scholarly journals Initiation of chromosome replication controls both division and replication cycles in E. coli through a double-adder mechanism

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Guillaume Witz ◽  
Erik van Nimwegen ◽  
Thomas Julou
Keyword(s):  
Cell Cycle ◽  
Time Lapse ◽  
Growth Conditions ◽  
Replication Initiation ◽  
Stochastic Simulations ◽  
E Coli ◽  
Time Lapse Microscopy ◽  
Statistical Framework ◽  
Wide Range ◽  
Cell Cycle Models

Living cells proliferate by completing and coordinating two cycles, a division cycle controlling cell size and a DNA replication cycle controlling the number of chromosomal copies. It remains unclear how bacteria such as Escherichia coli tightly coordinate those two cycles across a wide range of growth conditions. Here, we used time-lapse microscopy in combination with microfluidics to measure growth, division and replication in single E. coli cells in both slow and fast growth conditions. To compare different phenomenological cell cycle models, we introduce a statistical framework assessing their ability to capture the correlation structure observed in the data. In combination with stochastic simulations, our data indicate that the cell cycle is driven from one initiation event to the next rather than from birth to division and is controlled by two adder mechanisms: the added volume since the last initiation event determines the timing of both the next division and replication initiation events.

scholarly journals Initiation of chromosome replication controls both division and replication cycles in E. coli through a double-adder mechanism

2019 ◽  
Author(s):  
Guillaume Witz ◽  
Erik van Nimwegen ◽  
Thomas Julou
Keyword(s):  
Cell Cycle ◽  
Cell Size ◽  
Cell Cycle Control ◽  
Size Control ◽  
Time Lapse ◽  
Growth Conditions ◽  
Replication Initiation ◽  
Stochastic Simulations ◽  
E Coli ◽  
Wide Range

AbstractLiving cells proliferate by completing and coordinating two essential cycles, a division cycle that controls cell size, and a DNA replication cycle that controls the number of chromosomal copies in the cell. Despite lacking dedicated cell cycle control regulators such as cyclins in eukaryotes, bacteria such as E. coli manage to tightly coordinate those two cycles across a wide range of growth conditions, including situations where multiple nested rounds of replication progress simultaneously. Various cell cycle models have been proposed to explain this feat, but it has been impossible to validate them so far due to a lack of experimental tools for systematically testing their different predictions. Recently new insights have been gained on the division cycle through the study of the structure of fluctuations in growth, size, and division in individual cells. In particular, it was found that cell size appears to be controlled by an adder mechanism, i.e. the added volume between divisions is held approximately constant and fluctuates independently of growth rate and cell size at birth. However, how replication initiation is regulated and coupled to cell size control remains unclear, mainly due to scarcity of experimental measurements on replication initiation at the single-cell level. Here, we used time-lapse microscopy in combination with microfluidics to directly measure growth, division and replication in thousands of single E. coli cells growing in both slow and fast growth conditions. In order to compare different phenomenological models of the cell cycle, we introduce a statistical framework which assess their ability to capture the correlation structure observed in the experimental data. Using this in combination with stochastic simulations, our data indicate that, instead of thinking of the cell cycle as running from birth to division, the cell cycle is controlled by two adder mechanisms starting at the initiation of replication: the added volume since the last initiation event controls the timing of both the next division event and the next replication initiation event. Interestingly the double-adder mechanism identified in this study has recently been found to explain the more complex cell cycle of mycobacteria, suggesting shared control strategies across species.

scholarly journals Response to comment on ‘Initiation of chromosome replication controls both division and replication cycles in E. coli through a double-adder mechanism’

2020 ◽  
Author(s):  
Guillaume Witz ◽  
Thomas Julou ◽  
Erik van Nimwegen
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Control ◽  
Time Lapse ◽  
Analysis Method ◽  
E Coli ◽  
Statistical Analysis Method ◽  
Bacterial Cell Cycle ◽  
The One ◽  
Analysis Errors ◽  
Cell Cycle Models

AbstractLast year we published an article (Witz et al., 2019) in which we used time-lapse microscopy in combination with microfluidics to measure growth, division and replication in single E. coli cells on the one hand, and developed a new statistical analysis method to calculate the ability of different cell cycle models to capture the correlation structure observed in the data on the other hand. This led us to propose a new model of cell cycle control in E. coli which we called the double-adder model.Recently Le Treut et al. published a comment (Le Treut et al., 2020) on our article which made a number of highly critical claims, including allegations that our own data support a different model than the one we proposed, and that our model cannot reproduce the ‘adder phenotype’ observed in the data. We here show that all these allegations are false and based on basic analysis errors. Although our focus is on explaining the errors in the analysis of Le Treut et al, we have attempted to make the presentation of interest to a broader scientific audience by discussing the issues in the context of what our current understanding is of the bacterial cell cycle, and to what extent recent data either support or reject various proposed models.

scholarly journals Use of time-lapse microscopy to visualize rapid movement of the replication origin region of the chromosome during the cell cycle in Bacillus subtilis

1998 ◽  
Vol 28 (5) ◽  
pp. 883-892 ◽  
Author(s):  
Chris D. Webb ◽  
Peter L. Graumann ◽  
Jason A. Kahana ◽  
Aurelio A. Teleman ◽  
Pamela A. Silver ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Bacillus Subtilis ◽  
Replication Origin ◽  
Time Lapse ◽  
Time Lapse Microscopy ◽  
Rapid Movement ◽  
Use Of Time ◽  
Origin Region

scholarly journals A study of SeqA subcellular localization in Escherichia coli using photo-activated localization microscopy

2015 ◽  
Vol 184 ◽  
pp. 425-450 ◽  
Author(s):  
Jacek T. Mika ◽  
Aster Vanhecke ◽  
Peter Dedecker ◽  
Toon Swings ◽  
Jeroen Vangindertael ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Cell Cycle ◽  
Bacterial Genome ◽  
Genetically Engineered ◽  
Replication Initiation ◽  
Cell Protein ◽  
Experimental Conditions ◽  
Localization Microscopy ◽  
E Coli ◽  
Copy Numbers

Escherichia coli (E. coli) cells replicate their genome once per cell cycle to pass on genetic information to the daughter cells. The SeqA protein binds the origin of replication, oriC, after DNA replication initiation and sequesters it from new initiations in order to prevent overinitiation. Conventional fluorescence microscopy studies of SeqA localization in bacterial cells have shown that the protein is localized to discrete foci. In this study we have used photo-activated localization microscopy (PALM) to determine the localization of SeqA molecules, tagged with fluorescent proteins, with a localization precision of 20–30 nm with the aim to visualize the SeqA subcellular structures in more detail than previously possible. SeqA–PAmCherry was imaged in wild type E. coli, expressed from plasmid or genetically engineered into the bacterial genome, replacing the native seqA gene. Unsynchronized cells as well as cells with a synchronized cell cycle were imaged at various time points, in order to investigate the evolution of SeqA localization during the cell cycle. We found that SeqA indeed localized into discrete foci but these were not the only subcellular localizations of the protein. A significant amount of SeqA–PAmCherry molecules was localized outside the foci and in a fraction of cells we saw patterns indicating localization at the membrane. Using quantitative PALM, we counted protein copy numbers per cell, protein copy numbers per focus, the numbers of foci per cell and the sizes of the SeqA clusters. The data showed broad cell-to-cell variation and we did not observe a correlation between SeqA–PAmCherry protein numbers and the cell cycle under the experimental conditions of this study. The numbers of SeqA–PAmCherry molecules per focus as well as the foci sizes also showed broad distributions indicating that the foci are likely not characterized by a fixed number of molecules. We also imaged an E. coli strain devoid of the dam methylase (Δdam) and observed that SeqA–PAmCherry no longer formed foci, and was dispersed throughout the cell and localized to the plasma membrane more readily. We discuss our results in the context of the limitations of the technique.

scholarly journals Microtubules in Candida albicans Hyphae Drive Nuclear Dynamics and Connect Cell Cycle Progression to Morphogenesis

2005 ◽  
Vol 4 (10) ◽  
pp. 1697-1711 ◽  
Author(s):  
Kenneth R. Finley ◽  
Judith Berman
Keyword(s):  
Cell Cycle ◽  
Candida Albicans ◽  
Basal Cell ◽  
Time Lapse ◽  
Nuclear Migration ◽  
Microtubule Dynamics ◽  
Growth Defect ◽  
Cell Cortex ◽  
Long Distance ◽  
Time Lapse Microscopy

ABSTRACT Candida albicans is an opportunistic fungal pathogen whose virulence is related to its ability to switch between yeast, pseudohyphal, and true-hyphal morphologies. To ask how long-distance nuclear migration occurs in C. albicans hyphae, we identified the fundamental properties of nuclear movements and microtubule dynamics using time-lapse microscopy. In hyphae, nuclei migrate to, and divide across, the presumptive site of septation, which forms 10 to 15 μm distal to the basal cell. The mother nucleus returns to the basal cell, while the daughter nucleus reiterates the process. We used time-lapse microscopy to identify the mechanisms by which C. albicans nuclei move over long distances and are coordinated with hyphal morphology. We followed nuclear migration and spindle dynamics, as well as the time and position of septum specification, defined it as the presumptum, and established a chronology of nuclear, spindle, and morphological events. Analysis of microtubule dynamics revealed that premitotic forward nuclear migration is due to the repetitive sliding of astral microtubules along the cell cortex but that postmitotic forward and reverse nuclear migrations are due primarily to spindle elongation. Free microtubules exhibit cell cycle regulation; they are present during interphase and disappear at the time of spindle assembly. Finally, a growth defect in strains expressing Tub2-green fluorescent protein revealed a connection between hyphal elongation and the nuclear cell cycle that is coordinated by hyphal length and/or volume.

scholarly journals Pharmacophore-guided discovery of CDC25 inhibitors causing cell cycle arrest and cell death

2018 ◽  
Author(s):  
Zeynep Kabakci ◽  
Simon Käppeli ◽  
Giorgio Cozza ◽  
Claudio Cantù ◽  
Christiane König ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Mixed Type ◽  
Molecular Level ◽  
Time Lapse ◽  
Guided Discovery ◽  
Enzymatic Assays ◽  
Intestinal Crypt ◽  
Time Lapse Microscopy ◽  
Cycle Arrest ◽  
Mechanism Of Inhibition

ABSTRACTCDC25 phosphatases have a key role in cell cycle transitions and are important targets for cancer therapy. Here, we set out to discover novel CDC25 inhibitors. Using a combination of computational approaches we defined a minimal common pharmacophore in established CDC25 inhibitors and performed a virtual screening of a proprietary library. Taking advantage of the availability of crystal structures for CDC25A and CDC25B and using a molecular docking strategy, we carried out hit expansion/optimization. Enzymatic assays revealed that naphthoquinone scaffolds were the most promising CDC25 inhibitors among selected hits. At the molecular level, the compounds acted through a mixed-type mechanism of inhibition of phosphatase activity, involving reversible oxidation of cysteine residues. In 2D cell cultures, the compounds caused arrest of the cell cycle at the G1/S or at the G2/M transition. Mitotic markers analysis and time-lapse microscopy confirmed that CDK1 activity was impaired and that mitotic arrest was followed by death. Finally, studies on 3D organoids derived from intestinal crypt stem cells of Apc/K-Ras mice revealed that the compounds caused arrest of proliferation.

scholarly journals Instructive simulation of the bacterial cell division cycle

Microbiology ◽  
2011 ◽  
Vol 157 (7) ◽  
pp. 1876-1885 ◽  
Author(s):  
Arieh Zaritsky ◽  
Ping Wang ◽  
Norbert O. E. Vischer
Keyword(s):  
Cell Cycle ◽  
Cell Division ◽  
Dna Replication ◽  
Cell Mass ◽  
Time Lapse ◽  
Replication Initiation ◽  
Bacterial Cells ◽  
Bacterial Cell Division ◽  
Cycle Simulation ◽  
New Ideas

The coupling between chromosome replication and cell division includes temporal and spatial elements. In bacteria, these have globally been resolved during the last 40 years, but their full details and action mechanisms are still under intensive study. The physiology of growth and the cell cycle are reviewed in the light of an established dogma that has formed a framework for development of new ideas, as exemplified here, using the Cell Cycle Simulation (CCSim) program. CCSim, described here in detail for the first time, employs four parameters related to time (replication, division and inter-division) and size (cell mass at replication initiation) that together are sufficient to describe bacterial cells under various conditions and states, which can be manipulated environmentally and genetically. Testing the predictions of CCSim by analysis of time-lapse micrographs of Escherichia coli during designed manipulations of the rate of DNA replication identified aspects of both coupling elements. Enhanced frequencies of cell division were observed following an interval of reduced DNA replication rate, consistent with the prediction of a minimum possible distance between successive replisomes (an eclipse). As a corollary, the notion that cell poles are not always inert was confirmed by observed placement of division planes at perpendicular planes in monstrous and cuboidal cells containing multiple, segregating nucleoids.

scholarly journals Characterization of Dependencies Between Growth and Division in Budding Yeast

2016 ◽  
Author(s):  
Michael B. Mayhew ◽  
Edwin S. Iversen ◽  
Alexander J. Hartemink
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Progression ◽  
Budding Yeast ◽  
Size Control ◽  
Inverse Correlation ◽  
Time Lapse ◽  
Independent Manner ◽  
Statistical Framework ◽  
Cell Variation

AbstractCell growth and division are processes vital to the proliferation and development of life. Coordination between these two processes has been recognized for decades in a variety of organisms. In the budding yeastSaccharomyces cerevisiae, this coordination or ‘size control’ appears as an inverse correlation between cell size and the rate of cell-cycle progression, routinely observed in G1prior to cell division commitment. Beyond this point, cells are presumed to complete S/G2/M at similar rates and in a size-independent manner. As such, studies of dependence between growth and division have focused on G1. Moreover, coordination between growth and division has commonly been analyzedwithinthe cycle of a single cell without accounting for correlations in growth and division characteristicsbetweencycles of related cells. In a comprehensive analysis of three published time-lapse microscopy datasets, we analyze both intra-and inter-cycle dependencies between growth and division, revisiting assumptions about the coordination between these two processes. Interestingly, we find evidence (1) that S/G2/M durations are systematically longer in daughters than in mothers, (2) of dependencies between S/G2/M and size at budding that echo the classical G1dependencies, and, (3) in contrast with recent bacterial studies, of negative dependencies between size at birth and size accumulated during the cell cycle. In addition, we develop a novel hierarchical model to uncover inter-cycle dependencies, and we find evidence for such dependencies in cells growing in sugar-poor environments. Our analysis highlights the need for experimentalists and modelers to account for new sources of cell-to-cell variation in growth and division, and our model provides a formal statistical framework for the continued study of dependencies between biological processes.

scholarly journals Coordination between E. coli Cell Size and Cell Cycle Mediated by DnaA

2020 ◽  
Author(s):  
Qing Zhang ◽  
Zhichao Zhang ◽  
Hualin Shi
Keyword(s):  
Cell Cycle ◽  
Growth Rate ◽  
Dna Replication ◽  
Cell Size ◽  
Doubling Time ◽  
Cell Mass ◽  
Replication Initiation ◽  
General Relationship ◽  
E Coli ◽  
Regulatory Processes

Sixty years ago, bacterial cell size was found as an exponential function of growth rate. Fifty years ago, a more general relationship was proposed, in which the cell mass was equal to the initiation mass multiplied by the ratio of the total time of the C and D periods to the doubling time. This relationship has recently been experimentally confirmed by perturbing doubling time, C period, D period or the initiation mass. However, the underlying molecular mechanism remains unclear. Here, we developed a mechanistic and kinetic model to describe how the initiator protein DnaA mediates the initiation of DNA replication in E. coli. In the model, we introduced an initiation probability function involving competitive binding of DnaA-ATP (active) and DnaA-ADP (inactive) at replication origin to determine the initiation of replication. In addition, we considered RNAP availability, ppGpp inhibition, DnaA autorepression, DnaA titration by chromosomal sites, hydrolysis of DnaA-ATP along with DNA replication, reactivation of DnaA-ADP and established a kinetic description of these DnaA regulatory processes. We simulated DnaA kinetics and obtained a self-consistent cell size and a regular DnaA oscillation coordinated with the cell cycle at steady state. The relationship between the cell size obtained by the simulation and the growth rate, C period, D period or initiation mass reproduces the results of the experiment. This model also predicts how the number of DnaA and the initiation mass vary with the perturbation parameters (including those reflecting the mutation or interference of DnaA regulatory processes), which is comparable to experimental data. The results suggest that the regulatory mechanisms of DnaA level and activity are associated with the invariance of initiation mass and the cell size general relationship for matching frequencies of replication initiation and cell division. This study may provide clues for concerted control of cell size and cell cycle in synthetic biology.

scholarly journals Energy Starvation Induces a Cell Cycle Arrest in Escherichia coli by Triggering Degradation of the DnaA Initiator Protein

2021 ◽  
Vol 8 ◽  
Author(s):  
Godefroid Charbon ◽  
Belén Mendoza-Chamizo ◽  
Christopher Campion ◽  
Xiaobo Li ◽  
Peter Ruhdal Jensen ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Cell Cycle ◽  
Growth Conditions ◽  
Chromosome Replication ◽  
Replication Initiation ◽  
Atp Depletion ◽  
Initiator Protein ◽  
Cycle Arrest ◽  
A Cell

During steady-state Escherichia coli growth, the amount and activity of the initiator protein, DnaA, controls chromosome replication tightly so that initiation only takes place once per origin in each cell cycle, regardless of growth conditions. However, little is known about the mechanisms involved during transitions from one environmental condition to another or during starvation stress. ATP depletion is one of the consequences of long-term carbon starvation. Here we show that DnaA is degraded in ATP-depleted cells. A chromosome replication initiation block is apparent in such cells as no new rounds of DNA replication are initiated while replication events that have already started proceed to completion.

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