistry, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Groningen, the Netherlands
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11
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Fluctuating Diffusivity of RNA-Protein Particles: Analogy with Thermodynamics. ENTROPY 2021; 23:e23030333. [PMID: 33808996 PMCID: PMC8002026 DOI: 10.3390/e23030333] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 02/22/2021] [Revised: 03/05/2021] [Accepted: 03/08/2021] [Indexed: 01/01/2023]
Abstract
A formal analogy of fluctuating diffusivity to thermodynamics is discussed for messenger RNA molecules fluorescently fused to a protein in living cells. Regarding the average value of the fluctuating diffusivity of such RNA-protein particles as the analog of the internal energy, the analogs of the quantity of heat and work are identified. The Clausius-like inequality is shown to hold for the entropy associated with diffusivity fluctuations, which plays a role analogous to the thermodynamic entropy, and the analog of the quantity of heat. The change of the statistical fluctuation distribution is also examined from a geometric perspective. The present discussions may contribute to a deeper understanding of the fluctuating diffusivity in view of the laws of thermodynamics.
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12
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Itto Y, Beck C. Superstatistical modelling of protein diffusion dynamics in bacteria. J R Soc Interface 2021; 18:20200927. [PMID: 33653112 PMCID: PMC8086855 DOI: 10.1098/rsif.2020.0927] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2020] [Accepted: 02/04/2021] [Indexed: 01/18/2023] Open
Abstract
A recent experiment (Sadoon AA, Wang Y. 2018 Phys. Rev. E98, 042411. (doi:10.1103/PhysRevE.98.042411)) has revealed that nucleoid-associated proteins (i.e. DNA-binding proteins) exhibit highly heterogeneous diffusion processes in bacteria where not only the diffusion constant but also the anomalous diffusion exponent fluctuates for the various proteins. The distribution of displacements of such proteins is observed to take a q-Gaussian form, which decays as a power law. Here, a statistical model is developed for the diffusive motion of the proteins within the bacterium, based on a superstatistics with two variables. This model hierarchically takes into account the joint fluctuations of both the anomalous diffusion exponents and the diffusion constants. A fractional Brownian motion is discussed as a possible local model. Good agreement with the experimental data is obtained.
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Affiliation(s)
- Yuichi Itto
- ICP, Universität Stuttgart, 70569 Stuttgart, Germany
- Science Division, Center for General Education, Aichi Institute of Technology, Aichi 470-0392, Japan
| | - Christian Beck
- School of Mathematical Sciences, Queen Mary University of London, London E1 4NS, UK
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13
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Stracy M, Schweizer J, Sherratt DJ, Kapanidis AN, Uphoff S, Lesterlin C. Transient non-specific DNA binding dominates the target search of bacterial DNA-binding proteins. Mol Cell 2021; 81:1499-1514.e6. [PMID: 33621478 PMCID: PMC8022225 DOI: 10.1016/j.molcel.2021.01.039] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2020] [Revised: 11/24/2020] [Accepted: 01/27/2021] [Indexed: 12/18/2022]
Abstract
Despite their diverse biochemical characteristics and functions, all DNA-binding proteins share the ability to accurately locate their target sites among the vast excess of non-target DNA. Toward identifying universal mechanisms of the target search, we used single-molecule tracking of 11 diverse DNA-binding proteins in living Escherichia coli. The mobility of these proteins during the target search was dictated by DNA interactions rather than by their molecular weights. By generating cells devoid of all chromosomal DNA, we discovered that the nucleoid is not a physical barrier for protein diffusion but significantly slows the motion of DNA-binding proteins through frequent short-lived DNA interactions. The representative DNA-binding proteins (irrespective of their size, concentration, or function) spend the majority (58%–99%) of their search time bound to DNA and occupy as much as ∼30% of the chromosomal DNA at any time. Chromosome crowding likely has important implications for the function of all DNA-binding proteins. Protein motion was compared between unperturbed cells and DNA-free cells Protein mobility was dictated by DNA interactions rather than molecular weight The nucleoid is not a physical barrier for protein diffusion The proteins studied spend most (58%–99%) of their search time bound to DNA
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Affiliation(s)
- Mathew Stracy
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK.
| | - Jakob Schweizer
- Max Planck Institute for Dynamics of Complex Technical Systems, 39106 Magdeburg, Germany
| | - David J Sherratt
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK
| | - Achillefs N Kapanidis
- Biological Physics Research Group, Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, UK
| | - Stephan Uphoff
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK.
| | - Christian Lesterlin
- Molecular Microbiology and Structural Biochemistry (MMSB), Université Lyon 1, CNRS, INSERM, UMR5086, 69007 Lyon, France.
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14
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Ahmadzadegan A, Ardekani AM, Vlachos PP. Estimation of the probability density function of random displacements from images. Phys Rev E 2020; 102:033305. [PMID: 33075892 DOI: 10.1103/physreve.102.033305] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Accepted: 08/12/2020] [Indexed: 11/07/2022]
Abstract
We introduce an image-based algorithm to find the probability density function (PDF) of particle displacements from a sequence of images. Conventionally methods based on cross correlation (CC) of image ensembles estimate the standard deviation of an assumed Gaussian PDF from the width of the CC peak. These methods are subject to limiting assumptions that the particle intensity profile and distribution of particle displacements are both Gaussian. Here, we introduce an approach to image-based probability estimation of displacement (iPED) without making any assumptions about the shape of particles' intensity profile or the PDF of the displacements. In addition, we provide a statistical convergence criterion for iPED to achieve an accurate estimate of the underlying PDF. We compare iPED's performance with the previous CC method for both Gaussian and non-Gaussian particle intensity profiles undergoing Gaussian or non-Gaussian processes. We validate iPED using synthetic images and show that it accurately resolves the PDF of particle displacements with no underlying assumptions. Finally, we demonstrate the application of iPED to real experimental data sets and evaluate its performance. In conclusion, this work presents a method for the estimation of the probability density function of random displacements from images. This method is generalized and independent of any assumptions about the underlying process and is applicable to any moving objects of any arbitrary shape.
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Affiliation(s)
- Adib Ahmadzadegan
- School of Mechanical Engineering, Purdue University, West Lafayette, Indiana 47907, USA
| | - Arezoo M Ardekani
- School of Mechanical Engineering, Purdue University, West Lafayette, Indiana 47907, USA
| | - Pavlos P Vlachos
- School of Mechanical Engineering, Purdue University, West Lafayette, Indiana 47907, USA
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15
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Yadav I, Basak R, Yan P, van Kan JA, Arluison V, van der Maarel JRC. Role of Internal DNA Motion on the Mobility of a Nucleoid-Associated Protein. J Phys Chem Lett 2020; 11:8424-8429. [PMID: 32930601 DOI: 10.1021/acs.jpclett.0c02251] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Protein transport on DNA is at the core of the machinery of life. Here we investigated the influence of DNA internal motion on the mobility of Hfq, which is involved in several aspects of nucleic acid metabolism and is one of the nucleoid-associated proteins that shape the bacterial chromosome. Fluorescence microscopy was used to follow Hfq on double-stranded DNA that was stretched by confinement to a channel with a diameter of 125 nm. The protein mobility shows a strong dependence on the internal motion of DNA in that slower motion results in faster protein diffusion. A model of released diffusion is proposed that is based on three-dimensional diffusion through the interior of the DNA coil interspersed by periods in which the protein is immobilized in a bound state. We surmise that the coupling between DNA internal motion and protein mobility has important implications for DNA metabolism and protein-binding-related regulation of gene expression.
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Affiliation(s)
- Indresh Yadav
- Department of Physics, National University of Singapore, Singapore 117542
| | - Rajib Basak
- Department of Physics, National University of Singapore, Singapore 117542
| | - Peiyan Yan
- Department of Physics, National University of Singapore, Singapore 117542
| | - Jeroen A van Kan
- Department of Physics, National University of Singapore, Singapore 117542
| | - Véronique Arluison
- Université de Paris, UFR SDV, 75006 Paris, France
- Laboratoire Léon Brillouin, CEA, CNRS, Université Paris Saclay, 91191 Gif-sur-Yvette, France
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16
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El Hamoui O, Yadav I, Radiom M, Wien F, Berret JF, van der Maarel JRC, Arluison V. Interactions between DNA and the Hfq Amyloid-like Region Trigger a Viscoelastic Response. Biomacromolecules 2020; 21:3668-3677. [PMID: 32786728 DOI: 10.1021/acs.biomac.0c00747] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Molecular transport of biomolecules plays a pivotal role in the machinery of life. Yet, this role is poorly understood due the lack of quantitative information. Here, the role and properties of the C-terminal region of Escherichia coli Hfq is reported, involved in controlling the flow of a DNA solution. A combination of experimental methodologies has been used to probe the interaction of Hfq with DNA and to measure the rheological properties of the complex. A physical gel with a temperature reversible elasticity modulus is formed due to the formation of noncovalent cross-links. The mechanical response of the complexes shows that they are inhomogeneous soft solids. Our experiments indicate that the Hfq C-terminal region could contribute to the genome's mechanical response. The reported viscoelasticity of the DNA-protein complex might have implications for cellular processes involving molecular transport of DNA or segments thereof.
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Affiliation(s)
| | - Indresh Yadav
- Department of Physics, National University of Singapore, Singapore 117542, Singapore
| | - Milad Radiom
- Matière et Systèmes Complexes, UMR 7057 CNRS Université de Paris, Bâtiment Condorcet, 10 rue Alice Domon et Léonie Duquet, F-75205 Paris, France
| | - Frank Wien
- Synchrotron SOLEIL, F-91192 Gif-sur-Yvette, France
| | - Jean-Francois Berret
- Matière et Systèmes Complexes, UMR 7057 CNRS Université de Paris, Bâtiment Condorcet, 10 rue Alice Domon et Léonie Duquet, F-75205 Paris, France
| | | | - Véronique Arluison
- Laboratoire Léon Brillouin LLB, CEA, CNRS UMR12, Université Paris Saclay, CEA Saclay, F-91191 Gif-sur-Yvette, France.,Université de Paris, F-75006 Paris, France
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17
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Garamella J, Regan K, Aguirre G, McGorty RJ, Robertson-Anderson RM. Anomalous and heterogeneous DNA transport in biomimetic cytoskeleton networks. SOFT MATTER 2020; 16:6344-6353. [PMID: 32555863 PMCID: PMC7388685 DOI: 10.1039/d0sm00544d] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
The cytoskeleton, a complex network of protein filaments and crosslinking proteins, dictates diverse cellular processes ranging from division to cargo transport. Yet, the role the cytoskeleton plays in the intracellular transport of DNA and other macromolecules remains poorly understood. Here, using single-molecule conformational tracking, we measure the transport and conformational dynamics of linear and relaxed circular (ring) DNA in composite networks of actin and microtubules with variable types of crosslinking. While both linear and ring DNA undergo anomalous, non-Gaussian, and non-ergodic subdiffusion, the detailed dynamics are controlled by both DNA topology (linear vs. ring) and crosslinking motif. Ring DNA swells, exhibiting heterogeneous subdiffusion controlled via threading by cytoskeleton filaments, while linear DNA compacts, exhibiting transport via caging and hopping. Importantly, while the crosslinking motif has little effect on ring DNA, linear DNA in networks with actin-microtubule crosslinking is significantly less ergodic and shows more heterogeneous transport than with actin-actin or microtubule-microtubule crosslinking.
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Affiliation(s)
- Jonathan Garamella
- Department of Physics & Biophysics, University of San Diego, San Diego, CA 92110, USA.
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18
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Singh RK, Mahato J, Chowdhury A, Sain A, Nandi A. Non-Gaussian subdiffusion of single-molecule tracers in a hydrated polymer network. J Chem Phys 2020; 152:024903. [PMID: 31941310 DOI: 10.1063/1.5128743] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Single molecule tracking experiments inside a hydrated polymer network have shown that the tracer motion is subdiffusive due to the viscoelastic environment inside the gel-like network. This property can be related to the negative autocorrelation of the instantaneous displacements at short times. Although the displacements of the individual tracers exhibit Gaussian statistics, the displacement distribution of all the trajectories combined from different spatial locations of the polymer network exhibits a non-Gaussian distribution. Here, we analyze many individual tracer trajectories to show that the central portion of the non-Gaussian distribution can be well approximated by an exponential distribution that spreads sublinearly with time. We explain all these features seen in the experiment by a generalized Langevin model for an overdamped particle with algebraically decaying correlations. We show that the degree of non-Gaussianity can change with the extent of heterogeneity, which is controlled in our model by the experimentally observed distributions of the motion parameters.
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Affiliation(s)
- R K Singh
- Department of Physics, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
| | - Jaladhar Mahato
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
| | - Arindam Chowdhury
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
| | - Anirban Sain
- Department of Physics, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
| | - Amitabha Nandi
- Department of Physics, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
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19
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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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20
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Dey KK. Dynamic Coupling at Low Reynolds Number. Angew Chem Int Ed Engl 2019; 58:2208-2228. [DOI: 10.1002/anie.201804599] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2018] [Indexed: 01/10/2023]
Affiliation(s)
- Krishna Kanti Dey
- Discipline of PhysicsIndian Institute of Technology Gandhinagar Gandhinagar Gujarat 382355 India
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21
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Affiliation(s)
- Krishna Kanti Dey
- Discipline of Physics; Indian Institute of Technology Gandhinagar; Gandhinagar Gujarat 382355 Indien
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22
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Stylianidou S, Lampo TJ, Spakowitz AJ, Wiggins PA. Strong disorder leads to scale invariance in complex biological systems. Phys Rev E 2018; 97:062410. [PMID: 30011517 DOI: 10.1103/physreve.97.062410] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2017] [Indexed: 11/07/2022]
Abstract
Despite the innate complexity of the cell, emergent scale-invariant behavior is observed in many biological systems. We investigate one example of this phenomenon: the dynamics of large complexes in the bacterial cytoplasm. The observed dynamics of these complexes is scale invariant in three measures of dynamics: mean-squared displacement (MSD), velocity autocorrelation function, and the step-size distribution. To investigate the physical mechanism for this emergent scale invariance, we explore minimal models in which mobility is modeled as diffusion on a rough free-energy landscape in one dimension. We discover that all three scale-invariant characteristics emerge generically in the strong disorder limit. (Strong disorder is defined by the divergence of the ensemble-averaged hop time between lattice sites.) In particular, we demonstrate how the scale invariance of the relative step-size distribution can be understood from the perspective of extreme-value theory in statistics (EVT). We show that the Gumbel scale parameter is simply related to the MSD scaling parameter. The EVT mechanism of scale invariance is expected to be generic to strongly disordered systems and therefore a powerful tool for the analysis of other systems in biology and beyond.
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Affiliation(s)
- Stella Stylianidou
- Departments Physics, Bioengineering and Microbiology, University of Washington, Seattle, Washington 98195, USA
| | - Thomas J Lampo
- Department of Chemical Engineering, Applied Physics, Materials Science and Biophysics Program, Stanford University, Stanford, California 94305, USA
| | - Andrew J Spakowitz
- Department of Chemical Engineering, Applied Physics, Materials Science and Biophysics Program, Stanford University, Stanford, California 94305, USA
| | - Paul A Wiggins
- Departments Physics, Bioengineering and Microbiology, University of Washington, Seattle, Washington 98195, USA
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23
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Abstract
Non-Gaussian diffusion is commonly considered as a result of fluctuating diffusivity, which is correlated in time or in space or both. In this work, we investigate the non-Gaussian diffusion in static disordered media via a quenched trap model, where the diffusivity is spatially correlated. Several unique effects due to quenched disorder are reported. We analytically estimate the diffusion coefficient D_{dis} and its fluctuation over samples of finite size. We show a mechanism of population splitting in the non-Gaussian diffusion. It results in a sharp peak in the distribution of displacement P(x,t) around x=0, that has frequently been observed in experiments. We examine the fidelity of the coarse-grained diffusion map, which is reconstructed from particle trajectories. Finally, we propose a procedure to estimate the correlation length in static disordered environments, where the information stored in the sample-to-sample fluctuation has been utilized.
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Affiliation(s)
- Liang Luo
- Department of Physics, Huazhong Agricultural University, Wuhan 430070, China
- Institute of Applied Physics, Huazhong Agricultural University, Wuhan 430070, China
| | - Ming Yi
- Department of Physics, Huazhong Agricultural University, Wuhan 430070, China
- Institute of Applied Physics, Huazhong Agricultural University, Wuhan 430070, China
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24
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Stefferson MW, Norris SL, Vernerey FJ, Betterton MD, Hough LE. Effects of soft interactions and bound mobility on diffusion in crowded environments: a model of sticky and slippery obstacles. Phys Biol 2017; 14:045008. [PMID: 28597848 DOI: 10.1088/1478-3975/aa7869] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Crowded environments modify the diffusion of macromolecules, generally slowing their movement and inducing transient anomalous subdiffusion. The presence of obstacles also modifies the kinetics and equilibrium behavior of tracers. While previous theoretical studies of particle diffusion have typically assumed either impenetrable obstacles or binding interactions that immobilize the particle, in many cellular contexts bound particles remain mobile. Examples include membrane proteins or lipids with some entry and diffusion within lipid domains and proteins that can enter into membraneless organelles or compartments such as the nucleolus. Using a lattice model, we studied the diffusive movement of tracer particles which bind to soft obstacles, allowing tracers and obstacles to occupy the same lattice site. For sticky obstacles, bound tracer particles are immobile, while for slippery obstacles, bound tracers can hop without penalty to adjacent obstacles. In both models, binding significantly alters tracer motion. The type and degree of motion while bound is a key determinant of the tracer mobility: slippery obstacles can allow nearly unhindered diffusion, even at high obstacle filling fraction. To mimic compartmentalization in a cell, we examined how obstacle size and a range of bound diffusion coefficients affect tracer dynamics. The behavior of the model is similar in two and three spatial dimensions. Our work has implications for protein movement and interactions within cells.
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Affiliation(s)
- Michael W Stefferson
- Department of Physics, University of Colorado, Boulder, United States of America
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25
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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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26
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Lampo TJ, Stylianidou S, Backlund MP, Wiggins PA, Spakowitz AJ. Cytoplasmic RNA-Protein Particles Exhibit Non-Gaussian Subdiffusive Behavior. Biophys J 2017; 112:532-542. [PMID: 28088300 DOI: 10.1016/j.bpj.2016.11.3208] [Citation(s) in RCA: 93] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2016] [Revised: 08/31/2016] [Accepted: 11/07/2016] [Indexed: 02/06/2023] Open
Abstract
The cellular cytoplasm is a complex, heterogeneous environment (both spatially and temporally) that exhibits viscoelastic behavior. To further develop our quantitative insight into cellular transport, we analyze data sets of mRNA molecules fluorescently labeled with MS2-GFP tracked in real time in live Escherichia coli and Saccharomyces cerevisiae cells. As shown previously, these RNA-protein particles exhibit subdiffusive behavior that is viscoelastic in its origin. Examining the ensemble of particle displacements reveals a Laplace distribution at all observed timescales rather than the Gaussian distribution predicted by the central limit theorem. This ensemble non-Gaussian behavior is caused by a combination of an exponential distribution in the time-averaged diffusivities and non-Gaussian behavior of individual trajectories. We show that the non-Gaussian behavior is a consequence of significant heterogeneity between trajectories and dynamic heterogeneity along single trajectories. Informed by theory and simulation, our work provides an in-depth analysis of the complex diffusive behavior of RNA-protein particles in live cells.
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Affiliation(s)
- Thomas J Lampo
- Department of Chemical Engineering, Stanford University, Stanford, California
| | | | | | - Paul A Wiggins
- Department of Physics, Washington University, Seattle, Washington; Department of Bioengineering, Washington University, Seattle, Washington; Department of Microbiology, Washington University, Seattle, Washington
| | - Andrew J Spakowitz
- Department of Chemical Engineering, Stanford University, Stanford, California; Department of Applied Physics, Stanford University, Stanford, California; Department of Materials Science, Stanford University, Stanford, California; Biophysics Program, Stanford University, Stanford, California.
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27
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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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28
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Lampo TJ, Kennard AS, Spakowitz AJ. Physical Modeling of Dynamic Coupling between Chromosomal Loci. Biophys J 2016; 110:338-347. [PMID: 26789757 DOI: 10.1016/j.bpj.2015.11.3520] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2015] [Revised: 11/05/2015] [Accepted: 11/23/2015] [Indexed: 11/15/2022] Open
Abstract
The motion of chromosomal DNA is essential to many biological processes, including segregation, transcriptional regulation, recombination, and packaging. Physical understanding of these processes would be dramatically enhanced through predictive, quantitative modeling of chromosome dynamics of multiple loci. Using a polymer dynamics framework, we develop a prediction for the correlation in the velocities of two loci on a single chromosome or otherwise connected by chromatin. These predictions reveal that the signature of correlated motion between two loci can be identified by varying the lag time between locus position measurements. In general, this theory predicts that as the lag time interval increases, the dual-loci dynamic behavior transitions from being completely uncorrelated to behaving as an effective single locus. This transition corresponds to the timescale of the stress communication between loci through the intervening segment. This relatively simple framework makes quantitative predictions based on a single timescale fit parameter that can be directly compared to the in vivo motion of fluorescently labeled chromosome loci. Furthermore, this theoretical framework enables the detection of dynamically coupled chromosome regions from the signature of their correlated motion.
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Affiliation(s)
- Thomas J Lampo
- Chemical Engineering, Stanford University, Stanford, California
| | | | - Andrew J Spakowitz
- Chemical Engineering, Stanford University, Stanford, California; Biophysics Program, Stanford University, Stanford, California; Department of Materials Science and Engineering, Stanford University, Stanford, California; Department of Applied Physics, Stanford University, Stanford, California.
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29
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Abstract
In bacteria such as Escherichia coli, DNA is compacted into a nucleoid near the cell center, whereas ribosomes-molecular complexes that translate mRNAs into proteins-are mainly localized to the poles. We study the impact of this spatial organization using a minimal reaction-diffusion model for the cellular transcriptional-translational machinery. Although genome-wide mRNA-nucleoid segregation still lacks experimental validation, our model predicts that [Formula: see text] of mRNAs are segregated to the poles. In addition, our analysis reveals a "circulation" of ribosomes driven by the flux of mRNAs, from synthesis in the nucleoid to degradation at the poles. We show that our results are robust with respect to multiple, biologically relevant factors, such as mRNA degradation by RNase enzymes, different phases of the cell division cycle and growth rates, and the existence of nonspecific, transient interactions between ribosomes and mRNAs. Finally, we confirm that the observed nucleoid size stems from a balance between the forces that the chromosome and mRNAs exert on each other. This suggests a potential global feedback circuit in which gene expression feeds back on itself via nucleoid compaction.
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30
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Bacterial partition complexes segregate within the volume of the nucleoid. Nat Commun 2016; 7:12107. [PMID: 27377966 PMCID: PMC4935973 DOI: 10.1038/ncomms12107] [Citation(s) in RCA: 79] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2015] [Accepted: 05/31/2016] [Indexed: 11/08/2022] Open
Abstract
Precise and rapid DNA segregation is required for proper inheritance of genetic material. In most bacteria and archaea, this process is assured by a broadly conserved mitotic-like apparatus in which a NTPase (ParA) displaces the partition complex. Competing observations and models imply starkly different 3D localization patterns of the components of the partition machinery during segregation. Here we use super-resolution microscopies to localize in 3D each component of the segregation apparatus with respect to the bacterial chromosome. We show that Par proteins locate within the nucleoid volume and reveal that proper volumetric localization and segregation of partition complexes requires ATPase and DNA-binding activities of ParA. Finally, we find that the localization patterns of the different components of the partition system highly correlate with dense chromosomal regions. We propose a new mechanism in which the nucleoid provides a scaffold to guide the proper segregation of partition complexes. In most bacteria and archaea, a broadly conserved mitotic-like apparatus assures the inheritance of duplicated genetic material before cell division. Here, the authors use super-resolution microscopies to dissect the activities required for proper DNA segregation through the nucleoid interior.
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31
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Oliveira SMD, Neeli-Venkata R, Goncalves NSM, Santinha JA, Martins L, Tran H, Mäkelä J, Gupta A, Barandas M, Häkkinen A, Lloyd-Price J, Fonseca JM, Ribeiro AS. Increased cytoplasm viscosity hampers aggregate polar segregation inEscherichia coli. Mol Microbiol 2015; 99:686-99. [DOI: 10.1111/mmi.13257] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/25/2015] [Indexed: 12/11/2022]
Affiliation(s)
- Samuel M. D. Oliveira
- Laboratory of Biosystem Dynamics; Department of Signal Processing; Tampere University of Technology; 33101 Tampere Finland
| | - Ramakanth Neeli-Venkata
- Laboratory of Biosystem Dynamics; Department of Signal Processing; Tampere University of Technology; 33101 Tampere Finland
| | - Nadia S. M. Goncalves
- Laboratory of Biosystem Dynamics; Department of Signal Processing; Tampere University of Technology; 33101 Tampere Finland
| | - João A. Santinha
- UNINOVA; Instituto de Desenvolvimento de Novas Tecnologias; Campus FCT-UNL; 2829-516 Caparica Portugal
| | - Leonardo Martins
- UNINOVA; Instituto de Desenvolvimento de Novas Tecnologias; Campus FCT-UNL; 2829-516 Caparica Portugal
| | - Huy Tran
- Laboratory of Biosystem Dynamics; Department of Signal Processing; Tampere University of Technology; 33101 Tampere Finland
| | - Jarno Mäkelä
- Laboratory of Biosystem Dynamics; Department of Signal Processing; Tampere University of Technology; 33101 Tampere Finland
| | - Abhishekh Gupta
- Laboratory of Biosystem Dynamics; Department of Signal Processing; Tampere University of Technology; 33101 Tampere Finland
| | - Marilia Barandas
- UNINOVA; Instituto de Desenvolvimento de Novas Tecnologias; Campus FCT-UNL; 2829-516 Caparica Portugal
| | - Antti Häkkinen
- Laboratory of Biosystem Dynamics; Department of Signal Processing; Tampere University of Technology; 33101 Tampere Finland
| | - Jason Lloyd-Price
- Laboratory of Biosystem Dynamics; Department of Signal Processing; Tampere University of Technology; 33101 Tampere Finland
| | - José M. Fonseca
- UNINOVA; Instituto de Desenvolvimento de Novas Tecnologias; Campus FCT-UNL; 2829-516 Caparica Portugal
| | - Andre S. Ribeiro
- Laboratory of Biosystem Dynamics; Department of Signal Processing; Tampere University of Technology; 33101 Tampere Finland
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32
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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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