scholarly journals Response of single bacterial cells to stress gives rise to complex history dependence at the population level

2016 ◽  
Vol 113 (15) ◽  
pp. 4224-4229 ◽  
Author(s):  
Roland Mathis ◽  
Martin Ackermann
Keyword(s):  
Cell Cycle ◽  
Sodium Chloride ◽  
Caulobacter Crescentus ◽  
Single Cells ◽  
Population Level ◽  
Time Interval ◽  
Bacterial Cells ◽  
History Dependence ◽  
Cell Cycle Synchronization ◽  
Subsequent Exposure

Most bacteria live in ever-changing environments where periods of stress are common. One fundamental question is whether individual bacterial cells have an increased tolerance to stress if they recently have been exposed to lower levels of the same stressor. To address this question, we worked with the bacteriumCaulobacter crescentusand asked whether exposure to a moderate concentration of sodium chloride would affect survival during later exposure to a higher concentration. We found that the effects measured at the population level depended in a surprising and complex way on the time interval between the two exposure events: The effect of the first exposure on survival of the second exposure was positive for some time intervals but negative for others. We hypothesized that the complex pattern of history dependence at the population level was a consequence of the responses of individual cells to sodium chloride that we observed: (i) exposure to moderate concentrations of sodium chloride caused delays in cell division and led to cell-cycle synchronization, and (ii) whether a bacterium would survive subsequent exposure to higher concentrations was dependent on the cell-cycle state. Using computational modeling, we demonstrated that indeed the combination of these two effects could explain the complex patterns of history dependence observed at the population level. Our insight into how the behavior of single cells scales up to processes at the population level provides a perspective on how organisms operate in dynamic environments with fluctuating stress exposure.

scholarly journals Sensory domain of the cell cycle kinase CckA inCaulobacter crescentusregulates the differential DNA binding activity of the master regulator CtrA

2018 ◽  
Author(s):  
Sharath Narayanan ◽  
Lokesh Kumar ◽  
Sunish Kumar Radhakrishnan
Keyword(s):  
Cell Cycle ◽  
Dna Binding ◽  
Caulobacter Crescentus ◽  
Point Mutations ◽  
Signal Transduction Pathway ◽  
Binding Activity ◽  
Cellular Damage ◽  
Bacterial Cells ◽  
Topoisomerase Iv ◽  
A Genome

Sophisticated signaling mechanisms allow bacterial cells to cope with environmental and intracellular challenges. Activation of specific pathways facilitates the cells to overcome cellular damage and thereby warrant integrity. Here we demonstrate the pliability of the CckA-CtrA two component signaling system in the freshwater bacteriumCaulobacter crescentus. Our forward genetic screen to analyse suppressor mutations that can negate the chromosome segregation block induced by the topoisomerase IV inhibitor, NstA, yielded various point mutations in the cell cycle histidine kinase, CckA. Notably, we identified a point mutation in the PAS-B domain of CckA, which resulted in increased levels of phosphorylated CtrA (CtrA~P), the master cell cycle regulator. Surprisingly, this increase in CtrA~P levels did not translate into a genome-wide increase in the DNA occupancy of CtrA, but specifically enriched its affinity to the chromosomal origin of replication, Cori, and a very small sub-set of CtrA regulated promoters. We show that through this enhanced binding of CtrA to the Cori, cells are able to overcome the toxic defects rendered by stable NstA through a possible slow down in the chromosome cycle. Taken together, our work opens up an unexplored and intriguing aspect of the CckA-CtrA signal transduction pathway. The distinctive DNA binding nature of CtrA and its regulation by CckA might also be crucial for pathogenesis because of the highly conserved nature of CckA-CtrA pathway in alphaproteobacteria.

scholarly journals Single-cell intracellular pH measurements reveal cell-cycle linked pH dynamics

2021 ◽  
Author(s):  
Julia S Spear ◽  
Katharine A White
Keyword(s):  
Cell Cycle ◽  
Single Cell ◽  
Intracellular Ph ◽  
Cell Cycle Progression ◽  
Single Cells ◽  
Population Level ◽  
Growth Factor Signaling ◽  
Cycle Progression ◽  
Cell Behaviors ◽  
Sinusoidal Pattern

Transient changes in intracellular pH (pHi) have been shown to regulate normal cell behaviors like migration and cell-cycle progression, while dysregulated pHi dynamics are a hallmark of cancer. However, little is known about how pHi heterogeneity and dynamics influence population-level measurements or single-cell behaviors. Here, we present and characterize single-cell pHi heterogeneity distributions in both normal and cancer cells and measure dynamic pHi increases in single cells in response to growth factor signaling. Next, we measure pHi dynamics in single cells during cell cycle progression. We determined that single-cell pHi is significantly decreased at the G1/S boundary, increases from S phase to the G2/M transition, rapidly acidifies during mitosis, and recovers in daughter cells. This sinusoidal pattern of pHi dynamics was linked to cell cycle timing regardless of synchronization method. This work confirms prior work at the population level and reveals distinct advantages of single-cell pHi measurements in capturing pHi heterogeneity across a population and dynamics within single cells.

scholarly journals Robust, linear correlations between growth rates and β-lactam–mediated lysis rates

2018 ◽  
Vol 115 (16) ◽  
pp. 4069-4074 ◽  
Author(s):  
Anna J. Lee ◽  
Shangying Wang ◽  
Hannah R. Meredith ◽  
Bihan Zhuang ◽  
Zhuojun Dai ◽  
...  
Keyword(s):  
Growth Rate ◽  
Single Cells ◽  
Bacterial Species ◽  
Population Level ◽  
Instantaneous Growth Rate ◽  
Bacterial Cells ◽  
Bacterial Growth Rate ◽  
Lysis Rate ◽  
Dynamic Signature ◽  
Linear Correlations

It is widely acknowledged that faster-growing bacteria are killed faster by β-lactam antibiotics. This notion serves as the foundation for the concept of bacterial persistence: dormant bacterial cells that do not grow are phenotypically tolerant against β-lactam treatment. Such correlation has often been invoked in the mathematical modeling of bacterial responses to antibiotics. Due to the lack of thorough quantification, however, it is unclear whether and to what extent the bacterial growth rate can predict the lysis rate upon β-lactam treatment under diverse conditions. Enabled by experimental automation, here we measured >1,000 growth/killing curves for eight combinations of antibiotics and bacterial species and strains, including clinical isolates of bacterial pathogens. We found that the lysis rate of a bacterial population linearly depends on the instantaneous growth rate of the population, regardless of how the latter is modulated. We further demonstrate that this predictive power at the population level can be explained by accounting for bacterial responses to the antibiotic treatment by single cells. This linear dependence of the lysis rate on the growth rate represents a dynamic signature associated with each bacterium–antibiotic pair and serves as the quantitative foundation for designing combination antibiotic therapy and predicting the population-structure change in a population with mixed phenotypes.

scholarly journals When size matters – coordination of growth and cell cycle in bacteria

2019 ◽  
Author(s):  
Joanna Morcinek-Orłowska ◽  
Justyna Galińska ◽  
Monika Katarzyna Glinkowska
Keyword(s):  
Cell Cycle ◽  
Dna Replication ◽  
Driving Forces ◽  
Control Strategies ◽  
Bacterial Species ◽  
Control Cell ◽  
Genetic Material ◽  
Alternative View ◽  
Time Interval ◽  
Bacterial Cells

Bacterial cells often inhabit environments where conditions can change rapidly. Therefore, a lot of bacterial species developed control strategies allowing them to grow and divide very fast during feast and slow down both parameters during famine. Under rich nutritional conditions, fast-growing bacteria can divide with time interval equal to half of the period required to synthesize their chromosomes. This is possible due to multifork replication which allows ancestor cells to start copying genetic material for their descendants. This reproduction scheme was most likely selected for, since it enables maximization of growth rate and hence – effective competition for resources, while ensuring that DNA replication will not become limiting for cell division. Even with this complexity of cell cycle, isogenic bacterial cells grown under defined conditions display remarkably narrow distribution of sizes. This may suggest that mechanisms exists to control cell size at division step. Alternative view, with great support in experimental data is that the only step coordinated with cell growth is the initiation of DNA replication. Despite decades of research we are still not sure what the driving forces in bacterial cell cycle are. In this work we review recent advances in understanding coordination of growth with DNA replication coming from single cell studies and systems biology approaches.

scholarly journals CcnA, a novel non-coding RNA regulating the bacterial cell cycle

2019 ◽  
Author(s):  
Wanassa Beroual ◽  
David Lalaouna ◽  
Nadia Ben Zaina ◽  
Odile Valette ◽  
Karine Prévost ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Sinorhizobium Meliloti ◽  
Caulobacter Crescentus ◽  
Direct Interaction ◽  
Cell Types ◽  
Bacterial Cells ◽  
Non Coding Rna ◽  
Sequential Activation ◽  
Bacterial Cell Cycle ◽  
Different Cell Types

SummaryBacterial cells are powerful models for understanding how cells divide and accomplish global regulatory programs. In Caulobacter crescentus a cascade of essential master regulators regulate the correct and sequential activation of DNA replication, cell division and development of different cell types. Among them CtrA plays a crucial role coordinating all those functions. Despite decades of investigation, no control by non-coding RNAs (ncRNAs) has been linked to Caulobacter cell cycle. Here, for the first time we describe the role of a novel essential factor named CcnA, a ncRNA located at the origin of replication, activated by CtrA and responsible for the rapid and strong accumulation of CtrA itself. In addition CcnA is also responsible for the inhibition of GcrA translation by direct interaction with its UTR region. By a combination of probing experiments and mutagenesis, we propose a new mechanism by liberation (CtrA) or sequestration (GcrA) of the Ribosome Binding Site (RBS). CcnA role is conserved in other alphaproteobacterial species, such as Sinorhizobium meliloti, representing indeed a conserved and fundamental process regulating cell cycle in Rhizobiales and Caulobacterales.

scholarly journals DivIVA concentrates mycobacterial cell envelope assembly for initiation and stabilization of polar growth

2018 ◽  
Author(s):  
Emily S. Melzer ◽  
Caralyn E. Sein ◽  
James J. Chambers ◽  
M. Sloan Siegrist
Keyword(s):  
Cell Wall ◽  
Mycobacterium Smegmatis ◽  
De Novo ◽  
Caulobacter Crescentus ◽  
Cell Envelope ◽  
Population Level ◽  
Model Organisms ◽  
Bacterial Cells ◽  
Peptidoglycan Synthesis ◽  
Mycobacterial Cell

AbstractIn many model organisms, diffuse patterning of cell wall peptidoglycan synthesis by the actin homolog MreB enables the bacteria to maintain their characteristic rod shape. InCaulobacter crescentusandEscherichia coli, MreB is also required to sculpt this morphologyde novo. Mycobacteria are rod-shaped but expand their cell wall from discrete polar or sub-polar zones. In this genus, the tropomyosin-like protein DivIVA is required for the maintenance of cell morphology. DivIVA has also been proposed to direct peptidoglycan synthesis to the tips of the mycobacterial cell. The precise nature of this regulation is unclear, as is its role in creating rod shape from scratch. We find that DivIVA localizes nascent cell wall and covalently associated mycomembrane but is dispensable for the assembly process itself.Mycobacterium smegmatisrendered spherical by peptidoglycan digestion or by DivIVA depletion are able to regain rod shape at the population level in the presence of DivIVA. At the single cell level, there is a close spatiotemporal correlation between DivIVA foci, rod extrusion and concentrated cell wall synthesis. Thus, although the precise mechanistic details differ from other organisms,M. smegmatisalso establish and propagate rod shape by cytoskeleton-controlled patterning of peptidoglycan. Our data further support the emerging notion that morphology is a hardwired trait of bacterial cells.

scholarly journals Regulation of Cell Division in Bacteria by Monitoring Genome Integrity and DNA Replication Status

2019 ◽  
Vol 202 (2) ◽  
Author(s):  
Peter E. Burby ◽  
Lyle A. Simmons
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Cell Division ◽  
Dna Replication ◽  
Cell Cycle Progression ◽  
Genome Instability ◽  
Sos Response ◽  
Bacterial Cells ◽  
Cycle Progression ◽  
Content Type

ABSTRACT All organisms regulate cell cycle progression by coordinating cell division with DNA replication status. In eukaryotes, DNA damage or problems with replication fork progression induce the DNA damage response (DDR), causing cyclin-dependent kinases to remain active, preventing further cell cycle progression until replication and repair are complete. In bacteria, cell division is coordinated with chromosome segregation, preventing cell division ring formation over the nucleoid in a process termed nucleoid occlusion. In addition to nucleoid occlusion, bacteria induce the SOS response after replication forks encounter DNA damage or impediments that slow or block their progression. During SOS induction, Escherichia coli expresses a cytoplasmic protein, SulA, that inhibits cell division by directly binding FtsZ. After the SOS response is turned off, SulA is degraded by Lon protease, allowing for cell division to resume. Recently, it has become clear that SulA is restricted to bacteria closely related to E. coli and that most bacteria enforce the DNA damage checkpoint by expressing a small integral membrane protein. Resumption of cell division is then mediated by membrane-bound proteases that cleave the cell division inhibitor. Further, many bacterial cells have mechanisms to inhibit cell division that are regulated independently from the canonical LexA-mediated SOS response. In this review, we discuss several pathways used by bacteria to prevent cell division from occurring when genome instability is detected or before the chromosome has been fully replicated and segregated.

Cell Cycle Synchronization of the Murine EO771 Cell Line Using Double Thymidine Block Treatment

BioEssays ◽  
2020 ◽  
Vol 42 (9) ◽  
pp. 1900116
Author(s):  
Marie Goepp ◽  
Delphine Le Guennec ◽  
Adrien Rossary ◽  
Marie‐Paule Vasson
Keyword(s):  
Cell Cycle ◽  
Cell Line ◽  
Cell Cycle Synchronization

scholarly journals Stochasticity in Colonial Growth Dynamics of Individual Bacterial Cells

2013 ◽  
Vol 79 (7) ◽  
pp. 2294-2301 ◽  
Author(s):  
Konstantinos P. Koutsoumanis ◽  
Alexandra Lianou
Keyword(s):  
Kinetic Parameters ◽  
Single Cells ◽  
Growth Curves ◽  
Growth Dynamics ◽  
Time Lapse ◽  
Initial Population ◽  
Bacterial Cells ◽  
Stochastic Growth ◽  
Bacterial Populations ◽  
Content Type

ABSTRACTConventional bacterial growth studies rely on large bacterial populations without considering the individual cells. Individual cells, however, can exhibit marked behavioral heterogeneity. Here, we present experimental observations on the colonial growth of 220 individual cells ofSalmonella entericaserotype Typhimurium using time-lapse microscopy videos. We found a highly heterogeneous behavior. Some cells did not grow, showing filamentation or lysis before division. Cells that were able to grow and form microcolonies showed highly diverse growth dynamics. The quality of the videos allowed for counting the cells over time and estimating the kinetic parameters lag time (λ) and maximum specific growth rate (μmax) for each microcolony originating from a single cell. To interpret the observations, the variability of the kinetic parameters was characterized using appropriate probability distributions and introduced to a stochastic model that allows for taking into account heterogeneity using Monte Carlo simulation. The model provides stochastic growth curves demonstrating that growth of single cells or small microbial populations is a pool of events each one of which has its own probability to occur. Simulations of the model illustrated how the apparent variability in population growth gradually decreases with increasing initial population size (N0). For bacterial populations withN0of >100 cells, the variability is almost eliminated and the system seems to behave deterministically, even though the underlying law is stochastic. We also used the model to demonstrate the effect of the presence and extent of a nongrowing population fraction on the stochastic growth of bacterial populations.

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