Dissecting the role of conformational change and membrane binding by the bacterial cell division regulator MinE in the stimulation of MinD ATPase activity.

PubMed

Ayed, Saud H; Cloutier, Adam D; McLeod, Laura J; Foo, Alexander C Y; Damry, Adam M; Goto, Natalie K

2017-12-15

The bacterial cell division regulators MinD and MinE together with the division inhibitor MinC localize to the membrane in concentrated zones undergoing coordinated pole-to-pole oscillation to help ensure that the cytokinetic division septum forms only at the mid-cell position. This dynamic localization is driven by MinD-catalyzed ATP hydrolysis, stimulated by interactions with MinE's anti-MinCD domain. This domain is buried in the 6-β-stranded MinE "closed" structure, but is liberated for interactions with MinD, giving rise to a 4-β-stranded "open" structure through an unknown mechanism. Here we show that MinE-membrane interactions induce a structural change into a state resembling the open conformation. However, MinE mutants lacking the MinE membrane-targeting sequence stimulated higher ATP hydrolysis rates than the full-length protein, indicating that binding to MinD is sufficient to trigger this conformational transition in MinE. In contrast, conformational change between the open and closed states did not affect stimulation of ATP hydrolysis rates in the absence of membrane binding, although the MinD-binding residue Ile-25 is critical for this conformational transition. We therefore propose an updated model where MinE is brought to the membrane through interactions with MinD. After stimulation of ATP hydrolysis, MinE remains bound to the membrane in a state that does not catalyze additional rounds of ATP hydrolysis. Although the molecular basis for this inhibited state is unknown, previous observations of higher-order MinE self-association may explain this inhibition. Overall, our findings have general implications for Min protein oscillation cycles, including those that regulate cell division in bacterial pathogens. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

Stable Regulation of Cell Cycle Events in Mycobacteria: Insights From Inherently Heterogeneous Bacterial Populations.

PubMed

Logsdon, Michelle M; Aldridge, Bree B

2018-01-01

Model bacteria, such as E. coli and B. subtilis , tightly regulate cell cycle progression to achieve consistent cell size distributions and replication dynamics. Many of the hallmark features of these model bacteria, including lateral cell wall elongation and symmetric growth and division, do not occur in mycobacteria. Instead, mycobacterial growth is characterized by asymmetric polar growth and division. This innate asymmetry creates unequal birth sizes and growth rates for daughter cells with each division, generating a phenotypically heterogeneous population. Although the asymmetric growth patterns of mycobacteria lead to a larger variation in birth size than typically seen in model bacterial populations, the cell size distribution is stable over time. Here, we review the cellular mechanisms of growth, division, and cell cycle progression in mycobacteria in the face of asymmetry and inherent heterogeneity. These processes coalesce to control cell size. Although Mycobacterium smegmatis and Mycobacterium bovis Bacillus Calmette-Guérin (BCG) utilize a novel model of cell size control, they are similar to previously studied bacteria in that initiation of DNA replication is a key checkpoint for cell division. We compare the regulation of DNA replication initiation and strategies used for cell size homeostasis in mycobacteria and model bacteria. Finally, we review the importance of cellular organization and chromosome segregation relating to the physiology of mycobacteria and consider how new frameworks could be applied across the wide spectrum of bacterial diversity.

Cell Division Synchronization

DTIC Science & Technology

The report summarizes the progress in the design and construction of automatic equipment for synchronizing cell division in culture by periodic...Concurrent experiments in hypothermic synchronization of algal cell division are reported.

Cell division and turgor mediate enhanced plant growth in Arabidopsis plants treated with the bacterial signalling molecule lumichrome.

PubMed

Pholo, Motlalepula; Coetzee, Beatrix; Maree, Hans J; Young, Philip R; Lloyd, James R; Kossmann, Jens; Hills, Paul N

2018-05-17

Transcriptomic analysis indicates that the bacterial signalling molecule lumichrome enhances plant growth through a combination of enhanced cell division and cell enlargement, and possibly enhances photosynthesis. Lumichrome (7,8 dimethylalloxazine), a novel multitrophic signal molecule produced by Sinorhizobium meliloti bacteria, has previously been shown to elicit growth promotion in different plant species (Phillips et al. in Proc Natl Acad Sci USA 96:12275-12280, https://doi.org/10.1073/pnas.96.22.12275 , 1999). However, the molecular mechanisms that underlie this plant growth promotion remain obscure. Global transcript profiling using RNA-seq suggests that lumichrome enhances growth by inducing genes impacting on turgor driven growth and mitotic cell cycle that ensures the integration of cell division and expansion of developing leaves. The abundance of XTH9 and XPA4 transcripts was attributed to improved mediation of cell-wall loosening to allow turgor-driven cell enlargement. Mitotic CYCD3.3, CYCA1.1, SP1L3, RSW7 and PDF1 transcripts were increased in lumichrome-treated Arabidopsis thaliana plants, suggesting enhanced growth was underpinned by increased cell differentiation and expansion with a consequential increase in biomass. Synergistic ethylene-auxin cross-talk was also observed through reciprocal over-expression of ACO1 and SAUR54, in which ethylene activates the auxin signalling pathway and regulates Arabidopsis growth by both stimulating auxin biosynthesis and modulating the auxin transport machinery to the leaves. Decreased transcription of jasmonate biosynthesis and responsive-related transcripts (LOX2; LOX3; LOX6; JAL34; JR1) might contribute towards suppression of the negative effects of methyl jasmonate (MeJa) such as chlorophyll loss and decreases in RuBisCO and photosynthesis. This work contributes towards a deeper understanding of how lumichrome enhances plant growth and development.

Pathogenic Chlamydia Lack a Classical Sacculus but Synthesize a Narrow, Mid-cell Peptidoglycan Ring, Regulated by MreB, for Cell Division

PubMed Central

Packiam, Mathanraj; Hsu, Yen-Pang; Tekkam, Srinivas; Hall, Edward; Rittichier, Jonathan T.; VanNieuwenhze, Michael; Brun, Yves V.; Maurelli, Anthony T.

2016-01-01

The peptidoglycan (PG) cell wall is a peptide cross-linked glycan polymer essential for bacterial division and maintenance of cell shape and hydrostatic pressure. Bacteria in the Chlamydiales were long thought to lack PG until recent advances in PG labeling technologies revealed the presence of this critical cell wall component in Chlamydia trachomatis. In this study, we utilize bio-orthogonal D-amino acid dipeptide probes combined with super-resolution microscopy to demonstrate that four pathogenic Chlamydiae species each possess a ≤ 140 nm wide PG ring limited to the division plane during the replicative phase of their developmental cycles. Assembly of this PG ring is rapid, processive, and linked to the bacterial actin-like protein, MreB. Both MreB polymerization and PG biosynthesis occur only in the intracellular form of pathogenic Chlamydia and are required for cell enlargement, division, and transition between the microbe’s developmental forms. Our kinetic, molecular, and biochemical analyses suggest that the development of this limited, transient, PG ring structure is the result of pathoadaptation by Chlamydia to an intracellular niche within its vertebrate host. PMID:27144308

Pathogenic Chlamydia Lack a Classical Sacculus but Synthesize a Narrow, Mid-cell Peptidoglycan Ring, Regulated by MreB, for Cell Division.

PubMed

Liechti, George; Kuru, Erkin; Packiam, Mathanraj; Hsu, Yen-Pang; Tekkam, Srinivas; Hall, Edward; Rittichier, Jonathan T; VanNieuwenhze, Michael; Brun, Yves V; Maurelli, Anthony T

2016-05-01

The peptidoglycan (PG) cell wall is a peptide cross-linked glycan polymer essential for bacterial division and maintenance of cell shape and hydrostatic pressure. Bacteria in the Chlamydiales were long thought to lack PG until recent advances in PG labeling technologies revealed the presence of this critical cell wall component in Chlamydia trachomatis. In this study, we utilize bio-orthogonal D-amino acid dipeptide probes combined with super-resolution microscopy to demonstrate that four pathogenic Chlamydiae species each possess a ≤ 140 nm wide PG ring limited to the division plane during the replicative phase of their developmental cycles. Assembly of this PG ring is rapid, processive, and linked to the bacterial actin-like protein, MreB. Both MreB polymerization and PG biosynthesis occur only in the intracellular form of pathogenic Chlamydia and are required for cell enlargement, division, and transition between the microbe's developmental forms. Our kinetic, molecular, and biochemical analyses suggest that the development of this limited, transient, PG ring structure is the result of pathoadaptation by Chlamydia to an intracellular niche within its vertebrate host.

Using stochastic cell division and death to probe minimal units of cellular replication

NASA Astrophysics Data System (ADS)

Chib, Savita; Das, Suman; Venkatesan, Soumya; Sai Narain Seshasayee, Aswin; Thattai, Mukund

2018-03-01

The invariant cell initiation mass measured in bacterial growth experiments has been interpreted as a minimal unit of cellular replication. Here we argue that the existence of such minimal units induces a coupling between the rates of stochastic cell division and death. To probe this coupling we tracked live and dead cells in Escherichia coli populations treated with a ribosome-targeting antibiotic. We find that the growth exponent from macroscopic cell growth or decay measurements can be represented as the difference of microscopic first-order cell division and death rates. The boundary between cell growth and decay, at which the number of live cells remains constant over time, occurs at the minimal inhibitory concentration (MIC) of the antibiotic. This state appears macroscopically static but is microscopically dynamic: division and death rates exactly cancel at MIC but each is remarkably high, reaching 60% of the antibiotic-free division rate. A stochastic model of cells as collections of minimal replicating units we term ‘widgets’ reproduces both steady-state and transient features of our experiments. Sub-cellular fluctuations of widget numbers stochastically drive each new daughter cell to one of two alternate fates, division or death. First-order division or death rates emerge as eigenvalues of a stationary Markov process, and can be expressed in terms of the widget’s molecular properties. High division and death rates at MIC arise due to low mean and high relative fluctuations of widget number. Isolating cells at the threshold of irreversible death might allow molecular characterization of this minimal replication unit.

Cell division and the ESCRT complex: A surprise from the archaea.

PubMed

Ettema, Thijs Jg; Bernander, Rolf

2009-01-01

The Archaea constitute the third domain of life, a separate evolutionary lineage together with the Bacteria and the Eukarya.1 Species belonging to the Archaea contain a surprising mix of bacterial (metabolism, life style, genomic organization) and eukaryotic (replication, transcription, translation) features.2 The archaeal kingdom comprises two main phyla, the Crenarchaeota and the Euryarchaeota. Regarding the cell division process in archaeal species (reviewed in ref. 3), members of the Euryarchaeota rely on an FtsZ-based cell division mechanism4 whereas, previously, no division genes had been detected in the crenarchaea. However, we recently reported the discovery of the elusive cell division machinery in crenarchaea from the genus Sulfolobus.5 The minimal machinery consists of three genes, which we designated cdvA, B and C (for cell division), organized into an operon that is widely conserved among crenarchaea. The gene products polymerize between segregating nucleoids at the early mitotic stage, forming a complex that remains associated with the leading edge of constriction throughout cytokinesis. Interestingly, CdvB and CdvC were shown to be related to the eukaryotic ESCRT-III protein sorting machinery (reviewed in ref. 6), indicating shared common ancestry and mechanistic similarities to endosomal vesicle formation and viral (HIV) budding in eukaryotes. We also demonstrated that the cdv operon is subject to checkpoint-like regulation, and that the genes display a complementary phylogenetic distribution within the Archaea domain relative to FtsZ-dependent division systems.5 Here, the findings are further explored and discussed, and topics for further investigation are suggested.

Dynamic single-cell NAD(P)H measurement reveals oscillatory metabolism throughout the E. coli cell division cycle.

PubMed

Zhang, Zheng; Milias-Argeitis, Andreas; Heinemann, Matthias

2018-02-01

Recent work has shown that metabolism between individual bacterial cells in an otherwise isogenetic population can be different. To investigate such heterogeneity, experimental methods to zoom into the metabolism of individual cells are required. To this end, the autofluoresence of the redox cofactors NADH and NADPH offers great potential for single-cell dynamic NAD(P)H measurements. However, NAD(P)H excitation requires UV light, which can cause cell damage. In this work, we developed a method for time-lapse NAD(P)H imaging in single E. coli cells. Our method combines a setup with reduced background emission, UV-enhanced microscopy equipment and optimized exposure settings, overall generating acceptable NAD(P)H signals from single cells, with minimal negative effect on cell growth. Through different experiments, in which we perturb E. coli's redox metabolism, we demonstrated that the acquired fluorescence signal indeed corresponds to NAD(P)H. Using this new method, for the first time, we report that intracellular NAD(P)H levels oscillate along the bacterial cell division cycle. The developed method for dynamic measurement of NAD(P)H in single bacterial cells will be an important tool to zoom into metabolism of individual cells.

Endosymbiosis in trypanosomatid protozoa: the bacterium division is controlled during the host cell cycle

PubMed Central

Catta-Preta, Carolina M. C.; Brum, Felipe L.; da Silva, Camila C.; Zuma, Aline A.; Elias, Maria C.; de Souza, Wanderley; Schenkman, Sergio; Motta, Maria Cristina M.

2015-01-01

Mutualism is defined as a beneficial relationship for the associated partners and usually assumes that the symbiont number is controlled. Some trypanosomatid protozoa co-evolve with a bacterial symbiont that divides in coordination with the host in a way that results in its equal distribution between daughter cells. The mechanism that controls this synchrony is largely unknown, and its comprehension might provide clues to understand how eukaryotic cells evolved when acquiring symbionts that later became organelles. Here, we approached this question by studying the effects of inhibitors that affect the host exclusively in two symbiont-bearing trypanosomatids, Strigomonas culicis and Angomonas deanei. We found that inhibiting host protein synthesis using cycloheximide or host DNA replication using aphidicolin did not affect the duplication of bacterial DNA. Although the bacteria had autonomy to duplicate their DNA when host protein synthesis was blocked by cycloheximide, they could not complete cytokinesis. Aphidicolin promoted the inhibition of the trypanosomatid cell cycle in the G1/S phase, leading to symbiont filamentation in S. culicis but not in A. deanei. Treatment with camptothecin blocked the host protozoa cell cycle in the G2 phase and induced the formation of filamentous symbionts in both species. Oryzalin, which affects host microtubule polymerization, blocked trypanosomatid mitosis and abrogated symbiont division. Our results indicate that host factors produced during the cell division cycle are essential for symbiont segregation and may control the bacterial cell number. PMID:26082757

Ruthenium red-induced bundling of bacterial cell division protein, FtsZ.

PubMed

Santra, Manas Kumar; Beuria, Tushar K; Banerjee, Abhijit; Panda, Dulal

2004-06-18

The assembly of FtsZ plays a major role in bacterial cell division, and it is thought that the assembly dynamics of FtsZ is a finely regulated process. Here, we show that ruthenium red is able to modulate FtsZ assembly in vitro. In contrast to the inhibitory effects of ruthenium red on microtubule polymerization, we found that a substoichiometric concentration of ruthenium red strongly increased the light-scattering signal of FtsZ assembly. Further, sedimentable polymer mass was increased by 1.5- and 2-fold in the presence of 2 and 10 microm ruthenium red, respectively. In addition, ruthenium red strongly reduced the GTPase activity and prevented dilution-induced disassembly of FtsZ polymers. Electron microscopic analysis showed that 4-10 microm of ruthenium red produced thick bundles of FtsZ polymers. The significant increase in the light-scattering signal and pelletable polymer mass in the presence of ruthenium red seemed to be due to the bundling of FtsZ protofilaments into larger polymers rather than the actual increase in the level of polymeric FtsZ. Furthermore, ruthenium red was found to copolymerize with FtsZ, and the copolymerization of substoichiometric amounts of ruthenium red with FtsZ polymers promoted cooperative assembly of FtsZ that produced large bundles. Calcium inhibited the binding of ruthenium red to FtsZ. However, a concentration of calcium 1000-fold higher than that of ruthenium red was required to produce similar effects on FtsZ assembly. Ruthenium red strongly modulated FtsZ polymerization, suggesting the presence of an important regulatory site on FtsZ and suggesting that a natural ligand, which mimics the action of ruthenium red, may regulate the assembly of FtsZ in bacteria.

Colocalization of cell division proteins FtsZ and FtsA to cytoskeletal structures in living Escherichia coli cells by using green fluorescent protein

PubMed Central

Ma, Xiaolan; Ehrhardt, David W.; Margolin, William

1996-01-01

In the current model for bacterial cell division, FtsZ protein forms a ring that marks the division plane, creating a cytoskeletal framework for the subsequent action of other proteins such as FtsA. This putative protein complex ultimately generates the division septum. Herein we report that FtsZ and FtsA proteins tagged with green fluorescent protein (GFP) colocalize to division-site ring-like structures in living bacterial cells in a visible space between the segregated nucleoids. Cells with higher levels of FtsZ–GFP or with FtsA–GFP plus excess wild-type FtsZ were inhibited for cell division and often exhibited bright fluorescent spiral tubules that spanned the length of the filamentous cells. This suggests that FtsZ may switch from a septation-competent localized ring to an unlocalized spiral under some conditions and that FtsA can bind to FtsZ in both conformations. FtsZ–GFP also formed nonproductive but localized aggregates at a higher concentration that could represent FtsZ nucleation sites. The general domain structure of FtsZ–GFP resembles that of tubulin, since the C terminus of FtsZ is not required for polymerization but may regulate polymerization state. The N-terminal portion of Rhizobium FtsZ polymerized in Escherichia coli and appeared to copolymerize with E. coli FtsZ, suggesting a degree of interspecies functional conservation. Analysis of several deletions of FtsA–GFP suggests that multiple segments of FtsA are important for its localization to the FtsZ ring. PMID:8917533

Biological consequences and advantages of asymmetric bacterial growth.

PubMed

Kysela, David T; Brown, Pamela J B; Huang, Kerwyn Casey; Brun, Yves V

2013-01-01

Asymmetries in cell growth and division occur in eukaryotes and prokaryotes alike. Even seemingly simple and morphologically symmetric cell division processes belie inherent underlying asymmetries in the composition of the resulting daughter cells. We consider the types of asymmetry that arise in various bacterial cell growth and division processes, which include both conditionally activated mechanisms and constitutive, hardwired aspects of bacterial life histories. Although asymmetry disposes some cells to the deleterious effects of aging, it may also benefit populations by efficiently purging accumulated damage and rejuvenating newborn cells. Asymmetries may also generate phenotypic variation required for successful exploitation of variable environments, even when extrinsic changes outpace the capacity of cells to sense and respond to challenges. We propose specific experimental approaches to further develop our understanding of the prevalence and the ultimate importance of asymmetric bacterial growth.

A novel cell division factor from tobacco 2B-13 cells that induced cell division in auxin-starved tobacco BY-2 cells

NASA Astrophysics Data System (ADS)

Shimizu, Takashi; Eguchi, Kentaro; Nishida, Ikuo; Laukens, Kris; Witters, Erwin; van Onckelen, Harry; Nagata, Toshiyuki

2006-06-01

Effects of auxin as plant hormones are widespread; in fact in almost all aspects of plant growth and development auxin plays a pivotal role. Although auxin is required for propagating cell division in plant cells, its effect upon cell division is least understood. If auxin is depleted from the culture medium, cultured cells cease to divide. It has been demonstrated in this context that the addition of auxin to auxin-starved nondividing tobacco BY-2 cells induced semisynchronous cell division. On the other hand, there are some cell lines, named habituated cells, that can grow without auxin. The cause and reason for the habituated cells have not been clarified. A habituated cell line named 2B-13 is derived from the tobacco BY-2 cell line, which has been most intensively studied among plant cell lines. When we tried to find the difference between two cell lines of BY-2 and 2B-13 cells, we found that the addition of culture filtrated from the auxin-habituated 2B-13 cells induced semisynchronous cell division in auxin-starved BY-2 cells. The cell division factor (CDF) that is responsible for inducing cell division in auxin-starved BY-2 cells was purified to near-homogeneity by sequential passage through a hydroxyapatite column, a ConA Sepharose column and a Sephadex gel filtration column. The resulting purified fraction appeared as a single band of high molecular weight on sodium dodecyl sulfate-polyacrylamide gel electrophoresis gels by silver staining and was able to induce cell division in auxin-starved BY-2 cells. Identification of the protein by MALD-TOF-MS/MS revealed that it is structurally related to P-glycoprotein from Gossypioides kirkii, which belongs to ATP-binding cassette (ABC)-transporters. The significance of CDF as a possible ABC-transporter is discussed in relationship to auxin-autotrophic growth and auxin-signaling pathway.

MinCD cell division proteins form alternating co-polymeric cytomotive filaments

PubMed Central

Ghosal, Debnath; Trambaiolo, Daniel; Amos, Linda A.; Löwe, Jan

2014-01-01

Summary During bacterial cell division, filaments of the tubulin-like protein FtsZ assemble at midcell to form the cytokinetic Z-ring. Its positioning is regulated by the oscillation of MinCDE proteins. MinC is activated by MinD through an unknown mechanism and prevents Z-ring assembly anywhere but midcell. Here, using X-ray crystallography, electron microscopy and in vivo analyses we show that MinD activates MinC by forming a new class of alternating copolymeric filaments that show similarity to eukaryotic septin filaments A non-polymerising mutation in MinD causes aberrant cell division in E. coli. MinCD copolymers bind to membrane, interact with FtsZ, and are disassembled by MinE. Imaging a functional msfGFP-MinC fusion protein in MinE deleted cells reveals filamentous structures. EM imaging of our reconstitution of the MinCD-FtsZ interaction on liposome surfaces reveals a plausible mechanism for regulation of FtsZ ring assembly by MinCD copolymers. PMID:25500731

Concerted control of Escherichia coli cell division

PubMed Central

Osella, Matteo; Nugent, Eileen; Cosentino Lagomarsino, Marco

2014-01-01

The coordination of cell growth and division is a long-standing problem in biology. Focusing on Escherichia coli in steady growth, we quantify cell division control using a stochastic model, by inferring the division rate as a function of the observable parameters from large empirical datasets of dividing cells. We find that (i) cells have mechanisms to control their size, (ii) size control is effected by changes in the doubling time, rather than in the single-cell elongation rate, (iii) the division rate increases steeply with cell size for small cells, and saturates for larger cells. Importantly, (iv) the current size is not the only variable controlling cell division, but the time spent in the cell cycle appears to play a role, and (v) common tests of cell size control may fail when such concerted control is in place. Our analysis illustrates the mechanisms of cell division control in E. coli. The phenomenological framework presented is sufficiently general to be widely applicable and opens the way for rigorous tests of molecular cell-cycle models. PMID:24550446

Nucleoid Condensation and Cell Division in Escherichia coli MX74T2 ts52 After Inhibition of Protein Synthesis

PubMed Central

Zusman, David R.; Carbonell, Augustina; Haga, Juli Y.

1973-01-01

The reorganization of the bacterial nucleoid of an Escherichia coli mutant, MX74T2 ts52, was studied by electron microscopy after protein synthesis inhibition by using whole mounts of cell ghosts, ultrathin-sectioning, and freeze-etching. The bacterial nucleoid showed two morphological changes after chloramphenicol addition: deoxyribonucleic acid (DNA) localization and DNA condensation. DNA localization was observed 10 min after chloramphenicol addition; the DNA appeared as a compact, solid mass. DNA condensation was observed at 25 min; the nucleoid appeared as a cytoplasm-filled sphere, often opened at one end. Ribosomes were observed in the center. Giant nucleoids present in some mutant filaments showed fused, spherical nucleoids arranged linearly, suggesting that the tertiary structure of the nucleoid reflects the number of replicated genomes. Inhibitors which directly or indirectly blocked protein synthesis and caused DNA condensation were chloramphenicol, puromycin, amino acid starvation, rifampicin, or carbonyl cyanide m-chlorophenyl hydrazone. All inhibitors that caused cell division in the mutant also caused condensation, although some inhibitors caused condensation without cell division. Nucleoid condensation appears to be related to chromosome structure rather than to DNA segregation upon cell division. Images PMID:4580561

Chlamydia co-opts the rod shape-determining proteins MreB and Pbp2 for cell division.

PubMed

Ouellette, Scot P; Karimova, Gouzel; Subtil, Agathe; Ladant, Daniel

2012-07-01

Chlamydiae are obligate intracellular bacterial pathogens that have extensively reduced their genome in adapting to the intracellular environment. The chlamydial genome contains only three annotated cell division genes and lacks ftsZ. How this obligate intracellular pathogen divides is uncharacterized. Chlamydiae contain two high-molecular-weight (HMW) penicillin binding proteins (Pbp) implicated in peptidoglycan synthesis, Pbp2 and Pbp3/FtsI. We show here, using HMW Pbp-specific penicillin derivatives, that both Pbp2 and Pbp3 are essential for chlamydial cell division. Ultrastructural analyses of antibiotic-treated cultures revealed distinct phenotypes: Pbp2 inhibition induced internal cell bodies within a single outer membrane whereas Pbp3 inhibition induced elongated phenotypes with little internal division. Each HMW Pbp interacts with the Chlamydia cell division protein FtsK. Chlamydiae are coccoid yet contain MreB, a rod shape-determining protein linked to Pbp2 in bacilli. Using MreB-specific antibiotics, we show that MreB is essential for chlamydial growth and division. Importantly, co-treatment with MreB-specific and Pbp-specific antibiotics resulted in the MreB-inhibited phenotype, placing MreB upstream of Pbp function in chlamydial cell division. Finally, we showed that MreB also interacts with FtsK. We propose that, in Chlamydia, MreB acts as a central co-ordinator at the division site to substitute for the lack of FtsZ in this bacterium. © 2012 Blackwell Publishing Ltd.

The stem cell division theory of cancer.

PubMed

López-Lázaro, Miguel

2018-03-01

All cancer registries constantly show striking differences in cancer incidence by age and among tissues. For example, lung cancer is diagnosed hundreds of times more often at age 70 than at age 20, and lung cancer in nonsmokers occurs thousands of times more frequently than heart cancer in smokers. An analysis of these differences using basic concepts in cell biology indicates that cancer is the end-result of the accumulation of cell divisions in stem cells. In other words, the main determinant of carcinogenesis is the number of cell divisions that the DNA of a stem cell has accumulated in any type of cell from the zygote. Cell division, process by which a cell copies and separates its cellular components to finally split into two cells, is necessary to produce the large number of cells required for living. However, cell division can lead to a variety of cancer-promoting errors, such as mutations and epigenetic mistakes occurring during DNA replication, chromosome aberrations arising during mitosis, errors in the distribution of cell-fate determinants between the daughter cells, and failures to restore physical interactions with other tissue components. Some of these errors are spontaneous, others are promoted by endogenous DNA damage occurring during quiescence, and others are influenced by pathological and environmental factors. The cell divisions required for carcinogenesis are primarily caused by multiple local and systemic physiological signals rather than by errors in the DNA of the cells. As carcinogenesis progresses, the accumulation of DNA errors promotes cell division and eventually triggers cell division under permissive extracellular environments. The accumulation of cell divisions in stem cells drives not only the accumulation of the DNA alterations required for carcinogenesis, but also the formation and growth of the abnormal cell populations that characterize the disease. This model of carcinogenesis provides a new framework for understanding the

Gravity and the orientation of cell division

NASA Technical Reports Server (NTRS)

Helmstetter, C. E.

1997-01-01

A novel culture system for mammalian cells was used to investigate division orientations in populations of Chinese hamster ovary cells and the influence of gravity on the positioning of division axes. The cells were tethered to adhesive sites, smaller in diameter than a newborn cell, distributed over a nonadhesive substrate positioned vertically. The cells grew and divided while attached to the sites, and the angles and directions of elongation during anaphase, projected in the vertical plane, were found to be random with respect to gravity. However, consecutive divisions of individual cells were generally along the same axis or at 90 degrees to the previous division, with equal probability. Thus, successive divisions were restricted to orthogonal planes, but the choice of plane appeared to be random, unlike the ordered sequence of cleavage orientations seen during early embryo development.

Intracellular crowding effects on the self-association of the bacterial cell division protein FtsZ.

PubMed

Naddaf, Lamis; Sayyed-Ahmad, Abdallah

2014-12-15

The dimerization rate of the bacterial cell division protein FtsZ is strongly affected by the intracellular crowding. Yet the complexity of the intracellular environment makes it difficult to investigate via all-atom molecular dynamics or other detailed theoretical methods. We study the crowding effect on FtsZ dimerization which is the first step of an oligomerization process that results in more elaborate supramolecular structures. In particular, we consider the effect of intracellular crowding on the reaction rates, and their dependence on the different concentrations of crowding agents. We achieved this goal by using Brownian dynamics (BD) simulation techniques and a modified post-processing approach in which we decompose the rate constant in crowded media as a product of the rate constant in the dilute solution times a factor that incorporates the crowding effect. The latter factor accounts for the diffusion reduction and crowder induced energy. In addition we include the crowding effects on water viscosity in the BD simulations of crowded media. We finally show that biomolecular crowding has a considerable effect on the FtsZ dimerization by increasing the dimerization rate constant from 2.6×10(7)M(-1)s(-1) in the absence of crowders to 1.0×10(8)M(-1)s(-1) at crowding level of 0.30. Copyright © 2014 Elsevier Inc. All rights reserved.

New insights into FtsZ rearrangements during the cell division of Escherichia coli from single-molecule localization microscopy of fixed cells.

PubMed

Vedyaykin, Alexey D; Vishnyakov, Innokentii E; Polinovskaya, Vasilisa S; Khodorkovskii, Mikhail A; Sabantsev, Anton V

2016-06-01

FtsZ - a prokaryotic tubulin homolog - is one of the central components of bacterial division machinery. At the early stage of cytokinesis FtsZ forms the so-called Z-ring at mid-cell that guides septum formation. Many approaches were used to resolve the structure of the Z-ring, however, researchers are still far from consensus on this question. We utilized single-molecule localization microscopy (SMLM) in combination with immunofluorescence staining to visualize FtsZ in Esherichia coli fixed cells that were grown under slow and fast growth conditions. This approach allowed us to obtain images of FtsZ structures at different stages of cell division and accurately measure Z-ring dimensions. Analysis of these images demonstrated that Z-ring thickness increases during constriction, starting at about 70 nm at the beginning of division and increasing by approximately 25% half-way through constriction. © 2016 The Authors. MicrobiologyOpen published by John Wiley & Sons Ltd.

A specific role for the ZipA protein in cell division: stabilization of the FtsZ protein.

PubMed

Pazos, Manuel; Natale, Paolo; Vicente, Miguel

2013-02-01

In Escherichia coli, the cell division protein FtsZ is anchored to the cytoplasmic membrane by the action of the bitopic membrane protein ZipA and the cytoplasmic protein FtsA. Although the presence of both ZipA and FtsA is strictly indispensable for cell division, an FtsA gain-of-function mutant FtsA* (R286W) can bypass the ZipA requirement for cell division. This observation casts doubts on the role of ZipA and its need for cell division. Maxicells are nucleoid-free bacterial cells used as a whole cell in vitro system to probe protein-protein interactions without the need of protein purification. We show that ZipA protects FtsZ from the ClpXP-directed degradation observed in E. coli maxicells and that ZipA-stabilized FtsZ forms membrane-attached spiral-like structures in the bacterial cytoplasm. The overproduction of the FtsZ-binding ZipA domain is sufficient to protect FtsZ from degradation, whereas other C-terminal ZipA partial deletions lacking it are not. Individual overproduction of the proto-ring component FtsA or its gain-of-function mutant FtsA* does not result in FtsZ protection. Overproduction of FtsA or FtsA* together with ZipA does not interfere with the FtsZ protection. Moreover, neither FtsA nor FtsA* protects FtsZ when overproduced together with ZipA mutants lacking the FZB domain. We propose that ZipA protects FtsZ from degradation by ClpP by making the FtsZ site of interaction unavailable to the ClpX moiety of the ClpXP protease. This role cannot be replaced by either FtsA or FtsA*, suggesting a unique function for ZipA in proto-ring stability.

Alignment of cell division axes in directed epithelial cell migration

NASA Astrophysics Data System (ADS)

Marel, Anna-Kristina; Podewitz, Nils; Zorn, Matthias; Oskar Rädler, Joachim; Elgeti, Jens

2014-11-01

Cell division is an essential dynamic event in tissue remodeling during wound healing, cancer and embryogenesis. In collective migration, tensile stresses affect cell shape and polarity, hence, the orientation of the cell division axis is expected to depend on cellular flow patterns. Here, we study the degree of orientation of cell division axes in migrating and resting epithelial cell sheets. We use microstructured channels to create a defined scenario of directed cell invasion and compare this situation to resting but proliferating cell monolayers. In experiments, we find a strong alignment of the axis due to directed flow while resting sheets show very weak global order, but local flow gradients still correlate strongly with the cell division axis. We compare experimental results with a previously published mesoscopic particle based simulation model. Most of the observed effects are reproduced by the simulations.

Automated cell tracking identifies mechanically oriented cell divisions during Drosophila axis elongation.

PubMed

Wang, Michael F Z; Hunter, Miranda V; Wang, Gang; McFaul, Christopher; Yip, Christopher M; Fernandez-Gonzalez, Rodrigo

2017-04-01

Embryos extend their anterior-posterior (AP) axis in a conserved process known as axis elongation. Drosophila axis elongation occurs in an epithelial monolayer, the germband, and is driven by cell intercalation, cell shape changes, and oriented cell divisions at the posterior germband. Anterior germband cells also divide during axis elongation. We developed image analysis and pattern-recognition methods to track dividing cells from confocal microscopy movies in a generally applicable approach. Mesectoderm cells, forming the ventral midline, divided parallel to the AP axis, while lateral cells displayed a uniform distribution of division orientations. Mesectoderm cells did not intercalate and sustained increased AP strain before cell division. After division, mesectoderm cell density increased along the AP axis, thus relieving strain. We used laser ablation to isolate mesectoderm cells from the influence of other tissues. Uncoupling the mesectoderm from intercalating cells did not affect cell division orientation. Conversely, separating the mesectoderm from the anterior and posterior poles of the embryo resulted in uniformly oriented divisions. Our data suggest that mesectoderm cells align their division angle to reduce strain caused by mechanical forces along the AP axis of the embryo. © 2017. Published by The Company of Biologists Ltd.

Stationary Size Distributions of Growing Cells with Binary and Multiple Cell Division

NASA Astrophysics Data System (ADS)

Rading, M. M.; Engel, T. A.; Lipowsky, R.; Valleriani, A.

2011-10-01

Populations of unicellular organisms that grow under constant environmental conditions are considered theoretically. The size distribution of these cells is calculated analytically, both for the usual process of binary division, in which one mother cell produces always two daughter cells, and for the more complex process of multiple division, in which one mother cell can produce 2 n daughter cells with n=1,2,3,… . The latter mode of division is inspired by the unicellular algae Chlamydomonas reinhardtii. The uniform response of the whole population to different environmental conditions is encoded in the individual rates of growth and division of the cells. The analytical treatment of the problem is based on size-dependent rules for cell growth and stochastic transition processes for cell division. The comparison between binary and multiple division shows that these different division processes lead to qualitatively different results for the size distribution and the population growth rates.

Bacterial Cell Mechanics.

PubMed

Auer, George K; Weibel, Douglas B

2017-07-25

Cellular mechanical properties play an integral role in bacterial survival and adaptation. Historically, the bacterial cell wall and, in particular, the layer of polymeric material called the peptidoglycan were the elements to which cell mechanics could be primarily attributed. Disrupting the biochemical machinery that assembles the peptidoglycan (e.g., using the β-lactam family of antibiotics) alters the structure of this material, leads to mechanical defects, and results in cell lysis. Decades after the discovery of peptidoglycan-synthesizing enzymes, the mechanisms that underlie their positioning and regulation are still not entirely understood. In addition, recent evidence suggests a diverse group of other biochemical elements influence bacterial cell mechanics, may be regulated by new cellular mechanisms, and may be triggered in different environmental contexts to enable cell adaptation and survival. This review summarizes the contributions that different biomolecular components of the cell wall (e.g., lipopolysaccharides, wall and lipoteichoic acids, lipid bilayers, peptidoglycan, and proteins) make to Gram-negative and Gram-positive bacterial cell mechanics. We discuss the contribution of individual proteins and macromolecular complexes in cell mechanics and the tools that make it possible to quantitatively decipher the biochemical machinery that contributes to bacterial cell mechanics. Advances in this area may provide insight into new biology and influence the development of antibacterial chemotherapies.

Cell division cycle 45 promotes papillary thyroid cancer progression via regulating cell cycle.

PubMed

Sun, Jing; Shi, Run; Zhao, Sha; Li, Xiaona; Lu, Shan; Bu, Hemei; Ma, Xianghua

2017-05-01

Cell division cycle 45 was reported to be overexpressed in some cancer-derived cell lines and was predicted to be a candidate oncogene in cervical cancer. However, the clinical and biological significance of cell division cycle 45 in papillary thyroid cancer has never been investigated. We determined the expression level and clinical significance of cell division cycle 45 using The Cancer Genome Atlas, quantitative real-time polymerase chain reaction, and immunohistochemistry. A great upregulation of cell division cycle 45 was observed in papillary thyroid cancer tissues compared with adjacent normal tissues. Furthermore, overexpression of cell division cycle 45 positively correlates with more advanced clinical characteristics. Silence of cell division cycle 45 suppressed proliferation of papillary thyroid cancer cells via G1-phase arrest and inducing apoptosis. The oncogenic activity of cell division cycle 45 was also confirmed in vivo. In conclusion, cell division cycle 45 may serve as a novel biomarker and a potential therapeutic target for papillary thyroid cancer.

Strategic incorporation of fluorine in the drug discovery of new-generation antitubercular agents targeting bacterial cell division protein FtsZ⋆

PubMed Central

Ojima, Iwao; Awasthi, Divya; Wei, Longfei; Haranahalli, Krupanandan

2016-01-01

This article presents an account of our research on the discovery and development of new-generation fluorine-containing antibacterial agents against drug-resistant tuberculosis, targeting FtsZ. FtsZ is an essential protein for bacterial cell division and a highly promising therapeutic target for antibacterial drug discovery. Through design, synthesis and semi-HTP screening of libraries of novel benzimidazoles, followed by SAR studies, we identified highly potent lead compounds. However, these lead compounds were found to lack sufficient metabolic and plasma stabilities. Accordingly, we have performed extensive study on the strategic incorporation of fluorine into lead compounds to improve pharmacological properties. This study has led to the development of highly efficacious fluorine-containing benzimidazoles as potential drug candidates. We have also performed computational docking analysis of these novel FtsZ inhibitors to identify their putative binding site. Based on the structural data and docking analysis, a plausible mode-of-action for this novel class of FtsZ inhibitors is proposed. PMID:28555087

LexA Binds to Transcription Regulatory Site of Cell Division Gene ftsZ in Toxic Cyanobacterium Microcystis aeruginosa.

PubMed

Honda, Takashi; Morimoto, Daichi; Sako, Yoshihiko; Yoshida, Takashi

2018-05-17

Previously, we showed that DNA replication and cell division in toxic cyanobacterium Microcystis aeruginosa are coordinated by transcriptional regulation of cell division gene ftsZ and that an unknown protein specifically bound upstream of ftsZ (BpFz; DNA-binding protein to an upstream site of ftsZ) during successful DNA replication and cell division. Here, we purified BpFz from M. aeruginosa strain NIES-298 using DNA-affinity chromatography and gel-slicing combined with gel electrophoresis mobility shift assay (EMSA). The N-terminal amino acid sequence of BpFz was identified as TNLESLTQ, which was identical to that of transcription repressor LexA from NIES-843. EMSA analysis using mutant probes showed that the sequence GTACTAN 3 GTGTTC was important in LexA binding. Comparison of the upstream regions of lexA in the genomes of closely related cyanobacteria suggested that the sequence TASTRNNNNTGTWC could be a putative LexA recognition sequence (LexA box). Searches for TASTRNNNNTGTWC as a transcriptional regulatory site (TRS) in the genome of M. aeruginosa NIES-843 showed that it was present in genes involved in cell division, photosynthesis, and extracellular polysaccharide biosynthesis. Considering that BpFz binds to the TRS of ftsZ during normal cell division, LexA may function as a transcriptional activator of genes related to cell reproduction in M. aeruginosa, including ftsZ. This may be an example of informality in the control of bacterial cell division.

Teaching Cell Division: Basics and Recommendations.

ERIC Educational Resources Information Center

Smith, Mike U.; Kindfield, Ann C. H.

1999-01-01

Presents a concise overview of cell division that includes only the essential concepts necessary for understanding genetics and evolution. Makes recommendations based on published research and teaching experiences that can be used to judge the merits of potential activities and materials for teaching cell division. Makes suggestions regarding the…

Bacterial cytoskeleton and implications for new antibiotic targets.

PubMed

Wang, Huan; Xie, Longxiang; Luo, Hongping; Xie, Jianping

2016-01-01

Traditionally eukaryotes exclusive cytoskeleton has been found in bacteria and other prokaryotes. FtsZ, MreB and CreS are bacterial counterpart of eukaryotic tubulin, actin filaments and intermediate filaments, respectively. FtsZ can assemble to a Z-ring at the cell division site, regulate bacterial cell division; MreB can form helical structure, and involve in maintaining cell shape, regulating chromosome segregation; CreS, found in Caulobacter crescentus (C. crescentus), can form curve or helical filaments in intracellular membrane. CreS is crucial for cell morphology maintenance. There are also some prokaryotic unique cytoskeleton components playing crucial roles in cell division, chromosome segregation and cell morphology. The cytoskeleton components of Mycobacterium tuberculosis (M. tuberculosis), together with their dynamics during exposure to antibiotics are summarized in this article to provide insights into the unique organization of this formidable pathogen and druggable targets for new antibiotics.

Asymmetric cell division of stem cells in the lung and other systems

PubMed Central

Berika, Mohamed; Elgayyar, Marwa E.; El-Hashash, Ahmed H. K.

2014-01-01

New insights have been added to identification, behavior and cellular properties of embryonic and tissue-specific stem cells over the last few years. The modes of stem cell division, asymmetric vs. symmetric, are tightly regulated during development and regeneration. The proper choice of a stem cell to divide asymmetrically or symmetrically has great consequences for development and disease because inappropriate asymmetric division disrupts organ morphogenesis, whereas uncontrolled symmetric division induces tumorigenesis. Therefore, understanding the behavior of lung stem cells could identify innovative solutions for restoring normal morphogenesis and/or regeneration of different organs. In this concise review, we describe recent studies in our laboratory about the mode of division of lung epithelial stem cells. We also compare asymmetric cell division (ACD) in the lung stem cells with other tissues in different organisms. PMID:25364740

Spatial Patterning of Newly-Inserted Material during Bacterial Cell Growth

NASA Astrophysics Data System (ADS)

Ursell, Tristan

2012-02-01

In the life cycle of a bacterium, rudimentary microscopy demonstrates that cell growth and elongation are essential characteristics of cellular reproduction. The peptidoglycan cell wall is the main load-bearing structure that determines both cell shape and overall size. However, simple imaging of cellular growth gives no indication of the spatial patterning nor mechanism by which material is being incorporated into the pre-existing cell wall. We employ a combination of high-resolution pulse-chase fluorescence microscopy, 3D computational microscopy, and detailed mechanistic simulations to explore how spatial patterning results in uniform growth and maintenance of cell shape. We show that growth is happening in discrete bursts randomly distributed over the cell surface, with a well-defined mean size and average rate. We further use these techniques to explore the effects of division and cell wall disrupting antibiotics, like cephalexin and A22, respectively, on the patterning of cell wall growth in E. coli. Finally, we explore the spatial correlation between presence of the bacterial actin-like cytoskeletal protein, MreB, and local cell wall growth. Together these techniques form a powerful method for exploring the detailed dynamics and involvement of antibiotics and cell wall-associated proteins in bacterial cell growth.[4pt] In collaboration with Kerwyn Huang, Stanford University.

An archaebacterial homologue of the essential eubacterial cell division protein FtsZ.

PubMed Central

Baumann, P; Jackson, S P

1996-01-01

Life falls into three fundamental domains--Archaea, Bacteria, and Eucarya (formerly archaebacteria, eubacteria, and eukaryotes,. respectively). Though Archaea lack nuclei and share many morphological features with Bacteria, molecular analyses, principally of the transcription and translation machineries, have suggested that Archaea are more related to Eucarya than to Bacteria. Currently, little is known about the archaeal cell division apparatus. In Bacteria, a crucial component of the cell division machinery is FtsZ, a GTPase that localizes to a ring at the site of septation. Interestingly, FtsZ is distantly related in sequence to eukaryotic tubulins, which also interact with GTP and are components of the eukaryotic cell cytoskeleton. By screening for the ability to bind radiolabeled nucleotides, we have identified a protein of the hyperthermophilic archaeon Pyrococcus woesei that interacts tightly and specifically with GTP. Furthermore, through screening an expression library of P. woesei genomic DNA, we have cloned the gene encoding this protein. Sequence comparisons reveal that the P. woesei GTP-binding protein is strikingly related in sequence to eubacterial FtsZ and is marginally more similar to eukaryotic tubulins than are bacterial FtsZ proteins. Phylogenetic analyses reinforce the notion that there is an evolutionary linkage between FtsZ and tubulins. These findings suggest that the archaeal cell division apparatus may be fundamentally similar to that of Bacteria and lead us to consider the evolutionary relationships between Archaea, Bacteria, and Eucarya. Images Fig. 1 Fig. 2 PMID:8692886

An archaebacterial homologue of the essential eubacterial cell division protein FtsZ.

PubMed

Baumann, P; Jackson, S P

1996-06-25

Life falls into three fundamental domains--Archaea, Bacteria, and Eucarya (formerly archaebacteria, eubacteria, and eukaryotes,. respectively). Though Archaea lack nuclei and share many morphological features with Bacteria, molecular analyses, principally of the transcription and translation machineries, have suggested that Archaea are more related to Eucarya than to Bacteria. Currently, little is known about the archaeal cell division apparatus. In Bacteria, a crucial component of the cell division machinery is FtsZ, a GTPase that localizes to a ring at the site of septation. Interestingly, FtsZ is distantly related in sequence to eukaryotic tubulins, which also interact with GTP and are components of the eukaryotic cell cytoskeleton. By screening for the ability to bind radiolabeled nucleotides, we have identified a protein of the hyperthermophilic archaeon Pyrococcus woesei that interacts tightly and specifically with GTP. Furthermore, through screening an expression library of P. woesei genomic DNA, we have cloned the gene encoding this protein. Sequence comparisons reveal that the P. woesei GTP-binding protein is strikingly related in sequence to eubacterial FtsZ and is marginally more similar to eukaryotic tubulins than are bacterial FtsZ proteins. Phylogenetic analyses reinforce the notion that there is an evolutionary linkage between FtsZ and tubulins. These findings suggest that the archaeal cell division apparatus may be fundamentally similar to that of Bacteria and lead us to consider the evolutionary relationships between Archaea, Bacteria, and Eucarya.

SuperSegger: robust image segmentation, analysis and lineage tracking of bacterial cells.

PubMed

Stylianidou, Stella; Brennan, Connor; Nissen, Silas B; Kuwada, Nathan J; Wiggins, Paul A

2016-11-01

Many quantitative cell biology questions require fast yet reliable automated image segmentation to identify and link cells from frame-to-frame, and characterize the cell morphology and fluorescence. We present SuperSegger, an automated MATLAB-based image processing package well-suited to quantitative analysis of high-throughput live-cell fluorescence microscopy of bacterial cells. SuperSegger incorporates machine-learning algorithms to optimize cellular boundaries and automated error resolution to reliably link cells from frame-to-frame. Unlike existing packages, it can reliably segment microcolonies with many cells, facilitating the analysis of cell-cycle dynamics in bacteria as well as cell-contact mediated phenomena. This package has a range of built-in capabilities for characterizing bacterial cells, including the identification of cell division events, mother, daughter and neighbouring cells, and computing statistics on cellular fluorescence, the location and intensity of fluorescent foci. SuperSegger provides a variety of postprocessing data visualization tools for single cell and population level analysis, such as histograms, kymographs, frame mosaics, movies and consensus images. Finally, we demonstrate the power of the package by analyzing lag phase growth with single cell resolution. © 2016 John Wiley & Sons Ltd.

ZapE Is a Novel Cell Division Protein Interacting with FtsZ and Modulating the Z-Ring Dynamics

PubMed Central

Marteyn, Benoit S.; Karimova, Gouzel; Fenton, Andrew K.; Gazi, Anastasia D.; West, Nicholas; Touqui, Lhousseine; Prevost, Marie-Christine; Betton, Jean-Michel; Poyraz, Oemer; Ladant, Daniel; Gerdes, Kenn; Sansonetti, Philippe J.; Tang, Christoph M.

2014-01-01

ABSTRACT Bacterial cell division requires the formation of a mature divisome complex positioned at the midcell. The localization of the divisome complex is determined by the correct positioning, assembly, and constriction of the FtsZ ring (Z-ring). Z-ring constriction control remains poorly understood and (to some extent) controversial, probably due to the fact that this phenomenon is transient and controlled by numerous factors. Here, we characterize ZapE, a novel ATPase found in Gram-negative bacteria, which is required for growth under conditions of low oxygen, while loss of zapE results in temperature-dependent elongation of cell shape. We found that ZapE is recruited to the Z-ring during late stages of the cell division process and correlates with constriction of the Z-ring. Overexpression or inactivation of zapE leads to elongation of Escherichia coli and affects the dynamics of the Z-ring during division. In vitro, ZapE destabilizes FtsZ polymers in an ATP-dependent manner. PMID:24595368

Chromosome segregation drives division site selection in Streptococcus pneumoniae.

PubMed

van Raaphorst, Renske; Kjos, Morten; Veening, Jan-Willem

2017-07-18

Accurate spatial and temporal positioning of the tubulin-like protein FtsZ is key for proper bacterial cell division. Streptococcus pneumoniae (pneumococcus) is an oval-shaped, symmetrically dividing opportunistic human pathogen lacking the canonical systems for division site control (nucleoid occlusion and the Min-system). Recently, the early division protein MapZ was identified and implicated in pneumococcal division site selection. We show that MapZ is important for proper division plane selection; thus, the question remains as to what drives pneumococcal division site selection. By mapping the cell cycle in detail, we show that directly after replication both chromosomal origin regions localize to the future cell division sites, before FtsZ. Interestingly, Z-ring formation occurs coincidently with initiation of DNA replication. Perturbing the longitudinal chromosomal organization by mutating the condensin SMC, by CRISPR/Cas9-mediated chromosome cutting, or by poisoning DNA decatenation resulted in mistiming of MapZ and FtsZ positioning and subsequent cell elongation. Together, we demonstrate an intimate relationship between DNA replication, chromosome segregation, and division site selection in the pneumococcus, providing a simple way to ensure equally sized daughter cells.

Cell Division and Evolution of Biological Tissues

NASA Astrophysics Data System (ADS)

Rivier, Nicolas; Arcenegui-Siemens, Xavier; Schliecker, Gudrun

A tissue is a geometrical, space-filling, random cellular network; it remains in this steady state while individual cells divide. Cell division (fragmentation) is a local, elementary topological transformation which establishes statistical equilibrium of the structure. Statistical equilibrium is characterized by observable relations (Lewis, Aboav) between cell shapes, sizes and those of their neighbours, obtained through maximum entropy and topological correlation extending to nearest neighbours only, i.e. maximal randomness. For a two-dimensional tissue (epithelium), the distribution of cell shapes and that of mother and daughter cells can be obtained from elementary geometrical and physical arguments, except for an exponential factor favouring division of larger cells, and exponential and combinatorial factors encouraging a most symmetric division. The resulting distributions are very narrow, and stationarity severely restricts the range of an adjustable structural parameter

BT-benzo-29 inhibits bacterial cell proliferation by perturbing FtsZ assembly.

PubMed

Ray, Shashikant; Jindal, Bhavya; Kunal, Kishore; Surolia, Avadhesha; Panda, Dulal

2015-10-01

We have identified a potent antibacterial agent N-(4-sec-butylphenyl)-2-(thiophen-2-yl)-1H-benzo[d]imidazole-4-carboxamide (BT-benzo-29) from a library of benzimidazole derivatives that stalled bacterial division by inhibiting FtsZ assembly. A short (5 min) exposure of BT-benzo-29 disassembled the cytokinetic Z-ring in Bacillus subtilis cells without affecting the cell length and nucleoids. BT-benzo-29 also perturbed the localization of early and late division proteins such as FtsA, ZapA and SepF at the mid-cell. Further, BT-benzo-29 bound to FtsZ with a dissociation constant of 24 ± 3 μm and inhibited the assembly and GTPase activity of purified FtsZ. A docking analysis suggested that BT-benzo-29 may bind to FtsZ at the C-terminal domain near the T7 loop. BT-benzo-29 displayed significantly weaker inhibitory effects on the assembly and GTPase activity of two mutants (L272A and V275A) of FtsZ supporting the prediction of the docking analysis. Further, BT-benzo-29 did not appear to inhibit DNA duplication and nucleoid segregation and it did not perturb the membrane potential of B. subtilis cells. The results suggested that BT-benzo-29 exerts its potent antibacterial activity by inhibiting FtsZ assembly. Interestingly, BT-benzo-29 did not affect the membrane integrity of mammalian red blood cells. BT-benzo-29 bound to tubulin with a much weaker affinity than FtsZ and exerted significantly weaker effects on mammalian cells than on the bacterial cells indicating that the compound may have a strong antibacterial potential. © 2015 FEBS.

Quantitative regulation of B cell division destiny by signal strength.

PubMed

Turner, Marian L; Hawkins, Edwin D; Hodgkin, Philip D

2008-07-01

Differentiation to Ab secreting and isotype-switched effector cells is tightly linked to cell division and therefore the degree of proliferation strongly influences the nature of the immune response. The maximum number of divisions reached, termed the population division destiny, is stochastically distributed in the population and is an important parameter in the quantitative outcome of lymphocyte responses. In this study, we further assessed the variables that regulate B cell division destiny in vitro in response to T cell- and TLR-dependent stimuli. Both the concentration and duration of stimulation were able to regulate the average maximum number of divisions undergone for each stimulus. Notably, a maximum division destiny was reached during provision of repeated saturating stimulation, revealing that an intrinsic limit to proliferation exists even under these conditions. This limit was linked directly to division number rather than time of exposure to stimulation and operated independently of the survival regulation of the cells. These results demonstrate that a B cell population's division destiny is regulable by the stimulatory conditions up to an inherent maximum value. Division destiny is a crucial parameter in regulating the extent of B cell responses and thereby also the nature of the immune response mounted.

Division Planes Alternate in Spherical Cells of Escherichia coli

PubMed Central

Begg, K. J.; Donachie, W. D.

1998-01-01

In the spherical cells of Escherichia coli rodA mutants, division is initiated at a single point, from which a furrow extends progressively around the cell. Using “giant” rodA ftsA cells, we confirmed that each new division furrow is initiated at the midpoint of the previous division plane and runs perpendicular to it. PMID:9573213

Asymmetries in Cell Division, Cell Size, and Furrowing in the Xenopus laevis Embryo.

PubMed

Tassan, Jean-Pierre; Wühr, Martin; Hatte, Guillaume; Kubiak, Jacek

2017-01-01

Asymmetric cell divisions produce two daughter cells with distinct fate. During embryogenesis, this mechanism is fundamental to build tissues and organs because it generates cell diversity. In adults, it remains crucial to maintain stem cells. The enthusiasm for asymmetric cell division is not only motivated by the beauty of the mechanism and the fundamental questions it raises, but has also very pragmatic reasons. Indeed, misregulation of asymmetric cell divisions is believed to have dramatic consequences potentially leading to pathogenesis such as cancers. In diverse model organisms, asymmetric cell divisions result in two daughter cells, which differ not only by their fate but also in size. This is the case for the early Xenopus laevis embryo, in which the two first embryonic divisions are perpendicular to each other and generate two pairs of blastomeres, which usually differ in size: one pair of blastomeres is smaller than the other. Small blastomeres will produce embryonic dorsal structures, whereas the larger pair will evolve into ventral structures. Here, we present a speculative model on the origin of the asymmetry of this cell division in the Xenopus embryo. We also discuss the apparently coincident asymmetric distribution of cell fate determinants and cell-size asymmetry of the 4-cell stage embryo. Finally, we discuss the asymmetric furrowing during epithelial cell cytokinesis occurring later during Xenopus laevis embryo development.

CbtA toxin of Escherichia coli inhibits cell division and cell elongation via direct and independent interactions with FtsZ and MreB.

PubMed

Heller, Danielle M; Tavag, Mrinalini; Hochschild, Ann

2017-09-01

The toxin components of toxin-antitoxin modules, found in bacterial plasmids, phages, and chromosomes, typically target a single macromolecule to interfere with an essential cellular process. An apparent exception is the chromosomally encoded toxin component of the E. coli CbtA/CbeA toxin-antitoxin module, which can inhibit both cell division and cell elongation. A small protein of only 124 amino acids, CbtA, was previously proposed to interact with both FtsZ, a tubulin homolog that is essential for cell division, and MreB, an actin homolog that is essential for cell elongation. However, whether or not the toxic effects of CbtA are due to direct interactions with these predicted targets is not known. Here, we genetically separate the effects of CbtA on cell elongation and cell division, showing that CbtA interacts directly and independently with FtsZ and MreB. Using complementary genetic approaches, we identify the functionally relevant target surfaces on FtsZ and MreB, revealing that in both cases, CbtA binds to surfaces involved in essential cytoskeletal filament architecture. We show further that each interaction contributes independently to CbtA-mediated toxicity and that disruption of both interactions is required to alleviate the observed toxicity. Although several other protein modulators are known to target FtsZ, the CbtA-interacting surface we identify represents a novel inhibitory target. Our findings establish CbtA as a dual function toxin that inhibits both cell division and cell elongation via direct and independent interactions with FtsZ and MreB.

CbtA toxin of Escherichia coli inhibits cell division and cell elongation via direct and independent interactions with FtsZ and MreB

PubMed Central

Heller, Danielle M.; Tavag, Mrinalini

2017-01-01

The toxin components of toxin-antitoxin modules, found in bacterial plasmids, phages, and chromosomes, typically target a single macromolecule to interfere with an essential cellular process. An apparent exception is the chromosomally encoded toxin component of the E. coli CbtA/CbeA toxin-antitoxin module, which can inhibit both cell division and cell elongation. A small protein of only 124 amino acids, CbtA, was previously proposed to interact with both FtsZ, a tubulin homolog that is essential for cell division, and MreB, an actin homolog that is essential for cell elongation. However, whether or not the toxic effects of CbtA are due to direct interactions with these predicted targets is not known. Here, we genetically separate the effects of CbtA on cell elongation and cell division, showing that CbtA interacts directly and independently with FtsZ and MreB. Using complementary genetic approaches, we identify the functionally relevant target surfaces on FtsZ and MreB, revealing that in both cases, CbtA binds to surfaces involved in essential cytoskeletal filament architecture. We show further that each interaction contributes independently to CbtA-mediated toxicity and that disruption of both interactions is required to alleviate the observed toxicity. Although several other protein modulators are known to target FtsZ, the CbtA-interacting surface we identify represents a novel inhibitory target. Our findings establish CbtA as a dual function toxin that inhibits both cell division and cell elongation via direct and independent interactions with FtsZ and MreB. PMID:28931012

Mechanical stretch triggers rapid epithelial cell division through Piezo1.

PubMed

Gudipaty, S A; Lindblom, J; Loftus, P D; Redd, M J; Edes, K; Davey, C F; Krishnegowda, V; Rosenblatt, J

2017-03-02

Despite acting as a barrier for the organs they encase, epithelial cells turn over at some of the fastest rates in the body. However, epithelial cell division must be tightly linked to cell death to preserve barrier function and prevent tumour formation. How does the number of dying cells match those dividing to maintain constant numbers? When epithelial cells become too crowded, they activate the stretch-activated channel Piezo1 to trigger extrusion of cells that later die. However, it is unclear how epithelial cell division is controlled to balance cell death at the steady state. Here we show that mammalian epithelial cell division occurs in regions of low cell density where cells are stretched. By experimentally stretching epithelia, we find that mechanical stretch itself rapidly stimulates cell division through activation of the Piezo1 channel. To stimulate cell division, stretch triggers cells that are paused in early G2 phase to activate calcium-dependent phosphorylation of ERK1/2, thereby activating the cyclin B transcription that is necessary to drive cells into mitosis. Although both epithelial cell division and cell extrusion require Piezo1 at the steady state, the type of mechanical force controls the outcome: stretch induces cell division, whereas crowding induces extrusion. How Piezo1-dependent calcium transients activate two opposing processes may depend on where and how Piezo1 is activated, as it accumulates in different subcellular sites with increasing cell density. In sparse epithelial regions in which cells divide, Piezo1 localizes to the plasma membrane and cytoplasm, whereas in dense regions in which cells extrude, it forms large cytoplasmic aggregates. Because Piezo1 senses both mechanical crowding and stretch, it may act as a homeostatic sensor to control epithelial cell numbers, triggering extrusion and apoptosis in crowded regions and cell division in sparse regions.

Mycoplasma pneumoniae, an Underutilized Model for Bacterial Cell Biology

PubMed Central

2014-01-01

In recent decades, bacterial cell biology has seen great advances, and numerous model systems have been developed to study a wide variety of cellular processes, including cell division, motility, assembly of macromolecular structures, and biogenesis of cell polarity. Considerable attention has been given to these model organisms, which include Escherichia coli, Bacillus subtilis, Caulobacter crescentus, and Myxococcus xanthus. Studies of these processes in the pathogenic bacterium Mycoplasma pneumoniae and its close relatives have also been carried out on a smaller scale, but this work is often overlooked, in part due to this organism's reputation as minimalistic and simple. In this minireview, I discuss recent work on the role of the M. pneumoniae attachment organelle (AO), a structure required for adherence to host cells, in these processes. The AO is constructed from proteins that generally lack homology to those found in other organisms, and this construction occurs in coordination with cell cycle events. The proteins of the M. pneumoniae AO share compositional features with proteins with related roles in model organisms. Once constructed, the AO becomes activated for its role in a form of gliding motility whose underlying mechanism appears to be distinct from that of other gliding bacteria, including Mycoplasma mobile. Together with the FtsZ cytoskeletal protein, motility participates in the cell division process. My intention is to bring this deceptively complex organism into alignment with the better-known model systems. PMID:25157081

Cell cycles and cell division in the archaea.

PubMed

Samson, Rachel Y; Bell, Stephen D

2011-06-01

Until recently little was known about the cell cycle parameters and division mechanisms of archaeal organisms. Although this is still the case for the majority of archaea, significant advances have been made in some model species. The information that has been gleaned thus far points to a remarkable degree of diversity within the archaeal domain of life. More specifically, members of distinct phyla have very different chromosome copy numbers, replication control systems and even employ distinct machineries for cell division. Copyright © 2011 Elsevier Ltd. All rights reserved.

Universal rule for the symmetric division of plant cells

PubMed Central

Besson, Sébastien; Dumais, Jacques

2011-01-01

The division of eukaryotic cells involves the assembly of complex cytoskeletal structures to exert the forces required for chromosome segregation and cytokinesis. In plants, empirical evidence suggests that tensional forces within the cytoskeleton cause cells to divide along the plane that minimizes the surface area of the cell plate (Errera’s rule) while creating daughter cells of equal size. However, exceptions to Errera’s rule cast doubt on whether a broadly applicable rule can be formulated for plant cell division. Here, we show that the selection of the plane of division involves a competition between alternative configurations whose geometries represent local area minima. We find that the probability of observing a particular division configuration increases inversely with its relative area according to an exponential probability distribution known as the Gibbs measure. Moreover, a comparison across land plants and their most recent algal ancestors confirms that the probability distribution is widely conserved and independent of cell shape and size. Using a maximum entropy formulation, we show that this empirical division rule is predicted by the dynamics of the tense cytoskeletal elements that lead to the positioning of the preprophase band. Based on the fact that the division plane is selected from the sole interaction of the cytoskeleton with cell shape, we posit that the new rule represents the default mechanism for plant cell division when internal or external cues are absent. PMID:21383128

Oriented cell division: new roles in guiding skin wound repair and regeneration

PubMed Central

Yang, Shaowei; Ma, Kui; Geng, Zhijun; Sun, Xiaoyan; Fu, Xiaobing

2015-01-01

Tissue morphogenesis depends on precise regulation and timely co-ordination of cell division and also on the control of the direction of cell division. Establishment of polarity division axis, correct alignment of the mitotic spindle, segregation of fate determinants equally or unequally between daughter cells, are essential for the realization of oriented cell division. Furthermore, oriented cell division is regulated by intrinsic cues, extrinsic cues and other cues, such as cell geometry and polarity. However, dysregulation of cell division orientation could lead to abnormal tissue development and function. In the present study, we review recent studies on the molecular mechanism of cell division orientation and explain their new roles in skin repair and regeneration. PMID:26582817

Bacterial Cell Enlargement Requires Control of Cell Wall Stiffness Mediated by Peptidoglycan Hydrolases.

PubMed

Wheeler, Richard; Turner, Robert D; Bailey, Richard G; Salamaga, Bartłomiej; Mesnage, Stéphane; Mohamad, Sharifah A S; Hayhurst, Emma J; Horsburgh, Malcolm; Hobbs, Jamie K; Foster, Simon J

2015-07-28

Most bacterial cells are enclosed in a single macromolecule of the cell wall polymer, peptidoglycan, which is required for shape determination and maintenance of viability, while peptidoglycan biosynthesis is an important antibiotic target. It is hypothesized that cellular enlargement requires regional expansion of the cell wall through coordinated insertion and hydrolysis of peptidoglycan. Here, a group of (apparent glucosaminidase) peptidoglycan hydrolases are identified that are together required for cell enlargement and correct cellular morphology of Staphylococcus aureus, demonstrating the overall importance of this enzyme activity. These are Atl, SagA, ScaH, and SagB. The major advance here is the explanation of the observed morphological defects in terms of the mechanical and biochemical properties of peptidoglycan. It was shown that cells lacking groups of these hydrolases have increased surface stiffness and, in the absence of SagB, substantially increased glycan chain length. This indicates that, beyond their established roles (for example in cell separation), some hydrolases enable cellular enlargement by making peptidoglycan easier to stretch, providing the first direct evidence demonstrating that cellular enlargement occurs via modulation of the mechanical properties of peptidoglycan. Understanding bacterial growth and division is a fundamental problem, and knowledge in this area underlies the treatment of many infectious diseases. Almost all bacteria are surrounded by a macromolecule of peptidoglycan that encloses the cell and maintains shape, and bacterial cells must increase the size of this molecule in order to enlarge themselves. This requires not only the insertion of new peptidoglycan monomers, a process targeted by antibiotics, including penicillin, but also breakage of existing bonds, a potentially hazardous activity for the cell. Using Staphylococcus aureus, we have identified a set of enzymes that are critical for cellular enlargement. We

Cell division and endoreduplication: doubtful engines of vegetative growth.

PubMed

John, Peter C L; Qi, Ruhu

2008-03-01

Currently, there is little information to indicate whether plant cell division and development is the collective effect of individual cell programming (cell-based) or is determined by organ-wide growth (organismal). Modulation of cell division does not confirm cell autonomous programming of cell expansion; instead, final cell size seems to be determined by the balance between cells formed and subsequent tissue growth. Control of growth in regions of the plant therefore has great importance in determining cell, organ and plant development. Here, we question the view that formation of new cells and their programmed expansion is the driving force of growth. We believe there is evidence that division does not drive, but requires, cell growth and a similar requirement for growth is detected in the modified cycle termed endoreduplication.

The SPOR Domain, a Widely Conserved Peptidoglycan Binding Domain That Targets Proteins to the Site of Cell Division.

PubMed

Yahashiri, Atsushi; Jorgenson, Matthew A; Weiss, David S

2017-07-15

Sporulation-related repeat (SPOR) domains are small peptidoglycan (PG) binding domains found in thousands of bacterial proteins. The name "SPOR domain" stems from the fact that several early examples came from proteins involved in sporulation, but SPOR domain proteins are quite diverse and contribute to a variety of processes that involve remodeling of the PG sacculus, especially with respect to cell division. SPOR domains target proteins to the division site by binding to regions of PG devoid of stem peptides ("denuded" glycans), which in turn are enriched in septal PG by the intense, localized activity of cell wall amidases involved in daughter cell separation. This targeting mechanism sets SPOR domain proteins apart from most other septal ring proteins, which localize via protein-protein interactions. In addition to SPOR domains, bacteria contain several other PG-binding domains that can exploit features of the cell wall to target proteins to specific subcellular sites. Copyright © 2017 American Society for Microbiology.

Lipid Cell Biology: A Focus on Lipids in Cell Division.

PubMed

Storck, Elisabeth M; Özbalci, Cagakan; Eggert, Ulrike S

2018-06-20

Cells depend on hugely diverse lipidomes for many functions. The actions and structural integrity of the plasma membrane and most organelles also critically depend on membranes and their lipid components. Despite the biological importance of lipids, our understanding of lipid engagement, especially the roles of lipid hydrophobic alkyl side chains, in key cellular processes is still developing. Emerging research has begun to dissect the importance of lipids in intricate events such as cell division. This review discusses how these structurally diverse biomolecules are spatially and temporally regulated during cell division, with a focus on cytokinesis. We analyze how lipids facilitate changes in cellular morphology during division and how they participate in key signaling events. We identify which cytokinesis proteins are associated with membranes, suggesting lipid interactions. More broadly, we highlight key unaddressed questions in lipid cell biology and techniques, including mass spectrometry, advanced imaging, and chemical biology, which will help us gain insights into the functional roles of lipids.

Colon-targeted delivery of live bacterial cell biotherapeutics including microencapsulated live bacterial cells

PubMed Central

Prakash, Satya; Malgorzata Urbanska, Aleksandra

2008-01-01

There has been an ample interest in delivery of therapeutic molecules using live cells. Oral delivery has been stipulated as best way to deliver live cells to humans for therapy. Colon, in particular, is a part of gastrointestinal (GI) tract that has been proposed to be an oral targeted site. The main objective of these oral therapy procedures is to deliver live cells not only to treat diseases like colorectal cancer, inflammatory bowel disease, and other GI tract diseases like intestinal obstruction and gastritis, but also to deliver therapeutic molecules for overall therapy in various diseases such as renal failure, coronary heart disease, hypertension, and others. This review provides a comprehensive summary of recent advancement in colon targeted live bacterial cell biotherapeutics. Current status of bacterial cell therapy, principles of artificial cells and its potentials in oral delivery of live bacterial cell biotherapeutics for clinical applications as well as biotherapeutic future perspectives are also discussed in our review. PMID:19707368

Kinetics of cell division in epidermal maintenance

NASA Astrophysics Data System (ADS)

Klein, Allon M.; Doupé, David P.; Jones, Phillip H.; Simons, Benjamin D.

2007-08-01

The rules governing cell division and differentiation are central to understanding the mechanisms of development, aging, and cancer. By utilizing inducible genetic labeling, recent studies have shown that the clonal population in transgenic mouse epidermis can be tracked in vivo. Drawing on these results, we explain how clonal fate data may be used to infer the rules of cell division and differentiation underlying the maintenance of adult murine tail-skin. We show that the rates of cell division and differentiation may be evaluated by considering the long-time and short-time clone fate data, and that the data is consistent with cells dividing independently rather than synchronously. Motivated by these findings, we consider a mechanism for cancer onset based closely on the model for normal adult skin. By analyzing the expected changes to clonal fate in cancer emerging from a simple two-stage mutation, we propose that clonal fate data may provide a novel method for studying the earliest stages of the disease.

Absence of the Polar Organizing Protein PopZ Results in Reduced and Asymmetric Cell Division in Agrobacterium tumefaciens

PubMed Central

Howell, Matthew; Aliashkevich, Alena; Salisbury, Anne K.; Cava, Felipe; Bowman, Grant R.

2017-01-01

ABSTRACT Agrobacterium tumefaciens is a rod-shaped bacterium that grows by polar insertion of new peptidoglycan during cell elongation. As the cell cycle progresses, peptidoglycan synthesis at the pole ceases prior to insertion of new peptidoglycan at midcell to enable cell division. The A. tumefaciens homolog of the Caulobacter crescentus polar organelle development protein PopZ has been identified as a growth pole marker and a candidate polar growth-promoting factor. Here, we characterize the function of PopZ in cell growth and division of A. tumefaciens. Consistent with previous observations, we observe that PopZ localizes specifically to the growth pole in wild-type cells. Despite the striking localization pattern of PopZ, we find the absence of the protein does not impair polar elongation or cause major changes in the peptidoglycan composition. Instead, we observe an atypical cell length distribution, including minicells, elongated cells, and cells with ectopic poles. Most minicells lack DNA, suggesting a defect in chromosome segregation. Furthermore, the canonical cell division proteins FtsZ and FtsA are misplaced, leading to asymmetric sites of cell constriction. Together, these data suggest that PopZ plays an important role in the regulation of chromosome segregation and cell division. IMPORTANCE A. tumefaciens is a bacterial plant pathogen and a natural genetic engineer. However, very little is known about the spatial and temporal regulation of cell wall biogenesis that leads to polar growth in this bacterium. Understanding the molecular basis of A. tumefaciens growth may allow for the development of innovations to prevent disease or to promote growth during biotechnology applications. Finally, since many closely related plant and animal pathogens exhibit polar growth, discoveries in A. tumefaciens may be broadly applicable for devising antimicrobial strategies. PMID:28630123

Hematopoietic stem cells can differentiate into restricted myeloid progenitors before cell division in mice.

PubMed

Grinenko, Tatyana; Eugster, Anne; Thielecke, Lars; Ramasz, Beáta; Krüger, Anja; Dietz, Sevina; Glauche, Ingmar; Gerbaulet, Alexander; von Bonin, Malte; Basak, Onur; Clevers, Hans; Chavakis, Triantafyllos; Wielockx, Ben

2018-05-15

Hematopoietic stem cells (HSCs) continuously replenish all blood cell types through a series of differentiation steps and repeated cell divisions that involve the generation of lineage-committed progenitors. However, whether cell division in HSCs precedes differentiation is unclear. To this end, we used an HSC cell-tracing approach and Ki67 RFP knock-in mice, in a non-conditioned transplantation model, to assess divisional history, cell cycle progression, and differentiation of adult HSCs. Our results reveal that HSCs are able to differentiate into restricted progenitors, especially common myeloid, megakaryocyte-erythroid and pre-megakaryocyte progenitors, without undergoing cell division and even before entering the S phase of the cell cycle. Additionally, the phenotype of the undivided but differentiated progenitors correlated with the expression of lineage-specific genes and loss of multipotency. Thus HSC fate decisions can be uncoupled from physical cell division. These results facilitate a better understanding of the mechanisms that control fate decisions in hematopoietic cells.

CELL DIVISION IN A SPECIES OF ERWINIA. III. REVERSAL OF INHIBITION OF CELL DIVISION CAUSED BY D-AMINO ACIDS, PENICILLIN, AND ULTRA-VIOLET LIGHT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grula, E.A.; Grula, M.M.

Inhibition of cell division in an Erwinia sp. occurs in the presence of any of six D-amino acids, penicillin, or ultraviolet light. Cell-division inhibition caused by D-amino acids is pH-dependent; however, elongation caused by penicillin occurs over a wide range of pH. Bulging and spheroplast formation in the presence of penicillin occurs only at pH values below 7.6; however, division continues to be inhibited at higher pH levels. Reversal of cell-division inhibition caused by two D-amino acids (phenylalanine and histidine) can be partially overcome by their respective L-isomers. Divalent cations (Zn, Ca, Mn) cause varying amounts of reversal of divisionmore » inhibition in all systems studied; each system appears to have an individual requirement. All induced division inhibitions, including that caused by penicillin, can be reversed by pantoyl lactone or omega methylpantoyl lactone. Evidence is presented and discussed concerning the possible importance of pantoyl lactone and divalent cations in terminal steps of the cell-division process in this organism. (auth)« less

Cell division is dispensable but not irrelevant in Streptomyces.

PubMed

McCormick, Joseph R

2009-12-01

In part, members of the genus Streptomyces have been studied because they produce many important secondary metabolites with antibiotic activity and for the interest in their relatively elaborate life cycle. These sporulating filamentous bacteria are remarkably synchronous for division and genome segregation in specialized aerial hyphae. Streptomycetes share some, but not all, of the division genes identified in the historic model rod-shaped organisms. Curiously, normally essential cell division genes are dispensable for growth and viability of Streptomyces coelicolor. Mainly, cell division plays a more important role in the developmental phase of life than during vegetative growth. Dispensability provides an advantageous genetic system to probe the mechanisms of division proteins, especially those with functions that are poorly understood.

Asymmetric cell division during T cell development controls downstream fate

PubMed Central

Pham, Kim; Shimoni, Raz; Charnley, Mirren; Ludford-Menting, Mandy J.; Hawkins, Edwin D.; Ramsbottom, Kelly; Oliaro, Jane; Izon, David; Ting, Stephen B.; Reynolds, Joseph; Lythe, Grant; Molina-Paris, Carmen; Melichar, Heather; Robey, Ellen; Humbert, Patrick O.; Gu, Min

2015-01-01

During mammalian T cell development, the requirement for expansion of many individual T cell clones, rather than merely expansion of the entire T cell population, suggests a possible role for asymmetric cell division (ACD). We show that ACD of developing T cells controls cell fate through differential inheritance of cell fate determinants Numb and α-Adaptin. ACD occurs specifically during the β-selection stage of T cell development, and subsequent divisions are predominantly symmetric. ACD is controlled by interaction with stromal cells and chemokine receptor signaling and uses a conserved network of polarity regulators. The disruption of polarity by deletion of the polarity regulator, Scribble, or the altered inheritance of fate determinants impacts subsequent fate decisions to influence the numbers of DN4 cells arising after the β-selection checkpoint. These findings indicate that ACD enables the thymic microenvironment to orchestrate fate decisions related to differentiation and self-renewal. PMID:26370500

Calculations of binding affinity between C8-substituted GTP analogs and the bacterial cell-division protein FtsZ

PubMed Central

Hritz, Jozef; Läppchen, Tilman

2010-01-01

The FtsZ protein is a self-polymerizing GTPase that plays a central role in bacterial cell division. Several C8-substituted GTP analogs are known to inhibit the polymerization of FtsZ by competing for the same binding site as its endogenous activating ligand GTP. Free energy calculations of the relative binding affinities to FtsZ for a set of five C8-substituted GTP analogs were performed. The calculated values agree well with the available experimental data, and the main contribution to the free energy differences is determined to be the conformational restriction of the ligands. The dihedral angle distributions around the glycosidic bond of these compounds in water are known to vary considerably depending on the physicochemical properties of the substituent at C8. However, within the FtsZ protein, this substitution has a negligible influence on the dihedral angle distributions, which fall within the narrow range of −140° to −90° for all investigated compounds. The corresponding ensemble average of the coupling constants 3J(C4,H1′) is calculated to be 2.95 ± 0.1 Hz. The contribution of the conformational selection of the GTP analogs upon binding was quantified from the corresponding populations. The obtained restraining free energy values follow the same trend as the relative binding affinities to FtsZ, indicating their dominant contribution. PMID:20559630

Functional redundancy of division specific penicillin-binding proteins in Bacillus subtilis.

PubMed

Sassine, Jad; Xu, Meizhu; Sidiq, Karzan R; Emmins, Robyn; Errington, Jeff; Daniel, Richard A

2017-10-01

Bacterial cell division involves the dynamic assembly of a diverse set of proteins that coordinate the invagination of the cell membrane and synthesis of cell wall material to create the new cell poles of the separated daughter cells. Penicillin-binding protein PBP 2B is a key cell division protein in Bacillus subtilis proposed to have a specific catalytic role in septal wall synthesis. Unexpectedly, we find that a catalytically inactive mutant of PBP 2B supports cell division, but in this background the normally dispensable PBP 3 becomes essential. Phenotypic analysis of pbpC mutants (encoding PBP 3) shows that PBP 2B has a crucial structural role in assembly of the division complex, independent of catalysis, and that its biochemical activity in septum formation can be provided by PBP 3. Bioinformatic analysis revealed a close sequence relationship between PBP 3 and Staphylococcus aureus PBP 2A, which is responsible for methicillin resistance. These findings suggest that mechanisms for rescuing cell division when the biochemical activity of PBP 2B is perturbed evolved prior to the clinical use of β-lactams. © 2017 The Authors. Molecular Microbiology published by John Wiley & Sons Ltd.

Tissue damage-induced intestinal stem cell division in Drosophila

PubMed Central

Amcheslavsky, Alla; Jiang, Jin; Ip, Y. Tony

2009-01-01

SUMMARY Stem cell division is essential for tissue integrity during growth, aging, and pathogenic assaults. Adult gastrointestinal tract encounters numerous stimulations and impaired tissue regeneration may lead to inflammatory diseases and cancer. Intestinal stem cells in adult Drosophila have recently been identified and shown to replenish the various cell types within the midgut. However, it is not known whether these intestinal stem cells can respond to environmental challenges. By feeding dextran sulfate sodium and bleomycin to flies and by expressing apoptotic proteins, we show that Drosophila intestinal stem cells can increase the rate of division in response to tissue damage. Moreover, if tissue damage results in epithelial cell loss, the newly formed enteroblasts can differentiate into mature epithelial cells. By using this newly established system of intestinal stem cell proliferation and tissue regeneration, we find that the insulin receptor signaling pathway is required for intestinal stem cell division. PMID:19128792

Asymmetric cell division requires specific mechanisms for adjusting global transcription.

PubMed

Mena, Adriana; Medina, Daniel A; García-Martínez, José; Begley, Victoria; Singh, Abhyudai; Chávez, Sebastián; Muñoz-Centeno, Mari C; Pérez-Ortín, José E

2017-12-01

Most cells divide symmetrically into two approximately identical cells. There are many examples, however, of asymmetric cell division that can generate sibling cell size differences. Whereas physical asymmetric division mechanisms and cell fate consequences have been investigated, the specific problem caused by asymmetric division at the transcription level has not yet been addressed. In symmetrically dividing cells the nascent transcription rate increases in parallel to cell volume to compensate it by keeping the actual mRNA synthesis rate constant. This cannot apply to the yeast Saccharomyces cerevisiae, where this mechanism would provoke a never-ending increasing mRNA synthesis rate in smaller daughter cells. We show here that, contrarily to other eukaryotes with symmetric division, budding yeast keeps the nascent transcription rates of its RNA polymerases constant and increases mRNA stability. This control on RNA pol II-dependent transcription rate is obtained by controlling the cellular concentration of this enzyme. © The Author(s) 2017. Published by Oxford University Press on behalf of Nucleic Acids Research.

Dynamic self-organisation of haematopoiesis and (a)symmetric cell division.

PubMed

Måløy, Marthe; Måløy, Frode; Jakobsen, Per; Olav Brandsdal, Bjørn

2017-02-07

A model of haematopoiesis that links self-organisation with symmetric and asymmetric cell division is presented in this paper. It is assumed that all cell divisions are completely random events, and that the daughter cells resulting from symmetric and asymmetric stem cell divisions are, in general, phenotypically identical, and still, the haematopoietic system has the flexibility to self-renew, produce mature cells by differentiation, and regenerate undifferentiated and differentiated cells when necessary, due to self-organisation. As far as we know, no previous model implements symmetric and asymmetric division as the result of self-organisation. The model presented in this paper is inspired by experiments on the Drosophila germline stem cell, which imply that under normal conditions, the stem cells typically divide asymmetrically, whereas during regeneration, the rate of symmetric division increases. Moreover, the model can reproduce several of the results from experiments on female Safari cats. In particular, the model can explain why significant fluctuation in the phenotypes of haematopoietic cells was observed in some cats, when the haematopoietic system had reached normal population level after regeneration. To our knowledge, no previous model of haematopoiesis in Safari cats has captured this phenomenon. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

Cell division plane orientation based on tensile stress in Arabidopsis thaliana

PubMed Central

Louveaux, Marion; Julien, Jean-Daniel; Mirabet, Vincent; Boudaoud, Arezki; Hamant, Olivier

2016-01-01

Cell geometry has long been proposed to play a key role in the orientation of symmetric cell division planes. In particular, the recently proposed Besson–Dumais rule generalizes Errera’s rule and predicts that cells divide along one of the local minima of plane area. However, this rule has been tested only on tissues with rather local spherical shape and homogeneous growth. Here, we tested the application of the Besson–Dumais rule to the divisions occurring in the Arabidopsis shoot apex, which contains domains with anisotropic curvature and differential growth. We found that the Besson–Dumais rule works well in the central part of the apex, but fails to account for cell division planes in the saddle-shaped boundary region. Because curvature anisotropy and differential growth prescribe directional tensile stress in that region, we tested the putative contribution of anisotropic stress fields to cell division plane orientation at the shoot apex. To do so, we compared two division rules: geometrical (new plane along the shortest path) and mechanical (new plane along maximal tension). The mechanical division rule reproduced the enrichment of long planes observed in the boundary region. Experimental perturbation of mechanical stress pattern further supported a contribution of anisotropic tensile stress in division plane orientation. Importantly, simulations of tissues growing in an isotropic stress field, and dividing along maximal tension, provided division plane distributions comparable to those obtained with the geometrical rule. We thus propose that division plane orientation by tensile stress offers a general rule for symmetric cell division in plants. PMID:27436908

Symmetric vs. Asymmetric Stem Cell Divisions: An Adaptation against Cancer?

PubMed Central

Shahriyari, Leili; Komarova, Natalia L.

2013-01-01

Traditionally, it has been held that a central characteristic of stem cells is their ability to divide asymmetrically. Recent advances in inducible genetic labeling provided ample evidence that symmetric stem cell divisions play an important role in adult mammalian homeostasis. It is well understood that the two types of cell divisions differ in terms of the stem cells' flexibility to expand when needed. On the contrary, the implications of symmetric and asymmetric divisions for mutation accumulation are still poorly understood. In this paper we study a stochastic model of a renewing tissue, and address the optimization problem of tissue architecture in the context of mutant production. Specifically, we study the process of tumor suppressor gene inactivation which usually takes place as a consequence of two “hits”, and which is one of the most common patterns in carcinogenesis. We compare and contrast symmetric and asymmetric (and mixed) stem cell divisions, and focus on the rate at which double-hit mutants are generated. It turns out that symmetrically-dividing cells generate such mutants at a rate which is significantly lower than that of asymmetrically-dividing cells. This result holds whether single-hit (intermediate) mutants are disadvantageous, neutral, or advantageous. It is also independent on whether the carcinogenic double-hit mutants are produced only among the stem cells or also among more specialized cells. We argue that symmetric stem cell divisions in mammals could be an adaptation which helps delay the onset of cancers. We further investigate the question of the optimal fraction of stem cells in the tissue, and quantify the contribution of non-stem cells in mutant production. Our work provides a hypothesis to explain the observation that in mammalian cells, symmetric patterns of stem cell division seem to be very common. PMID:24204602

Auxin-Dependent Cell Division and Cell Elongation. 1-Naphthaleneacetic Acid and 2,4-Dichlorophenoxyacetic Acid Activate Different Pathways1

PubMed Central

Campanoni, Prisca; Nick, Peter

2005-01-01

During exponential phase, the tobacco (Nicotiana tabacum) cell line cv Virginia Bright Italia-0 divides axially to produce linear cell files of distinct polarity. This axial division is controlled by exogenous auxin. We used exponential tobacco cv Virginia Bright Italia-0 cells to dissect early auxin signaling, with cell division and cell elongation as physiological markers. Experiments with 1-naphthaleneacetic acid (NAA) and 2,4-dichlorophenoxyacetic acid (2,4-D) demonstrated that these 2 auxin species affect cell division and cell elongation differentially; NAA stimulates cell elongation at concentrations that are much lower than those required to stimulate cell division. In contrast, 2,4-D promotes cell division but not cell elongation. Pertussis toxin, a blocker of heterotrimeric G-proteins, inhibits the stimulation of cell division by 2,4-D but does not affect cell elongation. Aluminum tetrafluoride, an activator of the G-proteins, can induce cell division at NAA concentrations that are not permissive for division and even in the absence of any exogenous auxin. The data are discussed in a model where the two different auxins activate two different pathways for the control of cell division and cell elongation. PMID:15734918

Genome organization during the cell cycle: unity in division.

PubMed

Golloshi, Rosela; Sanders, Jacob T; McCord, Rachel Patton

2017-09-01

During the cell cycle, the genome must undergo dramatic changes in structure, from a decondensed, yet highly organized interphase structure to a condensed, generic mitotic chromosome and then back again. For faithful cell division, the genome must be replicated and chromosomes and sister chromatids physically segregated from one another. Throughout these processes, there is feedback and tension between the information-storing role and the physical properties of chromosomes. With a combination of recent techniques in fluorescence microscopy, chromosome conformation capture (Hi-C), biophysical experiments, and computational modeling, we can now attribute mechanisms to many long-observed features of chromosome structure changes during cell division. Apparent conflicts that arise when integrating the concepts from these different proposed mechanisms emphasize that orchestrating chromosome organization during cell division requires a complex system of factors rather than a simple pathway. Cell division is both essential for and threatening to proper genome organization. As interphase three-dimensional (3D) genome structure is quite static at a global level, cell division provides an important window of opportunity to make substantial changes in 3D genome organization in daughter cells, allowing for proper differentiation and development. Mistakes in the process of chromosome condensation or rebuilding the structure after mitosis can lead to diseases such as cancer, premature aging, and neurodegeneration. WIREs Syst Biol Med 2017, 9:e1389. doi: 10.1002/wsbm.1389 For further resources related to this article, please visit the WIREs website. © 2017 Wiley Periodicals, Inc.

Sporulation-specific cell division defects in ylmE mutants of Streptomyces coelicolor are rescued by additional deletion of ylmD.

PubMed

Zhang, Le; Willemse, Joost; Hoskisson, Paul A; van Wezel, Gilles P

2018-05-09

Cell division during the reproductive phase of the Streptomyces life-cycle requires tight coordination between synchronous formation of multiple septa and DNA segregation. One remarkable difference with most other bacterial systems is that cell division in Streptomyces is positively controlled by the recruitment of FtsZ by SsgB. Here we show that deletion of ylmD (SCO2081) or ylmE (SCO2080), which lie in operon with ftsZ in the dcw cluster of actinomycetes, has major consequences for sporulation-specific cell division in Streptomyces coelicolor. Electron and fluorescence microscopy demonstrated that ylmE mutants have a highly aberrant phenotype with defective septum synthesis, and produce very few spores with low viability and high heat sensitivity. FtsZ-ring formation was also highly disturbed in ylmE mutants. Deletion of ylmD had a far less severe effect on sporulation. Interestingly, the additional deletion of ylmD restored sporulation to the ylmE null mutant. YlmD and YlmE are not part of the divisome, but instead localize diffusely in aerial hyphae, with differential intensity throughout the sporogenic part of the hyphae. Taken together, our work reveals a function for YlmD and YlmE in the control of sporulation-specific cell division in S. coelicolor, whereby the presence of YlmD alone results in major developmental defects.

Partial genome assembly for a candidate division OP11 single cell from an anoxic spring (Zodletone Spring, Oklahoma).

PubMed

Youssef, Noha H; Blainey, Paul C; Quake, Stephen R; Elshahed, Mostafa S

2011-11-01

Members of candidate division OP11 are widely distributed in terrestrial and marine ecosystems, yet little information regarding their metabolic capabilities and ecological role within such habitats is currently available. Here, we report on the microfluidic isolation, multiple-displacement-amplification, pyrosequencing, and genomic analysis of a single cell (ZG1) belonging to candidate division OP11. Genome analysis of the ∼270-kb partial genome assembly obtained showed that it had no particular similarity to a specific phylum. Four hundred twenty-three open reading frames were identified, 46% of which had no function prediction. In-depth analysis revealed a heterotrophic lifestyle, with genes encoding endoglucanase, amylopullulanase, and laccase enzymes, suggesting a capacity for utilization of cellulose, starch, and, potentially, lignin, respectively. Genes encoding several glycolysis enzymes as well as formate utilization were identified, but no evidence for an electron transport chain was found. The presence of genes encoding various components of lipopolysaccharide biosynthesis indicates a Gram-negative bacterial cell wall. The partial genome also provides evidence for antibiotic resistance (β-lactamase, aminoglycoside phosphotransferase), as well as antibiotic production (bacteriocin) and extracellular bactericidal peptidases. Multiple mechanisms for stress response were identified, as were elements of type I and type IV secretion systems. Finally, housekeeping genes identified within the partial genome were used to demonstrate the OP11 affiliation of multiple hitherto unclassified genomic fragments from multiple database-deposited metagenomic data sets. These results provide the first glimpse into the lifestyle of a member of a ubiquitous, yet poorly understood bacterial candidate division.

Bestatin Inhibits Cell Growth, Cell Division, and Spore Cell Differentiation in Dictyostelium discoideum

PubMed Central

Poloz, Yekaterina; Catalano, Andrew

2012-01-01

Bestatin methyl ester (BME) is an inhibitor of Zn2+-binding aminopeptidases that inhibits cell proliferation and induces apoptosis in normal and cancer cells. We have used Dictyostelium as a model organism to study the effects of BME. Only two Zn2+-binding aminopeptidases have been identified in Dictyostelium to date, puromycin-sensitive aminopeptidase A and B (PsaA and PsaB). PSA from other organisms is known to regulate cell division and differentiation. Here we show that PsaA is differentially expressed throughout growth and development of Dictyostelium, and its expression is regulated by developmental morphogens. We present evidence that BME specifically interacts with PsaA and inhibits its aminopeptidase activity. Treatment of cells with BME inhibited the rate of cell growth and the frequency of cell division in growing cells and inhibited spore cell differentiation during late development. Overexpression of PsaA-GFP (where GFP is green fluorescent protein) also inhibited spore cell differentiation but did not affect growth. Using chimeras, we have identified that nuclear versus cytoplasmic localization of PsaA affects the choice between stalk or spore cell differentiation pathway. Cells that overexpressed PsaA-GFP (primarily nuclear) differentiated into stalk cells, while cells that overexpressed PsaAΔNLS2-GFP (cytoplasmic) differentiated into spores. In conclusion, we have identified that BME inhibits cell growth, division, and differentiation in Dictyostelium likely through inhibition of PsaA. PMID:22345351

Long-range ordered vorticity patterns in living tissue induced by cell division

NASA Astrophysics Data System (ADS)

Rossen, Ninna S.; Tarp, Jens M.; Mathiesen, Joachim; Jensen, Mogens H.; Oddershede, Lene B.

2014-12-01

In healthy blood vessels with a laminar blood flow, the endothelial cell division rate is low, only sufficient to replace apoptotic cells. The division rate significantly increases during embryonic development and under halted or turbulent flow. Cells in barrier tissue are connected and their motility is highly correlated. Here we investigate the long-range dynamics induced by cell division in an endothelial monolayer under non-flow conditions, mimicking the conditions during vessel formation or around blood clots. Cell divisions induce long-range, well-ordered vortex patterns extending several cell diameters away from the division site, in spite of the system’s low Reynolds number. Our experimental results are reproduced by a hydrodynamic continuum model simulating division as a local pressure increase corresponding to a local tension decrease. Such long-range physical communication may be crucial for embryonic development and for healing tissue, for instance around blood clots.

Cell-Division Behavior in a Heterogeneous Swarm Environment.

PubMed

Erskine, Adam; Herrmann, J Michael

2015-01-01

We present a system of virtual particles that interact using simple kinetic rules. It is known that heterogeneous mixtures of particles can produce particularly interesting behaviors. Here we present a two-species three-dimensional swarm in which a behavior emerges that resembles cell division. We show that the dividing behavior exists across a narrow but finite band of parameters and for a wide range of population sizes. When executed in a two-dimensional environment the swarm's characteristics and dynamism manifest differently. In further experiments we show that repeated divisions can occur if the system is extended by a biased equilibrium process to control the split of populations. We propose that this repeated division behavior provides a simple model for cell-division mechanisms and is of interest for the formation of morphological structure and to swarm robotics.

Oriented cell division shapes carnivorous pitcher leaves of Sarracenia purpurea.

PubMed

Fukushima, Kenji; Fujita, Hironori; Yamaguchi, Takahiro; Kawaguchi, Masayoshi; Tsukaya, Hirokazu; Hasebe, Mitsuyasu

2015-03-16

Complex morphology is an evolutionary outcome of phenotypic diversification. In some carnivorous plants, the ancestral planar leaf has been modified to form a pitcher shape. However, how leaf development was altered during evolution remains unknown. Here we show that the pitcher leaves of Sarracenia purpurea develop through cell division patterns of adaxial tissues that are distinct from those in bifacial and peltate leaves, subsequent to standard expression of adaxial and abaxial marker genes. Differences in the orientation of cell divisions in the adaxial domain cause bifacial growth in the distal region and adaxial ridge protrusion in the middle region. These different growth patterns establish pitcher morphology. A computer simulation suggests that the cell division plane is critical for the pitcher morphogenesis. Our results imply that tissue-specific changes in the orientation of cell division underlie the development of a morphologically complex leaf.

A crucial step in cell division identified | Center for Cancer Research

Cancer.gov

When cell division doesn’t go according to plan, the resulting daughter cells can become unstable or even cancerous. A team of CCR investigators has now discovered a crucial step required for normal cell division to occur. Read more...

A plant cell division algorithm based on cell biomechanics and ellipse-fitting.

PubMed

Abera, Metadel K; Verboven, Pieter; Defraeye, Thijs; Fanta, Solomon Workneh; Hertog, Maarten L A T M; Carmeliet, Jan; Nicolai, Bart M

2014-09-01

The importance of cell division models in cellular pattern studies has been acknowledged since the 19th century. Most of the available models developed to date are limited to symmetric cell division with isotropic growth. Often, the actual growth of the cell wall is either not considered or is updated intermittently on a separate time scale to the mechanics. This study presents a generic algorithm that accounts for both symmetrically and asymmetrically dividing cells with isotropic and anisotropic growth. Actual growth of the cell wall is simulated simultaneously with the mechanics. The cell is considered as a closed, thin-walled structure, maintained in tension by turgor pressure. The cell walls are represented as linear elastic elements that obey Hooke's law. Cell expansion is induced by turgor pressure acting on the yielding cell-wall material. A system of differential equations for the positions and velocities of the cell vertices as well as for the actual growth of the cell wall is established. Readiness to divide is determined based on cell size. An ellipse-fitting algorithm is used to determine the position and orientation of the dividing wall. The cell vertices, walls and cell connectivity are then updated and cell expansion resumes. Comparisons are made with experimental data from the literature. The generic plant cell division algorithm has been implemented successfully. It can handle both symmetrically and asymmetrically dividing cells coupled with isotropic and anisotropic growth modes. Development of the algorithm highlighted the importance of ellipse-fitting to produce randomness (biological variability) even in symmetrically dividing cells. Unlike previous models, a differential equation is formulated for the resting length of the cell wall to simulate actual biological growth and is solved simultaneously with the position and velocity of the vertices. The algorithm presented can produce different tissues varying in topological and geometrical

A plant cell division algorithm based on cell biomechanics and ellipse-fitting

PubMed Central

Abera, Metadel K.; Verboven, Pieter; Defraeye, Thijs; Fanta, Solomon Workneh; Hertog, Maarten L. A. T. M.; Carmeliet, Jan; Nicolai, Bart M.

2014-01-01

Background and Aims The importance of cell division models in cellular pattern studies has been acknowledged since the 19th century. Most of the available models developed to date are limited to symmetric cell division with isotropic growth. Often, the actual growth of the cell wall is either not considered or is updated intermittently on a separate time scale to the mechanics. This study presents a generic algorithm that accounts for both symmetrically and asymmetrically dividing cells with isotropic and anisotropic growth. Actual growth of the cell wall is simulated simultaneously with the mechanics. Methods The cell is considered as a closed, thin-walled structure, maintained in tension by turgor pressure. The cell walls are represented as linear elastic elements that obey Hooke's law. Cell expansion is induced by turgor pressure acting on the yielding cell-wall material. A system of differential equations for the positions and velocities of the cell vertices as well as for the actual growth of the cell wall is established. Readiness to divide is determined based on cell size. An ellipse-fitting algorithm is used to determine the position and orientation of the dividing wall. The cell vertices, walls and cell connectivity are then updated and cell expansion resumes. Comparisons are made with experimental data from the literature. Key Results The generic plant cell division algorithm has been implemented successfully. It can handle both symmetrically and asymmetrically dividing cells coupled with isotropic and anisotropic growth modes. Development of the algorithm highlighted the importance of ellipse-fitting to produce randomness (biological variability) even in symmetrically dividing cells. Unlike previous models, a differential equation is formulated for the resting length of the cell wall to simulate actual biological growth and is solved simultaneously with the position and velocity of the vertices. Conclusions The algorithm presented can produce different

Oriented cell division shapes carnivorous pitcher leaves of Sarracenia purpurea

PubMed Central

Fukushima, Kenji; Fujita, Hironori; Yamaguchi, Takahiro; Kawaguchi, Masayoshi; Tsukaya, Hirokazu; Hasebe, Mitsuyasu

2015-01-01

Complex morphology is an evolutionary outcome of phenotypic diversification. In some carnivorous plants, the ancestral planar leaf has been modified to form a pitcher shape. However, how leaf development was altered during evolution remains unknown. Here we show that the pitcher leaves of Sarracenia purpurea develop through cell division patterns of adaxial tissues that are distinct from those in bifacial and peltate leaves, subsequent to standard expression of adaxial and abaxial marker genes. Differences in the orientation of cell divisions in the adaxial domain cause bifacial growth in the distal region and adaxial ridge protrusion in the middle region. These different growth patterns establish pitcher morphology. A computer simulation suggests that the cell division plane is critical for the pitcher morphogenesis. Our results imply that tissue-specific changes in the orientation of cell division underlie the development of a morphologically complex leaf. PMID:25774486

Characterization of dependencies between growth and division in budding yeast

PubMed Central

Iversen, Edwin S.; Hartemink, Alexander J.

2017-01-01

Cell 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 yeast Saccharomyces cerevisiae, this coordination or ‘size control’ appears as an inverse correlation between cell size and the rate of cell-cycle progression, routinely observed in G1 prior 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, in unicellular organisms, coordination between growth and division has commonly been analysed within the cycle of a single cell without accounting for correlations in growth and division characteristics between cycles of related cells. In a comprehensive analysis of three published time-lapse microscopy datasets, we analyse both intra- and inter-cycle dependencies between growth and division, revisiting assumptions about the coordination between these two processes. Interestingly, we find evidence (i) that S/G2/M durations are systematically longer in daughters than in mothers, (ii) of dependencies between S/G2/M and size at budding that echo the classical G1 dependencies, and (iii) 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 modellers 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. PMID:28228543

Characterization of dependencies between growth and division in budding yeast.

PubMed

Mayhew, Michael B; Iversen, Edwin S; Hartemink, Alexander J

2017-02-01

Cell 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 yeast Saccharomyces cerevisiae , this coordination or 'size control' appears as an inverse correlation between cell size and the rate of cell-cycle progression, routinely observed in G 1 prior to cell division commitment. Beyond this point, cells are presumed to complete S/G 2 /M at similar rates and in a size-independent manner. As such, studies of dependence between growth and division have focused on G 1 Moreover, in unicellular organisms, coordination between growth and division has commonly been analysed within the cycle of a single cell without accounting for correlations in growth and division characteristics between cycles of related cells. In a comprehensive analysis of three published time-lapse microscopy datasets, we analyse both intra- and inter-cycle dependencies between growth and division, revisiting assumptions about the coordination between these two processes. Interestingly, we find evidence (i) that S/G 2 /M durations are systematically longer in daughters than in mothers, (ii) of dependencies between S/G 2 /M and size at budding that echo the classical G 1 dependencies, and (iii) 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 modellers 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. © 2017 The Author(s).

Characterization of dependencies between growth and division in budding yeast

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mayhew, Michael B.; Iversen, Edwin S.; Hartemink, Alexander J.

Cell 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 yeast Saccharomyces cerevisiae, this coordination or ‘size control’ appears as an inverse correlation between cell size and the rate of cell-cycle progression, routinely observed in G1 prior to cell division commitment. Beyond this point, cells are presumed to complete S/G 2/M at similar rates and in a size-independent manner. As such, studies of dependence between growth and division have focused on G1. Moreover, in unicellular organisms, coordination betweenmore » growth and division has commonly been analyzed within the cycle of a single cell without accounting for correlations in growth and division characteristics between cycles 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/G 2/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 G1 dependencies, 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.« less

Characterization of dependencies between growth and division in budding yeast

DOE PAGES

Mayhew, Michael B.; Iversen, Edwin S.; Hartemink, Alexander J.

2017-02-01

Cell 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 yeast Saccharomyces cerevisiae, this coordination or ‘size control’ appears as an inverse correlation between cell size and the rate of cell-cycle progression, routinely observed in G1 prior to cell division commitment. Beyond this point, cells are presumed to complete S/G 2/M at similar rates and in a size-independent manner. As such, studies of dependence between growth and division have focused on G1. Moreover, in unicellular organisms, coordination betweenmore » growth and division has commonly been analyzed within the cycle of a single cell without accounting for correlations in growth and division characteristics between cycles 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/G 2/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 G1 dependencies, 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.« less

Periplasmic Acid Stress Increases Cell Division Asymmetry (Polar Aging) of Escherichia coli

PubMed Central

Clark, Michelle W.; Yie, Anna M.; Eder, Elizabeth K.; Dennis, Richard G.; Basting, Preston J.; Martinez, Keith A.; Jones, Brian D.; Slonczewski, Joan L.

2015-01-01

Under certain kinds of cytoplasmic stress, Escherichia coli selectively reproduce by distributing the newer cytoplasmic components to new-pole cells while sequestering older, damaged components in cells inheriting the old pole. This phenomenon is termed polar aging or cell division asymmetry. It is unknown whether cell division asymmetry can arise from a periplasmic stress, such as the stress of extracellular acid, which is mediated by the periplasm. We tested the effect of periplasmic acid stress on growth and division of adherent single cells. We tracked individual cell lineages over five or more generations, using fluorescence microscopy with ratiometric pHluorin to measure cytoplasmic pH. Adherent colonies were perfused continually with LBK medium buffered at pH 6.00 or at pH 7.50; the external pH determines periplasmic pH. In each experiment, cell lineages were mapped to correlate division time, pole age and cell generation number. In colonies perfused at pH 6.0, the cells inheriting the oldest pole divided significantly more slowly than the cells inheriting the newest pole. In colonies perfused at pH 7.50 (near or above cytoplasmic pH), no significant cell division asymmetry was observed. Under both conditions (periplasmic pH 6.0 or pH 7.5) the cells maintained cytoplasmic pH values at 7.2–7.3. No evidence of cytoplasmic protein aggregation was seen. Thus, periplasmic acid stress leads to cell division asymmetry with minimal cytoplasmic stress. PMID:26713733

The C. elegans engrailed homolog ceh-16 regulates the self-renewal expansion division of stem cell-like seam cells.

PubMed

Huang, Xinxin; Tian, E; Xu, Yanhua; Zhang, Hong

2009-09-15

Stem cells undergo symmetric and asymmetric division to maintain the dynamic equilibrium of the stem cell pool and also to generate a variety of differentiated cells. The homeostatic mechanism controlling the choice between self-renewal and differentiation of stem cells is poorly understood. We show here that ceh-16, encoding the C. elegans ortholog of the transcription factor Engrailed, controls symmetric and asymmetric division of stem cell-like seam cells. Loss of function of ceh-16 causes certain seam cells, which normally undergo symmetric self-renewal expansion division with both daughters adopting the seam cell fate, to divide asymmetrically with only one daughter retaining the seam cell fate. The human engrailed homolog En2 functionally substitutes the role of ceh-16 in promoting self-renewal expansion division of seam cells. Loss of function of apr-1, encoding the C. elegans homolog of the Wnt signaling component APC, results in transformation of self-renewal maintenance seam cell division to self-renewal expansion division, leading to seam cell hyperplasia. The apr-1 mutation suppresses the seam cell division defect in ceh-16 mutants. Our study reveals that ceh-16 interacts with the Wnt signaling pathway to control the choice between self-renewal expansion and maintenance division and also demonstrates an evolutionarily conserved function of engrailed in promoting cell proliferation.

Cell and plastid division are coordinated through the prereplication factor AtCDT1

PubMed Central

Raynaud, Cécile; Perennes, Claudette; Reuzeau, Christophe; Catrice, Olivier; Brown, Spencer; Bergounioux, Catherine

2005-01-01

The cell division cycle involves nuclear and cytoplasmic events, namely organelle multiplication and distribution between the daughter cells. Until now, plastid and plant cell division have been considered as independent processes because they can be uncoupled. Here, down-regulation of AtCDT1a and AtCDT1b, members of the prereplication complex, is shown to alter both nuclear DNA replication and plastid division in Arabidopsis thaliana. These data constitute molecular evidence for relationships between the cell-cycle and plastid division. Moreover, the severe developmental defects observed in AtCDT1-RNA interference (RNAi) plants underline the importance of coordinated cell and organelle division for plant growth and morphogenesis. PMID:15928083

Mechanical Forces Program the Orientation of Cell Division during Airway Tube Morphogenesis.

PubMed

Tang, Zan; Hu, Yucheng; Wang, Zheng; Jiang, Kewu; Zhan, Cheng; Marshall, Wallace F; Tang, Nan

2018-02-05

Oriented cell division plays a key role in controlling organogenesis. The mechanisms for regulating division orientation at the whole-organ level are only starting to become understood. By combining 3D time-lapse imaging, mouse genetics, and mathematical modeling, we find that global orientation of cell division is the result of a combination of two types of spindles with distinct spindle dynamic behaviors in the developing airway epithelium. Fixed spindles follow the classic long-axis rule and establish their division orientation before metaphase. In contrast, rotating spindles do not strictly follow the long-axis rule and determine their division orientation during metaphase. By using both a cell-based mechanical model and stretching-lung-explant experiments, we showed that mechanical force can function as a regulatory signal in maintaining the stable ratio between fixed spindles and rotating spindles. Our findings demonstrate that mechanical forces, cell geometry, and oriented cell division function together in a highly coordinated manner to ensure normal airway tube morphogenesis. Copyright © 2017 Elsevier Inc. All rights reserved.

Droplet size influences division of mammalian cell factories in droplet microfluidic cultivation.

PubMed

Periyannan Rajeswari, Prem Kumar; Joensson, Haakan N; Andersson-Svahn, Helene

2017-01-01

The potential of using droplet microfluidics for screening mammalian cell factories has been limited by the difficulty in achieving continuous cell division during cultivation in droplets. Here, we report the influence of droplet size on mammalian cell division and viability during cultivation in droplets. Chinese Hamster Ovary (CHO) cells, the most widely used mammalian host cells for biopharmaceuticals production were encapsulated and cultivated in 33, 180 and 320 pL droplets for 3 days. Periodic monitoring of the droplets during incubation showed that the cell divisions in 33 pL droplets stopped after 24 h, whereas continuous cell division was observed in 180 and 320 pL droplets for 72 h. The viability of the cells cultivated in the 33 pL droplets also dropped to about 50% in 72 h. In contrast, the viability of the cells in the larger droplets was above 90% even after 72 h of cultivation, making them a more suitable droplet size for 72-h cultivation. This study shows a direct correlation of microfluidic droplet size to the division and viability of mammalian cells. This highlights the importance of selecting suitable droplet size for mammalian cell factory screening assays. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Cortical PAR polarity proteins promote robust cytokinesis during asymmetric cell division

PubMed Central

Jordan, Shawn N.; Davies, Tim; Zhuravlev, Yelena; Dumont, Julien; Shirasu-Hiza, Mimi

2016-01-01

Cytokinesis, the physical division of one cell into two, is thought to be fundamentally similar in most animal cell divisions and driven by the constriction of a contractile ring positioned and controlled solely by the mitotic spindle. During asymmetric cell divisions, the core polarity machinery (partitioning defective [PAR] proteins) controls the unequal inheritance of key cell fate determinants. Here, we show that in asymmetrically dividing Caenorhabditis elegans embryos, the cortical PAR proteins (including the small guanosine triphosphatase CDC-42) have an active role in regulating recruitment of a critical component of the contractile ring, filamentous actin (F-actin). We found that the cortical PAR proteins are required for the retention of anillin and septin in the anterior pole, which are cytokinesis proteins that our genetic data suggest act as inhibitors of F-actin at the contractile ring. Collectively, our results suggest that the cortical PAR proteins coordinate the establishment of cell polarity with the physical process of cytokinesis during asymmetric cell division to ensure the fidelity of daughter cell formation. PMID:26728855

Planar cell polarity signaling coordinates oriented cell division and cell rearrangement in clonally expanding growth plate cartilage

PubMed Central

Li, Yuwei; Li, Ang; Junge, Jason

2017-01-01

Both oriented cell divisions and cell rearrangements are critical for proper embryogenesis and organogenesis. However, little is known about how these two cellular events are integrated. Here we examine the linkage between these processes in chick limb cartilage. By combining retroviral-based multicolor clonal analysis with live imaging, the results show that single chondrocyte precursors can generate both single-column and multi-column clones through oriented division followed by cell rearrangements. Focusing on single column formation, we show that this stereotypical tissue architecture is established by a pivot-like process between sister cells. After mediolateral cell division, N-cadherin is enriched in the post-cleavage furrow; then one cell pivots around the other, resulting in stacking into a column. Perturbation analyses demonstrate that planar cell polarity signaling enables cells to pivot in the direction of limb elongation via this N-cadherin-mediated coupling. Our work provides new insights into the mechanisms generating appropriate tissue architecture of limb skeleton. PMID:28994649

Planar cell polarity signaling coordinates oriented cell division and cell rearrangement in clonally expanding growth plate cartilage.

PubMed

Li, Yuwei; Li, Ang; Junge, Jason; Bronner, Marianne

2017-10-10

Both oriented cell divisions and cell rearrangements are critical for proper embryogenesis and organogenesis. However, little is known about how these two cellular events are integrated. Here we examine the linkage between these processes in chick limb cartilage. By combining retroviral-based multicolor clonal analysis with live imaging, the results show that single chondrocyte precursors can generate both single-column and multi-column clones through oriented division followed by cell rearrangements. Focusing on single column formation, we show that this stereotypical tissue architecture is established by a pivot-like process between sister cells. After mediolateral cell division, N-cadherin is enriched in the post-cleavage furrow; then one cell pivots around the other, resulting in stacking into a column. Perturbation analyses demonstrate that planar cell polarity signaling enables cells to pivot in the direction of limb elongation via this N-cadherin-mediated coupling. Our work provides new insights into the mechanisms generating appropriate tissue architecture of limb skeleton.

Physics of Bacterial Morphogenesis

PubMed Central

Sun, Sean X.; Jiang, Hongyuan

2011-01-01

Summary: Bacterial cells utilize three-dimensional (3D) protein assemblies to perform important cellular functions such as growth, division, chemoreception, and motility. These assemblies are composed of mechanoproteins that can mechanically deform and exert force. Sometimes, small-nucleotide hydrolysis is coupled to mechanical deformations. In this review, we describe the general principle for an understanding of the coupling of mechanics with chemistry in mechanochemical systems. We apply this principle to understand bacterial cell shape and morphogenesis and how mechanical forces can influence peptidoglycan cell wall growth. We review a model that can potentially reconcile the growth dynamics of the cell wall with the role of cytoskeletal proteins such as MreB and crescentin. We also review the application of mechanochemical principles to understand the assembly and constriction of the FtsZ ring. A number of potential mechanisms are proposed, and important questions are discussed. PMID:22126993

A role for the ESCRT system in cell division in archaea.

PubMed

Samson, Rachel Y; Obita, Takayuki; Freund, Stefan M; Williams, Roger L; Bell, Stephen D

2008-12-12

Archaea are prokaryotic organisms that lack endomembrane structures. However, a number of hyperthermophilic members of the Kingdom Crenarchaea, including members of the Sulfolobus genus, encode homologs of the eukaryotic endosomal sorting system components Vps4 and ESCRT-III (endosomal sorting complex required for transport-III). We found that Sulfolobus ESCRT-III and Vps4 homologs underwent regulation of their expression during the cell cycle. The proteins interacted and we established the structural basis of this interaction. Furthermore, these proteins specifically localized to the mid-cell during cell division. Overexpression of a catalytically inactive mutant Vps4 in Sulfolobus resulted in the accumulation of enlarged cells, indicative of failed cell division. Thus, the archaeal ESCRT system plays a key role in cell division.

High frame-rate resolution of cell division during Candida albicans filamentation

PubMed Central

Thomson, Darren D.; Berman, Judith; Brand, Alexandra C.

2016-01-01

The commensal yeast, Candida albicans, is an opportunistic pathogen in humans and forms filaments called hyphae and pseudohyphae, in which cell division requires precise temporal and spatial control to produce mononuclear cell compartments. High-frame-rate live-cell imaging (1 frame/min) revealed that nuclear division did not occur across the septal plane. We detected the presence of nucleolar fragments that may be extrachromosomal molecules carrying the ribosomal RNA genes. Cells occasionally maintained multiple nucleoli, suggesting either polyploidy, multiple nuclei and/or aneuploidy of ChrR., while the migration pattern of sister nuclei differed between unbranched and branched hyphae. The presented movie challenges and extends previous concepts of C. albicans cell division. PMID:26854071

The Caenorhabditis elegans gene ham-1 regulates daughter cell size asymmetry primarily in divisions that produce a small anterior daughter cell

PubMed Central

Kovacevic, Ismar; Bao, Zhirong

2018-01-01

C. elegans cell divisions that produce an apoptotic daughter cell exhibit Daughter Cell Size Asymmetry (DCSA), producing a larger surviving daughter cell and a smaller daughter cell fated to die. Genetic screens for mutants with defects in apoptosis identified several genes that are also required for the ability of these divisions to produce daughter cells that differ in size. One of these genes, ham-1, encodes a putative transcription factor that regulates a subset of the asymmetric cell divisions that produce an apoptotic daughter cell. In a survey of C. elegans divisions, we found that ham-1 mutations affect primarily anterior/posterior divisions that produce a small anterior daughter cell. The affected divisions include those that generate an apoptotic cell as well as those that generate two surviving cells. Our findings suggest that HAM-1 primarily promotes DCSA in a certain class of asymmetric divisions. PMID:29668718

Plant cell division is specifically affected by nitrotyrosine

PubMed Central

Jovanović, Aleksandra M.; Durst, Steffen; Nick, Peter

2010-01-01

Virtually all eukaryotic α-tubulins harbour a C-terminal tyrosine that can be reversibly removed and religated, catalysed by a specific tubulin–tyrosine carboxypeptidase (TTC) and a specific tubulin–tyrosine ligase (TTL), respectively. The biological function of this post-translational modification has remained enigmatic. 3-nitro-L-tyrosine (nitrotyrosine, NO2Tyr), can be incorporated into detyrosinated α-tubulin instead of tyrosine, producing irreversibly nitrotyrosinated α-tubulin. To gain insight into the possible function of detyrosination, the effect of NO2Tyr has been assessed in two plant model organisms (rice and tobacco). NO2Tyr causes a specific, sensitive, and dose-dependent inhibition of cell division that becomes detectable from 1 h after treatment and which is not observed with non-nitrosylated tyrosine. These effects are most pronounced in cycling tobacco BY-2 cells, where the inhibition of cell division is accompanied by a stimulation of cell length, and a misorientation of cross walls. NO2Tyr reduces the abundance of the detyrosinated form of α-tubulin whereas the tyrosinated α-tubulin is not affected. These findings are discussed with respect to a model where NO2Tyr is accepted as substrate by TTL and subsequently blocks TTC activity. The irreversibly tyrosinated α-tubulin impairs microtubular functions that are relevant to cell division in general, and cell wall deposition in particular. PMID:20018903

Architecture of the ring formed by the tubulin homologue FtsZ in bacterial cell division

PubMed Central

Szwedziak, Piotr; Wang, Qing; Bharat, Tanmay A M; Tsim, Matthew; Löwe, Jan

2014-01-01

Membrane constriction is a prerequisite for cell division. The most common membrane constriction system in prokaryotes is based on the tubulin homologue FtsZ, whose filaments in E. coli are anchored to the membrane by FtsA and enable the formation of the Z-ring and divisome. The precise architecture of the FtsZ ring has remained enigmatic. In this study, we report three-dimensional arrangements of FtsZ and FtsA filaments in C. crescentus and E. coli cells and inside constricting liposomes by means of electron cryomicroscopy and cryotomography. In vivo and in vitro, the Z-ring is composed of a small, single-layered band of filaments parallel to the membrane, creating a continuous ring through lateral filament contacts. Visualisation of the in vitro reconstituted constrictions as well as a complete tracing of the helical paths of the filaments with a molecular model favour a mechanism of FtsZ-based membrane constriction that is likely to be accompanied by filament sliding. DOI: http://dx.doi.org/10.7554/eLife.04601.001 PMID:25490152

A theory of germinal center B cell selection, division, and exit.

PubMed

Meyer-Hermann, Michael; Mohr, Elodie; Pelletier, Nadége; Zhang, Yang; Victora, Gabriel D; Toellner, Kai-Michael

2012-07-26

High-affinity antibodies are generated in germinal centers in a process involving mutation and selection of B cells. Information processing in germinal center reactions has been investigated in a number of recent experiments. These have revealed cell migration patterns, asymmetric cell divisions, and cell-cell interaction characteristics, used here to develop a theory of germinal center B cell selection, division, and exit (the LEDA model). According to this model, B cells selected by T follicular helper cells on the basis of successful antigen processing always return to the dark zone for asymmetric division, and acquired antigen is inherited by one daughter cell only. Antigen-retaining B cells differentiate to plasma cells and leave the germinal center through the dark zone. This theory has implications for the functioning of germinal centers because compared to previous models, high-affinity antibodies appear one day earlier and the amount of derived plasma cells is considerably larger. Copyright © 2012 The Authors. Published by Elsevier Inc. All rights reserved.

Ploidy-Dependent Unreductional Meiotic Cell Division in Polyploid Wheat

USDA-ARS?s Scientific Manuscript database

Meiosis includes one round of DNA replication and two successive nuclear divisions, i.e. meiosis I (reductional) and meiosis II (equational). This specialized cell division reduces chromosomes in half and generates haploid gametes in sexual reproduction of eukaryotes. It ensures faithful transmiss...

Noise and Epigenetic Inheritance of Single-Cell Division Times Influence Population Fitness.

PubMed

Cerulus, Bram; New, Aaron M; Pougach, Ksenia; Verstrepen, Kevin J

2016-05-09

The fitness effect of biological noise remains unclear. For example, even within clonal microbial populations, individual cells grow at different speeds. Although it is known that the individuals' mean growth speed can affect population-level fitness, it is unclear how or whether growth speed heterogeneity itself is subject to natural selection. Here, we show that noisy single-cell division times can significantly affect population-level growth rate. Using time-lapse microscopy to measure the division times of thousands of individual S. cerevisiae cells across different genetic and environmental backgrounds, we find that the length of individual cells' division times can vary substantially between clonal individuals and that sublineages often show epigenetic inheritance of division times. By combining these experimental measurements with mathematical modeling, we find that, for a given mean division time, increasing heterogeneity and epigenetic inheritance of division times increases the population growth rate. Furthermore, we demonstrate that the heterogeneity and epigenetic inheritance of single-cell division times can be linked with variation in the expression of catabolic genes. Taken together, our results reveal how a change in noisy single-cell behaviors can directly influence fitness through dynamics that operate independently of effects caused by changes to the mean. These results not only allow a better understanding of microbial fitness but also help to more accurately predict fitness in other clonal populations, such as tumors. Copyright © 2016 Elsevier Ltd. All rights reserved.

Kinetics of large-scale chromosomal movement during asymmetric cell division in Escherichia coli

PubMed Central

Männik, Jaana; O’Neill, Jordan C.

2017-01-01

Coordination between cell division and chromosome replication is essential for a cell to produce viable progeny. In the commonly accepted view, Escherichia coli realize this coordination via the accurate positioning of its cell division apparatus relative to the nucleoids. However, E. coli lacking proper positioning of its cell division planes can still successfully propagate. Here, we characterize how these cells partition their chromosomes into daughters during such asymmetric divisions. Using quantitative time-lapse imaging, we show that DNA translocase, FtsK, can pump as much as 80% (3.7 Mb) of the chromosome between daughters at an average rate of 1700±800 bp/s. Pauses in DNA translocation are rare, and in no occasions did we observe reversals at experimental time scales of a few minutes. The majority of DNA movement occurs at the latest stages of cell division when the cell division protein ZipA has already dissociated from the septum, and the septum has closed to a narrow channel with a diameter much smaller than the resolution limit of the microscope (~250 nm). Our data suggest that the narrow constriction is necessary for effective translocation of DNA by FtsK. PMID:28234902

A new class of cyclin dependent kinase in Chlamydomonas is required for coupling cell size to cell division

PubMed Central

Li, Yubing; Liu, Dianyi; López-Paz, Cristina; Olson, Bradley JSC; Umen, James G

2016-01-01

Proliferating cells actively control their size by mechanisms that are poorly understood. The unicellular green alga Chlamydomonas reinhardtii divides by multiple fission, wherein a ‘counting’ mechanism couples mother cell-size to cell division number allowing production of uniform-sized daughters. We identified a sizer protein, CDKG1, that acts through the retinoblastoma (RB) tumor suppressor pathway as a D-cyclin-dependent RB kinase to regulate mitotic counting. Loss of CDKG1 leads to fewer mitotic divisions and large daughters, while mis-expression of CDKG1 causes supernumerous mitotic divisions and small daughters. The concentration of nuclear-localized CDKG1 in pre-mitotic cells is set by mother cell size, and its progressive dilution and degradation with each round of cell division may provide a link between mother cell-size and mitotic division number. Cell-size-dependent accumulation of limiting cell cycle regulators such as CDKG1 is a potentially general mechanism for size control. DOI: http://dx.doi.org/10.7554/eLife.10767.001 PMID:27015111

Analysis of cell division patterns in the Arabidopsis shoot apical meristem

DOE PAGES

Shapiro, Bruce E.; Tobin, Cory; Mjolsness, Eric; ...

2015-03-30

The stereotypic pattern of cell shapes in the Arabidopsis shoot apical meristem (SAM) suggests that strict rules govern the placement of new walls during cell division. When a cell in the SAM divides, a new wall is built that connects existing walls and divides the cytoplasm of the daughter cells. Because features that are determined by the placement of new walls such as cell size, shape, and number of neighbors are highly regular, rules must exist for maintaining such order. Here in this paper we present a quantitative model of these rules that incorporates different observed features of cell division.more » Each feature is incorporated into a "potential function" that contributes a single term to a total analog of potential energy. New cell walls are predicted to occur at locations where the potential function is minimized. Quantitative terms that represent the well-known historical rules of plant cell division, such as those given by Hofmeister, Errera, and Sachs are developed and evaluated against observed cell divisions in the epidermal layer (L1) of Arabidopsis thaliana SAM. The method is general enough to allow additional terms for nongeometric properties such as internal concentration gradients and mechanical tensile forces.« less

A genetic screen for temperature-sensitive cell-division mutants of Caenorhabditis elegans.

PubMed Central

O'Connell, K F; Leys, C M; White, J G

1998-01-01

A novel screen to isolate conditional cell-division mutants in Caenorhabditis elegans has been developed. The screen is based on the phenotypes associated with existing cell-division mutations: some disrupt postembryonic divisions and affect formation of the gonad and ventral nerve cord-resulting in sterile, uncoordinated animals-while others affect embryonic divisions and result in lethality. We obtained 19 conditional mutants that displayed these phenotypes when shifted to the restrictive temperature at the appropriate developmental stage. Eighteen of these mutations have been mapped; 17 proved to be single alleles of newly identified genes, while 1 proved to be an allele of a previously identified gene. Genetic tests on the embryonic lethal phenotypes indicated that for 13 genes, embryogenesis required maternal expression, while for 6, zygotic expression could suffice. In all cases, maternal expression of wild-type activity was found to be largely sufficient for embryogenesis. Cytological analysis revealed that 10 mutants possessed embryonic cell-division defects, including failure to properly segregate DNA, failure to assemble a mitotic spindle, late cytokinesis defects, prolonged cell cycles, and improperly oriented mitotic spindles. We conclude that this approach can be used to identify mutations that affect various aspects of the cell-division cycle. PMID:9649522

TfVPS32 Regulates Cell Division in the Parasite Tritrichomonas foetus.

PubMed

Iriarte, Lucrecia S; Midlej, Victor; Frontera, Lorena S; Moros Duarte, Daniel; Barbeito, Claudio G; de Souza, Wanderley; Benchimol, Marlene; de Miguel, Natalia; Coceres, Veronica M

2018-01-01

The flagellated protist Tritrichomonas foetus is a parasite that causes bovine trichomonosis, a major sexually transmitted disease in cattle. Cell division has been described as a key player in controlling cell survival in other cells, including parasites but there is no information on the regulation of this process in T. foetus. The regulation of cytokinetic abscission, the final stage of cell division, is mediated by members of the ESCRT (endosomal sorting complex required for transport) machinery. VPS32 is a subunit within the ESCRTIII complex and here, we report that TfVPS32 is localized on cytoplasmic vesicles and a redistribution of the protein to the midbody is observed during the cellular division. In concordance with its localization, deletion of TfVPS32 C-terminal alpha helices (α5 helix and/or α4-5 helix) leads to abnormal T. foetus growth, an increase in the percentage of multinucleated parasites and cell cycle arrest at G2/M phase. Together, these results indicate a role of this protein in controlling normal cell division. © 2017 The Author(s) Journal of Eukaryotic Microbiology © 2017 International Society of Protistologists.

CD8 Memory Cells Develop Unique DNA Repair Mechanisms Favoring Productive Division.

PubMed

Galgano, Alessia; Barinov, Aleksandr; Vasseur, Florence; de Villartay, Jean-Pierre; Rocha, Benedita

2015-01-01

Immune responses are efficient because the rare antigen-specific naïve cells are able to proliferate extensively and accumulate upon antigen stimulation. Moreover, differentiation into memory cells actually increases T cell accumulation, indicating improved productive division in secondary immune responses. These properties raise an important paradox: how T cells may survive the DNA lesions necessarily induced during their extensive division without undergoing transformation. We here present the first data addressing the DNA damage responses (DDRs) of CD8 T cells in vivo during exponential expansion in primary and secondary responses in mice. We show that during exponential division CD8 T cells engage unique DDRs, which are not present in other exponentially dividing cells, in T lymphocytes after UV or X irradiation or in non-metastatic tumor cells. While in other cell types a single DDR pathway is affected, all DDR pathways and cell cycle checkpoints are affected in dividing CD8 T cells. All DDR pathways collapse in secondary responses in the absence of CD4 help. CD8 T cells are driven to compulsive suicidal divisions preventing the propagation of DNA lesions. In contrast, in the presence of CD4 help all the DDR pathways are up regulated, resembling those present in metastatic tumors. However, this up regulation is present only during the expansion phase; i.e., their dependence on antigen stimulation prevents CD8 transformation. These results explain how CD8 T cells maintain genome integrity in spite of their extensive division, and highlight the fundamental role of DDRs in the efficiency of CD8 immune responses.

Lightning Talks 2015: Theoretical Division

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shlachter, Jack S.

2015-11-25

This document is a compilation of slides from a number of student presentations given to LANL Theoretical Division members. The subjects cover the range of activities of the Division, including plasma physics, environmental issues, materials research, bacterial resistance to antibiotics, and computational methods.

RanGAP1 is a continuous marker of the Arabidopsis cell division plane

PubMed Central

Xu, Xianfeng Morgan; Zhao, Qiao; Rodrigo-Peiris, Thushani; Brkljacic, Jelena; He, Chao Sylvia; Müller, Sabine; Meier, Iris

2008-01-01

In higher plants, the plane of cell division is faithfully predicted by the preprophase band (PPB). The PPB, a cortical ring of microtubules and F-actin, disassembles upon nuclear-envelope breakdown. During cytokinesis, the expanding cell plate fuses with the plasma membrane at the cortical division site, the site of the former PPB. The nature of the “molecular memory” that is left behind by the PPB and is proposed to guide the cell plate to the cortical division site is unknown. RanGAP is the GTPase activating protein of the small GTPase Ran, which provides spatial information for nucleocytoplasmic transport and various mitotic processes in animals. Here, we show that, in dividing root cells, Arabidopsis RanGAP1 concentrates at the PPB and remains associated with the cortical division site during mitosis and cytokinesis, requiring its N-terminal targeting domain. In a fass/ton2 mutant, which affects PPB formation, RanGAP1 recruitment to the PPB site is lost, while its PPB retention is microtubule-independent. RanGAP1 persistence at the cortical division site, but not its initial accumulation at the PPB requires the 2 cytokinesis-regulating kinesins POK1 and POK2. Depletion of RanGAP by inducible RNAi leads to oblique cell walls and cell-wall stubs in root cell files, consistent with cytokinesis defects. We propose that Arabidopsis RanGAP, a continuous positive protein marker of the plant division plane, has a role in spatial signaling during plant cell division. PMID:19011093

Spire, an actin nucleation factor, regulates cell division during Drosophila heart development.

PubMed

Xu, Peng; Johnson, Tamara L; Stoller-Conrad, Jessica R; Schulz, Robert A

2012-01-01

The Drosophila dorsal vessel is a beneficial model system for studying the regulation of early heart development. Spire (Spir), an actin-nucleation factor, regulates actin dynamics in many developmental processes, such as cell shape determination, intracellular transport, and locomotion. Through protein expression pattern analysis, we demonstrate that the absence of spir function affects cell division in Myocyte enhancer factor 2-, Tinman (Tin)-, Even-skipped- and Seven up (Svp)-positive heart cells. In addition, genetic interaction analysis shows that spir functionally interacts with Dorsocross, tin, and pannier to properly specify the cardiac fate. Furthermore, through visualization of double heterozygous embryos, we determines that spir cooperates with CycA for heart cell specification and division. Finally, when comparing the spir mutant phenotype with that of a CycA mutant, the results suggest that most Svp-positive progenitors in spir mutant embryos cannot undergo full cell division at cell cycle 15, and that Tin-positive progenitors are arrested at cell cycle 16 as double-nucleated cells. We conclude that Spir plays a crucial role in controlling dorsal vessel formation and has a function in cell division during heart tube morphogenesis.

Mechanisms of Regulating Tissue Elongation in Drosophila Wing: Impact of Oriented Cell Divisions, Oriented Mechanical Forces, and Reduced Cell Size

PubMed Central

Li, Yingzi; Naveed, Hammad; Kachalo, Sema; Xu, Lisa X.; Liang, Jie

2014-01-01

Regulation of cell growth and cell division plays fundamental roles in tissue morphogenesis. However, the mechanisms of regulating tissue elongation through cell growth and cell division are still not well understood. The wing imaginal disc of Drosophila provides a model system that has been widely used to study tissue morphogenesis. Here we use a recently developed two-dimensional cellular model to study the mechanisms of regulating tissue elongation in Drosophila wing. We simulate the effects of directional cues on tissue elongation. We also computationally analyze the role of reduced cell size. Our simulation results indicate that oriented cell divisions, oriented mechanical forces, and reduced cell size can all mediate tissue elongation, but they function differently. We show that oriented cell divisions and oriented mechanical forces act as directional cues during tissue elongation. Between these two directional cues, oriented mechanical forces have a stronger influence than oriented cell divisions. In addition, we raise the novel hypothesis that reduced cell size may significantly promote tissue elongation. We find that reduced cell size alone cannot drive tissue elongation. However, when combined with directional cues, such as oriented cell divisions or oriented mechanical forces, reduced cell size can significantly enhance tissue elongation in Drosophila wing. Furthermore, our simulation results suggest that reduced cell size has a short-term effect on cell topology by decreasing the frequency of hexagonal cells, which is consistent with experimental observations. Our simulation results suggest that cell divisions without cell growth play essential roles in tissue elongation. PMID:24504016

Tiny cells meet big questions: a closer look at bacterial cell biology.

PubMed

Goley, Erin D

2013-04-01

While studying actin assembly as a graduate student with Matt Welch at the University of California at Berkeley, my interest was piqued by reports of surprising observations in bacteria: the identification of numerous cytoskeletal proteins, actin homologues fulfilling spindle-like functions, and even the presence of membrane-bound organelles. Curiosity about these phenomena drew me to Lucy Shapiro's lab at Stanford University for my postdoctoral research. In the Shapiro lab, and now in my lab at Johns Hopkins, I have focused on investigating the mechanisms of bacterial cytokinesis. Spending time as both a eukaryotic cell biologist and a bacterial cell biologist has convinced me that bacterial cells present the same questions as eukaryotic cells: How are chromosomes organized and accurately segregated? How is force generated for cytokinesis? How is polarity established? How are signals transduced within and between cells? These problems are conceptually similar between eukaryotes and bacteria, although their solutions can differ significantly in specifics. In this Perspective, I provide a broad view of cell biological phenomena in bacteria, the technical challenges facing those of us who peer into bacterial cells, and areas of common ground as research in eukaryotic and bacterial cell biology moves forward.

An Equatorial Contractile Mechanism Drives Cell Elongation but not Cell Division

PubMed Central

Denker, Elsa; Bhattachan, Punit; Deng, Wei; Mathiesen, Birthe T.; Jiang, Di

2014-01-01

Cell shape changes and proliferation are two fundamental strategies for morphogenesis in animal development. During embryogenesis of the simple chordate Ciona intestinalis, elongation of individual notochord cells constitutes a crucial stage of notochord growth, which contributes to the establishment of the larval body plan. The mechanism of cell elongation is elusive. Here we show that although notochord cells do not divide, they use a cytokinesis-like actomyosin mechanism to drive cell elongation. The actomyosin network forming at the equator of each notochord cell includes phosphorylated myosin regulatory light chain, α-actinin, cofilin, tropomyosin, and talin. We demonstrate that cofilin and α-actinin are two crucial components for cell elongation. Cortical flow contributes to the assembly of the actomyosin ring. Similar to cytokinetic cells, membrane blebs that cause local contractions form at the basal cortex next to the equator and participate in force generation. We present a model in which the cooperation of equatorial actomyosin ring-based constriction and bleb-associated contractions at the basal cortex promotes cell elongation. Our results demonstrate that a cytokinesis-like contractile mechanism is co-opted in a completely different developmental scenario to achieve cell shape change instead of cell division. We discuss the occurrences of actomyosin rings aside from cell division, suggesting that circumferential contraction is an evolutionally conserved mechanism to drive cell or tissue elongation. PMID:24503569

Isolation of cell-free bacterial inclusion bodies.

PubMed

Rodríguez-Carmona, Escarlata; Cano-Garrido, Olivia; Seras-Franzoso, Joaquin; Villaverde, Antonio; García-Fruitós, Elena

2010-09-17

Bacterial inclusion bodies are submicron protein clusters usually found in recombinant bacteria that have been traditionally considered as undesirable products from protein production processes. However, being fully biocompatible, they have been recently characterized as nanoparticulate inert materials useful as scaffolds for tissue engineering, with potentially wider applicability in biomedicine and material sciences. Current protocols for inclusion body isolation from Escherichia coli usually offer between 95 to 99% of protein recovery, what in practical terms, might imply extensive bacterial cell contamination, not compatible with the use of inclusion bodies in biological interfaces. Using an appropriate combination of chemical and mechanical cell disruption methods we have established a convenient procedure for the recovery of bacterial inclusion bodies with undetectable levels of viable cell contamination, below 10⁻¹ cfu/ml, keeping the particulate organization of these aggregates regarding size and protein folding features. The application of the developed protocol allows obtaining bacterial free inclusion bodies suitable for use in mammalian cell cultures and other biological interfaces.

Cyclin D regulation of a sexually dimorphic asymmetric cell division

PubMed Central

Tilmann, Christopher; Kimble, Judith

2006-01-01

SUMMARY The C. elegans somatic gonadal precursor cell (SGP) divides asymmetrically to establish gonad-specific coordinates in both sexes. In addition, the SGP division is sexually dimorphic and initiates sex-specific programs of gonadogenesis. Wnt/MAPK signaling determines the gonadal axes, and the FKH-6 transcription factor specifies the male mode of SGP division. In this paper, we demonstrate that C. elegans cyclin D controls POP-1/TCF asymmetry in the SGP daughters as well as fkh-6 and rnr expression in the SGPs. Although cyclin D mutants have delayed SGP divisions, the cyclin D defects are not mimicked by other methods of retarding the SGP division. We find that EFL-1/E2F has an antagonistic effect on fkh-6 expression and gonadogenesis, which is relieved by cyclin D activity. We propose that cyclin D and other canonical regulators of the G1/S transition coordinate key regulators of axis formation and sex determination with cell cycle progression to achieve the sexually dimorphic SGP asymmetric division. PMID:16198291

The FBPase Encoding Gene glpX Is Required for Gluconeogenesis, Bacterial Proliferation and Division In Vivo of Mycobacterium marinum

PubMed Central

Lyu, Liangdong; Wang, Chuan; Li, Yang; Gao, Qian; Yang, Chen

2016-01-01

Lipids have been identified as important carbon sources for Mycobacterium tuberculosis (Mtb) to utilize in vivo. Thus gluconeogenesis bears a key role for Mtb to survive and replicate in host. A rate-limiting enzyme of gluconeogenesis, fructose 1, 6-bisphosphatase (FBPase) is encoded by the gene glpX. The functions of glpX were studied in M. marinum, a closely related species to Mtb. The glpX deletion strain (ΔglpX) displayed altered gluconeogenesis, attenuated virulence, and altered bacterial proliferation. Metabolic profiles indicate an accumulation of the FBPase substrate, fructose 1, 6-bisphosphate (FBP) and altered gluconeogenic flux when ΔglpX is cultivated in a gluconeogenic carbon substrate, acetate. In both macrophages and zebrafish, the proliferation of ΔglpX was halted, resulting in dramatically attenuated virulence. Intracellular ΔglpX exhibited an elongated morphology, which was also observed when ΔglpX was grown in a gluconeogenic carbon source. This elongated morphology is also supported by the observation of unseparated multi-nucleoid cell, indicating that a complete mycobacterial division in vivo is correlated with intact gluconeogenesis. Together, our results indicate that glpX has essential functions in gluconeogenesis, and plays an indispensable role in bacterial proliferation in vivo and virulence of M. marinum. PMID:27233038

The FBPase Encoding Gene glpX Is Required for Gluconeogenesis, Bacterial Proliferation and Division In Vivo of Mycobacterium marinum.

PubMed

Tong, Jingfeng; Meng, Lu; Wang, Xinwei; Liu, Lixia; Lyu, Liangdong; Wang, Chuan; Li, Yang; Gao, Qian; Yang, Chen; Niu, Chen

2016-01-01

Lipids have been identified as important carbon sources for Mycobacterium tuberculosis (Mtb) to utilize in vivo. Thus gluconeogenesis bears a key role for Mtb to survive and replicate in host. A rate-limiting enzyme of gluconeogenesis, fructose 1, 6-bisphosphatase (FBPase) is encoded by the gene glpX. The functions of glpX were studied in M. marinum, a closely related species to Mtb. The glpX deletion strain (ΔglpX) displayed altered gluconeogenesis, attenuated virulence, and altered bacterial proliferation. Metabolic profiles indicate an accumulation of the FBPase substrate, fructose 1, 6-bisphosphate (FBP) and altered gluconeogenic flux when ΔglpX is cultivated in a gluconeogenic carbon substrate, acetate. In both macrophages and zebrafish, the proliferation of ΔglpX was halted, resulting in dramatically attenuated virulence. Intracellular ΔglpX exhibited an elongated morphology, which was also observed when ΔglpX was grown in a gluconeogenic carbon source. This elongated morphology is also supported by the observation of unseparated multi-nucleoid cell, indicating that a complete mycobacterial division in vivo is correlated with intact gluconeogenesis. Together, our results indicate that glpX has essential functions in gluconeogenesis, and plays an indispensable role in bacterial proliferation in vivo and virulence of M. marinum.

Mammalian aPKC/Par polarity complex mediated regulation of epithelial division orientation and cell fate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vorhagen, Susanne; Niessen, Carien M., E-mail: carien.niessen@uni-koeln.de

2014-11-01

Oriented cell division is a key regulator of tissue architecture and crucial for morphogenesis and homeostasis. Balanced regulation of proliferation and differentiation is an essential property of tissues not only to drive morphogenesis but also to maintain and restore homeostasis. In many tissues orientation of cell division is coupled to the regulation of differentiation producing daughters with similar (symmetric cell division, SCD) or differential fate (asymmetric cell division, ACD). This allows the organism to generate cell lineage diversity from a small pool of stem and progenitor cells. Division orientation and/or the ratio of ACD/SCD need to be tightly controlled. Lossmore » of orientation or an altered ratio can promote overgrowth, alter tissue architecture and induce aberrant differentiation, and have been linked to morphogenetic diseases, cancer and aging. A key requirement for oriented division is the presence of a polarity axis, which can be established through cell intrinsic and/or extrinsic signals. Polarity proteins translate such internal and external cues to drive polarization. In this review we will focus on the role of the polarity complex aPKC/Par3/Par6 in the regulation of division orientation and cell fate in different mammalian epithelia. We will compare the conserved function of this complex in mitotic spindle orientation and distribution of cell fate determinants and highlight common and differential mechanisms in which this complex is used by tissues to adapt division orientation and cell fate to the specific properties of the epithelium.« less

Molecular mechanisms of cell-cell spread of intracellular bacterial pathogens.

PubMed

Ireton, Keith

2013-07-17

Several bacterial pathogens, including Listeria monocytogenes, Shigella flexneri and Rickettsia spp., have evolved mechanisms to actively spread within human tissues. Spreading is initiated by the pathogen-induced recruitment of host filamentous (F)-actin. F-actin forms a tail behind the microbe, propelling it through the cytoplasm. The motile pathogen then encounters the host plasma membrane, forming a bacterium-containing protrusion that is engulfed by an adjacent cell. Over the past two decades, much progress has been made in elucidating mechanisms of F-actin tail formation. Listeria and Shigella produce tails of branched actin filaments by subverting the host Arp2/3 complex. By contrast, Rickettsia forms tails with linear actin filaments through a bacterial mimic of eukaryotic formins. Compared with F-actin tail formation, mechanisms controlling bacterial protrusions are less well understood. However, recent findings have highlighted the importance of pathogen manipulation of host cell-cell junctions in spread. Listeria produces a soluble protein that enhances bacterial protrusions by perturbing tight junctions. Shigella protrusions are engulfed through a clathrin-mediated pathway at 'tricellular junctions'--specialized membrane regions at the intersection of three epithelial cells. This review summarizes key past findings in pathogen spread, and focuses on recent developments in actin-based motility and the formation and internalization of bacterial protrusions.

FORMATION OF INTRACYTOPLASMIC MEMBRANE SYSTEM OF MYCOBACTERIA RELATED TO CELL DIVISION

PubMed Central

Imaeda, Tamotsu; Ogura, Mituo

1963-01-01

Imaeda, Tamotsu (Instituto Venezolano de Investigaciones Científicas, Caracas, Venezuela) and Mitua Ogura. Formation of intracytoplasmic membrane system of mycobacteria related to cell division. J. Bacteriol. 85:150–163. 1963.—Mycobacterium leprae, M. lepraemurium, and a Mycobacterium sp. were observed with an electron microscope. In these bacilli, the three-dimensional structure of the intracytoplasmic membrane system consists of tubular infoldings of the invaginated plasma membrane. The moderately dense substance, presumably representing the cell-wall precursor, is found in the membranous system, especially in the rapid growth phase of mycobacteria. This system always shows an intimate relationship with cell division. A low-density zone, probably corresponding to the low-density substance which coats the cell wall, appears in the connecting regions of the system and in the longitudinal portion of the cell wall. These zones extend centripetally, and the separation of the cell wall occurs after the two zones meet. Based on these results, we hypothesize that the intracytoplasmic membrane system may produce cell-wall material during cell division of mycobacteria. Images PMID:13956365

Formation of a cylindrical bridge in cell division

NASA Astrophysics Data System (ADS)

Citron, Daniel; Schmidt, Laura E.; Reichl, Elizabeth; Ren, Yixin; Robinson, Douglas; Zhang, Wendy W.

2007-11-01

In nature, the shape transition associated with the division of a mother cell into two daughter cells proceeds via a variety of routes. In the cylinder-thinning route, which has been observed in Dictyostelium and most animal cells, the mother cell first forms a broad bridge-like region, also known as a furrow, between two daughter cells. The furrow then rapidly evolves into a cylindrical bridge, which thins and eventually severs the mother cell into two. The fundamental mechanism underlying this division route is not understood. Recent experiments on Dictyostelium found that, while the cylinder-thinning route persists even when key actin cross-linking proteins are missing, it is disrupted by the removal of force-generating myosin-II proteins. Other measurements revealed that mutant cells lacking myosin-II have a much more uniform tension over the cell surface than wild-type cells. This suggests that tension variation may be important. Here we use a fluid model, previously shown to reproduce the thinning dynamics [Zhang & Robinson, PNAS 102, 7186 (2005)], to test this idea. Consistent with the experiments, the model shows that the cylinder formation process occurs regardless of the exact viscoelastic properties of the cell. In contrast to the experiments, a tension variation in the model hinders, rather then expedites, the cylinder formation.

Cellulose-ethylenediaminetetraacetic acid conjugates protect mammalian cells from bacterial cells.

PubMed

Luo, Jie; Lv, Wei; Deng, Ying; Sun, Yuyu

2013-04-08

Cellulose-ethylenediaminetetraacetic acid (EDTA) conjugates were synthesized by the esterification of cellulose with ethylenediaminetetraacetic dianhydride (EDTAD). The new materials provided potent antimicrobial activities against Staphylococcus aureus (S. aureus, Gram-positive bacteria) and Pseudomonas aeruginosa (P. aeruginosa, Gram-negative bacteria), and inhibited the formation of bacterial biofilms. The biocompatibility of the new cellulose-EDTA conjugates was evaluated with mouse skin fibroblasts for up to 14 days. SEM observation and DNA content analysis suggested that the new materials sustained the viability of fibroblast cells. Moreover, in mouse skin fibroblast-bacteria co-culture systems, the new cellulose-EDTA conjugates prevented bacterial biofilm formation and protected the mammalian cells from the bacterial cells for at least one day.

CyDiv, a Conserved and Novel Filamentous Cyanobacterial Cell Division Protein Involved in Septum Localization.

PubMed

Mandakovic, Dinka; Trigo, Carla; Andrade, Derly; Riquelme, Brenda; Gómez-Lillo, Gabriela; Soto-Liebe, Katia; Díez, Beatriz; Vásquez, Mónica

2016-01-01

Cell division in bacteria has been studied mostly in Escherichia coli and Bacillus subtilis, model organisms for Gram-negative and Gram-positive bacteria, respectively. However, cell division in filamentous cyanobacteria is poorly understood. Here, we identified a novel protein, named CyDiv (Cyanobacterial Division), encoded by the all2320 gene in Anabaena sp. PCC 7120. We show that CyDiv plays a key role during cell division. CyDiv has been previously described only as an exclusive and conserved hypothetical protein in filamentous cyanobacteria. Using polyclonal antibodies against CyDiv, we showed that it localizes at different positions depending on cell division timing: poles, septum, in both daughter cells, but also in only one of the daughter cells. The partial deletion of CyDiv gene generates partial defects in cell division, including severe membrane instability and anomalous septum localization during late division. The inability to complete knock out CyDiv strains suggests that it is an essential gene. In silico structural protein analyses and our experimental results suggest that CyDiv is an FtsB/DivIC-like protein, and could therefore, be part of an essential late divisome complex in Anabaena sp. PCC 7120.

Are There Really Animals Like That? No Cell Division.

ERIC Educational Resources Information Center

Blackwelder, R. E.; Garoian, G. S.

1984-01-01

Provides examples of animals in which growth occurs without cell division. Indicates that this phenomenon (called cell constancy or eutely) is an oddity of development that has arisen independently in several animal groups. (JN)

Effects of Polyhydroxybutyrate Production on Cell Division

NASA Technical Reports Server (NTRS)

Miller, Kathleen; Rahman, Asif; Hadi, Masood Z.

2015-01-01

Synthetic biological engineering can be utilized to aide the advancement of improved long-term space flight. The potential to use synthetic biology as a platform to biomanufacture desired equipment on demand using the three dimensional (3D) printer on the International Space Station (ISS) gives long-term NASA missions the flexibility to produce materials as needed on site. Polyhydroxybutyrates (PHBs) are biodegradable, have properties similar to plastics, and can be produced in Escherichia coli using genetic engineering. Using PHBs during space flight could assist mission success by providing a valuable source of biomaterials that can have many potential applications, particularly through 3D printing. It is well documented that during PHB production E. coli cells can become significantly elongated. The elongation of cells reduces the ability of the cells to divide and thus to produce PHB. I aim to better understand cell division during PHB production, through the design, building, and testing of synthetic biological circuits, and identify how to potentially increase yields of PHB with FtsZ overexpression, the gene responsible for cell division. Ultimately, an increase in the yield will allow more products to be created using the 3D printer on the ISS and beyond, thus aiding astronauts in their missions.

Cell Division Induces and Switches Coherent Angular Motion within Bounded Cellular Collectives.

PubMed

Siedlik, Michael J; Manivannan, Sriram; Kevrekidis, Ioannis G; Nelson, Celeste M

2017-06-06

Collective cell migration underlies many biological processes, including embryonic development, wound healing, and cancer progression. In the embryo, cells have been observed to move collectively in vortices using a mode of collective migration known as coherent angular motion (CAM). To determine how CAM arises within a population and changes over time, here, we study the motion of mammary epithelial cells within engineered monolayers, in which the cells move collectively about a central axis in the tissue. Using quantitative image analysis, we find that CAM is significantly reduced when mitosis is suppressed. Particle-based simulations recreate the observed trends, suggesting that cell divisions drive the robust emergence of CAM and facilitate switches in the direction of collective rotation. Our simulations predict that the location of a dividing cell, rather than the orientation of the division axis, facilitates the onset of this motion. These predictions agree with experimental observations, thereby providing, to our knowledge, new insight into how cell divisions influence CAM within a tissue. Overall, these findings highlight the dynamic nature of CAM and suggest that regulating cell division is crucial for tuning emergent collective migratory behaviors, such as vortical motions observed in vivo. Copyright © 2017 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Role of asymmetric cell division in lifespan control in Saccharomyces cerevisiae

PubMed Central

Higuchi-Sanabria, Ryo; Pernice, Wolfgang M A; Vevea, Jason D; Alessi Wolken, Dana M; Boldogh, Istvan R; Pon, Liza A

2014-01-01

Aging determinants are asymmetrically distributed during cell division in S. cerevisiae, which leads to production of an immaculate, age-free daughter cell. During this process, damaged components are sequestered and retained in the mother cell, and higher functioning organelles and rejuvenating factors are transported to and/or enriched in the bud. Here, we will describe the key quality control mechanisms in budding yeast that contribute to asymmetric cell division of aging determinants including mitochondria, endoplasmic reticulum (ER), vacuoles, extrachromosomal rDNA circles (ERCs), and protein aggregates. PMID:25263578

Occludin Independently Regulates Permeability under Hydrostatic Pressure and Cell Division in Retinal Pigment Epithelial Cells

PubMed Central

Phillips, Brett E.; Cancel, Limary; Tarbell, John M.; Antonetti, David A.

2008-01-01

Purpose The aim of this study was to determine the function of the tight junction protein occludin in the control of permeability, under diffusive and hydrostatic pressures, and its contribution to the control of cell division in retinal pigment epithelium. Methods Occludin expression was inhibited in the human retinal pigment epithelial cell line ARPE-19 by siRNA. Depletion of occludin was confirmed by Western blot, confocal microscopy, and RT-PCR. Paracellular permeability of cell monolayers to fluorescently labeled 70 kDa dextran, 10 kDa dextran, and 467 Da tetramethylrhodamine (TAMRA) was examined under diffusive conditions or after the application of 10 cm H2O transmural pressure. Cell division rates were determined by tritiated thymidine incorporation and Ki67 immunoreactivity. Cell cycle inhibitors were used to determine whether changes in cell division affected permeability. Results Occludin depletion increased diffusive paracellular permeability to 467 Da TAMRA by 15%, and permeability under hydrostatic pressure was increased 50% compared with control. Conversely, depletion of occludin protein with siRNA did not alter diffusive permeability to 70 kDa and 10 kDa RITC-dextran, and permeability to 70 kDa dextran was twofold lower in occludin-depleted cells under hydrostatic pressure conditions. Occludin depletion also increased thymidine incorporation by 90% and Ki67-positive cells by 50%. Finally, cell cycle inhibitors did not alter the effect of occludin siRNA on paracellular permeability. Conclusions The data suggest that occludin regulates tight junction permeability in response to changes in hydrostatic pressure. Furthermore, these data suggest that occludin also contributes to the control of cell division, demonstrating a novel function for this tight junction protein. PMID:18263810

Label-free quantitative cell division monitoring of endothelial cells by digital holographic microscopy

NASA Astrophysics Data System (ADS)

Kemper, Björn; Bauwens, Andreas; Vollmer, Angelika; Ketelhut, Steffi; Langehanenberg, Patrik; Müthing, Johannes; Karch, Helge; von Bally, Gert

2010-05-01

Digital holographic microscopy (DHM) enables quantitative multifocus phase contrast imaging for nondestructive technical inspection and live cell analysis. Time-lapse investigations on human brain microvascular endothelial cells demonstrate the use of DHM for label-free dynamic quantitative monitoring of cell division of mother cells into daughter cells. Cytokinetic DHM analysis provides future applications in toxicology and cancer research.

Bacterial spread from cell to cell: beyond actin-based motility.

PubMed

Kuehl, Carole J; Dragoi, Ana-Maria; Talman, Arthur; Agaisse, Hervé

2015-09-01

Several intracellular pathogens display the ability to propagate within host tissues by displaying actin-based motility in the cytosol of infected cells. As motile bacteria reach cell-cell contacts they form plasma membrane protrusions that project into adjacent cells and resolve into vacuoles from which the pathogen escapes, thereby achieving spread from cell to cell. Seminal studies have defined the bacterial and cellular factors that support actin-based motility. By contrast, the mechanisms supporting the formation of protrusions and their resolution into vacuoles have remained elusive. Here, we review recent advances in the field showing that Listeria monocytogenes and Shigella flexneri have evolved pathogen-specific mechanisms of bacterial spread from cell to cell. Copyright © 2015 Elsevier Ltd. All rights reserved.

Molecular Programs Underlying Asymmetric Stem Cell Division and Their Disruption in Malignancy.

PubMed

Mukherjee, Subhas; Brat, Daniel J

2017-01-01

Asymmetric division of stem cells is a highly conserved and tightly regulated process by which a single stem cell produces two unequal daughter cells. One retains its stem cell identity while the other becomes specialized through a differentiation program and loses stem cell properties. Coordinating these events requires control over numerous intra- and extracellular biological processes and signaling networks. In the initial stages, critical events include the compartmentalization of fate determining proteins within the mother cell and their subsequent passage to the appropriate daughter cell in order to direct their destiny. Disturbance of these events results in an altered dynamic of self-renewing and differentiation within the cell population, which is highly relevant to the growth and progression of cancer. Other critical events include proper asymmetric spindle assembly, extrinsic regulation through micro-environmental cues, and non-canonical signaling networks that impact cell division and fate determination. In this review, we discuss mechanisms that maintain the delicate balance of asymmetric cell division in normal tissues and describe the current understanding how some of these mechanisms are deregulated in cancer.

Radioisotopic Method for Measuring Cell Division Rates of Individual Species of Diatoms from Natural Populations †

PubMed Central

Rivkin, Richard B.

1986-01-01

Silicon is an essential element for diatom frustule synthesis and is usually taken up only by dividing cells. With 68Ge, a radioactive analog of Si, the cell cycle marker event of frustule formation was identified for individual species of diatom. The frequency of cells within a population undergoing this division event was estimated, and the cell division rate was calculated. In laboratory cultures, these rates of cell division and those calculated from changes in cell numbers were similar. By dual labeling with 68Ge(OH)4 and NaH14CO3, rates of cell division and photosynthesis were coincidently measured for diatoms both in laboratory cultures and when isolated from natural populations in estuarine, offshore, and polar environments. These techniques permit the coupling between photosynthesis and cell division to be examined in situ for individual species of diatom. PMID:16347039

How PI3K-derived lipids control cell division.

PubMed

Campa, Carlo C; Martini, Miriam; De Santis, Maria C; Hirsch, Emilio

2015-01-01

To succeed in cell division, intense cytoskeletal and membrane remodeling are required to allow accurate chromosome segregation and cytoplasm partitioning. Spatial restriction of the actin dynamics and vesicle trafficking define the cell symmetry and equivalent membrane scission events, respectively. Protein complexes coordinating mitosis are recruited to membrane microdomains characterized by the presence of the phosphatidylinositol lipid members (PtdIns), like PtdIns(3,4,5)P 3,PtdIns(4,5)P 2, and PtdIns(3)P. These PtdIns represent a minor component of cell membranes, defining membrane domain identity, ultimately controlling cytoskeleton and membrane dynamics during mitosis. The coordinated presence of PtdIns(3,4,5)P 3 at the cell poles and PtdIns(4,5)P 2 at the cleavage furrow controls the polarity of the actin cytoskeleton leading to symmetrical cell division. In the endosomal compartment, the trafficking of PtdIns(3)P positive vesicles allows the recruitment of the protein machinery required for the abscission.

Division of Labor, Bet Hedging, and the Evolution of Mixed Biofilm Investment Strategies.

PubMed

Lowery, Nick Vallespir; McNally, Luke; Ratcliff, William C; Brown, Sam P

2017-08-08

Bacterial cells, like many other organisms, face a tradeoff between longevity and fecundity. Planktonic cells are fast growing and fragile, while biofilm cells are often slower growing but stress resistant. Here we ask why bacterial lineages invest simultaneously in both fast- and slow-growing types. We develop a population dynamic model of lineage expansion across a patchy environment and find that mixed investment is favored across a broad range of environmental conditions, even when transmission is entirely via biofilm cells. This mixed strategy is favored because of a division of labor where exponentially dividing planktonic cells can act as an engine for the production of future biofilm cells, which grow more slowly. We use experimental evolution to test our predictions and show that phenotypic heterogeneity is persistent even under selection for purely planktonic or purely biofilm transmission. Furthermore, simulations suggest that maintenance of a biofilm subpopulation serves as a cost-effective hedge against environmental uncertainty, which is also consistent with our experimental findings. IMPORTANCE Cell types specialized for survival have been observed and described within clonal bacterial populations for decades, but why are these specialists continually produced under benign conditions when such investment comes at a high reproductive cost? Conversely, when survival becomes an imperative, does it ever benefit the population to maintain a pool of rapidly growing but vulnerable planktonic cells? Using a combination of mathematical modeling, simulations, and experiments, we find that mixed investment strategies are favored over a broad range of environmental conditions and rely on a division of labor between cell types, where reproductive specialists amplify survival specialists, which can be transmitted through the environment with a limited mortality rate. We also show that survival specialists benefit rapidly growing populations by serving as a hedge

Sequence-Specific Affinity Chromatography of Bacterial Small Regulatory RNA-Binding Proteins from Bacterial Cells.

PubMed

Gans, Jonathan; Osborne, Jonathan; Cheng, Juliet; Djapgne, Louise; Oglesby-Sherrouse, Amanda G

2018-01-01

Bacterial small RNA molecules (sRNAs) are increasingly recognized as central regulators of bacterial stress responses and pathogenesis. In many cases, RNA-binding proteins are critical for the stability and function of sRNAs. Previous studies have adopted strategies to genetically tag an sRNA of interest, allowing isolation of RNA-protein complexes from cells. Here we present a sequence-specific affinity purification protocol that requires no prior genetic manipulation of bacterial cells, allowing isolation of RNA-binding proteins bound to native RNA molecules.

Hydroxychavicol, a key ingredient of Piper betle induces bacterial cell death by DNA damage and inhibition of cell division.

PubMed

Singh, Deepti; Narayanamoorthy, Shwetha; Gamre, Sunita; Majumdar, Ananda Guha; Goswami, Manish; Gami, Umesh; Cherian, Susan; Subramanian, Mahesh

2018-05-20

Antibiotic resistance is a global problem and there is an urgent need to augment the arsenal against pathogenic bacteria. The emergence of different drug resistant bacteria is threatening human lives to be pushed towards the pre-antibiotic era. Botanical sources remain a vital source of diverse organic molecules that possess antibacterial property as well as augment existing antibacterial molecules. Piper betle, a climber, is widely used in south and south-east Asia whose leaves and nuts are consumed regularly. Hydroxychavicol (HC) isolated from Piper betle has been reported to possess antibacterial activity. It is currently not clear how the antibacterial activity of HC is manifested. In this investigation we show HC generates superoxide in E. coli cells. Antioxidants protected E. coli against HC induced cell death while gshA mutant was more sensitive to HC than wild type. DNA damage repair deficient mutants are hypersensitive to HC and HC induces the expression of DNA damage repair genes that repair oxidative DNA damage. HC treated E. coli cells are inhibited from growth and undergo DNA condensation. In vitro HC binds to DNA and cleaves it in presence of copper. Our data strongly indicates HC mediates bacterial cell death by ROS generation and DNA damage. Damage to iron sulfur proteins in the cells contribute to amplification of oxidative stress initiated by HC. Further HC is active against a number of Gram negative bacteria isolated from patients with a wide range of clinical symptoms and varied antibiotic resistance profiles. Copyright © 2018 Elsevier Inc. All rights reserved.

Model-based analysis of Arabidopsis leaf epidermal cells reveals distinct division and expansion patterns for pavement and guard cells.

PubMed

Asl, Leila Kheibarshekan; Dhondt, Stijn; Boudolf, Véronique; Beemster, Gerrit T S; Beeckman, Tom; Inzé, Dirk; Govaerts, Willy; De Veylder, Lieven

2011-08-01

To efficiently capture sunlight for photosynthesis, leaves typically develop into a flat and thin structure. This development is driven by cell division and expansion, but the individual contribution of these processes is currently unknown, mainly because of the experimental difficulties to disentangle them in a developing organ, due to their tight interconnection. To circumvent this problem, we built a mathematic model that describes the possible division patterns and expansion rates for individual epidermal cells. This model was used to fit experimental data on cell numbers and sizes obtained over time intervals of 1 d throughout the development of the first leaf pair of Arabidopsis (Arabidopsis thaliana). The parameters were obtained by a derivative-free optimization method that minimizes the differences between the predicted and experimentally observed cell size distributions. The model allowed us to calculate probabilities for a cell to divide into guard or pavement cells, the maximum size at which it can divide, and its average cell division and expansion rates at each point during the leaf developmental process. Surprisingly, average cell cycle duration remained constant throughout leaf development, whereas no evidence for a maximum cell size threshold for cell division of pavement cells was found. Furthermore, the model predicted that neighboring cells of different sizes within the epidermis expand at distinctly different relative rates, which could be verified by direct observations. We conclude that cell division seems to occur independently from the status of cell expansion, whereas the cell cycle might act as a timer rather than as a size-regulated machinery.

Timing of Tissue-specific Cell Division Requires a Differential Onset of Zygotic Transcription during Metazoan Embryogenesis*

PubMed Central

Wong, Ming-Kin; Guan, Daogang; Ng, Kaoru Hon Chun; Ho, Vincy Wing Sze; An, Xiaomeng; Li, Runsheng; Ren, Xiaoliang

2016-01-01

Metazoan development demands not only precise cell fate differentiation but also accurate timing of cell division to ensure proper development. How cell divisions are temporally coordinated during development is poorly understood. Caenorhabditis elegans embryogenesis provides an excellent opportunity to study this coordination due to its invariant development and widespread division asynchronies. One of the most pronounced asynchronies is a significant delay of cell division in two endoderm progenitor cells, Ea and Ep, hereafter referred to as E2, relative to its cousins that mainly develop into mesoderm organs and tissues. To unravel the genetic control over the endoderm-specific E2 division timing, a total of 822 essential and conserved genes were knocked down using RNAi followed by quantification of cell cycle lengths using in toto imaging of C. elegans embryogenesis and automated lineage. Intriguingly, knockdown of numerous genes encoding the components of general transcription pathway or its regulatory factors leads to a significant reduction in the E2 cell cycle length but an increase in cell cycle length of the remaining cells, indicating a differential requirement of transcription for division timing between the two. Analysis of lineage-specific RNA-seq data demonstrates an earlier onset of transcription in endoderm than in other germ layers, the timing of which coincides with the birth of E2, supporting the notion that the endoderm-specific delay in E2 division timing demands robust zygotic transcription. The reduction in E2 cell cycle length is frequently associated with cell migration defect and gastrulation failure. The results suggest that a tissue-specific transcriptional activation is required to coordinate fate differentiation, division timing, and cell migration to ensure proper development. PMID:27056332

Localization of FtsZ in Helicobacter pylori and Consequences for Cell Division

PubMed Central

Specht, Mara; Dempwolff, Felix; Schätzle, Sarah; Thomann, Ralf

2013-01-01

Of the various kinds of cell division, the most common mode is binary fission, the division of a cell into two morphologically identical daughter cells. However, in the case of asymmetric cell division, Caulobacter crescentus produces two morphologically and functionally distinct cell types. Here, we have studied cell cycle progression of the human pathogen Helicobacter pylori using a functional green fluorescent protein (GFP) fusion of FtsZ protein and membrane staining. In small cells, representing newly divided cells, FtsZ localizes to a single cell pole. During the cell cycle, spiral intermediates are formed until an FtsZ ring is positioned with very little precision, such that central as well as acentral rings can be observed. Daughter cells showed considerably different sizes, suggesting that H. pylori divides asymmetrically. Fluorescence recovery after photobleaching (FRAP) analyses demonstrate that the H. pylori FtsZ ring is about as dynamic as that of Escherichia coli but that polar assemblies show less turnover. Strikingly, our results demonstrate that H. pylori cell division follows a different route from that in E. coli and Bacillus subtilis. It is also different from that in C. crescentus, where cytokinesis regulation proteins like MipZ play a role. Therefore, this report provides the first cell-biological analysis of FtsZ dynamics in the human pathogen H. pylori and even in epsilonproteobacteria to our knowledge. In addition, analysis of the filament architecture of H. pylori and E. coli FtsZ filaments in the heterologous system of Drosophila melanogaster S2 Schneider cells revealed that both have different filamentation properties in vivo, suggesting a unique intrinsic characteristic of each protein. PMID:23335414

Control of cell division in Streptococcus pneumoniae by the conserved Ser/Thr protein kinase StkP.

PubMed

Beilharz, Katrin; Nováková, Linda; Fadda, Daniela; Branny, Pavel; Massidda, Orietta; Veening, Jan-Willem

2012-04-10

How the human pathogen Streptococcus pneumoniae coordinates cell-wall synthesis during growth and division to achieve its characteristic oval shape is poorly understood. The conserved eukaryotic-type Ser/Thr kinase of S. pneumoniae, StkP, previously was reported to phosphorylate the cell-division protein DivIVA. Consistent with a role in cell division, GFP-StkP and its cognate phosphatase, GFP-PhpP, both localize to the division site. StkP localization depends on its penicillin-binding protein and Ser/Thr-associated domains that likely sense uncross-linked peptidoglycan, because StkP and PhpP delocalize in the presence of antibiotics that target the latest stages of cell-wall biosynthesis and in cells that have stopped dividing. Time-lapse microscopy shows that StkP displays an intermediate timing of recruitment to midcell: StkP arrives shortly after FtsA but before DivIVA. Furthermore, StkP remains at midcell longer than FtsA, until division is complete. Cells mutated for stkP are perturbed in cell-wall synthesis and display elongated morphologies with multiple, often unconstricted, FtsA and DivIVA rings. The data show that StkP plays an important role in regulating cell-wall synthesis and controls correct septum progression and closure. Overall, our results indicate that StkP signals information about the cell-wall status to key cell-division proteins and in this way acts as a regulator of cell division.

Morphodynamics of growing bacterial colony

NASA Astrophysics Data System (ADS)

Ghosh, Pushpita; Perlekar, Prasad; Rana, Navdeep

Self-organization into multicellular communities is a natural trend of most of the bacteria. Mutual interactions and competition among the bacterial cells in such multicellular organization play essential role in governing the spatiotemporal dynamics. We here present the spatiotemporal dynamics of growing bacterial colony using theory and a particle-based or individual-based simulation model of nonmotile cells growing utilizing a diffusing nutrient/food on a semi-solid surface by their growth and division forces and by pushing each-other through sliding motility. We show how the resource competition over a fixed amount of food, the diffusion coefficient of the nutrient and the random genetic noise govern the morphodynamics of a single species and a well-mixed two-species bacterial colonies. Our results show that for a very low initial food concentrations, colony develops fingering pattern at the front, while for intermediate values of initial food sources, the colony undergoes transitions to branched structures at the periphery and for very high values of food colony develops smoother fronts.

Intestinal Epithelial Cells Modulate Antigen-Presenting Cell Responses to Bacterial DNA

PubMed Central

Campeau, J. L.; Salim, S. Y.; Albert, E. J.; Hotte, N.

2012-01-01

Intestinal epithelial cells and antigen-presenting cells orchestrate mucosal innate immunity. This study investigated the role of bacterial DNA in modulating epithelial and bone marrow-derived antigen-presenting cells (BM-APCs) and subsequent T-lymphocyte responses. Murine MODE-K epithelial cells and BM-APCs were treated with DNA from either Bifidobacterium breve or Salmonella enterica serovar Dublin directly and under coculture conditions with CD4+ T cells. Apical stimulation of MODE-K cells with S. Dublin DNA enhanced secretion of cytokines from underlying BM-APCs and induced interleukin-17 (IL-17) and gamma interferon (IFN-γ) secretion from CD4+ T cells. Bacterial DNA isolated from either strain induced maturation and increased cytokine secretion from BM-APCs. Conditioned medium from S. Dublin-treated MODE-K cells elicited an increase in cytokine secretion similar to that seen for S. Dublin DNA. Treatment of conditioned medium from MODE-K cells with RNase and protease prevented the S. Dublin-induced increased cytokine secretion. Oral feeding of mice with B. breve DNA resulted in enhanced levels of colonic IL-10 and transforming growth factor β (TGFβ) compared with what was seen for mice treated with S. Dublin DNA. In contrast, feeding mice with S. Dublin DNA increased levels of colonic IL-17 and IL-12p70. T cells from S. Dublin DNA-treated mice secreted high levels of IL-12 and IFN-γ compared to controls and B. breve DNA-treated mice. These results demonstrate that intestinal epithelial cells are able to modulate subsequent antigen-presenting and T-cell responses to bacterial DNA with pathogenic but not commensal bacterial DNA inducing effector CD4+ T lymphocytes. PMID:22615241

Coupling Bacterial Activity Measurements with Cell Sorting by Flow Cytometry.

PubMed

Servais; Courties; Lebaron; Troussellier

1999-08-01

> Abstract A new procedure to investigate the relationship between bacterial cell size and activity at the cellular level has been developed; it is based on the coupling of radioactive labeling of bacterial cells and cell sorting by flow cytometry after SYTO 13 staining. Before sorting, bacterial cells were incubated in the presence of tritiated leucine using a procedure similar to that used for measuring bacterial production by leucine incorporation and then stained with SYTO 13. Subpopulations of bacterial cells were sorted according to their average right-angle light scatter (RALS) and fluorescence. Average RALS was shown to be significantly related to the average biovolume. Experiments were performed on samples collected at different times in a Mediterranean seawater mesocosm enriched with nitrogen and phosphorus. At four sampling times, bacteria were sorted in two subpopulations (cells smaller and larger than 0.25 µm(3)). The results indicate that, at each sampling time, the growth rate of larger cells was higher than that of smaller cells. In order to confirm this tendency, cell sorting was performed on six subpopulations differing in average biovolume during the mesocosm follow-up. A clear increase of the bacterial growth rates was observed with increasing cell size for the conditions met in this enriched mesocosm.http://link.springer-ny.com/link/service/journals/00248/bibs/38n2p180.html

Activity and Accumulation of Cell Division-Promoting Phenolics in Tobacco Tissue Cultures 1

PubMed Central

Teutonico, Rita A.; Dudley, Matthew W.; Orr, John D.; Lynn, David G.; Binns, Andrew N.

1991-01-01

Dehydrodiconiferyl alcohol glucosides (DCGs) are derivatives of the phenylpropanoid pathway that have been isolated from Catharansus roseus L. (Vinca rosea) crown gall tumors. Fractions containing purified DCGs have been shown previously to promote the growth of cytokinin-requiring tissues of tobacco in the absence of exogenous cytokinins. In this study, we utilized synthetic DCG isomers to confirm the cell division-promoting activity of DCG isomers A and B and show that they neither promote shoot meristem initiation on Nicotiana tabacum L., cv Havana 425, leaf explants nor induce betacyanin synthesis in amaranth seedlings. Analysis of cultured tobacco pith tissue demonstrated that DCG accumulation was stimulated by cytokinin treatment and correlated with cytokinin-induced cell division. Thus, the accumulation of metabolites that could replace cytokinin in cell division bioassays is stimulated by cytokinins. These data support the model that DCGs are a component of a cytokinin-mediated regulatory circuit controlling cell division. ImagesFigure 2 PMID:16668384

Tumor-Initiating Label-Retaining Cancer Cells in Human Gastrointestinal Cancers Undergo Asymmetric Cell Division

PubMed Central

Xin, Hong-Wu; Hari, Danielle M.; Mullinax, John E.; Ambe, Chenwi M.; Koizumi, Tomotake; Ray, Satyajit; Anderson, Andrew J.; Wiegand, Gordon W.; Garfield, Susan H.; Thorgeirsson, Snorri S.; Avital, Itzhak

2012-01-01

Label-retaining cells (LRCs) have been proposed to represent adult tissue stem cells. LRCs are hypothesized to result from either slow cycling or asymmetric cell division (ACD). However, the stem cell nature and whether LRC undergo ACD remain controversial. Here, we demonstrate label-retaining cancer cells (LRCCs) in several gastrointestinal (GI) cancers including fresh surgical specimens. Using a novel method for isolation of live LRCC, we demonstrate that a subpopulation of LRCC is actively dividing and exhibits stem cells and pluripotency gene expression profiles. Using real-time confocal microscopic cinematography, we show live LRCC undergoing asymmetric nonrandom chromosomal cosegregation LRC division. Importantly, LRCCs have greater tumor-initiating capacity than non-LRCCs. Based on our data and that cancers develop in tissues that harbor normal-LRC, we propose that LRCC might represent a novel population of GI stem-like cancer cells. LRCC may provide novel mechanistic insights into the biology of cancer and regenerative medicine and present novel targets for cancer treatment. PMID:22331764

Cell wall layers delimit cell groups derived from cell division in the foliose trebouxiophycean alga Prasiola japonica.

PubMed

Mine, Ichiro; Kinoshita, Urara; Kawashima, Shigetaka; Sekida, Satoko

2018-01-22

The cells in the foliose thallus of trebouxiophycean alga Prasiola japonica apparently develop into 2 × 2 cell groups composed of two two-celled groups, each of which is a pair of derivative cells of the latest cell division. In the present study, the structural features of cell walls of the alga P. japonica concerning the formation of the cell groups were investigated using histochemical methods. Thin cell layers stained by Calcofluor White appeared to envelope the two-celled and four-celled groups separately and, hence, separated them from neighboring cell groups, and the Calcofluor White-negative gaps between neighboring four-celled groups were specifically stained by lectins, such as soybean agglutinin, jacalin, and Vicia villosa lectin conjugated with fluorescein. These results indicated that the Calcofluor White-positive cell wall layer of parent cell that existed during two successive cell divisions structurally distinguished two-celled and four-celled groups from others in this alga. Moreover, the results suggested that the cell wall components of the Calcofluor White-negative gaps would possibly contribute to the formation of the planar thallus through lateral union of the cell groups.

Myo19 ensures symmetric partitioning of mitochondria and coupling of mitochondrial segregation to cell division.

PubMed

Rohn, Jennifer L; Patel, Jigna V; Neumann, Beate; Bulkescher, Jutta; Mchedlishvili, Nunu; McMullan, Rachel C; Quintero, Omar A; Ellenberg, Jan; Baum, Buzz

2014-11-03

During animal cell division, an actin-based ring cleaves the cell into two. Problems with this process can cause chromosome missegregation and defects in cytoplasmic inheritance and the partitioning of organelles, which in turn are associated with human diseases. Although much is known about how chromosome segregation is coupled to cell division, the way organelles coordinate their inheritance during partitioning to daughter cells is less well understood. Here, using a high-content live-imaging small interfering RNA screen, we identify Myosin-XIX (Myo19) as a novel regulator of cell division. Previously, this actin-based motor was shown to control the interphase movement of mitochondria. Our analysis shows that Myo19 is indeed localized to mitochondria and that its silencing leads to defects in the distribution of mitochondria within cells and in mitochondrial partitioning at division. Furthermore, many Myo19 RNAi cells undergo stochastic division failure--a phenotype that can be mimicked using a treatment that blocks mitochondrial fission and rescued by decreasing mitochondrial fusion, implying that mitochondria can physically interfere with cytokinesis. Strikingly, using live imaging we also observe the inappropriate movement of mitochondria to the poles of spindles in cells depleted for Myo19 as they enter anaphase. Since this phenocopies the results of an acute loss of actin filaments in anaphase, these data support a model whereby the Myo19 actin-based motor helps to control mitochondrial movement to ensure their faithful segregation during division. The presence of DNA within mitochondria makes their inheritance an especially important aspect of symmetrical cell division. Copyright © 2014 The Authors. Published by Elsevier Inc. All rights reserved.

Arabidopsis  SABRE and CLASP interact to stabilize cell division plane orientation and planar polarity

PubMed Central

Pietra, Stefano; Gustavsson, Anna; Kiefer, Christian; Kalmbach, Lothar; Hörstedt, Per; Ikeda, Yoshihisa; Stepanova, Anna N.; Alonso, Jose M.; Grebe, Markus

2013-01-01

The orientation of cell division and the coordination of cell polarity within the plane of the tissue layer (planar polarity) contribute to shape diverse multicellular organisms. The root of Arabidopsis thaliana displays regularly oriented cell divisions, cell elongation and planar polarity providing a plant model system to study these processes. Here we report that the SABRE protein, which shares similarity with proteins of unknown function throughout eukaryotes, has important roles in orienting cell division and planar polarity. SABRE localizes at the plasma membrane, endomembranes, mitotic spindle and cell plate. SABRE stabilizes the orientation of CLASP-labelled preprophase band microtubules predicting the cell division plane, and of cortical microtubules driving cell elongation. During planar polarity establishment, sabre is epistatic to clasp at directing polar membrane domains of Rho-of-plant GTPases. Our findings mechanistically link SABRE to CLASP-dependent microtubule organization, shedding new light on the function of SABRE-related proteins in eukaryotes. PMID:24240534

Arabidopsis  SABRE and CLASP interact to stabilize cell division plane orientation and planar polarity.

PubMed

Pietra, Stefano; Gustavsson, Anna; Kiefer, Christian; Kalmbach, Lothar; Hörstedt, Per; Ikeda, Yoshihisa; Stepanova, Anna N; Alonso, Jose M; Grebe, Markus

2013-01-01

The orientation of cell division and the coordination of cell polarity within the plane of the tissue layer (planar polarity) contribute to shape diverse multicellular organisms. The root of Arabidopsis thaliana displays regularly oriented cell divisions, cell elongation and planar polarity providing a plant model system to study these processes. Here we report that the SABRE protein, which shares similarity with proteins of unknown function throughout eukaryotes, has important roles in orienting cell division and planar polarity. SABRE localizes at the plasma membrane, endomembranes, mitotic spindle and cell plate. SABRE stabilizes the orientation of CLASP-labelled preprophase band microtubules predicting the cell division plane, and of cortical microtubules driving cell elongation. During planar polarity establishment, sabre is epistatic to clasp at directing polar membrane domains of Rho-of-plant GTPases. Our findings mechanistically link SABRE to CLASP-dependent microtubule organization, shedding new light on the function of SABRE-related proteins in eukaryotes.

Asymmetric stem-cell divisions define the architecture of human oesophageal epithelium.

PubMed

Seery, J P; Watt, F M

2000-11-16

In spite of its clinical importance, little is known about the stem-cell compartment of the human oesophageal epithelium [1,2]. The epithelial basal layer consists of two distinct zones, one overlying the papillae of the supporting connective tissue (PBL) and the other covering the interpapillary zone (IBL) [3]. In examining the oesophageal basal layer, we found that proliferating cells were rare in the IBL and a high proportion of mitoses were asymmetrical, giving rise to one basal daughter and one suprabasal, differentiating daughter. In the PBL, mitoses were more frequent and predominantly symmetrical. The IBL was characterised by low expression of ?1 integrins and high expression of the beta2 laminin chain. By combining fluorescence-activated cell sorting (FACS) with in vitro clonal analysis, we obtained evidence that the IBL is enriched for stem cells. A normal oesophageal epithelium with asymmetric divisions was reconstituted on denuded oesophageal connective tissue. In contrast, asymmetric divisions were not sustained on skin connective tissue, and the epithelium formed resembled epidermis. We propose that stem cells located in the IBL give rise to differentiating daughters through asymmetric divisions in response to cues from the underlying basement membrane. Until now, stem-cell fate in stratified squamous epithelia was believed to be achieved largely through populational asymmetry [4-6].

Targeting cell division: Small-molecule inhibitors of FtsZ GTPase perturb cytokinetic ring assembly and induce bacterial lethality

PubMed Central

Margalit, Danielle N.; Romberg, Laura; Mets, Rebecca B.; Hebert, Alan M.; Mitchison, Timothy J.; Kirschner, Marc W.; RayChaudhuri, Debabrata

2004-01-01

FtsZ, the ancestral homolog of eukaryotic tubulins, is a GTPase that assembles into a cytokinetic ring structure essential for cell division in prokaryotic cells. Similar to tubulin, purified FtsZ polymerizes into dynamic protofilaments in the presence of GTP; polymer assembly is accompanied by GTP hydrolysis. We used a high-throughput protein-based chemical screen to identify small molecules that target assembly-dependent GTPase activity of FtsZ. Here, we report the identification of five structurally diverse compounds, named Zantrins, which inhibit FtsZ GTPase either by destabilizing the FtsZ protofilaments or by inducing filament hyperstability through increased lateral association. These two classes of FtsZ inhibitors are reminiscent of the antitubulin drugs colchicine and Taxol, respectively. We also show that Zantrins perturb FtsZ ring assembly in Escherichia coli cells and cause lethality to a variety of bacteria in broth cultures, indicating that FtsZ antagonists may serve as chemical leads for the development of new broad-spectrum antibacterial agents. Our results illustrate the utility of small-molecule chemical probes to study FtsZ polymerization dynamics and the feasibility of FtsZ as a novel therapeutic target. PMID:15289600

Polarity, cell division, and out-of-equilibrium dynamics control the growth of epithelial structures

PubMed Central

Cerruti, Benedetta; Puliafito, Alberto; Shewan, Annette M.; Yu, Wei; Combes, Alexander N.; Little, Melissa H.; Chianale, Federica; Primo, Luca; Serini, Guido; Mostov, Keith E.; Celani, Antonio

2013-01-01

The growth of a well-formed epithelial structure is governed by mechanical constraints, cellular apico-basal polarity, and spatially controlled cell division. Here we compared the predictions of a mathematical model of epithelial growth with the morphological analysis of 3D epithelial structures. In both in vitro cyst models and in developing epithelial structures in vivo, epithelial growth could take place close to or far from mechanical equilibrium, and was determined by the hierarchy of time-scales of cell division, cell–cell rearrangements, and lumen dynamics. Equilibrium properties could be inferred by the analysis of cell–cell contact topologies, and the nonequilibrium phenotype was altered by inhibiting ROCK activity. The occurrence of an aberrant multilumen phenotype was linked to fast nonequilibrium growth, even when geometric control of cell division was correctly enforced. We predicted and verified experimentally that slowing down cell division partially rescued a multilumen phenotype induced by altered polarity. These results improve our understanding of the development of epithelial organs and, ultimately, of carcinogenesis. PMID:24145168

Symmetry of initial cell divisions among primitive hematopoietic progenitors is independent of ontogenic age and regulatory molecules.

PubMed

Huang, S; Law, P; Francis, K; Palsson, B O; Ho, A D

1999-10-15

We have developed a time-lapse camera system to follow the replication history and the fate of hematopoietic stem cells (HSC) at a single-cell level. Combined with single-cell culture, we correlated the early replication behavior with colony development after 14 days. The membrane dye PKH26 was used to monitor cell division. In addition to multiple, synchronous, and symmetric divisions, single-sorted CD34(+)/CD38(-) cells derived from fetal liver (FLV) also gave rise to a daughter cell that remained quiescent for up to 8 days, whereas the other daughter cell proliferated exponentially. Upon separation and replating as single cells onto medium containing a cytokine cocktail, 60.6% +/- 9.8% of the initially quiescent cells (PKH26 bright) gave rise again to colonies and 15.8% +/- 7.8% to blast colonies that could be replated. We have then determined the effects of various regulatory molecules on symmetry of initial cell divisions. After single-cell sorting, the CD34(+)/CD38(-) cells derived from FLV were exposed to flt3-ligand, thrombopoietin, stem cell factor (SCF), or medium containing a cytokine cocktail (with SCF, interleukin-3, interleukin-6, granulocyte-macrophage colony-stimulating factor, and erythropoietin). Whereas mitotic rate, colony efficiency, and asymmetric divisions could be altered using various regulatory molecules, the asymmetric division index, defined as the number of asymmetric divisions versus the number of dividing cells, was not altered significantly. This observation suggests that, although lineage commitment and cell proliferation can be skewed by extrinsic signaling, symmetry of early divisions is probably under the control of intrinsic factors.

Axenic Culture of a Candidate Division TM7 Bacterium from the Human Oral Cavity and Biofilm Interactions with Other Oral Bacteria

PubMed Central

Soro, Valeria; Dutton, Lindsay C.; Sprague, Susan V.; Nobbs, Angela H.; Ireland, Anthony J.; Sandy, Jonathan R.; Jepson, Mark A.; Micaroni, Massimo; Splatt, Peter R.; Dymock, David

2014-01-01

The diversity of bacterial species in the human oral cavity is well recognized, but a high proportion of them are presently uncultivable. Candidate division TM7 bacteria are almost always detected in metagenomic studies but have not yet been cultivated. In this paper, we identified candidate division TM7 bacterial phylotypes in mature plaque samples from around orthodontic bonds in subjects undergoing orthodontic treatment. Successive rounds of enrichment in laboratory media led to the isolation of a pure culture of one of these candidate division TM7 phylotypes. The bacteria formed filaments of 20 to 200 μm in length within agar plate colonies and in monospecies biofilms on salivary pellicle and exhibited some unusual morphological characteristics by transmission electron microscopy, including a trilaminated cell surface layer and dense cytoplasmic deposits. Proteomic analyses of cell wall protein extracts identified abundant polypeptides predicted from the TM7 partial genomic sequence. Pleiomorphic phenotypes were observed when the candidate division TM7 bacterium was grown in dual-species biofilms with representatives of six different oral bacterial genera. The TM7 bacterium formed long filaments in dual-species biofilm communities with Actinomyces oris or Fusobacterium nucleatum. However, the TM7 isolate grew as short rods or cocci in dual-species biofilms with Porphyromonas gingivalis, Prevotella intermedia, Parvimonas micra, or Streptococcus gordonii, forming notably robust biofilms with the latter two species. The ability to cultivate TM7 axenically should majorly advance understanding of the physiology, genetics, and virulence properties of this novel candidate division oral bacterium. PMID:25107981

Axenic culture of a candidate division TM7 bacterium from the human oral cavity and biofilm interactions with other oral bacteria.

PubMed

Soro, Valeria; Dutton, Lindsay C; Sprague, Susan V; Nobbs, Angela H; Ireland, Anthony J; Sandy, Jonathan R; Jepson, Mark A; Micaroni, Massimo; Splatt, Peter R; Dymock, David; Jenkinson, Howard F

2014-10-01

The diversity of bacterial species in the human oral cavity is well recognized, but a high proportion of them are presently uncultivable. Candidate division TM7 bacteria are almost always detected in metagenomic studies but have not yet been cultivated. In this paper, we identified candidate division TM7 bacterial phylotypes in mature plaque samples from around orthodontic bonds in subjects undergoing orthodontic treatment. Successive rounds of enrichment in laboratory media led to the isolation of a pure culture of one of these candidate division TM7 phylotypes. The bacteria formed filaments of 20 to 200 μm in length within agar plate colonies and in monospecies biofilms on salivary pellicle and exhibited some unusual morphological characteristics by transmission electron microscopy, including a trilaminated cell surface layer and dense cytoplasmic deposits. Proteomic analyses of cell wall protein extracts identified abundant polypeptides predicted from the TM7 partial genomic sequence. Pleiomorphic phenotypes were observed when the candidate division TM7 bacterium was grown in dual-species biofilms with representatives of six different oral bacterial genera. The TM7 bacterium formed long filaments in dual-species biofilm communities with Actinomyces oris or Fusobacterium nucleatum. However, the TM7 isolate grew as short rods or cocci in dual-species biofilms with Porphyromonas gingivalis, Prevotella intermedia, Parvimonas micra, or Streptococcus gordonii, forming notably robust biofilms with the latter two species. The ability to cultivate TM7 axenically should majorly advance understanding of the physiology, genetics, and virulence properties of this novel candidate division oral bacterium. Copyright © 2014, American Society for Microbiology. All Rights Reserved.

Drosophila Sulf1 is required for the termination of intestinal stem cell division during regeneration.

PubMed

Takemura, Masahiko; Nakato, Hiroshi

2017-01-15

Stem cell division is activated to trigger regeneration in response to tissue damage. The molecular mechanisms by which this stem cell mitotic activity is properly repressed at the end of regeneration are poorly understood. Here, we show that a specific modification of heparan sulfate is crucial for regulating Drosophila intestinal stem cell (ISC) division during normal midgut homeostasis and regeneration. Loss of the extracellular heparan sulfate endosulfatase Sulf1 resulted in increased ISC division during normal homeostasis, which was caused by upregulation of mitogenic signaling including the JAK-STAT, EGFR and Hedgehog pathways. Using a regeneration model, we found that ISCs failed to properly halt division at the termination stage in Sulf1 mutants, showing that Sulf1 is required for terminating ISC division at the end of regeneration. We propose that post-transcriptional regulation of mitogen signaling by heparan sulfate structural modifications provides a new regulatory step for precise temporal control of stem cell activity during regeneration. © 2017. Published by The Company of Biologists Ltd.

Drosophila Sulf1 is required for the termination of intestinal stem cell division during regeneration

PubMed Central

2017-01-01

ABSTRACT Stem cell division is activated to trigger regeneration in response to tissue damage. The molecular mechanisms by which this stem cell mitotic activity is properly repressed at the end of regeneration are poorly understood. Here, we show that a specific modification of heparan sulfate is crucial for regulating Drosophila intestinal stem cell (ISC) division during normal midgut homeostasis and regeneration. Loss of the extracellular heparan sulfate endosulfatase Sulf1 resulted in increased ISC division during normal homeostasis, which was caused by upregulation of mitogenic signaling including the JAK-STAT, EGFR and Hedgehog pathways. Using a regeneration model, we found that ISCs failed to properly halt division at the termination stage in Sulf1 mutants, showing that Sulf1 is required for terminating ISC division at the end of regeneration. We propose that post-transcriptional regulation of mitogen signaling by heparan sulfate structural modifications provides a new regulatory step for precise temporal control of stem cell activity during regeneration. PMID:27888216

Growth mechanics of bacterial cell wall and morphology of bacteria

NASA Astrophysics Data System (ADS)

Jiang, Hongyuan; Sun, Sean

2010-03-01

The peptidoglycan cell wall of bacteria is responsible for maintaining the cell shape and integrity. During the bacterial life cycle, the growth of the cell wall is affected by mechanical stress and osmotic pressure internal to the cell. We develop a theory to describe cell shape changes under the influence of mechanical forces. We find that the theory predicts a steady state size and shape for bacterial cells ranging from cocci to spirillum. Moreover, the theory suggest a mechanism by which bacterial cytoskeletal proteins such as MreB and crescentin can maintain the shape of the cell. The theory can also explain the several recent experiments on growing bacteria in micro-environments.

LocZ Is a New Cell Division Protein Involved in Proper Septum Placement in Streptococcus pneumoniae

PubMed Central

Holečková, Nela; Molle, Virginie; Buriánková, Karolína; Benada, Oldřich; Kofroňová, Olga; Ulrych, Aleš; Branny, Pavel

2014-01-01

ABSTRACT How bacteria control proper septum placement at midcell, to guarantee the generation of identical daughter cells, is still largely unknown. Although different systems involved in the selection of the division site have been described in selected species, these do not appear to be widely conserved. Here, we report that LocZ (Spr0334), a newly identified cell division protein, is involved in proper septum placement in Streptococcus pneumoniae. We show that locZ is not essential but that its deletion results in cell division defects and shape deformation, causing cells to divide asymmetrically and generate unequally sized, occasionally anucleated, daughter cells. LocZ has a unique localization profile. It arrives early at midcell, before FtsZ and FtsA, and leaves the septum early, apparently moving along with the equatorial rings that mark the future division sites. Consistently, cells lacking LocZ also show misplacement of the Z-ring, suggesting that it could act as a positive regulator to determine septum placement. LocZ was identified as a substrate of the Ser/Thr protein kinase StkP, which regulates cell division in S. pneumoniae. Interestingly, homologues of LocZ are found only in streptococci, lactococci, and enterococci, indicating that this close phylogenetically related group of bacteria evolved a specific solution to spatially regulate cell division. PMID:25550321

Dielectric modelling of cell division for budding and fission yeast

NASA Astrophysics Data System (ADS)

Asami, Koji; Sekine, Katsuhisa

2007-02-01

The frequency dependence of complex permittivity or the dielectric spectrum of a system including a cell in cell division has been simulated by a numerical technique based on the three-dimensional finite difference method. Two different types of cell division characteristic of budding and fission yeast were examined. The yeast cells are both regarded as a body of rotation, and thus have anisotropic polarization, i.e. the effective permittivity of the cell depends on the orientation of the cell to the direction of an applied electric field. In the perpendicular orientation, where the rotational axis of the cell is perpendicular to the electric field direction, the dielectric spectra for both yeast cells included one dielectric relaxation and its intensity depended on the cell volume. In the parallel orientation, on the other hand, two dielectric relaxations appeared with bud growth for budding yeast and with septum formation for fission yeast. The low-frequency relaxation was shifted to a lower frequency region by narrowing the neck between the bud and the mother cell for budding yeast and by increasing the degree of septum formation for fission yeast. After cell separation, the low-frequency relaxation disappeared. The simulations well interpreted the oscillation of the relative permittivity of culture broth found for synchronous cell growth of budding yeast.

Moving with the flow: what transport laws reveal about cell division and expansion.

PubMed

Silk, Wendy Kuhn

2006-01-01

This material was presented as a keynote talk for the symposium, "Crosstalk between cell division and expansion," organized by G.T.S. Beemster and H. Tsukaya at the International Botanical Congress, Vienna in July, 2005. The review focuses on the utility of continuity equations to understand relationships among cell size, division and expansion; insights from Lagrangian or cell-specific descriptions of developmental variables; and a growth-diffusion equation to show effects of root growth zones on the surrounding soil.

Analysis of Cell Division and Elongation Underlying the Developmental Acceleration of Root Growth in Arabidopsis thaliana1

PubMed Central

Beemster, Gerrit T.S.; Baskin, Tobias I.

1998-01-01

To investigate the relation between cell division and expansion in the regulation of organ growth rate, we used Arabidopsis thaliana primary roots grown vertically at 20°C with an elongation rate that increased steadily during the first 14 d after germination. We measured spatial profiles of longitudinal velocity and cell length and calculated parameters of cell expansion and division, including rates of local cell production (cells mm−1 h−1) and cell division (cells cell−1 h−1). Data were obtained for the root cortex and also for the two types of epidermal cell, trichoblasts and atrichoblasts. Accelerating root elongation was caused by an increasingly longer growth zone, while maximal strain rates remained unchanged. The enlargement of the growth zone and, hence, the accelerating root elongation rate, were accompanied by a nearly proportionally increased cell production. This increased production was caused by increasingly numerous dividing cells, whereas their rates of division remained approximately constant. Additionally, the spatial profile of cell division rate was essentially constant. The meristem was longer than generally assumed, extending well into the region where cells elongated rapidly. In the two epidermal cell types, meristem length and cell division rate were both very similar to that of cortical cells, and differences in cell length between the two epidermal cell types originated at the apex of the meristem. These results highlight the importance of controlling the number of dividing cells, both to generate tissues with different cell lengths and to regulate the rate of organ enlargement. PMID:9536070

Decoupling of Nuclear Division Cycles and Cell Size during the Coenocytic Growth of the Ichthyosporean Sphaeroforma arctica.

PubMed

Ondracka, Andrej; Dudin, Omaya; Ruiz-Trillo, Iñaki

2018-06-18

Coordination of the cell division cycle with the growth of the cell is critical to achieve cell size homeostasis [1]. Mechanisms coupling the cell division cycle with cell growth have been described across diverse eukaryotic taxa [2-4], but little is known about how these processes are coordinated in organisms that undergo more complex life cycles, such as coenocytic growth. Coenocytes (multinucleate cells formed by sequential nuclear divisions without cytokinesis) are commonly found across the eukaryotic kingdom, including in animal and plant tissues and several lineages of unicellular eukaryotes [5]. Among the organisms that form coenocytes are ichthyosporeans, a lineage of unicellular holozoans that are of significant interest due to their phylogenetic placement as one of the closest relatives of animals [6]. Here, we characterize the coenocytic cell division cycle in the ichthyosporean Sphaeroforma arctica. We observe that, in laboratory conditions, S. arctica cells undergo a uniform and easily synchronizable coenocytic cell cycle, reaching up to 128 nuclei per cell before cellularization and release of daughter cells. Cycles of nuclear division occur synchronously within the coenocyte and in regular time intervals (11-12 hr). We find that the growth of cell volume is dependent on concentration of nutrients in the media; in contrast, the rate of nuclear division cycles is constant over a range of nutrient concentrations. Together, the results suggest that nuclear division cycles in the coenocytic growth of S. arctica are driven by a timer, which ensures periodic and synchronous nuclear cycles independent of the cell size and growth. Copyright © 2018 The Author(s). Published by Elsevier Ltd.. All rights reserved.

Rules and Self-Organizing Properties of Post-embryonic Plant Organ Cell Division Patterns.

PubMed

von Wangenheim, Daniel; Fangerau, Jens; Schmitz, Alexander; Smith, Richard S; Leitte, Heike; Stelzer, Ernst H K; Maizel, Alexis

2016-02-22

Plants form new organs with patterned tissue organization throughout their lifespan. It is unknown whether this robust post-embryonic organ formation results from stereotypic dynamic processes, in which the arrangement of cells follows rigid rules. Here, we combine modeling with empirical observations of whole-organ development to identify the principles governing lateral root formation in Arabidopsis. Lateral roots derive from a small pool of founder cells in which some take a dominant role as seen by lineage tracing. The first division of the founders is asymmetric, tightly regulated, and determines the formation of a layered structure. Whereas the pattern of subsequent cell divisions is not stereotypic between different samples, it is characterized by a regular switch in division plane orientation. This switch is also necessary for the appearance of patterned layers as a result of the apical growth of the primordium. Our data suggest that lateral root morphogenesis is based on a limited set of rules. They determine cell growth and division orientation. The organ-level coupling of the cell behavior ensures the emergence of the lateral root's characteristic features. We propose that self-organizing, non-deterministic modes of development account for the robustness of plant organ morphogenesis. Copyright © 2016 Elsevier Ltd. All rights reserved.

Division of Labor, Bet Hedging, and the Evolution of Mixed Biofilm Investment Strategies

PubMed Central

McNally, Luke; Ratcliff, William C.

2017-01-01

ABSTRACT Bacterial cells, like many other organisms, face a tradeoff between longevity and fecundity. Planktonic cells are fast growing and fragile, while biofilm cells are often slower growing but stress resistant. Here we ask why bacterial lineages invest simultaneously in both fast- and slow-growing types. We develop a population dynamic model of lineage expansion across a patchy environment and find that mixed investment is favored across a broad range of environmental conditions, even when transmission is entirely via biofilm cells. This mixed strategy is favored because of a division of labor where exponentially dividing planktonic cells can act as an engine for the production of future biofilm cells, which grow more slowly. We use experimental evolution to test our predictions and show that phenotypic heterogeneity is persistent even under selection for purely planktonic or purely biofilm transmission. Furthermore, simulations suggest that maintenance of a biofilm subpopulation serves as a cost-effective hedge against environmental uncertainty, which is also consistent with our experimental findings. PMID:28790201

Incidence and Predictors of Bacterial infection in Febrile Children with Sickle Cell Disease.

PubMed

Morrissey, Benita J; Bycroft, Thomas P; Almossawi, Ofran; Wilkey, Olufunke B; Daniels, Justin G

2015-01-01

Children with sickle cell disease are at increased risk of developing bacteremia and other serious bacterial infections. Fever is a common symptom in sickle cell disease and can also occur with sickle cell crises and viral infections. We aimed to evaluate the incidence and predictors of bacteremia and bacterial infection in children with sickle cell disease presenting with fever to a district hospital and sickle cell center in London. A retrospective analysis was performed on all attendances of children (aged under 16 years) with sickle cell disease presenting with a fever of 38.5 °C or higher over a 1-year period. Confirmed bacterial infection was defined as bacteremia, bacterial meningitis, urinary tract infection (UTI), pneumonia, osteomyelitis or other bacterial infection with positive identification of organism. Children were defined as having a suspected bacterial infection if a bacterial infection was suspected clinically, but no organism was identified. Over a 1-year period there were 88 episodes analyzed in 59 children. Bacteremia occurred in 3.4% of episodes and confirmed bacterial infection in 7.0%. Suspected bacterial infection occurred in 33.0%. One death occurred from Salmonella typhirium septicemia. C-reactive protein (CRP) level and white blood cell (WBC) count were both significantly associated with bacterial infection (p = 0.004 and 0.02, respectively.) In conclusion, bacterial infections continue to be a significant problem in children with sickle cell disease. C-reactive protein was significantly associated with bacterial infections, and could be included in clinical risk criteria for febrile children with sickle cell disease.

Poisons, ruffles and rockets: bacterial pathogens and the host cell cytoskeleton.

PubMed

Steele-Mortimer, O; Knodler, L A; Finlay, B B

2000-02-01

The cytoskeleton of eukaryotic cells is affected by a number of bacterial and viral pathogens. In this review we consider three recurring themes of cytoskeletal involvement in bacterial pathogenesis: 1) the effect of bacterial toxins on actin-regulating small GTP-binding proteins; 2) the invasion of non-phagocytic cells by the bacterial induction of ruffles at the plasma membrane; 3) the formation of actin tails and pedestals by intracellular and extracellular bacteria, respectively. Considerable progress has been made recently in the characterization of these processes. It is becoming clear that bacterial pathogens have developed a variety of sophisticated mechanisms for utilizing the complex cytoskeletal system of host cells. These bacterially-induced processes are now providing unique insights into the regulation of fundamental eukaryotic mechanisms.

Control of cell division and the spatial localization of assembled gene products in Caulobacter crescentus

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nathan, P.D.

Experiments are described that examine the role of penicillin-binding proteins (PBPs) in the regulation of cell division in Caulobacter crescentus; and the spatial localization of methyl-accepting chemotaxis proteins (MCPs) in C. crescentus swarmer and predivisional cells. In the analysis of PBP function, in vivo and in vitro assays are used to directly label C. crescentus PBPs with (/sup 3/H) penicillin G in wild type strain CB15, in a series of conditional cell division mutants and in new temperature sensitive cephalosporin C resistant mutants PC8002 and PC8003. 14 PBPs are characterized and a high molecular weight PBP (PBP 1B) that ismore » required for cell division is identified. PBP 1B competes for ..beta..-lactams that induce filament formation and may be a high affinity binding protein. A second high molecular weight PBP (PBP 1C) is also associated with defective cell division. The examination of PBP patterns in synchronous swarmer cells reveals that the in vivo activity of PBP 1B and PBP 1C increases at the time that the cell division pathway is initiated. None of the PBPs, however, appear to be differentially localized in the C. crescentus cell. In the analysis of MCP localization, in vivo and in vitro assays are used to directly label C. crescentus MCPs with methyl-/sup 3/H. MCPs are examined in flagellated and non-flagellated vesicles prepared from cells by immunoaffinity chromatography.« less

Proteomic analysis of the bacterial cell cycle

PubMed Central

Grünenfelder, Björn; Rummel, Gabriele; Vohradsky, Jiri; Röder, Daniel; Langen, Hanno; Jenal, Urs

2001-01-01

A global approach was used to analyze protein synthesis and stability during the cell cycle of the bacterium Caulobacter crescentus. Approximately one-fourth (979) of the estimated C. crescentus gene products were detected by two-dimensional gel electrophoresis, 144 of which showed differential cell cycle expression patterns. Eighty-one of these proteins were identified by mass spectrometry and were assigned to a wide variety of functional groups. Pattern analysis revealed that coexpression groups were functionally clustered. A total of 48 proteins were rapidly degraded in the course of one cell cycle. More than half of these unstable proteins were also found to be synthesized in a cell cycle-dependent manner, establishing a strong correlation between rapid protein turnover and the periodicity of the bacterial cell cycle. This is, to our knowledge, the first evidence for a global role of proteolysis in bacterial cell cycle control. PMID:11287652

Biosensors for Whole-Cell Bacterial Detection

PubMed Central

Rushworth, Jo V.; Hirst, Natalie A.; Millner, Paul A.

2014-01-01

SUMMARY Bacterial pathogens are important targets for detection and identification in medicine, food safety, public health, and security. Bacterial infection is a common cause of morbidity and mortality worldwide. In spite of the availability of antibiotics, these infections are often misdiagnosed or there is an unacceptable delay in diagnosis. Current methods of bacterial detection rely upon laboratory-based techniques such as cell culture, microscopic analysis, and biochemical assays. These procedures are time-consuming and costly and require specialist equipment and trained users. Portable stand-alone biosensors can facilitate rapid detection and diagnosis at the point of care. Biosensors will be particularly useful where a clear diagnosis informs treatment, in critical illness (e.g., meningitis) or to prevent further disease spread (e.g., in case of food-borne pathogens or sexually transmitted diseases). Detection of bacteria is also becoming increasingly important in antibioterrorism measures (e.g., anthrax detection). In this review, we discuss recent progress in the use of biosensors for the detection of whole bacterial cells for sensitive and earlier identification of bacteria without the need for sample processing. There is a particular focus on electrochemical biosensors, especially impedance-based systems, as these present key advantages in terms of ease of miniaturization, lack of reagents, sensitivity, and low cost. PMID:24982325

Elucidating Duramycin's Bacterial Selectivity and Mode of Action on the Bacterial Cell Envelope.

PubMed

Hasim, Sahar; Allison, David P; Mendez, Berlin; Farmer, Abigail T; Pelletier, Dale A; Retterer, Scott T; Campagna, Shawn R; Reynolds, Todd B; Doktycz, Mitchel J

2018-01-01

The use of naturally occurring antimicrobial peptides provides a promising route to selectively target pathogenic agents and to shape microbiome structure. Lantibiotics, such as duramycin, are one class of bacterially produced peptidic natural products that can selectively inhibit the growth of other bacteria. However, despite longstanding characterization efforts, the microbial selectivity and mode of action of duramycin are still obscure. We describe here a suite of biological, chemical, and physical characterizations that shed new light on the selective and mechanistic aspects of duramycin activity. Bacterial screening assays have been performed using duramycin and Populus -derived bacterial isolates to determine species selectivity. Lipidomic profiles of selected resistant and sensitive strains show that the sensitivity of Gram-positive bacteria depends on the presence of phosphatidylethanolamine (PE) in the cell membrane. Further the surface and interface morphology were studied by high resolution atomic force microscopy and showed a progression of cellular changes in the cell envelope after treatment with duramycin for the susceptible bacterial strains. Together, these molecular and cellular level analyses provide insight into duramycin's mode of action and a better understanding of its selectivity.

An Improved Model of Nonuniform Coleochaete Cell Division.

PubMed

Wang, Yuandi; Cong, Jinyu

2016-08-01

Cell division is a key biological process in which cells divide forming new daughter cells. In the present study, we investigate continuously how a Coleochaete cell divides by introducing a modified differential equation model in parametric equation form. We discuss both the influence of "dead" cells and the effects of various end-points on the formation of the new cells' boundaries. We find that the boundary condition on the free end-point is different from that on the fixed end-point; the former has a direction perpendicular to the surface. It is also shown that the outer boundaries of new cells are arc-shaped. The numerical experiments and theoretical analyses for this model to construct the outer boundary are given.

The simulation model of growth and cell divisions for the root apex with an apical cell in application to Azolla pinnata.

PubMed

Piekarska-Stachowiak, Anna; Nakielski, Jerzy

2013-12-01

In contrast to seed plants, the roots of most ferns have a single apical cell which is the ultimate source of all cells in the root. The apical cell has a tetrahedral shape and divides asymmetrically. The root cap derives from the distal division face, while merophytes derived from three proximal division faces contribute to the root proper. The merophytes are produced sequentially forming three sectors along a helix around the root axis. During development, they divide and differentiate in a predictable pattern. Such growth causes cell pattern of the root apex to be remarkably regular and self-perpetuating. The nature of this regularity remains unknown. This paper shows the 2D simulation model for growth of the root apex with the apical cell in application to Azolla pinnata. The field of growth rates of the organ, prescribed by the model, is of a tensor type (symplastic growth) and cells divide taking principal growth directions into account. The simulations show how the cell pattern in a longitudinal section of the apex develops in time. The virtual root apex grows realistically and its cell pattern is similar to that observed in anatomical sections. The simulations indicate that the cell pattern regularity results from cell divisions which are oriented with respect to principal growth directions. Such divisions are essential for maintenance of peri-anticlinal arrangement of cell walls and coordinated growth of merophytes during the development. The highly specific division program that takes place in merophytes prior to differentiation seems to be regulated at the cellular level.

Estimation of lactic acid bacterial cell number by DNA quantification.

PubMed

Ishii, Masaki; Matsumoto, Yasuhiko; Sekimizu, Kazuhisa

2018-01-01

Lactic acid bacteria are provided by fermented foods, beverages, medicines, and supplements. Because the beneficial effects of medicines and supplements containing functional lactic acid bacteria are related to the bacterial cell number, it is important to establish a simple method for estimating the total number of lactic acid bacterial cells in the products for quality control. Almost all of the lactic acid bacteria in the products are dead, however, making it difficult to estimate the total number of lactic acid bacterial cells in the products using a standard colony-counting method. Here we estimated the total lactic acid bacterial cell number in samples containing dead bacteria by quantifying the DNA. The number of viable Enterococcus faecalis 0831-07 cells decreased to less than 1 × 10 -8 by 15 min of heat treatment at 80°C. The amount of extracted DNA from heat-treated cells was 78% that of non-heated cells. The number of viable Lactobacillus paraplantarum 11-1 cells decreased to 1 × 10 -4 after 4 days culture. The amount of extracted DNA of the long-cultured cells, however, was maintained at 97%. These results suggest that cell number of lactic acid bacteria killed by heat-treatment or long-term culture can be estimated by DNA quantification.

Model-Based Analysis of Arabidopsis Leaf Epidermal Cells Reveals Distinct Division and Expansion Patterns for Pavement and Guard Cells1[W][OA

PubMed Central

Asl, Leila Kheibarshekan; Dhondt, Stijn; Boudolf, Véronique; Beemster, Gerrit T.S.; Beeckman, Tom; Inzé, Dirk; Govaerts, Willy; De Veylder, Lieven

2011-01-01

To efficiently capture sunlight for photosynthesis, leaves typically develop into a flat and thin structure. This development is driven by cell division and expansion, but the individual contribution of these processes is currently unknown, mainly because of the experimental difficulties to disentangle them in a developing organ, due to their tight interconnection. To circumvent this problem, we built a mathematic model that describes the possible division patterns and expansion rates for individual epidermal cells. This model was used to fit experimental data on cell numbers and sizes obtained over time intervals of 1 d throughout the development of the first leaf pair of Arabidopsis (Arabidopsis thaliana). The parameters were obtained by a derivative-free optimization method that minimizes the differences between the predicted and experimentally observed cell size distributions. The model allowed us to calculate probabilities for a cell to divide into guard or pavement cells, the maximum size at which it can divide, and its average cell division and expansion rates at each point during the leaf developmental process. Surprisingly, average cell cycle duration remained constant throughout leaf development, whereas no evidence for a maximum cell size threshold for cell division of pavement cells was found. Furthermore, the model predicted that neighboring cells of different sizes within the epidermis expand at distinctly different relative rates, which could be verified by direct observations. We conclude that cell division seems to occur independently from the status of cell expansion, whereas the cell cycle might act as a timer rather than as a size-regulated machinery. PMID:21693673

Cell division patterns and chromosomal segregation defects in oral cancer stem cells.

PubMed

Kaseb, Hatem O; Lewis, Dale W; Saunders, William S; Gollin, Susanne M

2016-09-01

Oral squamous cell carcinoma (OSCC) is a serious public health problem caused primarily by smoking and alcohol consumption or human papillomavirus. The cancer stem cell (CSC) theory posits that CSCs show unique characteristics, including self-renewal and therapeutic resistance. Examining biomarkers and other features of CSCs is critical to better understanding their biology. To this end, the results show that cellular SOX2 immunostaining correlates with other CSC biomarkers in OSCC cell lines and marks the rare CSC population. To assess whether CSC division patterns are symmetrical, resulting in two CSC, or asymmetrical, leading to one CSC and one cancer cell, cell size and fluorescence intensity of mitotic cells stained with SOX2 were analyzed. Asymmetrical SOX2 distribution in ≈25% of the mitoses analyzed was detected. Chromosomal instability, some of which is caused by chromosome segregation defects (CSDs), is a feature of cancer cells that leads to altered gene copy numbers. We compare chromosomal instability (as measured by CSDs) between CSCs (SOX2+) and non-CSCs (SOX2-) from the same OSCC cell lines. CSDs were more common in non-CSCs (SOX2-) than CSCs (SOX2+) and in symmetrical CSC (SOX2+) mitotic pairs than asymmetrical CSC (SOX2+/SOX2-) mitotic pairs. CSCs showed fewer and different types of CSDs after ionizing radiation treatment than non-CSCs. Overall, these data are the first to demonstrate both symmetrical and asymmetrical cell divisions with CSDs in OSCC CSC. Further, the results suggest that CSCs may undergo altered behavior, including therapeutic resistance as a result of chromosomal instability due to chromosome segregation defects. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Identification of individual biofilm-forming bacterial cells using Raman tweezers

NASA Astrophysics Data System (ADS)

Samek, Ota; Bernatová, Silvie; Ježek, Jan; Šiler, Martin; Šerý, Mojmir; Krzyžánek, Vladislav; Hrubanová, Kamila; Zemánek, Pavel; Holá, Veronika; Růžička, Filip

2015-05-01

A method for in vitro identification of individual bacterial cells is presented. The method is based on a combination of optical tweezers for spatial trapping of individual bacterial cells and Raman microspectroscopy for acquisition of spectral "Raman fingerprints" obtained from the trapped cell. Here, Raman spectra were taken from the biofilm-forming cells without the influence of an extracellular matrix and were compared with biofilm-negative cells. Results of principal component analyses of Raman spectra enabled us to distinguish between the two strains of Staphylococcus epidermidis. Thus, we propose that Raman tweezers can become the technique of choice for a clearer understanding of the processes involved in bacterial biofilms which constitute a highly privileged way of life for bacteria, protected from the external environment.

Identification of individual biofilm-forming bacterial cells using Raman tweezers.

PubMed

Samek, Ota; Bernatová, Silvie; Ježek, Jan; Šiler, Martin; Šerý, Mojmir; Krzyžánek, Vladislav; Hrubanová, Kamila; Zemánek, Pavel; Holá, Veronika; Růžička, Filip

2015-05-01

A method for in vitro identification of individual bacterial cells is presented. The method is based on a combination of optical tweezers for spatial trapping of individual bacterial cells and Raman microspectroscopy for acquisition of spectral “Raman fingerprints” obtained from the trapped cell. Here, Raman spectra were taken from the biofilm-forming cells without the influence of an extracellular matrix and were compared with biofilm-negative cells. Results of principal component analyses of Raman spectra enabled us to distinguish between the two strains of Staphylococcus epidermidis. Thus, we propose that Raman tweezers can become the technique of choice for a clearer understanding of the processes involved in bacterial biofilms which constitute a highly privileged way of life for bacteria, protected from the external environment.

Bacterial SPOR domains are recruited to septal peptidoglycan by binding to glycan strands that lack stem peptides

PubMed Central

Yahashiri, Atsushi; Jorgenson, Matthew A.; Weiss, David S.

2015-01-01

Bacterial SPOR domains bind peptidoglycan (PG) and are thought to target proteins to the cell division site by binding to “denuded” glycan strands that lack stem peptides, but uncertainties remain, in part because septal-specific binding has yet to be studied in a purified system. Here we show that fusions of GFP to SPOR domains from the Escherichia coli cell-division proteins DamX, DedD, FtsN, and RlpA all localize to septal regions of purified PG sacculi obtained from E. coli and Bacillus subtilis. Treatment of sacculi with an amidase that removes stem peptides enhanced SPOR domain binding, whereas treatment with a lytic transglycosylase that removes denuded glycans reduced SPOR domain binding. These findings demonstrate unequivocally that SPOR domains localize by binding to septal PG, that the physiologically relevant binding site is indeed a denuded glycan, and that denuded glycans are enriched in septal PG rather than distributed uniformly around the sacculus. Accumulation of denuded glycans in the septal PG of both E. coli and B. subtilis, organisms separated by 1 billion years of evolution, suggests that sequential removal of stem peptides followed by degradation of the glycan backbone is an ancient feature of PG turnover during bacterial cell division. Linking SPOR domain localization to the abundance of a structure (denuded glycans) present only transiently during biogenesis of septal PG provides a mechanism for coordinating the function of SPOR domain proteins with the progress of cell division. PMID:26305949

Timing the start of division in E. coli: a single-cell study

NASA Astrophysics Data System (ADS)

Reshes, G.; Vanounou, S.; Fishov, I.; Feingold, M.

2008-12-01

We monitor the shape dynamics of individual E. coli cells using time-lapse microscopy together with accurate image analysis. This allows measuring the dynamics of single-cell parameters throughout the cell cycle. In previous work, we have used this approach to characterize the main features of single-cell morphogenesis between successive divisions. Here, we focus on the behavior of the parameters that are related to cell division and study their variation over a population of 30 cells. In particular, we show that the single-cell data for the constriction width dynamics collapse onto a unique curve following appropriate rescaling of the corresponding variables. This suggests the presence of an underlying time scale that determines the rate at which the cell cycle advances in each individual cell. For the case of cell length dynamics a similar rescaling of variables emphasizes the presence of a breakpoint in the growth rate at the time when division starts, τc. We also find that the τc of individual cells is correlated with their generation time, τg, and inversely correlated with the corresponding length at birth, L0. Moreover, the extent of the T-period, τg - τc, is apparently independent of τg. The relations between τc, τg and L0 indicate possible compensation mechanisms that maintain cell length variability at about 10%. Similar behavior was observed for both fast-growing cells in a rich medium (LB) and for slower growth in a minimal medium (M9-glucose). To reveal the molecular mechanisms that lead to the observed organization of the cell cycle, we should further extend our approach to monitor the formation of the divisome.

Circular Dichroism studies on the interactions of antimicrobial peptides with bacterial cells

NASA Astrophysics Data System (ADS)

Avitabile, Concetta; D'Andrea, Luca Domenico; Romanelli, Alessandra

2014-03-01

Studying how antimicrobial peptides interact with bacterial cells is pivotal to understand their mechanism of action. In this paper we explored the use of Circular Dichroism to detect the secondary structure of two antimicrobial peptides, magainin 2 and cecropin A, with E. coli bacterial cells. The results of our studies allow us to gain two important information in the context of antimicrobial peptides- bacterial cells interactions: peptides fold mainly due to interaction with LPS, which is the main component of the Gram negative bacteria outer membrane and the time required for the folding on the bacterial cells depends on the peptide analyzed.

Microgravity effects during fertilization, cell division, development, and calcium metabolism in sea urchins

NASA Technical Reports Server (NTRS)

Schatten, Heide

1996-01-01

The overall objectives of this project are to explore the role of microgravity during fertilization, early development, cytoskeletal organization, and skeletal calcium deposition in a model development system: the sea urchin eggs and embryos. While pursuing these objectives, we have also helped to develop, test, and fly the Aquatic Research Facility (ARF) system. Cells were fixed at preselected time points to preserve the structures and organelles of interest with regards to cell biology events during development. The protocols used for the analysis of the results had been developed during the earlier part of this research and were applied for post-flight analysis using light and (immuno)fluorescence microscopy, scanning electron microscopy, and transmission electron microscopy. The structures of interest are: microtubules during fertilization, cell division, and cilia movement; microfilaments during cell surface restructuring and cell division; centrosomes and centrioles during cell division, cell differentiation, and cilia formation and movement; membranes, Golgi, endoplasmic reticulum, mitochondria, and chromosomes at all stages of development; and calcium deposits during spicule formation in late-stage embryos. In addition to further explore aspects important or living in space, several aspects of this research are also aimed at understanding diseases that affect humans on Earth which may be accelerated in space.

Impedance spectroscopy of micro-Droplets reveals activation of Bacterial Mechanosensitive Channels in Hypotonic Solutions

NASA Astrophysics Data System (ADS)

Ebrahimi, Aida; Alam, Muhammad A.

Rapid detection of bacterial pathogens is of great importance in healthcare, food safety, environmental monitoring, and homeland security. Most bacterial detection platforms rely on binary fission (i.e. cell growth) to reach a threshold cell population that can be resolved by the sensing method. Since cell division depends on the bacteria type, the detection time of such methods can vary from hours to days. In contrast, in this work, we show that bacteria cells can be detected within minutes by relying on activation of specific protein channels, i.e. mechanosensitive channels (MS channels). When cells are exposed to hypotonic solutions, MS channels allow efflux of solutes to the external solution which leads to release the excessive membrane tension. Release of the cytoplasmic solutes, in turn, results in increase of the electrical conductance measured by droplet-based impedance sensing. The approach can be an effective technique for fast, pre-screening of bacterial contamination at ultra-low concentration.

Imaging mycobacterial growth and division with a fluorogenic probe.

PubMed

Hodges, Heather L; Brown, Robert A; Crooks, John A; Weibel, Douglas B; Kiessling, Laura L

2018-05-15

Control and manipulation of bacterial populations requires an understanding of the factors that govern growth, division, and antibiotic action. Fluorescent and chemically reactive small molecule probes of cell envelope components can visualize these processes and advance our knowledge of cell envelope biosynthesis (e.g., peptidoglycan production). Still, fundamental gaps remain in our understanding of the spatial and temporal dynamics of cell envelope assembly. Previously described reporters require steps that limit their use to static imaging. Probes that can be used for real-time imaging would advance our understanding of cell envelope construction. To this end, we synthesized a fluorogenic probe that enables continuous live cell imaging in mycobacteria and related genera. This probe reports on the mycolyltransferases that assemble the mycolic acid membrane. This peptidoglycan-anchored bilayer-like assembly functions to protect these cells from antibiotics and host defenses. Our probe, quencher-trehalose-fluorophore (QTF), is an analog of the natural mycolyltransferase substrate. Mycolyltransferases process QTF by diverting their normal transesterification activity to hydrolysis, a process that unleashes fluorescence. QTF enables high contrast continuous imaging and the visualization of mycolyltransferase activity in cells. QTF revealed that mycolyltransferase activity is augmented before cell division and localized to the septa and cell poles, especially at the old pole. This observed localization suggests that mycolyltransferases are components of extracellular cell envelope assemblies, in analogy to the intracellular divisomes and polar elongation complexes. We anticipate QTF can be exploited to detect and monitor mycobacteria in physiologically relevant environments.

Equilibrium between cell division and apoptosis in immortal cells as an alternative to the G1 restriction mechanism in mammalian cells.

PubMed

Dedov, Vadim N; Dedova, Irina V; Nicholson, Garth A

2004-04-01

Starvation arrests cultured mammalian cells in the G(1) restriction point of the cell cycle, whereas cancer cells generally lose the regulatory control of the cell cycle. Human lymphocytes, infected with Epstein-Barr virus (EBV), also lose their cell cycle control and produce immortal lymphoblastoid cell lines. We show that during starvation, EBV-lymphoblasts override the cell cycle arrest in the G(1) restriction point and continue cell division. Simultaneously, starvation activates apoptosis in an approximately half of the daughter cells in each cell generation. Continuos cell division and partial removal of cells by apoptosis results in stabilization of viable cell numbers, where a majority of viable cells are in the G(1) phase of the cell cycle. In contrast to starvation, anticancer drug etoposide activates apoptosis indiscriminately in all EBV-lymphoblasts and convertes all the viable cells into apoptotic. We conclude that the removal of surplus cells by apoptosis may represent a survival mechanism of transformed (i.e., cancer) cell population in nutrient restricted conditions, whereas nontransformed mammalian cells are arrested in the G(1) restriction point of the cell cycle.

Teaching Cell Division to Secondary School Students: An Investigation of Difficulties Experienced by Turkish Teachers

ERIC Educational Resources Information Center

Oztap, Haydar; Ozay, Esra; Oztap, Fulya

2003-01-01

This study examines the difficulties biology teachers face when teaching cell division in the secondary schools of the central part of the Erzurum province in Turkey. During this research, a questionnaire was distributed to a total of 36 secondary school biology teachers. Findings of the study indicate biology teachers perceive cell division as…

Identification of putative Z-ring-associated proteins, involved in cell division in human pathogenic bacteria Helicobacter pylori.

PubMed

Kamran, Mohammad; Sinha, Swati; Dubey, Priyanka; Lynn, Andrew M; Dhar, Suman K

2016-07-01

Cell division in bacteria is initiated by FtsZ, which forms a Z ring at the middle of the cell, between the nucleoids. The Z ring is stabilized by Z ring-associated proteins (Zaps), which crosslink the FtsZ filaments and provide strength. The deletion of Zaps leads to the elongation phenotype with an abnormal Z ring. The components of cell division in Helicobacter pylori are similar to other gram negative bacteria except for the absence of few components including Zaps. Here, we used HHsearch to identify homologs of the missing cell division proteins and got potential hits for ZapA and ZapB, as well as for few other cell division proteins. We further validated the function of the putative ZapA homolog by genetic complementation, immuno-colocalization and biochemical analysis. © 2016 Federation of European Biochemical Societies.

Biolistic transformation of tobacco and maize suspension cells using bacterial cells as microprojectiles.

PubMed

Rasmussen, J L; Kikkert, J R; Roy, M K; Sanford, J C

1994-01-01

We have used both Escherichia coli cells and Agrobacterium tumefaciens cells as microprojectiles to deliver DNA into suspension-cultured tobacco (Nicotiana tabacum L. line NT1) cells using a helium powered biolistic device. In addition, E. coli cells were used as microprojectiles for the transformation of suspension-cultured maize (Zea mays cv. Black Mexican Sweet) cells. Pretreating the bacterial cells with phenol at a concentration of 1.0%, and combining the bacterial cells with tungsten particles increased the rates of transformation. In N. tabacum, we obtained hundreds of transient transformants per bombardment, but were unable to recover any stable transformants. In Z. mays we obtained thousands of transient transformants and an average of six stable transformants per bombardment. This difference is discussed.

Detecting cell division of Pseudomonas aeruginosa bacteria from bright-field microscopy images with hidden conditional random fields.

PubMed

Ong, Lee-Ling S; Xinghua Zhang; Kundukad, Binu; Dauwels, Justin; Doyle, Patrick; Asada, H Harry

2016-08-01

An approach to automatically detect bacteria division with temporal models is presented. To understand how bacteria migrate and proliferate to form complex multicellular behaviours such as biofilms, it is desirable to track individual bacteria and detect cell division events. Unlike eukaryotic cells, prokaryotic cells such as bacteria lack distinctive features, causing bacteria division difficult to detect in a single image frame. Furthermore, bacteria may detach, migrate close to other bacteria and may orientate themselves at an angle to the horizontal plane. Our system trains a hidden conditional random field (HCRF) model from tracked and aligned bacteria division sequences. The HCRF model classifies a set of image frames as division or otherwise. The performance of our HCRF model is compared with a Hidden Markov Model (HMM). The results show that a HCRF classifier outperforms a HMM classifier. From 2D bright field microscopy data, it is a challenge to separate individual bacteria and associate observations to tracks. Automatic detection of sequences with bacteria division will improve tracking accuracy.

Selection of peptidoglycan-specific aptamers for bacterial cells identification.

PubMed

Ferreira, Iêda Mendes; de Souza Lacerda, Camila Maria; de Faria, Lígia Santana; Corrêa, Cristiane Rodrigues; de Andrade, Antero Silva Ribeiro

2014-12-01

Peptidoglycan is a highly complex and essential macromolecule of bacterial outer cell wall; it is a heteropolymer made up of linear glycan strands cross-linked by peptides. Peptidoglycan has a particular composition which makes it a possible target for specific bacterial recognition. Aptamers are single-stranded DNA or RNA oligonucleotides that bind to target molecules with high affinity and specificity. Aptamers can be labeled with different radioisotopes and possess several properties that make them suitable for molecular imaging. The purpose of this study was to obtain aptamers for use as radiopharmaceutical in bacterial infection diagnosis. Two aptamers (Antibac1 and Antibac2) against peptidoglycan were selected through the Systematic Evolution of Ligands by Exponential Enrichment (SELEX) methodology. The dissociation constant (Kd) for Antibac1 was 0.415 + 0.047 μM and for Antibac2 was 1.261 + 0.280 μM. These aptamers labeled with (32)P showed high affinity for Staphylococcus aureus cells. The binding to S. aureus and Escherichia coli in vitro were significantly higher than for Candida albicans and human fibroblasts, demonstrating their specificity for bacterial cells. These results point Antibac1 and Antibac2 as promising tools for bacterial infections identification.

Study of the mechanism of diatom cell division by means of 29Si isotope tracing

NASA Astrophysics Data System (ADS)

Audinot, J.-N.; Guignard, C.; Migeon, H.-N.; Hoffmann, L.

2006-07-01

Diatoms are delicate unicellular organisms enclosed in a silica frustule, that is made up of two valves. Multiplication of the diatoms occurs by ordinary mitotic cell division. During cell division each cell produces two daughter cells, each of them keeping one of the two valves of the mother cell and producing a new valve by absorbing the silicon present in the environment. The NanoSIMS 50 allows ion imaging to be performed on diatoms in order to determine the site of fixation of silicon. The aim of this study was to observe and compare the mechanism of the construction of the new valve after cell division. To this end, different types of diatoms have been transferred in a culture medium enriched with 29Si and after several days, the distribution of the different isotopes of silicon has been determined by NanoSIMS50 imaging. The construction of new valves has been observed and the isotopic ratio has been determined.

Elevated guanosine 5'-diphosphate 3'-diphosphate level inhibits bacterial growth and interferes with FtsZ assembly.

PubMed

Yamaguchi, Takayoshi; Iida, Ken-Ichiro; Shiota, Susumu; Nakayama, Hiroaki; Yoshida, Shin-Ichi

2015-12-01

FtsZ, a protein essential for prokaryotic cell division, forms a ring structure known as the Z-ring at the division site. FtsZ has a GTP binding site and is assembled into linear structures in a GTP-dependent manner in vitro. We assessed whether guanosine 5'-diphosphate 3'-diphosphate (ppGpp), a global regulator of gene expression in starved bacteria, affects cell division in Salmonella Paratyphi A. Elevation of intracellular ppGpp levels by using the relA expression vector induced repression of bacterial growth and incorrect FtsZ assembly. We found that FtsZ forms helical structures in the presence of ppGpp by using the GTP binding site; however, ppGpp levels required to form helical structures were at least 20-fold higher than the required GTP levels in vitro. Furthermore, once formed, helical structures did not change to the straight form even after GTP addition. Our data indicate that elevation of the ppGpp level leads to inhibition of bacterial growth and interferes with FtsZ assembly. © FEMS 2015. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Measuring bacterial cells size with AFM

PubMed Central

Osiro, Denise; Filho, Rubens Bernardes; Assis, Odilio Benedito Garrido; Jorge, Lúcio André de Castro; Colnago, Luiz Alberto

2012-01-01

Atomic Force Microscopy (AFM) can be used to obtain high-resolution topographical images of bacteria revealing surface details and cell integrity. During scanning however, the interactions between the AFM probe and the membrane results in distortion of the images. Such distortions or artifacts are the result of geometrical effects related to bacterial cell height, specimen curvature and the AFM probe geometry. The most common artifact in imaging is surface broadening, what can lead to errors in bacterial sizing. Several methods of correction have been proposed to compensate for these artifacts and in this study we describe a simple geometric model for the interaction between the tip (a pyramidal shaped AFM probe) and the bacterium (Escherichia coli JM-109 strain) to minimize the enlarging effect. Approaches to bacteria immobilization and examples of AFM images analysis are also described. PMID:24031837

Elucidating Duramycin’s Bacterial Selectivity and Mode of Action on the Bacterial Cell Envelope

DOE PAGES

Hasim, Sahar; Allison, David P.; Mendez, Berlin; ...

2018-02-14

The use of naturally occurring antimicrobial peptides provides a promising route to selectively target pathogenic agents and to shape microbiome structure. Lantibiotics, such as duramycin, are one class of bacterially produced peptidic natural products that can selectively inhibit the growth of other bacteria. However, despite longstanding characterization efforts, the microbial selectivity and mode of action of duramycin are still obscure. We describe here a suite of biological, chemical, and physical characterizations that shed new light on the selective and mechanistic aspects of duramycin activity. Bacterial screening assays have been performed using duramycin and Populus-derived bacterial isolates to determine species selectivity.more » Lipidomic profiles of selected resistant and sensitive strains show that the sensitivity of Gram-positive bacteria depends on the presence of phosphatidylethanolamine (PE) in the cell membrane. Further the surface and interface morphology were studied by high resolution atomic force microscopy and showed a progression of cellular changes in the cell envelope after treatment with duramycin for the susceptible bacterial strains. Together, these molecular and cellular level analyses provide insight into duramycin’s mode of action and a better understanding of its selectivity.« less

Elucidating Duramycin’s Bacterial Selectivity and Mode of Action on the Bacterial Cell Envelope

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hasim, Sahar; Allison, David P.; Mendez, Berlin

The use of naturally occurring antimicrobial peptides provides a promising route to selectively target pathogenic agents and to shape microbiome structure. Lantibiotics, such as duramycin, are one class of bacterially produced peptidic natural products that can selectively inhibit the growth of other bacteria. However, despite longstanding characterization efforts, the microbial selectivity and mode of action of duramycin are still obscure. We describe here a suite of biological, chemical, and physical characterizations that shed new light on the selective and mechanistic aspects of duramycin activity. Bacterial screening assays have been performed using duramycin and Populus-derived bacterial isolates to determine species selectivity.more » Lipidomic profiles of selected resistant and sensitive strains show that the sensitivity of Gram-positive bacteria depends on the presence of phosphatidylethanolamine (PE) in the cell membrane. Further the surface and interface morphology were studied by high resolution atomic force microscopy and showed a progression of cellular changes in the cell envelope after treatment with duramycin for the susceptible bacterial strains. Together, these molecular and cellular level analyses provide insight into duramycin’s mode of action and a better understanding of its selectivity.« less

Mechanics of Constriction during Cell Division: A Variational Approach

PubMed Central

Almendro-Vedia, Victor G.; Monroy, Francisco; Cao, Francisco J.

2013-01-01

During symmetric division cells undergo large constriction deformations at a stable midcell site. Using a variational approach, we investigate the mechanical route for symmetric constriction by computing the bending energy of deformed vesicles with rotational symmetry. Forces required for constriction are explicitly computed at constant area and constant volume, and their values are found to be determined by cell size and bending modulus. For cell-sized vesicles, considering typical bending modulus of , we calculate constriction forces in the range . The instability of symmetrical constriction is shown and quantified with a characteristic coefficient of the order of , thus evidencing that cells need a robust mechanism to stabilize constriction at midcell. PMID:23990888

Structure of a bacterial cell surface decaheme electron conduit

USDA-ARS?s Scientific Manuscript database

Some bacterial species are able to utilize extracellular mineral forms of iron and manganese as respiratory electron acceptors. In Shewanella oneidensis this involves decaheme cytochromes that are located on the bacterial cell surface at the termini of trans-outer-membrane electron transfer conduits...

Gibberellin reactivates and maintains ovary-wall cell division causing fruit set in parthenocarpic Citrus species.

PubMed

Mesejo, Carlos; Yuste, Roberto; Reig, Carmina; Martínez-Fuentes, Amparo; Iglesias, Domingo J; Muñoz-Fambuena, Natalia; Bermejo, Almudena; Germanà, M Antonietta; Primo-Millo, Eduardo; Agustí, Manuel

2016-06-01

Citrus is a wide genus in which most of the cultivated species and cultivars are natural parthenocarpic mutants or hybrids (i.e. orange, mandarin, tangerine, grapefruit). The autonomous increase in GA1 ovary concentration during anthesis was suggested as being the stimulus responsible for parthenocarpy in Citrus regardless of the species. To determine the exact GA-role in parthenocarpic fruit set, the following hypothesis was tested: GA triggers and maintains cell division in ovary walls causing fruit set. Obligate and facultative parthenocarpic Citrus species were used as a model system because obligate parthenocarpic Citrus sp (i.e. Citrus unshiu) have higher GA levels and better natural parthenocarpic fruit set compared to other facultative parthenocarpic Citrus (i.e. Citrus clementina). The autonomous activation of GA synthesis in C. unshiu ovary preceded cell division and CYCA1.1 up-regulation (a G2-stage cell cycle regulator) at anthesis setting a high proportion of fruits, whereas C. clementina lacked this GA-biosynthesis and CYCA1.1 up-regulation failing in fruit set. In situ hybridization experiments revealed a tissue-specific expression of GA20ox2 only in the dividing tissues of the pericarp. Furthermore, CYCA1.1 expression correlated endogenous GA1 content with GA3 treatment, which stimulated cell division and ovary growth, mostly in C. clementina. Instead, paclobutrazol (GA biosynthesis inhibitor) negated cell division and reduced fruit set. Results suggest that in parthenocarpic citrus the specific GA synthesis in the ovary walls at anthesis triggers cell division and, thus, the necessary ovary growth rate to set fruit. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

The TCP4 transcription factor of Arabidopsis blocks cell division in yeast at G1 {yields} S transition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aggarwal, Pooja; Padmanabhan, Bhavna; Bhat, Abhay

2011-07-01

Highlights: {yields} TCP4 is a class II TCP transcription factor, that represses cell division in Arabidopsis. {yields} TCP4 expression in yeast retards cell division by blocking G1 {yields} S transition. {yields} Genome-wide expression studies and Western analysis reveals stabilization of cell cycle inhibitor Sic1, as possible mechanism. -- Abstract: The TCP transcription factors control important aspects of plant development. Members of class I TCP proteins promote cell cycle by regulating genes directly involved in cell proliferation. In contrast, members of class II TCP proteins repress cell division. While it has been postulated that class II proteins induce differentiation signal, theirmore » exact role on cell cycle has not been studied. Here, we report that TCP4, a class II TCP protein from Arabidopsis that repress cell proliferation in developing leaves, inhibits cell division by blocking G1 {yields} S transition in budding yeast. Cells expressing TCP4 protein with increased transcriptional activity fail to progress beyond G1 phase. By analyzing global transcriptional status of these cells, we show that expression of a number of cell cycle genes is altered. The possible mechanism of G1 {yields} S arrest is discussed.« less

Bacterial cell identification in differential interference contrast microscopy images.

PubMed

Obara, Boguslaw; Roberts, Mark A J; Armitage, Judith P; Grau, Vicente

2013-04-23

Microscopy image segmentation lays the foundation for shape analysis, motion tracking, and classification of biological objects. Despite its importance, automated segmentation remains challenging for several widely used non-fluorescence, interference-based microscopy imaging modalities. For example in differential interference contrast microscopy which plays an important role in modern bacterial cell biology. Therefore, new revolutions in the field require the development of tools, technologies and work-flows to extract and exploit information from interference-based imaging data so as to achieve new fundamental biological insights and understanding. We have developed and evaluated a high-throughput image analysis and processing approach to detect and characterize bacterial cells and chemotaxis proteins. Its performance was evaluated using differential interference contrast and fluorescence microscopy images of Rhodobacter sphaeroides. Results demonstrate that the proposed approach provides a fast and robust method for detection and analysis of spatial relationship between bacterial cells and their chemotaxis proteins.

Comparison of the cytotoxic effect of polystyrene latex nanoparticles on planktonic cells and bacterial biofilms

NASA Astrophysics Data System (ADS)

Nomura, Toshiyuki; Fujisawa, Eri; Itoh, Shikibu; Konishi, Yasuhiro

2016-06-01

The cytotoxic effect of positively charged polystyrene latex nanoparticles (PSL NPs) was compared between planktonic bacterial cells and bacterial biofilms using confocal laser scanning microscopy, atomic force microscopy, and a colony counting method. Pseudomonas fluorescens, which is commonly used in biofilm studies, was employed as the model bacteria. We found that the negatively charged bacterial surface of the planktonic cells was almost completely covered with positively charged PSL NPs, leading to cell death, as indicated by the NP concentration being greater than that required to achieve single layer coverage. In addition, the relationship between surface coverage and cell viability of P. fluorescens cells correlated well with the findings in other bacterial cells ( Escherichia coli and Lactococcus lactis). However, most of the bacterial cells that formed the biofilm were viable despite the positively charged PSL NPs being highly toxic to planktonic bacterial cells. This indicated that bacterial cells embedded in the biofilm were protected by self-produced extracellular polymeric substances (EPS) that provide resistance to antibacterial agents. In conclusion, mature biofilms covered with EPS exhibit resistance to NP toxicity as well as antibacterial agents.

Evaluation of clinical methods for diagnosing bacterial vaginosis.

PubMed

Gutman, Robert E; Peipert, Jeffrey F; Weitzen, Sherry; Blume, Jeffrey

2005-03-01

To determine whether the current clinical criteria for diagnosing bacterial vaginosis can be simplified by using 2 clinical criteria rather than the standard 3 of 4 criteria (Amsel's criteria). This was a prospective observational study of 269 women undergoing a vaginal examination in the Women's Primary Care Center, Division of Research, or Colposcopy Clinic at Women & Infants Hospital. All 4 clinical criteria for diagnosing bacterial vaginosis were collected, and Gram stain was used as the gold standard. Sensitivity and specificity were calculated for each individual criterion, combinations of criteria, and a colorimetric pH and amine card. Receiver operating characteristic curve was generated to estimate the preferred pH and percentage of clue cells for diagnosing bacterial vaginosis. The prevalence of bacterial vaginosis in our study population was 38.7%. Vaginal pH was the most sensitive of all the criteria, at 89%, and a positive amine odor was the individual criteria with the highest specificity, at 93%. Similar specificity was seen with combinations of 2 criteria and Amsel's criteria. Receiver operating characteristic curve analysis yielded a preferred pH and percentage of clue cells of 5.0 and 20%, respectively. However, a pH of 4.5 or greater improves sensitivity with minimal loss of specificity. The clinical criteria for diagnosing bacterial vaginosis can be simplified to 2 clinical criteria without loss of sensitivity and specificity.

Individuality and universality in the growth-division laws of single E. coli cells

NASA Astrophysics Data System (ADS)

Kennard, Andrew S.; Osella, Matteo; Javer, Avelino; Grilli, Jacopo; Nghe, Philippe; Tans, Sander J.; Cicuta, Pietro; Cosentino Lagomarsino, Marco

2016-01-01

The mean size of exponentially dividing Escherichia coli cells in different nutrient conditions is known to depend on the mean growth rate only. However, the joint fluctuations relating cell size, doubling time, and individual growth rate are only starting to be characterized. Recent studies in bacteria reported a universal trend where the spread in both size and doubling times is a linear function of the population means of these variables. Here we combine experiments and theory and use scaling concepts to elucidate the constraints posed by the second observation on the division control mechanism and on the joint fluctuations of sizes and doubling times. We found that scaling relations based on the means collapse both size and doubling-time distributions across different conditions and explain how the shape of their joint fluctuations deviates from the means. Our data on these joint fluctuations highlight the importance of cell individuality: Single cells do not follow the dependence observed for the means between size and either growth rate or inverse doubling time. Our calculations show that these results emerge from a broad class of division control mechanisms requiring a certain scaling form of the "division hazard rate function," which defines the probability rate of dividing as a function of measurable parameters. This "model free" approach gives a rationale for the universal body-size distributions observed in microbial ecosystems across many microbial species, presumably dividing with multiple mechanisms. Additionally, our experiments show a crossover between fast and slow growth in the relation between individual-cell growth rate and division time, which can be understood in terms of different regimes of genome replication control.

Three-dimensional patterns of cell division and expansion throughout the development of Arabidopsis thaliana leaves.

PubMed

Kalve, Shweta; Fotschki, Joanna; Beeckman, Tom; Vissenberg, Kris; Beemster, Gerrit T S

2014-12-01

Variations in size and shape of multicellular organs depend on spatio-temporal regulation of cell division and expansion. Here, cell division and expansion rates were quantified relative to the three spatial axes in the first leaf pair of Arabidopsis thaliana. The results show striking differences in expansion rates: the expansion rate in the petiole is higher than in the leaf blade; expansion rates in the lateral direction are higher than longitudinal rates between 5 and 10 days after stratification, but become equal at later stages of leaf blade development; and anticlinal expansion co-occurs with, but is an order of magnitude slower than periclinal expansion. Anticlinal expansion rates also differed greatly between tissues: the highest rates occurred in the spongy mesophyll and the lowest in the epidermis. Cell division rates were higher and continued for longer in the epidermis compared with the palisade mesophyll, causing a larger increase of palisade than epidermal cell area over the course of leaf development. The cellular dynamics underlying the effect of shading on petiole length and leaf thickness were then investigated. Low light reduced leaf expansion rates, which was partly compensated by increased duration of the growth phase. Inversely, shading enhanced expansion rates in the petiole, so that the blade to petiole ratio was reduced by 50%. Low light reduced leaf thickness by inhibiting anticlinal cell expansion rates. This effect on cell expansion was preceded by an effect on cell division, leading to one less layer of palisade cells. The two effects could be uncoupled by shifting plants to contrasting light conditions immediately after germination. This extended kinematic analysis maps the spatial and temporal heterogeneity of cell division and expansion, providing a framework for further research to understand the molecular regulatory mechanisms involved. © The Author 2014. Published by Oxford University Press on behalf of the Society for

Combination of Synthetic Chemistry and Live-Cell Imaging Identified a Rapid Cell Division Inhibitor in Tobacco and Arabidopsis thaliana.

PubMed

Nambo, Masakazu; Kurihara, Daisuke; Yamada, Tomomi; Nishiwaki-Ohkawa, Taeko; Kadofusa, Naoya; Kimata, Yusuke; Kuwata, Keiko; Umeda, Masaaki; Ueda, Minako

2016-11-01

Cell proliferation is crucial to the growth of multicellular organisms, and thus the proper control of cell division is important to prevent developmental arrest or overgrowth. Nevertheless, tools for controlling cell proliferation are still poor in plant. To develop novel tools, we focused on a specific compound family, triarylmethanes, whose members show various antiproliferative activities in animals. By combining organic chemistry to create novel and diverse compounds containing the triarylmethyl moiety and biological screens based on live-cell imaging of a fluorescently labeled tobacco Bright Yellow-2 (BY-2) culture cell line (Nicotiana tabacum), we isolated (3-furyl)diphenylmethane as a strong but partially reversible inhibitor of plant cell division. We also found that this agent had efficient antiproliferative activity in developing organs of Arabidopsis thaliana without causing secondary defects in cell morphology, and induced rapid cell division arrest independent of the cell cycle stage. Given that (3-furyl)diphenylmethane did not affect the growth of a human cell line (HeLa) and a budding yeast (Saccharomyces cerevisiae), it should act specifically on plants. Taking our results together, we propose that the combination of desired chemical synthesis and detailed biological analysis is an effective tool to create novel drugs, and that (3-furyl)diphenylmethane is a specific antiproliferative agent for plants. © The Author 2016. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Harnessing cell-to-cell variations to probe bacterial structure and biophysics

NASA Astrophysics Data System (ADS)

Cass, Julie A.

Advances in microscopy and biotechnology have given us novel insights into cellular biology and physics. While bacteria were long considered to be relatively unstructured, the development of fluorescence microscopy techniques, and spatially and temporally resolved high-throughput quantitative studies, have uncovered that the bacterial cell is highly organized, and its structure rigorously maintained. In this thesis I will describe our gateTool software, designed to harness cell-to-cell variations to probe bacterial structure, and discuss two exciting aspects of structure that we have employed gateTool to investigate: (i) chromosome organization and the cellular mechanisms for controlling DNA dynamics, and (ii) the study of cell wall synthesis, and how the genes in the synthesis pathway impact cellular shape. In the first project, we develop a spatial and temporal mapping of cell-cycle-dependent chromosomal organization, and use this quantitative map to discover that chromosomal loci segregate from midcell with universal dynamics. In the second project, I describe preliminary time- lapse and snapshot imaging analysis suggesting phentoypical coherence across peptidoglycan synthesis pathways.

Inhibition of cell division in hupA hupB mutant bacteria lacking HU protein.

PubMed Central

Dri, A M; Rouviere-Yaniv, J; Moreau, P L

1991-01-01

Escherichia coli hupA hypB double mutants that lack HU protein have severe cellular defects in cell division, DNA folding, and DNA partitioning. Here we show that the sfiA11 mutation, which alters the SfiA cell division inhibitor, reduces filamentation and production of anucleate cells in AB1157 hupA hupB strains. However, lexA3(Ind-) and sfiB(ftsZ)114 mutations, which normally counteract the effect of the SfiA inhibitor, could not restore a normal morphology to hupA hupB mutant bacteria. The LexA repressor, which controls the expression of the sfiA gene, was present in hupA hupB mutant bacteria in concentrations half of those of the parent bacteria, but this decrease was independent of the specific cleavage of the LexA repressor by activated RecA protein. One possibility to account for the filamentous morphology of hupA hupB mutant bacteria is that the lack of HU protein alters the expression of specific genes, such as lexA and fts cell division genes. Images PMID:2019558

Note: An automated image analysis method for high-throughput classification of surface-bound bacterial cell motions.

PubMed

Shen, Simon; Syal, Karan; Tao, Nongjian; Wang, Shaopeng

2015-12-01

We present a Single-Cell Motion Characterization System (SiCMoCS) to automatically extract bacterial cell morphological features from microscope images and use those features to automatically classify cell motion for rod shaped motile bacterial cells. In some imaging based studies, bacteria cells need to be attached to the surface for time-lapse observation of cellular processes such as cell membrane-protein interactions and membrane elasticity. These studies often generate large volumes of images. Extracting accurate bacterial cell morphology features from these images is critical for quantitative assessment. Using SiCMoCS, we demonstrated simultaneous and automated motion tracking and classification of hundreds of individual cells in an image sequence of several hundred frames. This is a significant improvement from traditional manual and semi-automated approaches to segmenting bacterial cells based on empirical thresholds, and a first attempt to automatically classify bacterial motion types for motile rod shaped bacterial cells, which enables rapid and quantitative analysis of various types of bacterial motion.

Comparison of epifluorescent viable bacterial count methods

NASA Technical Reports Server (NTRS)

Rodgers, E. B.; Huff, T. L.

1992-01-01

Two methods, the 2-(4-Iodophenyl) 3-(4-nitrophenyl) 5-phenyltetrazolium chloride (INT) method and the direct viable count (DVC), were tested and compared for their efficiency for the determination of the viability of bacterial populations. Use of the INT method results in the formation of a dark spot within each respiring cell. The DVC method results in elongation or swelling of growing cells that are rendered incapable of cell division. Although both methods are subjective and can result in false positive results, the DVC method is best suited to analysis of waters in which the number of different types of organisms present in the same sample is assumed to be small, such as processed waters. The advantages and disadvantages of each method are discussed.

Different binarization processes validated against manual counts of fluorescent bacterial cells.

PubMed

Tamminga, Gerrit G; Paulitsch-Fuchs, Astrid H; Jansen, Gijsbert J; Euverink, Gert-Jan W

2016-09-01

State of the art software methods (such as fixed value approaches or statistical approaches) to create a binary image of fluorescent bacterial cells are not as accurate and precise as they should be for counting bacteria and measuring their area. To overcome these bottlenecks, we introduce biological significance to obtain a binary image from a greyscale microscopic image. Using our biological significance approach we are able to automatically count about the same number of cells as an individual researcher would do by manual/visual counting. Using the fixed value or statistical approach to obtain a binary image leads to about 20% less cells in automatic counting. In our procedure we included the area measurements of the bacterial cells to determine the right parameters for background subtraction and threshold values. In an iterative process the threshold and background subtraction values were incremented until the number of particles smaller than a typical bacterial cell is less than the number of bacterial cells with a certain area. This research also shows that every image has a specific threshold with respect to the optical system, magnification and staining procedure as well as the exposure time. The biological significance approach shows that automatic counting can be performed with the same accuracy, precision and reproducibility as manual counting. The same approach can be used to count bacterial cells using different optical systems (Leica, Olympus and Navitar), magnification factors (200× and 400×), staining procedures (DNA (Propidium Iodide) and RNA (FISH)) and substrates (polycarbonate filter or glass). Copyright © 2016 Elsevier B.V. All rights reserved.

Interplay between intrinsic noise and the stochasticity of the cell cycle in bacterial colonies.

PubMed

Canela-Xandri, Oriol; Sagués, Francesc; Buceta, Javier

2010-06-02

Herein we report on the effects that different stochastic contributions induce in bacterial colonies in terms of protein concentration and production. In particular, we consider for what we believe to be the first time cell-to-cell diversity due to the unavoidable randomness of the cell-cycle duration and its interplay with other noise sources. To that end, we model a recent experimental setup that implements a protein dilution protocol by means of division events to characterize the gene regulatory function at the single cell level. This approach allows us to investigate the effect of different stochastic terms upon the total randomness experimentally reported for the gene regulatory function. In addition, we show that the interplay between intrinsic fluctuations and the stochasticity of the cell-cycle duration leads to different constructive roles. On the one hand, we show that there is an optimal value of protein concentration (alternatively an optimal value of the cell cycle phase) such that the noise in protein concentration attains a minimum. On the other hand, we reveal that there is an optimal value of the stochasticity of the cell cycle duration such that the coherence of the protein production with respect to the colony average production is maximized. The latter can be considered as a novel example of the recently reported phenomenon of diversity induced resonance. Copyright (c) 2010 Biophysical Society. Published by Elsevier Inc. All rights reserved.

The Selective Value of Bacterial Shape

PubMed Central

Young, Kevin D.

2006-01-01

Why do bacteria have shape? Is morphology valuable or just a trivial secondary characteristic? Why should bacteria have one shape instead of another? Three broad considerations suggest that bacterial shapes are not accidental but are biologically important: cells adopt uniform morphologies from among a wide variety of possibilities, some cells modify their shape as conditions demand, and morphology can be tracked through evolutionary lineages. All of these imply that shape is a selectable feature that aids survival. The aim of this review is to spell out the physical, environmental, and biological forces that favor different bacterial morphologies and which, therefore, contribute to natural selection. Specifically, cell shape is driven by eight general considerations: nutrient access, cell division and segregation, attachment to surfaces, passive dispersal, active motility, polar differentiation, the need to escape predators, and the advantages of cellular differentiation. Bacteria respond to these forces by performing a type of calculus, integrating over a number of environmental and behavioral factors to produce a size and shape that are optimal for the circumstances in which they live. Just as we are beginning to answer how bacteria create their shapes, it seems reasonable and essential that we expand our efforts to understand why they do so. PMID:16959965

Bacterial Actins.

PubMed

Izoré, Thierry; van den Ent, Fusinita

2017-01-01

A diverse set of protein polymers, structurally related to actin filaments contributes to the organization of bacterial cells as cytomotive or cytoskeletal filaments. This chapter describes actin homologs encoded by bacterial chromosomes. MamK filaments, unique to magnetotactic bacteria, help establishing magnetic biological compasses by interacting with magnetosomes. Magnetosomes are intracellular membrane invaginations containing biomineralized crystals of iron oxide that are positioned by MamK along the long-axis of the cell. FtsA is widespread across bacteria and it is one of the earliest components of the divisome to arrive at midcell, where it anchors the cell division machinery to the membrane. FtsA binds directly to FtsZ filaments and to the membrane through its C-terminus. FtsA shows altered domain architecture when compared to the canonical actin fold. FtsA's subdomain 1C replaces subdomain 1B of other members of the actin family and is located on the opposite side of the molecule. Nevertheless, when FtsA assembles into protofilaments, the protofilament structure is preserved, as subdomain 1C replaces subdomain IB of the following subunit in a canonical actin filament. MreB has an essential role in shape-maintenance of most rod-shaped bacteria. Unusually, MreB filaments assemble from two protofilaments in a flat and antiparallel arrangement. This non-polar architecture implies that both MreB filament ends are structurally identical. MreB filaments bind directly to membranes where they interact with both cytosolic and membrane proteins, thereby forming a key component of the elongasome. MreB filaments in cells are short and dynamic, moving around the long axis of rod-shaped cells, sensing curvature of the membrane and being implicated in peptidoglycan synthesis.

Uhrf1 controls the self-renewal versus differentiation of hematopoietic stem cells by epigenetically regulating the cell-division modes

PubMed Central

Zhao, Jingyao; Chen, Xufeng; Song, Guangrong; Zhang, Jiali; Liu, Haifeng; Liu, Xiaolong

2017-01-01

Hematopoietic stem cells (HSCs) are able to both self-renew and differentiate. However, how individual HSC makes the decision between self-renewal and differentiation remains largely unknown. Here we report that ablation of the key epigenetic regulator Uhrf1 in the hematopoietic system depletes the HSC pool, leading to hematopoietic failure and lethality. Uhrf1-deficient HSCs display normal survival and proliferation, yet undergo erythroid-biased differentiation at the expense of self-renewal capacity. Notably, Uhrf1 is required for the establishment of DNA methylation patterns of erythroid-specific genes during HSC division. The expression of these genes is enhanced in the absence of Uhrf1, which disrupts the HSC-division modes by promoting the symmetric differentiation and suppressing the symmetric self-renewal. Moreover, overexpression of one of the up-regulated genes, Gata1, in HSCs is sufficient to phenocopy Uhrf1-deficient HSCs, which show impaired HSC symmetric self-renewal and increased differentiation commitment. Taken together, our findings suggest that Uhrf1 controls the self-renewal versus differentiation of HSC through epigenetically regulating the cell-division modes, thus providing unique insights into the relationship among Uhrf1-mediated DNA methylation, cell-division mode, and HSC fate decision. PMID:27956603

Isolation of biologically active nanomaterial (inclusion bodies) from bacterial cells.

PubMed

Peternel, Spela; Komel, Radovan

2010-09-10

In recent years bacterial inclusion bodies (IBs) were recognised as highly pure deposits of active proteins inside bacterial cells. Such active nanoparticles are very interesting for further downstream protein isolation, as well as for many other applications in nanomedicine, cosmetic, chemical and pharmaceutical industry.To prepare large quantities of a high quality product, the whole bioprocess has to be optimised. This includes not only the cultivation of the bacterial culture, but also the isolation step itself, which can be of critical importance for the production process.To determine the most appropriate method for the isolation of biologically active nanoparticles, three methods for bacterial cell disruption were analyzed. In this study, enzymatic lysis and two mechanical methods, high-pressure homogenization and sonication, were compared.During enzymatic lysis the enzyme lysozyme was found to attach to the surface of IBs, and it could not be removed by simple washing. As this represents an additional impurity in the engineered nanoparticles, we concluded that enzymatic lysis is not the most suitable method for IBs isolation.During sonication proteins are released (lost) from the surface of IBs and thus the surface of IBs appears more porous when compared to the other two methods. We also found that the acoustic output power needed to isolate the IBs from bacterial cells actually damages proteins structures, thereby causing a reduction in biological activity.High-pressure homogenization also caused some damage to IBs, however the protein loss from the IBs was negligible. Furthermore, homogenization had no side-effects on protein biological activity. The study shows that among the three methods tested, homogenization is the most appropriate method for the isolation of active nanoparticles from bacterial cells.

CedA is a novel Escherichia coli protein that activates the cell division inhibited by chromosomal DNA over-replication.

PubMed

Katayama, T; Takata, M; Sekimizu, K

1997-11-01

We isolated and characterized a new gene related to the control of cell division regulation in Escherichia coli. At 30 degrees C, the dnaAcos mutant causes over-replication of the chromosome, and colony formation is inhibited. We found that, at this temperature, the dnaAcos cells form filaments; therefore, septum formation is inhibited. This inhibition was independent of SfiA, an inhibitor of the septum-forming protein, FtsZ. To identify factors involved in this pathway of inhibition, we isolated seven multicopy suppressors for the cold-sensitive phenotype of the dnaAcos mutant. One of these proved to be a previously unknown gene, which we named cedA. This gene encoded a 12 kDa protein and resided at 38.9min on the E. coli genome map. A multicopy supply of the cedA gene to the dnaAcos cells did not repress over-replication of the chromosome but did stimulate cell division of the host, the result being growth of cells with an abnormally elevated chromosomal copy number. Therefore, the expression level of the cedA gene seems to be important for inhibiting cell division of the dnaAcos mutant at 30 degrees C. We propose that over-replication of the chromosome activates a pathway for inhibiting cell division and that the cedA gene modulates this division control. In the dnaA+ background, cedA also seems to affect cell division.

Stem cell divisions, somatic mutations, cancer etiology, and cancer prevention.

PubMed

Tomasetti, Cristian; Li, Lu; Vogelstein, Bert

2017-03-24

Cancers are caused by mutations that may be inherited, induced by environmental factors, or result from DNA replication errors (R). We studied the relationship between the number of normal stem cell divisions and the risk of 17 cancer types in 69 countries throughout the world. The data revealed a strong correlation (median = 0.80) between cancer incidence and normal stem cell divisions in all countries, regardless of their environment. The major role of R mutations in cancer etiology was supported by an independent approach, based solely on cancer genome sequencing and epidemiological data, which suggested that R mutations are responsible for two-thirds of the mutations in human cancers. All of these results are consistent with epidemiological estimates of the fraction of cancers that can be prevented by changes in the environment. Moreover, they accentuate the importance of early detection and intervention to reduce deaths from the many cancers arising from unavoidable R mutations. Copyright © 2017, American Association for the Advancement of Science.

ER-mitochondria contacts couple mtDNA synthesis with mitochondrial division in human cells.

PubMed

Lewis, Samantha C; Uchiyama, Lauren F; Nunnari, Jodi

2016-07-15

Mitochondrial DNA (mtDNA) encodes RNAs and proteins critical for cell function. In human cells, hundreds to thousands of mtDNA copies are replicated asynchronously, packaged into protein-DNA nucleoids, and distributed within a dynamic mitochondrial network. The mechanisms that govern how nucleoids are chosen for replication and distribution are not understood. Mitochondrial distribution depends on division, which occurs at endoplasmic reticulum (ER)-mitochondria contact sites. These sites were spatially linked to a subset of nucleoids selectively marked by mtDNA polymerase and engaged in mtDNA synthesis--events that occurred upstream of mitochondrial constriction and division machine assembly. Our data suggest that ER tubules proximal to nucleoids are necessary but not sufficient for mtDNA synthesis. Thus, ER-mitochondria contacts coordinate licensing of mtDNA synthesis with division to distribute newly replicated nucleoids to daughter mitochondria. Copyright © 2016, American Association for the Advancement of Science.

Accurate Cell Division in Bacteria: How Does a Bacterium Know Where its Middle Is?

NASA Astrophysics Data System (ADS)

Howard, Martin; Rutenberg, Andrew

2004-03-01

I will discuss the physical principles lying behind the acquisition of accurate positional information in bacteria. A good application of these ideas is to the rod-shaped bacterium E. coli which divides precisely at its cellular midplane. This positioning is controlled by the Min system of proteins. These proteins coherently oscillate from end to end of the bacterium. I will present a reaction-diffusion model that describes the diffusion of the Min proteins, and their binding/unbinding from the cell membrane. The system possesses an instability that spontaneously generates the Min oscillations, which control accurate placement of the midcell division site. I will then discuss the role of fluctuations in protein dynamics, and investigate whether fluctuations set optimal protein concentration levels. Finally I will examine cell division in a different bacteria, B. subtilis. where different physical principles are used to regulate accurate cell division. See: Howard, Rutenberg, de Vet: Dynamic compartmentalization of bacteria: accurate division in E. coli. Phys. Rev. Lett. 87 278102 (2001). Howard, Rutenberg: Pattern formation inside bacteria: fluctuations due to the low copy number of proteins. Phys. Rev. Lett. 90 128102 (2003). Howard: A mechanism for polar protein localization in bacteria. J. Mol. Biol. 335 655-663 (2004).

How to Foster an Understanding of Growth and Cell Division

ERIC Educational Resources Information Center

Kruger, Dirk; Fleige, Jennifer; Riemeier, Tanja

2006-01-01

The study presents the frequencies of students' conceptions of growth and cell division before and after one hour of instruction. The investigation supplements qualitative results by directing attention to those conceptions which might occur most frequently to students: teachers can then concentrate their preparation on practical requirements. A…

Ubiquitous marine bacterium inhibits diatom cell division.

PubMed

van Tol, Helena M; Amin, Shady A; Armbrust, E Virginia

2017-01-01

Intricate relationships between microorganisms structure the exchange of molecules between taxa, driving their physiology and evolution. On a global scale, this molecular trade is an integral component of biogeochemical cycling. As important microorganisms in the world's oceans, diatoms and bacteria have a large impact on marine biogeochemistry. Here, we describe antagonistic effects of the globally distributed flavobacterium Croceibacter atlanticus on a phylogenetically diverse group of diatoms. We used the model diatom Thalassiosira pseudonana to study the antagonistic impact in more detail. In co-culture, C. atlanticus attaches to T. pseudonana and inhibits cell division, inducing diatom cells to become larger and increase in chlorophyll a fluorescence. These changes could be explained by an absence of cytokinesis that causes individual T. pseudonana cells to elongate, accumulate more plastids and become polyploid. These morphological changes could benefit C. atlanticus by augmenting the colonizable surface area of the diatom, its photosynthetic capabilities and possibly its metabolic secretions.

Two Forkhead transcription factors regulate the division of cardiac progenitor cells by a Polo-dependent pathway

PubMed Central

Ahmad, Shaad M.; Tansey, Terese R.; Busser, Brian W.; Nolte, Michael T.; Jeffries, Neal; Gisselbrecht, Stephen S.; Rusan, Nasser M.; Michelson, Alan M.

2012-01-01

SUMMARY The development of a complex organ requires the specification of appropriate numbers of each of its constituent cell types, as well as their proper differentiation and correct positioning relative to each other. During Drosophila cardiogenesis, all three of these processes are controlled by jumeau (jumu) and Checkpoint suppressor homologue (CHES-1-like), two genes encoding forkhead transcription factors that we discovered utilizing an integrated genetic, genomic and computational strategy for identifying genes expressed in the developing Drosophila heart. Both jumu and CHES-1-like are required during asymmetric cell division for the derivation of two distinct cardiac cell types from their mutual precursor, and in symmetric cell divisions that produce yet a third type of heart cell. jumu and CHES-1-like control the division of cardiac progenitors by regulating the activity of Polo, a kinase involved in multiple steps of mitosis. This pathway demonstrates how transcription factors integrate diverse developmental processes during organogenesis. PMID:22814603

Division rate, cell size and proteome allocation: impact on gene expression noise and implications for the dynamics of genetic circuits

PubMed Central

2018-01-01

The cell division rate, size and gene expression programmes change in response to external conditions. These global changes impact on average concentrations of biomolecule and their variability or noise. Gene expression is inherently stochastic, and noise levels of individual proteins depend on synthesis and degradation rates as well as on cell-cycle dynamics. We have modelled stochastic gene expression inside growing and dividing cells to study the effect of division rates on noise in mRNA and protein expression. We use assumptions and parameters relevant to Escherichia coli, for which abundant quantitative data are available. We find that coupling of transcription, but not translation rates to the rate of cell division can result in protein concentration and noise homeostasis across conditions. Interestingly, we find that the increased cell size at fast division rates, observed in E. coli and other unicellular organisms, buffers noise levels even for proteins with decreased expression at faster growth. We then investigate the functional importance of these regulations using gene regulatory networks that exhibit bi-stability and oscillations. We find that network topology affects robustness to changes in division rate in complex and unexpected ways. In particular, a simple model of persistence, based on global physiological feedback, predicts increased proportion of persister cells at slow division rates. Altogether, our study reveals how cell size regulation in response to cell division rate could help controlling gene expression noise. It also highlights that understanding circuits' robustness across growth conditions is key for the effective design of synthetic biological systems. PMID:29657814

Facile method to stain the bacterial cell surface for super-resolution fluorescence microscopy†

PubMed Central

Gunsolus, Ian L.; Hu, Dehong; Mihai, Cosmin; Lohse, Samuel E.; Lee, Chang-soo; Torelli, Marco D.; Hamers, Robert J.; Murhpy, Catherine J.; Orr, Galya

2015-01-01

A method to fluorescently stain the surfaces of both Gram-negative and Gram-positive bacterial cells compatible with super-resolution fluorescence microscopy is presented. This method utilizes a commercially-available fluorescent probe to label primary amines at the surface of the cell. We demonstrate eficient staining of two bacterial strains, the Gram-negative Shewanella oneidensis MR-1 and the Gram-positive Bacillus subtilis 168. Using structured illumination microscopy and stochastic optical reconstruction microscopy, which require high quantum yield or specialized dyes, we show that this staining method may be used to resolve the bacterial cell surface with sub-diffraction-limited resolution. We further use this method to identify localization patterns of nanomaterials, specifically cadmium selenide quantum dots, following interaction with bacterial cells. PMID:24816810

Facile method to stain the bacterial cell surface for super-resolution fluorescence microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gunsolus, Ian L.; Hu, Dehong; Mihai, Cosmin

A method to fluorescently stain the surfaces of both Gram-negative and Gram-positive bacterial cells compatible with super-resolution fluorescence microscopy is presented. This method utilizes a commercially-available fluorescent probe to label primary amines at the surface of the cell. We demonstrate efficient staining of two bacterial strains, the Gram-negative Shewanella oneidensis MR-1 and the Gram-positive Bacillus subtilis 168. Using structured illumination microscopy and stochastic optical reconstruction microscopy, which require high quantum yield or specialized dyes, we show that this staining method may be used to resolve the bacterial cell surface with sub-diffraction-limited resolution. We further use this method to identify localizationmore » patterns of nanomaterials, specifically cadmium selenide quantum dots, following interaction with bacterial cells.« less

Control of the proportion of inner cells by asymmetric divisions and the ensuing resilience of cloned rabbit embryos

PubMed Central

Duranthon, Véronique

2018-01-01

ABSTRACT Mammalian embryo cloning by nuclear transfer has a low success rate. This is hypothesized to correlate with a high variability of early developmental steps that segregate outer cells, which are fated to extra-embryonic tissues, from inner cells, which give rise to the embryo proper. Exploring the cell lineage of wild-type embryos and clones, imaged in toto until hatching, highlights the respective contributions of cell proliferation, death and asymmetric divisions to phenotypic variability. Preferential cell death of inner cells in clones, probably pertaining to the epigenetic plasticity of the transferred nucleus, is identified as a major difference with effects on the proportion of inner cell. In wild type and clones, similar patterns of outer cell asymmetric divisions are shown to be essential to the robust proportion of inner cells observed in wild type. Asymmetric inner cell division, which is not described in mice, is identified as a regulator of the proportion of inner cells and likely gives rise to resilient clones. PMID:29567671

Myeloid-Derived Suppressor Cells in Bacterial Infections

PubMed Central

Ost, Michael; Singh, Anurag; Peschel, Andreas; Mehling, Roman; Rieber, Nikolaus; Hartl, Dominik

2016-01-01

Myeloid-derived suppressor cells (MDSCs) comprise monocytic and granulocytic innate immune cells with the capability of suppressing T- and NK-cell responses. While the role of MDSCs has been studied in depth in malignant diseases, the understanding of their regulation and function in infectious disease conditions has just begun to evolve. Here we summarize and discuss the current view how MDSCs participate in bacterial infections and how this knowledge could be exploited for potential future therapeutics. PMID:27066459

Isolation of biologically active nanomaterial (inclusion bodies) from bacterial cells

PubMed Central

2010-01-01

Background In recent years bacterial inclusion bodies (IBs) were recognised as highly pure deposits of active proteins inside bacterial cells. Such active nanoparticles are very interesting for further downstream protein isolation, as well as for many other applications in nanomedicine, cosmetic, chemical and pharmaceutical industry. To prepare large quantities of a high quality product, the whole bioprocess has to be optimised. This includes not only the cultivation of the bacterial culture, but also the isolation step itself, which can be of critical importance for the production process. To determine the most appropriate method for the isolation of biologically active nanoparticles, three methods for bacterial cell disruption were analyzed. Results In this study, enzymatic lysis and two mechanical methods, high-pressure homogenization and sonication, were compared. During enzymatic lysis the enzyme lysozyme was found to attach to the surface of IBs, and it could not be removed by simple washing. As this represents an additional impurity in the engineered nanoparticles, we concluded that enzymatic lysis is not the most suitable method for IBs isolation. During sonication proteins are released (lost) from the surface of IBs and thus the surface of IBs appears more porous when compared to the other two methods. We also found that the acoustic output power needed to isolate the IBs from bacterial cells actually damages proteins structures, thereby causing a reduction in biological activity. High-pressure homogenization also caused some damage to IBs, however the protein loss from the IBs was negligible. Furthermore, homogenization had no side-effects on protein biological activity. Conclusions The study shows that among the three methods tested, homogenization is the most appropriate method for the isolation of active nanoparticles from bacterial cells. PMID:20831775

The Antibacterial Cell Division Inhibitor PC190723 Is an FtsZ Polymer-stabilizing Agent That Induces Filament Assembly and Condensation*

PubMed Central

Andreu, José M.; Schaffner-Barbero, Claudia; Huecas, Sonia; Alonso, Dulce; Lopez-Rodriguez, María L.; Ruiz-Avila, Laura B.; Núñez-Ramírez, Rafael; Llorca, Oscar; Martín-Galiano, Antonio J.

2010-01-01

Cell division protein FtsZ can form single-stranded filaments with a cooperative behavior by self-switching assembly. Subsequent condensation and bending of FtsZ filaments are important for the formation and constriction of the cytokinetic ring. PC190723 is an effective bactericidal cell division inhibitor that targets FtsZ in the pathogen Staphylococcus aureus and Bacillus subtilis and does not affect Escherichia coli cells, which apparently binds to a zone equivalent to the binding site of the antitumor drug taxol in tubulin (Haydon, D. J., Stokes, N. R., Ure, R., Galbraith, G., Bennett, J. M., Brown, D. R., Baker, P. J., Barynin, V. V., Rice, D. W., Sedelnikova, S. E., Heal, J. R., Sheridan, J. M., Aiwale, S. T., Chauhan, P. K., Srivastava, A., Taneja, A., Collins, I., Errington, J., and Czaplewski, L. G. (2008) Science 312, 1673–1675). We have found that the benzamide derivative PC190723 is an FtsZ polymer-stabilizing agent. PC190723 induced nucleated assembly of Bs-FtsZ into single-stranded coiled protofilaments and polymorphic condensates, including bundles, coils, and toroids, whose formation could be modulated with different solution conditions. Under conditions for reversible assembly of Bs-FtsZ, PC190723 binding reduced the GTPase activity and induced the formation of straight bundles and ribbons, which was also observed with Sa-FtsZ but not with nonsusceptible Ec-FtsZ. The fragment 2,6-difluoro-3-methoxybenzamide also induced Bs-FtsZ bundling. We propose that polymer stabilization by PC190723 suppresses in vivo FtsZ polymer dynamics and bacterial division. The biochemical action of PC190723 on FtsZ parallels that of the microtubule-stabilizing agent taxol on the eukaryotic structural homologue tubulin. Both taxol and PC190723 stabilize polymers against disassembly by preferential binding to each assembled protein. It is yet to be investigated whether both ligands target structurally related assembly switches. PMID:20212044

Foundation laid for understanding essentials of cell division | Center for Cancer Research

Cancer.gov

NCI Center for Cancer Research (CCR) scientists reported new molecular insights into understanding a critical aspect of cell division through a cross-disciplinary effort that combines cryo-electron microscopy (cryo-EM), biochemical and cell biological approaches. Errors in segregation of chromosomes during mitosis can lead to an aberrant number of chromosomes, a condition

Electroporation of Functional Bacterial Effectors into Mammalian Cells

DOE PAGES

Sontag, Ryan L.; Mihai, Cosmin; Orr, Galya; ...

2015-01-19

Electroporation was used to insert purified bacterial virulence effector proteins directly into living eukaryotic cells. Protein localization was monitored by confocal immunofluorescence microscopy. This method allows for studies on trafficking, function, and protein-protein interactions using active exogenous proteins, avoiding the need for heterologous expression in eukaryotic cells.

Plant Cell Division Analyzed by Transient Agrobacterium-Mediated Transformation of Tobacco BY-2 Cells.

PubMed

Buschmann, Henrik

2016-01-01

The continuing analysis of plant cell division will require additional protein localization studies. This is greatly aided by GFP-technology, but plant transformation and the maintenance of transgenic lines can present a significant technical bottleneck. In this chapter I describe a method for the Agrobacterium-mediated genetic transformation of tobacco BY-2 cells. The method allows for the microscopic analysis of fluorescence-tagged proteins in dividing cells in within 2 days after starting a coculture. This transient transformation procedure requires only standard laboratory equipment. It is hoped that this rapid method would aid researchers conducting live-cell localization studies in plant mitosis and cytokinesis.

Do bacterial cell numbers follow a theoretical Poisson distribution? Comparison of experimentally obtained numbers of single cells with random number generation via computer simulation.

PubMed

Koyama, Kento; Hokunan, Hidekazu; Hasegawa, Mayumi; Kawamura, Shuso; Koseki, Shigenobu

2016-12-01

We investigated a bacterial sample preparation procedure for single-cell studies. In the present study, we examined whether single bacterial cells obtained via 10-fold dilution followed a theoretical Poisson distribution. Four serotypes of Salmonella enterica, three serotypes of enterohaemorrhagic Escherichia coli and one serotype of Listeria monocytogenes were used as sample bacteria. An inoculum of each serotype was prepared via a 10-fold dilution series to obtain bacterial cell counts with mean values of one or two. To determine whether the experimentally obtained bacterial cell counts follow a theoretical Poisson distribution, a likelihood ratio test between the experimentally obtained cell counts and Poisson distribution which parameter estimated by maximum likelihood estimation (MLE) was conducted. The bacterial cell counts of each serotype sufficiently followed a Poisson distribution. Furthermore, to examine the validity of the parameters of Poisson distribution from experimentally obtained bacterial cell counts, we compared these with the parameters of a Poisson distribution that were estimated using random number generation via computer simulation. The Poisson distribution parameters experimentally obtained from bacterial cell counts were within the range of the parameters estimated using a computer simulation. These results demonstrate that the bacterial cell counts of each serotype obtained via 10-fold dilution followed a Poisson distribution. The fact that the frequency of bacterial cell counts follows a Poisson distribution at low number would be applied to some single-cell studies with a few bacterial cells. In particular, the procedure presented in this study enables us to develop an inactivation model at the single-cell level that can estimate the variability of survival bacterial numbers during the bacterial death process. Copyright © 2016 Elsevier Ltd. All rights reserved.

Systemic control of cell division and endoreduplication by NAA and BAP by modulating CDKs in root tip cells of Allium cepa.

PubMed

Tank, Jigna G; Thaker, Vrinda S

2014-01-01

Molecular mechanism regulated by auxin and cytokinin during endoreduplication, cell division, and elongation process is studied by using Allium cepa roots as a model system. The activity of CDK genes modulated by auxin and cytokinin during cell division, elongation, and endoreduplication process is explained in this research work. To study the significance of auxin and cytokinin in the management of cell division and endoreduplication process in plant meristematic cells at molecular level endoreduplication was developed in root tips of Allium cepa by giving colchicine treatment. There were inhibition of vegetative growth, formation of c-tumor at root tip, and development of endoreduplicated cells after colchicine treatment. This c-tumor was further treated with NAA and BAP to reinitiate vegetative growth in roots. BAP gave positive response in reinitiation of vegetative growth of roots from center of c-tumor. However, NAA gave negative response in reinitiation of vegetative growth of roots from c-tumor. Further, CDKs gene expression analysis from normal, endoreduplicated, and phytohormone (NAA or BAP) treated root tip was done and remarkable changes in transcription level of CDK genes in normal, endoreduplicated, and phytohormones treated cells were observed.

Systemic Control of Cell Division and Endoreduplication by NAA and BAP by Modulating CDKs in Root Tip Cells of Allium cepa

PubMed Central

Tank, Jigna G.; Thaker, Vrinda S.

2014-01-01

Molecular mechanism regulated by auxin and cytokinin during endoreduplication, cell division, and elongation process is studied by using Allium cepa roots as a model system. The activity of CDK genes modulated by auxin and cytokinin during cell division, elongation, and endoreduplication process is explained in this research work. To study the significance of auxin and cytokinin in the management of cell division and endoreduplication process in plant meristematic cells at molecular level endoreduplication was developed in root tips of Allium cepa by giving colchicine treatment. There were inhibition of vegetative growth, formation of c-tumor at root tip, and development of endoreduplicated cells after colchicine treatment. This c-tumor was further treated with NAA and BAP to reinitiate vegetative growth in roots. BAP gave positive response in reinitiation of vegetative growth of roots from center of c-tumor. However, NAA gave negative response in reinitiation of vegetative growth of roots from c-tumor. Further, CDKs gene expression analysis from normal, endoreduplicated, and phytohormone (NAA or BAP) treated root tip was done and remarkable changes in transcription level of CDK genes in normal, endoreduplicated, and phytohormones treated cells were observed. PMID:24955358

Cell growth, division, and death in cohesive tissues: A thermodynamic approach

NASA Astrophysics Data System (ADS)

Yabunaka, Shunsuke; Marcq, Philippe

2017-08-01

Cell growth, division, and death are defining features of biological tissues that contribute to morphogenesis. In hydrodynamic descriptions of cohesive tissues, their occurrence implies a nonzero rate of variation of cell density. We show how linear nonequilibrium thermodynamics allows us to express this rate as a combination of relevant thermodynamic forces: chemical potential, velocity divergence, and activity. We illustrate the resulting effects of the nonconservation of cell density on simple examples inspired by recent experiments on cell monolayers, considering first the velocity of a spreading front, and second an instability leading to mechanical waves.

Host-induced bacterial cell wall decomposition mediates pattern-triggered immunity in Arabidopsis

PubMed Central

Liu, Xiaokun; Grabherr, Heini M; Willmann, Roland; Kolb, Dagmar; Brunner, Frédéric; Bertsche, Ute; Kühner, Daniel; Franz-Wachtel, Mirita; Amin, Bushra; Felix, Georg; Ongena, Marc; Nürnberger, Thorsten; Gust, Andrea A

2014-01-01

Peptidoglycans (PGNs) are immunogenic bacterial surface patterns that trigger immune activation in metazoans and plants. It is generally unknown how complex bacterial structures such as PGNs are perceived by plant pattern recognition receptors (PRRs) and whether host hydrolytic activities facilitate decomposition of bacterial matrices and generation of soluble PRR ligands. Here we show that Arabidopsis thaliana, upon bacterial infection or exposure to microbial patterns, produces a metazoan lysozyme-like hydrolase (lysozyme 1, LYS1). LYS1 activity releases soluble PGN fragments from insoluble bacterial cell walls and cleavage products are able to trigger responses typically associated with plant immunity. Importantly, LYS1 mutant genotypes exhibit super-susceptibility to bacterial infections similar to that observed on PGN receptor mutants. We propose that plants employ hydrolytic activities for the decomposition of complex bacterial structures, and that soluble pattern generation might aid PRR-mediated immune activation in cell layers adjacent to infection sites. DOI: http://dx.doi.org/10.7554/eLife.01990.001 PMID:24957336

Egf Signaling Directs Neoblast Repopulation by Regulating Asymmetric Cell Division in Planarians.

PubMed

Lei, Kai; Thi-Kim Vu, Hanh; Mohan, Ryan D; McKinney, Sean A; Seidel, Chris W; Alexander, Richard; Gotting, Kirsten; Workman, Jerry L; Sánchez Alvarado, Alejandro

2016-08-22

A large population of proliferative stem cells (neoblasts) is required for physiological tissue homeostasis and post-injury regeneration in planarians. Recent studies indicate that survival of a few neoblasts after sublethal irradiation results in the clonal expansion of the surviving stem cells and the eventual restoration of tissue homeostasis and regenerative capacity. However, the precise mechanisms regulating the population dynamics of neoblasts remain largely unknown. Here, we uncovered a central role for epidermal growth factor (EGF) signaling during in vivo neoblast expansion mediated by Smed-egfr-3 (egfr-3) and its putative ligand Smed-neuregulin-7 (nrg-7). Furthermore, the EGF receptor-3 protein localizes asymmetrically on the cytoplasmic membrane of neoblasts, and the ratio of asymmetric to symmetric cell divisions decreases significantly in egfr-3(RNAi) worms. Our results not only provide the first molecular evidence of asymmetric stem cell divisions in planarians, but also demonstrate that EGF signaling likely functions as an essential regulator of neoblast clonal expansion. Copyright © 2016 Elsevier Inc. All rights reserved.

Mechanics of kinetochore microtubules and their interactions with chromosomes during cell division

NASA Astrophysics Data System (ADS)

Nazockdast, Ehssan; Fürthauer, Sebastian; Redemann, Stephanie; Baumgart, Johannes; Lindow, Norbert; Kratz, Andrea; Prohaska, Steffen; Müller-Reichert, Thomas; Shelley, Michael

2016-11-01

The accurate segregation of chromosomes, and subsequent cell division, in Eukaryotic cells is achieved by the interactions of an assembly of microtubules (MTs) and motor-proteins, known as the mitotic spindle. We use a combination of our computational platform for simulating cytoskeletal assemblies and our structural data from high-resolution electron tomography of the mitotic spindle, to study the kinetics and mechanics of MTs in the spindle, and their interactions with chromosomes during chromosome segregation in the first cell division in C.elegans embryo. We focus on kinetochore MTs, or KMTs, which have one end attached to a chromosome. KMTs are thought to be a key mechanical component in chromosome segregation. Using exploratory simulations of MT growth, bending, hydrodynamic interactions, and attachment to chromosomes, we propose a mechanical model for KMT-chromosome interactions that reproduces observed KMT length and shape distributions from electron tomography. We find that including detailed hydrodynamic interactions between KMTs is essential for agreement with the experimental observations.

Bacterial effectors target the plant cell nucleus to subvert host transcription.

PubMed

Canonne, Joanne; Rivas, Susana

2012-02-01

In order to promote virulence, Gram-negative bacteria have evolved the ability to inject so-called type III effector proteins into host cells. The plant cell nucleus appears to be a subcellular compartment repeatedly targeted by bacterial effectors. In agreement with this observation, mounting evidence suggests that manipulation of host transcription is a major strategy developed by bacteria to counteract plant defense responses. It has been suggested that bacterial effectors may adopt at least three alternative, although not mutually exclusive, strategies to subvert host transcription. T3Es may (1) act as transcription factors that directly activate transcription in host cells, (2) affect histone packing and chromatin configuration, and/or (3) target host transcription factor activity. Here, we provide an overview on how all these strategies may lead to host transcriptional re-programming and, as a result, to improved bacterial multiplication inside plant cells.

Peptidoglycan Synthesis Machinery in Agrobacterium tumefaciens During Unipolar Growth and Cell Division

PubMed Central

Cameron, Todd A.; Anderson-Furgeson, James; Zupan, John R.; Zik, Justin J.

2014-01-01

ABSTRACT The synthesis of peptidoglycan (PG) in bacteria is a crucial process controlling cell shape and vitality. In contrast to bacteria such as Escherichia coli that grow by dispersed lateral insertion of PG, little is known of the processes that direct polar PG synthesis in other bacteria such as the Rhizobiales. To better understand polar growth in the Rhizobiales Agrobacterium tumefaciens, we first surveyed its genome to identify homologs of (~70) well-known PG synthesis components. Since most of the canonical cell elongation components are absent from A. tumefaciens, we made fluorescent protein fusions to other putative PG synthesis components to assay their subcellular localization patterns. The cell division scaffolds FtsZ and FtsA, PBP1a, and a Rhizobiales- and Rhodobacterales-specific l,d-transpeptidase (LDT) all associate with the elongating cell pole. All four proteins also localize to the septum during cell division. Examination of the dimensions of growing cells revealed that new cell compartments gradually increase in width as they grow in length. This increase in cell width is coincident with an expanded region of LDT-mediated PG synthesis activity, as measured directly through incorporation of exogenous d-amino acids. Thus, unipolar growth in the Rhizobiales is surprisingly dynamic and represents a significant departure from the canonical growth mechanism of E. coli and other well-studied bacilli. PMID:24865559

Stoichiometry of mercury-thiol complexes on bacterial cell envelopes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mishra, Bhoopesh; Shoenfelt, Elizabeth; Yu, Qiang

We have examined the speciation of Hg(II) complexed with intact cell suspensions (1013 cells L- 1) of Bacillus subtilis, a common gram-positive soil bacterium, Shewanella oneidensis MR-1, a facultative gram-negative aquatic organism, and Geobacter sulfurreducens, a gram-negative anaerobic bacterium capable of Hg-methylation at Hg(II) loadings spanning four orders of magnitude (120 nM to 350 μM) at pH 5.5 (± 0.2). The coordination environments of Hg on bacterial cells were analyzed using synchrotron based X-ray Absorption Near Edge Structure (XANES) and Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy at the Hg LIII edge. The abundance of thiols on intact cells wasmore » determined by a fluorescence-spectroscopy based method using a soluble bromobimane, monobromo(trimethylammonio)bimane (qBBr) to block thiol sites, and potentiometric titrations of biomass with and without qBBr treatment. The chemical forms of S on intact bacterial cells were determined using S k-edge XANES spectroscopy.« less

Actin polymerization drives septation of Listeria monocytogenes namA hydrolase mutants, demonstrating host correction of a bacterial defect.

PubMed

Alonzo, Francis; McMullen, P David; Freitag, Nancy E

2011-04-01

The Gram-positive bacterial cell wall presents a structural barrier that requires modification for protein secretion and large-molecule transport as well as for bacterial growth and cell division. The Gram-positive bacterium Listeria monocytogenes adjusts cell wall architecture to promote its survival in diverse environments that include soil and the cytosol of mammalian cells. Here we provide evidence for the enzymatic flexibility of the murein hydrolase NamA and demonstrate that bacterial septation defects associated with a loss of NamA are functionally complemented by physical forces associated with actin polymerization within the host cell cytosol. L. monocytogenes ΔnamA mutants formed long bacterial chains during exponential growth in broth culture; however, normal septation could be restored if mutant cells were cocultured with wild-type L. monocytogenes bacteria or by the addition of exogenous NamA. Surprisingly, ΔnamA mutants were not significantly attenuated for virulence in mice despite the pronounced exponential growth septation defect. The physical force of L. monocytogenes-mediated actin polymerization within the cytosol was sufficient to sever ΔnamA mutant intracellular chains and thereby enable the process of bacterial cell-to-cell spread so critical for L. monocytogenes virulence. The inhibition of actin polymerization by cytochalasin D resulted in extended intracellular bacterial chains for which septation was restored following drug removal. Thus, despite the requirement for NamA for the normal septation of exponentially growing L. monocytogenes cells, the hydrolase is essentially dispensable once L. monocytogenes gains access to the host cell cytosol. This phenomenon represents a notable example of eukaryotic host cell complementation of a bacterial defect.

Microspectrometric insights on the uptake of antibiotics at the single bacterial cell level

PubMed Central

Cinquin, Bertrand; Maigre, Laure; Pinet, Elizabeth; Chevalier, Jacqueline; Stavenger, Robert A.; Mills, Scott; Réfrégiers, Matthieu; Pagès, Jean-Marie

2015-01-01

Bacterial multidrug resistance is a significant health issue. A key challenge, particularly in Gram-negative antibacterial research, is to better understand membrane permeation of antibiotics in clinically relevant bacterial pathogens. Passing through the membrane barrier to reach the required concentration inside the bacterium is a pivotal step for most antibacterials. Spectrometric methodology has been developed to detect drugs inside bacteria and recent studies have focused on bacterial cell imaging. Ultimately, we seek to use this method to identify pharmacophoric groups which improve penetration, and therefore accumulation, of small-molecule antibiotics inside bacteria. We developed a method to quantify the time scale of antibiotic accumulation in living bacterial cells. Tunable ultraviolet excitation provided by DISCO beamline (synchrotron Soleil) combined with microscopy allows spectroscopic analysis of the antibiotic signal in individual bacterial cells. Robust controls and measurement of the crosstalk between fluorescence channels can provide real time quantification of drug. This technique represents a new method to assay drug translocation inside the cell and therefore incorporate rational drug design to impact antibiotic uptake. PMID:26656111

Motion of single MreB bacterial actin proteins in Caulobacter show treadmilling in vivo

NASA Astrophysics Data System (ADS)

Moerner, W. E.; Kim, Soyeon; Gitai, Zemer; Kinkhabwala, Anika; McAdams, Harley; Shapiro, Lucy

2006-03-01

Ensemble imaging of a bacterial actin homologue, the MreB protein, suggests that the MreB proteins form a dynamic filamentous spiral along the long axis of the cell in Caulobacter crescentus. MreB contracts and expands along the cell axis and plays an important role in cell shape and polarity maintenance, as well as chromosome segregation and translocation of the origin of replication during cell division. In this study we investigated the real-time polymerization of MreB in Caulobacter crescentus using single-molecule fluorescence imaging. With time-lapse imaging, polymerized MreB could be distinguished from cytoplasmic MreB monomers, because single monomeric MreB showed fast motion characteristic of Brownian diffusion, while single polymerized MreB displayed slow, directed motion. This directional movement of labeled MreB in the growing polymer implies that treadmilling is the predominant mechanism in MreB filament formation. These single-molecule imaging experiments provide the first available information on the velocity of bacterial actin polymerization in a living cell.

Genetic reprogramming of host cells by bacterial pathogens.

PubMed

Tran Van Nhieu, Guy; Arbibe, Laurence

2009-10-29

During the course of infection, pathogens often induce changes in gene expression in host cells and these changes can be long lasting and global or transient and of limited amplitude. Defining how, when, and why bacterial pathogens reprogram host cells represents an exciting challenge that opens up the opportunity to grasp the essence of pathogenesis and its molecular details.

Modeling FtsZ ring formation in the bacterial cell-anisotropic aggregation via mutual interactions of polymer rods.

PubMed

Fischer-Friedrich, Elisabeth; Gov, Nir

2011-04-01

The cytoskeletal protein FtsZ polymerizes to a ring structure (Z ring) at the inner cytoplasmic membrane that marks the future division site and scaffolds the division machinery in many bacterial species. FtsZ is known to polymerize in the presence of GTP into single-stranded protofilaments. In vivo, FtsZ polymers become associated with the cytoplasmic membrane via interaction with the membrane-binding proteins FtsA and ZipA. The FtsZ ring structure is highly dynamic and undergoes constantly polymerization and depolymerization processes and exchange with the cytoplasmic pool. In this theoretical study, we consider a scenario of Z ring self-organization via self-enhanced attachment of FtsZ polymers due to end-to-end interactions and lateral interactions of FtsZ polymers on the membrane. With the assumption of exclusively circumferential polymer orientations, we derive coarse-grained equations for the dynamics of the pool of cytoplasmic and membrane-bound FtsZ. To capture stochastic effects expected in the system due to low particle numbers, we simulate our computational model using a Gillespie-type algorithm. We obtain ring- and arc-shaped aggregations of FtsZ polymers on the membrane as a function of monomer numbers in the cell. In particular, our model predicts the number of FtsZ rings forming in the cell as a function of cell geometry and FtsZ concentration. We also calculate the time of FtsZ ring localization to the midplane in the presence of Min oscillations. Finally, we demonstrate that the assumptions and results of our model are confirmed by 3D reconstructions of fluorescently-labeled FtsZ structures in E. coli that we obtained.

Structural characterization of the cell division cycle in Strigomonas culicis, an endosymbiont-bearing trypanosomatid.

PubMed

Brum, Felipe Lopes; Catta-Preta, Carolina Moura Costa; de Souza, Wanderley; Schenkman, Sergio; Elias, Maria Carolina; Motta, Maria Cristina Machado

2014-02-01

Strigomonas culicis (previously referred to as Blastocrithidia culicis) is a monoxenic trypanosomatid harboring a symbiotic bacterium, which maintains an obligatory relationship with the host protozoan. Investigations of the cell cycle in symbiont harboring trypanosomatids suggest that the bacterium divides in coordination with other host cell structures, particularly the nucleus. In this study we used light and electron microscopy followed by three-dimensional reconstruction to characterize the symbiont division during the cell cycle of S. culicis. We observed that during this process, the symbiotic bacterium presents different forms and is found at different positions in relationship to the host cell structures. At the G1/S phase of the protozoan cell cycle, the endosymbiont exhibits a constricted form that appears to elongate, resulting in the bacterium division, which occurs before kinetoplast and nucleus segregation. During cytokinesis, the symbionts are positioned close to each nucleus to ensure that each daughter cell will inherit a single copy of the bacterium. These observations indicated that the association of the bacterium with the protozoan nucleus coordinates the cell cycle in both organisms.

Inflating bacterial cells by increased protein synthesis

PubMed Central

Basan, Markus; Zhu, Manlu; Dai, Xiongfeng; Warren, Mya; Sévin, Daniel; Wang, Yi-Ping; Hwa, Terence

2015-01-01

Understanding how the homeostasis of cellular size and composition is accomplished by different organisms is an outstanding challenge in biology. For exponentially growing Escherichia coli cells, it is long known that the size of cells exhibits a strong positive relation with their growth rates in different nutrient conditions. Here, we characterized cell sizes in a set of orthogonal growth limitations. We report that cell size and mass exhibit positive or negative dependences with growth rate depending on the growth limitation applied. In particular, synthesizing large amounts of “useless” proteins led to an inversion of the canonical, positive relation, with slow growing cells enlarged 7- to 8-fold compared to cells growing at similar rates under nutrient limitation. Strikingly, this increase in cell size was accompanied by a 3- to 4-fold increase in cellular DNA content at slow growth, reaching up to an amount equivalent to ∼8 chromosomes per cell. Despite drastic changes in cell mass and macromolecular composition, cellular dry mass density remained constant. Our findings reveal an important role of protein synthesis in cell division control. PMID:26519362

Relationship between Milk Microbiota, Bacterial Load, Macronutrients, and Human Cells during Lactation.

PubMed

Boix-Amorós, Alba; Collado, Maria C; Mira, Alex

2016-01-01

Human breast milk is considered the optimal nutrition for infants, providing essential nutrients and a broad range of bioactive compounds, as well as its own microbiota. However, the interaction among those components and the biological role of milk microorganisms is still uncovered. Thus, our aim was to identify the relationships between milk microbiota composition, bacterial load, macronutrients, and human cells during lactation. Bacterial load was estimated in milk samples from a total of 21 healthy mothers through lactation time by bacteria-specific qPCR targeted to the single-copy gene fusA. Milk microbiome composition and diversity was estimated by 16S-pyrosequencing and the structure of these bacteria in the fluid was studied by flow cytometry, qPCR, and microscopy. Fat, protein, lactose, and dry extract of milk as well as the number of somatic cells were also analyzed. We observed that milk bacterial communities were generally complex, and showed individual-specific profiles. Milk microbiota was dominated by Staphylococcus, Pseudomonas, Streptococcus, and Acinetobacter. Staphylococcus aureus was not detected in any of these samples from healthy mothers. There was high variability in composition and number of bacteria per milliliter among mothers and in some cases even within mothers at different time points. The median bacterial load was 10(6) bacterial cells/ml through time, higher than those numbers reported by 16S gene PCR and culture methods. Furthermore, milk bacteria were present in a free-living, "planktonic" state, but also in equal proportion associated to human immune cells. There was no correlation between bacterial load and the amount of immune cells in milk, strengthening the idea that milk bacteria are not sensed as an infection by the immune system.

From centriole biogenesis to cellular function: centrioles are essential for cell division at critical developmental stages.

PubMed

Rodrigues-Martins, Ana; Riparbelli, Maria; Callaini, Giuliano; Glover, David M; Bettencourt-Dias, Monica

2008-01-01

Centrioles are essential for the formation of cilia, flagella and centrosome organization. Abnormalities in centrosome structure and number in many cancers can be associated with aberrant cell division and genomic instability.(1,2) Canonical centriole duplication occurs in coordination with the cell division cycle, such that a single new "daughter" centriole arises next to each "mother" centriole. If destroyed, or eliminated during development, centrioles can form de novo.(3-5) Here we discuss our recent data demonstrating a molecular pathway that operates in both de novo and canonical centriole biogenesis involving SAK/PLK4, SAS-6 and SAS-4.(6) We showed that centriole biogenesis is a self-assembly process locally triggered by high SAK/PLK4 activity that may or not be associated with an existing centriole. SAS-6 acts downstream of SAK/PLK4 to organize nine precentriolar units, which we call here enatosomes, fitting together laterally and longitudinally, specifying a tube-like centriole precursor.(7,8) The identification of mutants impaired in centriole biogenesis has permitted the study of the physiological consequences of their absence in the whole organism. In Drosophila, centrioles are not necessary for somatic cell divisions.(9,10) However, we show here that mitotic abnormalities arise in syncytial SAK/PLK4-derived mutant embryos resulting in lethality. Moreover male meiosis fails in both SAK/PLK4 and DSAS-4 mutant spermatids that have no centrioles. These results show diversity in the need for centrioles in cell division. This suggests that tissue specific constraints selected for different contributions of centrosome-independent and dependent mechanisms in spindle function. This heterogeneity should be taken into account both in reaching an understanding of spindle function and when designing drugs that target cell division.

Bacterial cell wall composition and the influence of antibiotics by cell-wall and whole-cell NMR

PubMed Central

Romaniuk, Joseph A. H.; Cegelski, Lynette

2015-01-01

The ability to characterize bacterial cell-wall composition and structure is crucial to understanding the function of the bacterial cell wall, determining drug modes of action and developing new-generation therapeutics. Solid-state NMR has emerged as a powerful tool to quantify chemical composition and to map cell-wall architecture in bacteria and plants, even in the context of unperturbed intact whole cells. In this review, we discuss solid-state NMR approaches to define peptidoglycan composition and to characterize the modes of action of old and new antibiotics, focusing on examples in Staphylococcus aureus. We provide perspectives regarding the selected NMR strategies as we describe the exciting and still-developing cell-wall and whole-cell NMR toolkit. We also discuss specific discoveries regarding the modes of action of vancomycin analogues, including oritavancin, and briefly address the reconsideration of the killing action of β-lactam antibiotics. In such chemical genetics approaches, there is still much to be learned from perturbations enacted by cell-wall assembly inhibitors, and solid-state NMR approaches are poised to address questions of cell-wall composition and assembly in S. aureus and other organisms. PMID:26370936

Inhibition of phenylpropanoid biosynthesis increases cell wall digestibility, protoplast isolation, and facilitates sustained cell division in American elm (Ulmus americana).

PubMed

Jones, A Maxwell P; Chattopadhyay, Abhishek; Shukla, Mukund; Zoń, Jerzy; Saxena, Praveen K

2012-05-30

Protoplast technologies offer unique opportunities for fundamental research and to develop novel germplasm through somatic hybridization, organelle transfer, protoclonal variation, and direct insertion of DNA. Applying protoplast technologies to develop Dutch elm disease resistant American elms (Ulmus americana L.) was proposed over 30 years ago, but has not been achieved. A primary factor restricting protoplast technology to American elm is the resistance of the cell walls to enzymatic degradation and a long lag phase prior to cell wall re-synthesis and cell division. This study suggests that resistance to enzymatic degradation in American elm was due to water soluble phenylpropanoids. Incubating tobacco (Nicotiana tabacum L.) leaf tissue, an easily digestible species, in aqueous elm extract inhibits cell wall digestion in a dose dependent manner. This can be mimicked by p-coumaric or ferulic acid, phenylpropanoids known to re-enforce cell walls. Culturing American elm tissue in the presence of 2-aminoindane-2-phosphonic acid (AIP; 10-150 μM), an inhibitor of phenylalanine ammonia lyase (PAL), reduced flavonoid content, decreased tissue browning, and increased isolation rates significantly from 11.8% (±3.27) in controls to 65.3% (±4.60). Protoplasts isolated from callus grown in 100 μM AIP developed cell walls by day 2, had a division rate of 28.5% (±3.59) by day 6, and proliferated into callus by day 14. Heterokaryons were successfully produced using electrofusion and fused protoplasts remained viable when embedded in agarose. This study describes a novel approach of modifying phenylpropanoid biosynthesis to facilitate efficient protoplast isolation which has historically been problematic for American elm. This isolation system has facilitated recovery of viable protoplasts capable of rapid cell wall re-synthesis and sustained cell division to form callus. Further, isolated protoplasts survived electrofusion and viable heterokaryons were produced. Together

Inhibition of phenylpropanoid biosynthesis increases cell wall digestibility, protoplast isolation, and facilitates sustained cell division in American elm (Ulmus americana)

PubMed Central

2012-01-01

Background Protoplast technologies offer unique opportunities for fundamental research and to develop novel germplasm through somatic hybridization, organelle transfer, protoclonal variation, and direct insertion of DNA. Applying protoplast technologies to develop Dutch elm disease resistant American elms (Ulmus americana L.) was proposed over 30 years ago, but has not been achieved. A primary factor restricting protoplast technology to American elm is the resistance of the cell walls to enzymatic degradation and a long lag phase prior to cell wall re-synthesis and cell division. Results This study suggests that resistance to enzymatic degradation in American elm was due to water soluble phenylpropanoids. Incubating tobacco (Nicotiana tabacum L.) leaf tissue, an easily digestible species, in aqueous elm extract inhibits cell wall digestion in a dose dependent manner. This can be mimicked by p-coumaric or ferulic acid, phenylpropanoids known to re-enforce cell walls. Culturing American elm tissue in the presence of 2-aminoindane-2-phosphonic acid (AIP; 10-150 μM), an inhibitor of phenylalanine ammonia lyase (PAL), reduced flavonoid content, decreased tissue browning, and increased isolation rates significantly from 11.8% (±3.27) in controls to 65.3% (±4.60). Protoplasts isolated from callus grown in 100 μM AIP developed cell walls by day 2, had a division rate of 28.5% (±3.59) by day 6, and proliferated into callus by day 14. Heterokaryons were successfully produced using electrofusion and fused protoplasts remained viable when embedded in agarose. Conclusions This study describes a novel approach of modifying phenylpropanoid biosynthesis to facilitate efficient protoplast isolation which has historically been problematic for American elm. This isolation system has facilitated recovery of viable protoplasts capable of rapid cell wall re-synthesis and sustained cell division to form callus. Further, isolated protoplasts survived electrofusion and viable

Acetyl phosphate and the phosphorylation of OmpR are involved in the regulation of the cell division rate in Escherichia coli.

PubMed

Prüss, B M

1998-09-01

Carbon sources that can be converted to acetate were added to the growth medium of Escherichia coli wild-type cells. Cells responded with an increased cell division rate. The addition of acetate also caused a decreased synthesis of flagella. Mutants in phosphotransacetylase, which are incapable of synthesizing acetyl phosphate, and mutants in the osmoregulator OmpR divided at a lower rate than did wild-type cells. The mutants did not increase their cell division rate upon the addition of serine, as observed for wild-type cells. These data are consistent with the idea that the previously described effect of serine upon the cell division rate is mediated by acetyl phosphate and phosphorylation of OmpR.

IFT Proteins Accumulate during Cell Division and Localize to the Cleavage Furrow in Chlamydomonas

PubMed Central

Wood, Christopher R.; Wang, Zhaohui; Diener, Dennis; Zones, James Matt; Rosenbaum, Joel; Umen, James G.

2012-01-01

Intraflagellar transport (IFT) proteins are well established as conserved mediators of flagellum/cilium assembly and disassembly. However, data has begun to accumulate in support of IFT protein involvement in other processes elsewhere in the cell. Here, we used synchronous cultures of Chlamydomonas to investigate the temporal patterns of accumulation and localization of IFT proteins during the cell cycle. Their mRNAs showed periodic expression that peaked during S and M phase (S/M). Unlike most proteins that are synthesized continuously during G1 phase, IFT27 and IFT46 levels were found to increase only during S/M phase. During cell division, IFT27, IFT46, IFT72, and IFT139 re-localized from the flagella and basal bodies to the cleavage furrow. IFT27 was further shown to be associated with membrane vesicles in this region. This localization pattern suggests a role for IFT in cell division. PMID:22328921

Foundation laid for understanding essentials of cell division | Center for Cancer Research

Cancer.gov

NCI Center for Cancer Research (CCR) scientists reported new molecular insights into understanding a critical aspect of cell division through a cross-disciplinary effort that combines cryo-electron microscopy (cryo-EM), biochemical and cell biological approaches. Errors in segregation of chromosomes during mitosis can lead to an aberrant number of chromosomes, a condition known as aneuploidy, which can lead to cancer and birth defects. Read more…

Disinfection byproduct formation from chlorination of pure bacterial cells and pipeline biofilms.

PubMed

Wang, Jun-Jian; Liu, Xin; Ng, Tsz Wai; Xiao, Jie-Wen; Chow, Alex T; Wong, Po Keung

2013-05-15

Disinfection byproduct (DBP) formation is commonly attributed to the reaction between natural organic matters and disinfectants, yet few have considered the contribution from disinfecting bacterial materials - the essential process of water disinfection. Here, we explored the DBP formation from chlorination and chloramination of Escherichia coli and found that most selected DBPs were detectable, including trihalomethanes, haloacetonitriles, chloral hydrate, chloropicrin, and 1,1,1-trichloro-2-propanone. A positive correlation (P = 0.08-0.09) between DBP formation and the log reduction of E. coli implied that breaking down of bacterial cells released precursors for DBP formation. As Pseudomonas aeruginosa is a dominant bacterial species in pipeline biofilms, the DBP formation potentials (DBPFPs) from its planktonic cells and biofilms were characterized. Planktonic cells formed 7-11 times greater trihalomethanes per carbon of those from biofilms but significantly lower (P < 0.05) chloral hydrate, highlighting the bacterial phenotype's impact on the bacteria-derived DBPFP. Pipe material appeared to affect the DBPFP of bacteria, with 4-28% lower bromine incorporation factor for biofilms on polyvinyl chloride compared to that on galvanized zinc. This study revealed both the in situ disinfection of bacterial planktonic cells in source water and ex situ reaction between biofilms and residual chlorine in pipeline networks as hitherto unknown DBP sources in drinking water. Copyright © 2013 Elsevier Ltd. All rights reserved.

Architecture and inherent robustness of a bacterial cell-cycle control system.

PubMed

Shen, Xiling; Collier, Justine; Dill, David; Shapiro, Lucy; Horowitz, Mark; McAdams, Harley H

2008-08-12

A closed-loop control system drives progression of the coupled stalked and swarmer cell cycles of the bacterium Caulobacter crescentus in a near-mechanical step-like fashion. The cell-cycle control has a cyclical genetic circuit composed of four regulatory proteins with tight coupling to processive chromosome replication and cell division subsystems. We report a hybrid simulation of the coupled cell-cycle control system, including asymmetric cell division and responses to external starvation signals, that replicates mRNA and protein concentration patterns and is consistent with observed mutant phenotypes. An asynchronous sequential digital circuit model equivalent to the validated simulation model was created. Formal model-checking analysis of the digital circuit showed that the cell-cycle control is robust to intrinsic stochastic variations in reaction rates and nutrient supply, and that it reliably stops and restarts to accommodate nutrient starvation. Model checking also showed that mechanisms involving methylation-state changes in regulatory promoter regions during DNA replication increase the robustness of the cell-cycle control. The hybrid cell-cycle simulation implementation is inherently extensible and provides a promising approach for development of whole-cell behavioral models that can replicate the observed functionality of the cell and its responses to changing environmental conditions.

Relationship between Milk Microbiota, Bacterial Load, Macronutrients, and Human Cells during Lactation

PubMed Central

Boix-Amorós, Alba; Collado, Maria C.; Mira, Alex

2016-01-01

Human breast milk is considered the optimal nutrition for infants, providing essential nutrients and a broad range of bioactive compounds, as well as its own microbiota. However, the interaction among those components and the biological role of milk microorganisms is still uncovered. Thus, our aim was to identify the relationships between milk microbiota composition, bacterial load, macronutrients, and human cells during lactation. Bacterial load was estimated in milk samples from a total of 21 healthy mothers through lactation time by bacteria-specific qPCR targeted to the single-copy gene fusA. Milk microbiome composition and diversity was estimated by 16S-pyrosequencing and the structure of these bacteria in the fluid was studied by flow cytometry, qPCR, and microscopy. Fat, protein, lactose, and dry extract of milk as well as the number of somatic cells were also analyzed. We observed that milk bacterial communities were generally complex, and showed individual-specific profiles. Milk microbiota was dominated by Staphylococcus, Pseudomonas, Streptococcus, and Acinetobacter. Staphylococcus aureus was not detected in any of these samples from healthy mothers. There was high variability in composition and number of bacteria per milliliter among mothers and in some cases even within mothers at different time points. The median bacterial load was 106 bacterial cells/ml through time, higher than those numbers reported by 16S gene PCR and culture methods. Furthermore, milk bacteria were present in a free-living, “planktonic” state, but also in equal proportion associated to human immune cells. There was no correlation between bacterial load and the amount of immune cells in milk, strengthening the idea that milk bacteria are not sensed as an infection by the immune system. PMID:27148183

Bacterial Cell Growth Inhibitors Targeting Undecaprenyl Diphosphate Synthase and Undecaprenyl Diphosphate Phosphatase.

PubMed

Wang, Yang; Desai, Janish; Zhang, Yonghui; Malwal, Satish R; Shin, Christopher J; Feng, Xinxin; Sun, Hong; Liu, Guizhi; Guo, Rey-Ting; Oldfield, Eric

2016-10-19

We synthesized a series of benzoic acids and phenylphosphonic acids and investigated their effects on the growth of Staphylococcus aureus and Bacillus subtilis. One of the most active compounds, 5-fluoro-2-(3-(octyloxy)benzamido)benzoic acid (7, ED 50 ∼0.15 μg mL -1 ) acted synergistically with seven antibiotics known to target bacterial cell-wall biosynthesis (a fractional inhibitory concentration index (FICI) of ∼0.35, on average) but had indifferent effects in combinations with six non-cell-wall biosynthesis inhibitors (average FICI∼1.45). The most active compounds were found to inhibit two enzymes involved in isoprenoid/bacterial cell-wall biosynthesis: undecaprenyl diphosphate synthase (UPPS) and undecaprenyl diphosphate phosphatase (UPPP), but not farnesyl diphosphate synthase, and there were good correlations between bacterial cell growth inhibition, UPPS inhibition, and UPPP inhibition. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Sonication reduces the attachment of Salmonella Typhimurium ATCC 14028 cells to bacterial cellulose-based plant cell wall models and cut plant material.

PubMed

Tan, Michelle S F; Rahman, Sadequr; Dykes, Gary A

2017-04-01

This study investigated the removal of bacterial surface structures, particularly flagella, using sonication, and examined its effect on the attachment of Salmonella Typhimurium ATCC 14028 cells to plant cell walls. S. Typhimurium ATCC 14028 cells were subjected to sonication at 20 kHz to remove surface structures without affecting cell viability. Effective removal of flagella was determined by staining flagella of sonicated cells with Ryu's stain and enumerating the flagella remaining by direct microscopic counting. The attachment of sonicated S. Typhimurium cells to bacterial cellulose-based plant cell wall models and cut plant material (potato, apple, lettuce) was then evaluated. Varying concentrations of pectin and/or xyloglucan were used to produce a range of bacterial cellulose-based plant cell wall models. As compared to the non-sonicated controls, sonicated S. Typhimurium cells attached in significantly lower numbers (between 0.5 and 1.0 log CFU/cm 2 ) to all surfaces except to the bacterial cellulose-only composite without pectin and xyloglucan. Since attachment of S. Typhimurium to the bacterial cellulose-only composite was not affected by sonication, this suggests that bacterial surface structures, particularly flagella, could have specific interactions with pectin and xyloglucan. This study indicates that sonication may have potential applications for reducing Salmonella attachment during the processing of fresh produce. Copyright © 2016 Elsevier Ltd. All rights reserved.

Patterns of oriented cell division during the steady-state morphogenesis of the body column in hydra.

PubMed

Shimizu, H; Bode, P M; Bode, H R

1995-12-01

In an adult hydra, the tissue of the body column is in a dynamic state. The epithelial cells of both layers are constantly in the mitotic cycle. As the tissue expands, it is continuously displaced along the body axis in either an apical or basal direction, but not in a circumferential direction. Using a modified whole mount method we examined the orientation of mitotic spindles to determine what role the direction of cell division plays in axial displacement. Surprisingly, the direction of cell division was found to differ in the two epithelial layers. In the ectoderm it was somewhat biased in an axial direction. In the endoderm it was strongly biased in a circumferential direction. For both layers, the directional biases occurred throughout the length of the body column, with some regional variation in its extent. As buds developed into adults, the bias in each layer increased from an almost random distribution to the distinctly different orientations of the adult. Thus, to maintain the observed axial direction of tissue displacement, rearrangement of the epithelial cells of both layers must occur continuously in the adult as well as in developing animals. How the locomotory and contractile behavior of the muscle processes of the epithelial cells may effect changes in cell shape, and thereby influence the direction of cell division in each layer, is discussed.

Characterization of a Null Allelic Mutant of the Rice NAL1 Gene Reveals Its Role in Regulating Cell Division

PubMed Central

Jiang, Dan; Fang, Jingjing; Lou, Lamei; Zhao, Jinfeng; Yuan, Shoujiang; Yin, Liang; Sun, Wei; Peng, Lixiang; Guo, Baotai; Li, Xueyong

2015-01-01

Leaf morphology is closely associated with cell division. In rice, mutations in Narrow leaf 1 (NAL1) show narrow leaf phenotypes. Previous studies have shown that NAL1 plays a role in regulating vein patterning and increasing grain yield in indica cultivars, but its role in leaf growth and development remains unknown. In this report, we characterized two allelic mutants of NARROW LEAF1 (NAL1), nal1-2 and nal1-3, both of which showed a 50% reduction in leaf width and length, as well as a dwarf culm. Longitudinal and transverse histological analyses of leaves and internodes revealed that cell division was suppressed in the anticlinal orientation but enhanced in the periclinal orientation in the mutants, while cell size remained unaltered. In addition to defects in cell proliferation, the mutants showed abnormal midrib in leaves. Map-based cloning revealed that nal1-2 is a null allelic mutant of NAL1 since both the whole promoter and a 404-bp fragment in the first exon of NAL1 were deleted, and that a 6-bp fragment was deleted in the mutant nal1-3. We demonstrated that NAL1 functions in the regulation of cell division as early as during leaf primordia initiation. The altered transcript level of G1- and S-phase-specific genes suggested that NAL1 affects cell cycle regulation. Heterogenous expression of NAL1 in fission yeast (Schizosaccharomyces pombe) further supported that NAL1 affects cell division. These results suggest that NAL1 controls leaf width and plant height through its effects on cell division. PMID:25658704

Dynamic FtsA and FtsZ localization and outer membrane alterations during polar growth and cell division in Agrobacterium tumefaciens

PubMed Central

Zupan, John R.; Cameron, Todd A.; Anderson-Furgeson, James; Zambryski, Patricia C.

2013-01-01

Growth and cell division in rod-shaped bacteria have been primarily studied in species that grow predominantly by peptidoglycan (PG) synthesis along the length of the cell. Rhizobiales species, however, predominantly grow by PG synthesis at a single pole. Here we characterize the dynamic localization of several Agrobacterium tumefaciens components during the cell cycle. First, the lipophilic dye FM 4-64 predominantly stains the outer membranes of old poles versus growing poles. In cells about to divide, however, both poles are equally labeled with FM 4-64, but the constriction site is not. Second, the cell-division protein FtsA alternates from unipolar foci in the shortest cells to unipolar and midcell localization in cells of intermediate length, to strictly midcell localization in the longest cells undergoing septation. Third, the cell division protein FtsZ localizes in a cell-cycle pattern similar to, but more complex than, FtsA. Finally, because PG synthesis is spatially and temporally regulated during the cell cycle, we treated cells with sublethal concentrations of carbenicillin (Cb) to assess the role of penicillin-binding proteins in growth and cell division. Cb-treated cells formed midcell circumferential bulges, suggesting that interrupted PG synthesis destabilizes the septum. Midcell bulges contained bands or foci of FtsA-GFP and FtsZ-GFP and no FM 4-64 label, as in untreated cells. There were no abnormal morphologies at the growth poles in Cb-treated cells, suggesting unipolar growth uses Cb-insensitive PG synthesis enzymes. PMID:23674672

The invariant cleavage pattern displayed by ascidian embryos depends on spindle positioning along the cell's longest axis in the apical plane and relies on asynchronous cell divisions

PubMed Central

Dumollard, Rémi; Minc, Nicolas; Salez, Gregory; Aicha, Sameh Ben; Bekkouche, Faisal; Hebras, Céline; Besnardeau, Lydia; McDougall, Alex

2017-01-01

The ascidian embryo is an ideal system to investigate how cell position is determined during embryogenesis. Using 3D timelapse imaging and computational methods we analyzed the planar cell divisions in ascidian early embryos and found that spindles in every cell tend to align at metaphase in the long length of the apical surface except in cells undergoing unequal cleavage. Furthermore, the invariant and conserved cleavage pattern of ascidian embryos was found to consist in alternate planar cell divisions between ectoderm and endomesoderm. In order to test the importance of alternate cell divisions we manipulated zygotic transcription induced by β-catenin or downregulated wee1 activity, both of which abolish this cell cycle asynchrony. Crucially, abolishing cell cycle asynchrony consistently disrupted the spindle orienting mechanism underpinning the invariant cleavage pattern. Our results demonstrate how an evolutionary conserved cell cycle asynchrony maintains the invariant cleavage pattern driving morphogenesis of the ascidian blastula. DOI: http://dx.doi.org/10.7554/eLife.19290.001 PMID:28121291

Bacterial filamentation accelerates colonization of adhesive spots embedded in biopassive surfaces

NASA Astrophysics Data System (ADS)

Möller, Jens; Emge, Philippe; Avalos Vizcarra, Ima; Kollmannsberger, Philip; Vogel, Viola

2013-12-01

Sessile bacteria adhere to engineered surfaces and host tissues and pose a substantial clinical and economical risk when growing into biofilms. Most engineered and biological interfaces are of chemically heterogeneous nature and provide adhesive islands for bacterial attachment and growth. To mimic either defects in a surface coating of biomedical implants or heterogeneities within mucosal layers (Peyer's patches), we embedded micrometre-sized adhesive islands in a poly(ethylene glycol) biopassive background. We show experimentally and computationally that filamentation of Escherichia coli can significantly accelerate the bacterial surface colonization under physiological flow conditions. Filamentation can thus provide an advantage to a bacterial population to bridge non-adhesive distances exceeding 5 μm. Bacterial filamentation, caused by blocking of bacterial division, is common among bacterial species and can be triggered by environmental conditions or antibiotic treatment. While great awareness exists that the build-up of antibiotic resistance serves as intrinsic survival strategy, we show here that antibiotic treatment can actually promote surface colonization by triggering filamentation, which in turn prevents daughter cells from being washed away. Our combined microfabrication and computational approaches provide quantitative insights into mechanisms that enable biofouling of biopassive surfaces with embedded adhesive spots, even for spot distances that are multiples of the bacterial length.

The disruptive effect of lysozyme on the bacterial cell wall explored by an in-silico structural outlook.

PubMed

Primo, Emiliano D; Otero, Lisandro H; Ruiz, Francisco; Klinke, Sebastián; Giordano, Walter

2018-01-01

The bacterial cell wall, a structural unit of peptidoglycan polymer comprised of glycan strands consisting of a repeating disaccharide motif [N-acetylglucosamine (NAG) and N-acetylmuramylpentapeptide (NAM pentapeptide)], encases bacteria and provides structural integrity and protection. Lysozymes are enzymes that break down the bacterial cell wall and disrupt the bacterial life cycle by cleaving the linkage between the NAG and NAM carbohydrates. Lab exercises focused on the effects of lysozyme on the bacterial cell wall are frequently incorporated in biochemistry classes designed for undergraduate students in diverse fields as biology, microbiology, chemistry, agronomy, medicine, and veterinary medicine. Such exercises typically do not include structural data. We describe here a sequence of computer tasks designed to illustrate and reinforce both physiological and structural concepts involved in lysozyme effects on the bacterial cell-wall structure. This lab class usually lasts 3.5 hours. First, the instructor presents introductory concepts of the bacterial cell wall and the effect of lysozyme on its structure. Then, students are taught to use computer modeling to visualize the three-dimensional structure of a lysozyme in complex with bacterial cell-wall fragments. Finally, the lysozyme inhibitory effect on a bacterial culture is optionally proposed as a simple microbiological assay. The computer lab exercises described here give students a realistic understanding of the disruptive effect of lysozymes on the bacterial cell wall, a crucial component in bacterial survival. © 2017 by The International Union of Biochemistry and Molecular Biology, 46(1):83-90, 2018. © 2017 The International Union of Biochemistry and Molecular Biology.

Bacterial safety of cell-based therapeutic preparations, focusing on haematopoietic progenitor cells.

PubMed

Störmer, M; Wood, E M; Schurig, U; Karo, O; Spreitzer, I; McDonald, C P; Montag, T

2014-05-01

Bacterial safety of cellular preparations, especially haematopoietic progenitor cells (HPCs), as well as advanced therapy medicinal products (ATMPs) derived from stem cells of various origins, present a challenge for physicians, manufacturers and regulators. The article describes the background and practical issues in this area and illustrates why sterility of these products cannot currently be guaranteed. Advantages and limitations of approaches both for classical sterility testing and for microbiological control using automated culture systems are discussed. The review considers novel approaches for growth-based rapid microbiological control with high sensitivity and faster availability of results, as well as new methods for rapid bacterial detection in cellular preparations enabling meaningful information about product contamination within one to two hours. Generally, however, these direct rapid methods are less sensitive and have greater sampling error compared with the growth-based methods. Opportunities for pyrogen testing of cell therapeutics are also discussed. There is an urgent need for development of novel principles and methods applicable to bacterial safety of cellular therapeutics. We also need a major shift in approach from the traditional view of sterility evaluation (identify anything and everything) to a new thinking about how to find what is clinically relevant within the time frame available for the special clinical circumstances in which these products are used. The review concludes with recommendations for optimization of microbiological control of cellular preparations, focusing on HPCs. © 2013 International Society of Blood Transfusion.

Mechanisms of bacterial morphogenesis: evolutionary cell biology approaches provide new insights.

PubMed

Jiang, Chao; Caccamo, Paul D; Brun, Yves V

2015-04-01

How Darwin's "endless forms most beautiful" have evolved remains one of the most exciting questions in biology. The significant variety of bacterial shapes is most likely due to the specific advantages they confer with respect to the diverse environments they occupy. While our understanding of the mechanisms generating relatively simple shapes has improved tremendously in the last few years, the molecular mechanisms underlying the generation of complex shapes and the evolution of shape diversity are largely unknown. The emerging field of bacterial evolutionary cell biology provides a novel strategy to answer this question in a comparative phylogenetic framework. This relatively novel approach provides hypotheses and insights into cell biological mechanisms, such as morphogenesis, and their evolution that would have been difficult to obtain by studying only model organisms. We discuss the necessary steps, challenges, and impact of integrating "evolutionary thinking" into bacterial cell biology in the genomic era. © 2015 WILEY Periodicals, Inc.

Biophysical model of bacterial cell interactions with nanopatterned cicada wing surfaces.

PubMed

Pogodin, Sergey; Hasan, Jafar; Baulin, Vladimir A; Webb, Hayden K; Truong, Vi Khanh; Phong Nguyen, The Hong; Boshkovikj, Veselin; Fluke, Christopher J; Watson, Gregory S; Watson, Jolanta A; Crawford, Russell J; Ivanova, Elena P

2013-02-19

The nanopattern on the surface of Clanger cicada (Psaltoda claripennis) wings represents the first example of a new class of biomaterials that can kill bacteria on contact based solely on their physical surface structure. The wings provide a model for the development of novel functional surfaces that possess an increased resistance to bacterial contamination and infection. We propose a biophysical model of the interactions between bacterial cells and cicada wing surface structures, and show that mechanical properties, in particular cell rigidity, are key factors in determining bacterial resistance/sensitivity to the bactericidal nature of the wing surface. We confirmed this experimentally by decreasing the rigidity of surface-resistant strains through microwave irradiation of the cells, which renders them susceptible to the wing effects. Our findings demonstrate the potential benefits of incorporating cicada wing nanopatterns into the design of antibacterial nanomaterials. Copyright © 2013 Biophysical Society. Published by Elsevier Inc. All rights reserved.

The Asymmetric Cell Division Regulators Par3, Scribble and Pins/Gpsm2 Are Not Essential for Erythroid Development or Enucleation

PubMed Central

Wölwer, Christina B.; Gödde, Nathan; Pase, Luke B.; Elsum, Imogen A.; Lim, Krystle Y. B.; Sacirbegovic, Faruk; Walkley, Carl R.; Ellis, Sarah; Ohno, Shigeo; Matsuzaki, Fumio; Russell, Sarah M.; Humbert, Patrick O.

2017-01-01

Erythroid enucleation is the process by which the future red blood cell disposes of its nucleus prior to entering the blood stream. This key event during red blood cell development has been likened to an asymmetric cell division (ACD), by which the enucleating erythroblast divides into two very different daughter cells of alternate molecular composition, a nucleated cell that will be removed by associated macrophages, and the reticulocyte that will mature to the definitive erythrocyte. Here we investigated gene expression of members of the Par, Scribble and Pins/Gpsm2 asymmetric cell division complexes in erythroid cells, and functionally tested their role in erythroid enucleation in vivo and ex vivo. Despite their roles in regulating ACD in other contexts, we found that these polarity regulators are not essential for erythroid enucleation, nor for erythroid development in vivo. Together our results put into question a role for cell polarity and asymmetric cell division in erythroid enucleation. PMID:28095473

The actin homologue MreB organizes the bacterial cell membrane

PubMed Central

Strahl, Henrik; Bürmann, Frank; Hamoen, Leendert W.

2014-01-01

The eukaryotic cortical actin cytoskeleton creates specific lipid domains, including lipid rafts, which determine the distribution of many membrane proteins. Here we show that the bacterial actin homologue MreB displays a comparable activity. MreB forms membrane-associated filaments that coordinate bacterial cell wall synthesis. We noticed that the MreB cytoskeleton influences fluorescent staining of the cytoplasmic membrane. Detailed analyses combining an array of mutants, using specific lipid staining techniques and spectroscopic methods, revealed that MreB filaments create specific membrane regions with increased fluidity (RIFs). Interference with these fluid lipid domains (RIFs) perturbs overall lipid homeostasis and affects membrane protein localization. The influence of MreB on membrane organization and fluidity may explain why the active movement of MreB stimulates membrane protein diffusion. These novel MreB activities add additional complexity to bacterial cell membrane organization and have implications for many membrane-associated processes. PMID:24603761

The actin homologue MreB organizes the bacterial cell membrane.

PubMed

Strahl, Henrik; Bürmann, Frank; Hamoen, Leendert W

2014-03-07

The eukaryotic cortical actin cytoskeleton creates specific lipid domains, including lipid rafts, which determine the distribution of many membrane proteins. Here we show that the bacterial actin homologue MreB displays a comparable activity. MreB forms membrane-associated filaments that coordinate bacterial cell wall synthesis. We noticed that the MreB cytoskeleton influences fluorescent staining of the cytoplasmic membrane. Detailed analyses combining an array of mutants, using specific lipid staining techniques and spectroscopic methods, revealed that MreB filaments create specific membrane regions with increased fluidity (RIFs). Interference with these fluid lipid domains (RIFs) perturbs overall lipid homeostasis and affects membrane protein localization. The influence of MreB on membrane organization and fluidity may explain why the active movement of MreB stimulates membrane protein diffusion. These novel MreB activities add additional complexity to bacterial cell membrane organization and have implications for many membrane-associated processes.

Estimating division and death rates from CFSE data

NASA Astrophysics Data System (ADS)

de Boer, Rob J.; Perelson, Alan S.

2005-12-01

The division tracking dye, carboxyfluorescin diacetate succinimidyl ester (CFSE) is currently the most informative labeling technique for characterizing the division history of cells in the immune system. Gett and Hodgkin (Nat. Immunol. 1 (2000) 239-244) have proposed to normalize CFSE data by the 2-fold expansion that is associated with each division, and have argued that the mean of the normalized data increases linearly with time, t, with a slope reflecting the division rate p. We develop a number of mathematical models for the clonal expansion of quiescent cells after stimulation and show, within the context of these models, under which conditions this approach is valid. We compare three means of the distribution of cells over the CFSE profile at time t: the mean, [mu](t), the mean of the normalized distribution, [mu]2(t), and the mean of the normalized distribution excluding nondivided cells, .In the simplest models, which deal with homogeneous populations of cells with constant division and death rates, the normalized frequency distribution of the cells over the respective division numbers is a Poisson distribution with mean [mu]2(t)=pt, where p is the division rate. The fact that in the data these distributions seem Gaussian is therefore insufficient to establish that the times at which cells are recruited into the first division have a Gaussian variation because the Poisson distribution approaches the Gaussian distribution for large pt. Excluding nondivided cells complicates the data analysis because , and only approaches a slope p after an initial transient.In models where the first division of the quiescent cells takes longer than later divisions, all three means have an initial transient before they approach an asymptotic regime, which is the expected [mu](t)=2pt and . Such a transient markedly complicates the data analysis. After the same initial transients, the normalized cell numbers tend to decrease at a rate e-dt, where d is the death rate

Process to Selectively Distinguish Viable from Non-Viable Bacterial Cells

NASA Technical Reports Server (NTRS)

LaDuc, Myron T.; Bernardini, Jame N.; Stam, Christina N.

2010-01-01

The combination of ethidium monoazide (EMA) and post-fragmentation, randomly primed DNA amplification technologies will enhance the analytical capability to discern viable from non-viable bacterial cells in spacecraft-related samples. Intercalating agents have been widely used since the inception of molecular biology to stain and visualize nucleic acids. Only recently, intercalating agents such as EMA have been exploited to selectively distinguish viable from dead bacterial cells. Intercalating dyes can only penetrate the membranes of dead cells. Once through the membrane and actually inside the cell, they intercalate DNA and, upon photolysis with visible light, produce stable DNA monoadducts. Once the DNA is crosslinked, it becomes insoluble and unable to be fragmented for post-fragmentation, randomly primed DNA library formation. Viable organisms DNA remains unaffected by the intercalating agents, allowing for amplification via post-fragmentation, randomly primed technologies. This results in the ability to carry out downstream nucleic acid-based analyses on viable microbes to the exclusion of all non-viable cells.

Template DNA-strand co-segregation and asymmetric cell division in skeletal muscle stem cells.

PubMed

Shinin, Vasily; Gayraud-Morel, Barbara; Tajbakhsh, Shahragim

2009-01-01

Stem cells are present in all tissues and organs, and are crucial for normal regulated growth. How the pool size of stem cells and their progeny is regulated to establish the tissue prenatally, then maintain it throughout life, is a key question in biology and medicine. The ability to precisely locate stem and progenitors requires defining lineage progression from stem to differentiated cells, assessing the mode of cell expansion and self-renewal and identifying markers to assess the different cell states within the lineage. We have shown that during lineage progression from a quiescent adult muscle satellite cell to a differentiated myofibre, both symmetric and asymmetric divisions take place. Furthermore, we provide evidence that a sub-population of label retaining satellite cells co-segregate template DNA strands to one daughter cell. These findings provide a means of identifying presumed stem and progenitor cells within the lineage. In addition, asymmetric segregation of template DNA and the cytoplasmic protein Numb provides a landmark to define cell behaviour as self-renewal and differentiation decisions are being executed.

Duplication and segregation of the actin (MreB) cytoskeleton during the prokaryotic cell cycle.

PubMed

Vats, Purva; Rothfield, Lawrence

2007-11-06

The bacterial actin homolog MreB exists as a single-copy helical cytoskeletal structure that extends between the two poles of rod-shaped bacteria. In this study, we show that equipartition of the MreB cytoskeleton into daughter cells is accomplished by division and segregation of the helical MreB array into two equivalent structures located in opposite halves of the predivisional cell. This process ensures that each daughter cell inherits one copy of the MreB cytoskeleton. The process is triggered by the membrane association of the FtsZ cell division protein. The cytoskeletal division and segregation events occur before and independently of cytokinesis and involve specialized MreB structures that appear to be intermediates in this process.

The effects of a low-intensity red laser on bacterial growth, filamentation and plasmid DNA

NASA Astrophysics Data System (ADS)

Roos, C.; Santos, J. N.; Guimarães, O. R.; Geller, M.; Paoli, F.; Fonseca, A. S.

2013-07-01

Exposure of nonphotosynthesizing microorganisms to light could increase cell division in cultures, a phenomenon denominated as biostimulation. However, data concerning the importance of the genetic characteristics of cells on this effect are as yet scarce. The aim of this work was to evaluate the effects of a low-intensity red laser on the growth, filamentation and plasmids in Escherichia coli cells proficient and deficient in DNA repair. E. coli cultures were exposed to a laser (658 nm, 10 mW, 1 and 8 J cm-2) to study bacterial growth and filamentation. Also, bacterial cultures hosting pBSK plasmids were exposed to the laser to study DNA topological forms from the electrophoretic profile in agarose gels. Data indicate the low-intensity red laser: (i) had no effect on the growth of E. coli wild type and exonuclease III deficient cells; (ii) induced bacterial filamentation, (iii) led to no alteration in the electrophoretic profile of plasmids from exonuclease III deficient cells, but plasmids from wild type cells were altered. A low-intensity red laser at the low fluences used in phototherapy has no effect on growth, but induces filamentation and alters the topological forms of plasmid DNA in E. coli cultures depending on the DNA repair mechanisms.

[Influence of human gastrointestinal tract bacterial pathogens on host cell apoptosis].

PubMed

Wronowska, Weronika; Godlewska, Renata; Jagusztyn-Krynicka, Elzbieta Katarzyna

2005-01-01

Several pathogenic bacteria are able to trigger apoptosis in the host cell, but the mechanisms by which it occurs differ, and the resulting pathology can take different courses. Induction and/or blockage of programmed cell death upon infection is a result of complex interaction of bacterial proteins with cellular proteins involved in signal transduction and apoptosis. In this review we focus on pro/anti-apoptotic activities exhibited by two enteric pathogens Salmonella enterica, Yersinia spp. and gastric pathogen Helicobacter pylori. We present current knowledge on how interaction between mammalian and bacterial cell relates to the molecular pathways of apoptosis, and what is the role of apoptosis in pathogenesis.

The impact of metabolic state on Cd adsorption onto bacterial cells

USGS Publications Warehouse

Johnson, K.J.; Ams, D.A.; Wedel, A.N.; Szymanowski, J.E.S.; Weber, D.L.; Schneegurt, M.A.; Fein, J.B.

2007-01-01

This study examines the effect of bacterial metabolism on the adsorption of Cd onto Gram-positive and Gram-negative bacterial cells. Metabolically active Gram-positive cells adsorbed significantly less Cd than non-metabolizing cells. Gram-negative cells, however, showed no systematic difference in Cd adsorption between metabolizing and non-metabolizing cells. The effect of metabolism on Cd adsorption to Gram-positive cells was likely due to an influx of protons in and around the cell wall from the metabolic proton motive force, promoting competition between Cd and protons for adsorption sites on the cell wall. The relative lack of a metabolic effect on Cd adsorption onto Gram-negative compared to Gram-positive cells suggests that Cd binding in Gram-negative cells is focused in a region of the cell wall that is not reached, or is unaffected by this proton flux. Thermodynamic modeling was used to estimate that proton pumping causes the pH in the cell wall of metabolizing Gram-positive bacteria to decrease from the bulk solution value of 7.0 to approximately 5.7. ?? 2007 The Authors.

Diurnal rhythm in the cell-division frequency of prochloron (prochlorophyta) in nature

NASA Technical Reports Server (NTRS)

Lewin, R. A.; Cheng, L.; Matta, J.

1983-01-01

Frequencies of cell division stages in suspensions of Prochloron cells, expressed at regular intervals throughout a natural day-night cycle from several colonies of four species of host didemnid, are given. The proportion of dividing cells of Prochloron living symbiotically in colonies of a didemnid, Diplosoma virens, rises from about 4% during the night (20.00-04.00 hrs.) to about 13% in the morning (0,.00-12.00 hrs.), and then falls again in the afternoon. Similiar, though less pronounced, changes were observed among Prochloron cells in two other symbiotic didemnids, Lissoclinum patella and L. voeltzkowi.

Loss of PodJ in Agrobacterium tumefaciens Leads to Ectopic Polar Growth, Branching, and Reduced Cell Division

PubMed Central

Anderson-Furgeson, James C.; Zupan, John R.; Grangeon, Romain

2016-01-01

ABSTRACT Agrobacterium tumefaciens is a rod-shaped Gram-negative bacterium that elongates by unipolar addition of new cell envelope material. Approaching cell division, the growth pole transitions to a nongrowing old pole, and the division site creates new growth poles in sibling cells. The A. tumefaciens homolog of the Caulobacter crescentus polar organizing protein PopZ localizes specifically to growth poles. In contrast, the A. tumefaciens homolog of the C. crescentus polar organelle development protein PodJ localizes to the old pole early in the cell cycle and accumulates at the growth pole as the cell cycle proceeds. FtsA and FtsZ also localize to the growth pole for most of the cell cycle prior to Z-ring formation. To further characterize the function of polar localizing proteins, we created a deletion of A. tumefaciens podJ (podJAt). ΔpodJAt cells display ectopic growth poles (branching), growth poles that fail to transition to an old pole, and elongated cells that fail to divide. In ΔpodJAt cells, A. tumefaciens PopZ-green fluorescent protein (PopZAt-GFP) persists at nontransitioning growth poles postdivision and also localizes to ectopic growth poles, as expected for a growth-pole-specific factor. Even though GFP-PodJAt does not localize to the midcell in the wild type, deletion of podJAt impacts localization, stability, and function of Z-rings as assayed by localization of FtsA-GFP and FtsZ-GFP. Z-ring defects are further evidenced by minicell production. Together, these data indicate that PodJAt is a critical factor for polar growth and that ΔpodJAt cells display a cell division phenotype, likely because the growth pole cannot transition to an old pole. IMPORTANCE How rod-shaped prokaryotes develop and maintain shape is complicated by the fact that at least two distinct species-specific growth modes exist: uniform sidewall insertion of cell envelope material, characterized in model organisms such as Escherichia coli, and unipolar growth, which occurs

Citral induces auxin and ethylene-mediated malformations and arrests cell division in Arabidopsis thaliana roots.

PubMed

Graña, E; Sotelo, T; Díaz-Tielas, C; Araniti, F; Krasuska, U; Bogatek, R; Reigosa, M J; Sánchez-Moreiras, A M

2013-02-01

Citral is a linear monoterpene which is present, as a volatile component, in the essential oil of several different aromatic plants. Previous studies have demonstrated the ability of citral to alter the mitotic microtubules of plant cells, especially at low concentrations. The changes to the microtubules may be due to the compound acting directly on the treated root and coleoptile cells or to indirect action through certain phytohormones. This study, performed in Arabidopsis thaliana, analysed the short-term effects of citral on the auxin content and mitotic cells, and the long-term effects of these alterations on root development and ethylene levels. The results of this study show that citral alters auxin content and cell division and has a strong long-term disorganising effect on cell ultra-structure in A. thaliana seedlings. Its effects on cell division, the thickening of the cell wall, the reduction in intercellular communication, and the absence of root hairs confirm that citral is a strong phytotoxic compound, which has persistent effects on root development.

Impact of physical confinement on nuclei geometry and cell division dynamics in 3D spheroids.

PubMed

Desmaison, Annaïck; Guillaume, Ludivine; Triclin, Sarah; Weiss, Pierre; Ducommun, Bernard; Lobjois, Valérie

2018-06-08

Multicellular tumour spheroids are used as a culture model to reproduce the 3D architecture, proliferation gradient and cell interactions of a tumour micro-domain. However, their 3D characterization at the cell scale remains challenging due to size and cell density issues. In this study, we developed a methodology based on 3D light sheet fluorescence microscopy (LSFM) image analysis and convex hull calculation that allows characterizing the 3D shape and orientation of cell nuclei relative to the spheroid surface. By using this technique and optically cleared spheroids, we found that in freely growing spheroids, nuclei display an elongated shape and are preferentially oriented parallel to the spheroid surface. This geometry is lost when spheroids are grown in conditions of physical confinement. Live 3D LSFM analysis of cell division revealed that confined growth also altered the preferential cell division axis orientation parallel to the spheroid surface and induced prometaphase delay. These results provide key information and parameters that help understanding the impact of physical confinement on cell proliferation within tumour micro-domains.

Chemically synthesized silver nanoparticles as cell lysis agent for bacterial genomic DNA isolation

NASA Astrophysics Data System (ADS)

Goswami, Gunajit; Boruah, Himangshu; Gautom, Trishnamoni; Jyoti Hazarika, Dibya; Barooah, Madhumita; Boro, Robin Chandra

2017-12-01

Silver nanoparticles (AgNPs) have seen a recent spurt of use in varied fields of science. In this paper, we showed a novel application of AgNP as a promising microbial cell-lysis agent for genomic DNA isolation. We utilized chemically synthesized AgNPs for lysing bacterial cells to isolate their genomic DNA. The AgNPs efficiently lysed bacterial cells to yield good quality DNA that could be subsequently used for several molecular biology works.

PGE2 suppresses intestinal T cell function in thermal injury: a cause of enhanced bacterial translocation.

PubMed

Choudhry, M A; Fazal, N; Namak, S Y; Haque, F; Ravindranath, T; Sayeed, M M

2001-09-01

Increased gut bacterial translocation in burn and trauma patients has been demonstrated in a number of previous studies, however, the mechanism for such an increased gut bacterial translocation in injured patients remains poorly understood. Utilizing a rat model of burn injury, in the present study we examined the role of intestinal immune defense by analyzing the T cell functions. We investigated if intestinal T cells dysfunction contributes to bacterial translocation after burn injury. Also our study determined if burn-mediated alterations in intestinal T cell functions are related to enhanced release of PGE2. Finally, we examined whether or not burn-related alterations in intestinal T cell function are due to inappropriate activation of signaling molecule P59fyn, which is required for T cell activation and proliferation. The results presented here showed an increase in gut bacterial accumulation in mesenteric lymph nodes after thermal injury. This was accompanied by a decrease in the intestinal T cell proliferative responses. Furthermore, the treatments of burn-injured animals with PGE2 synthesis blocker (indomethacin or NS398) prevented both the decrease in intestinal T cell proliferation and enhanced bacterial translocation. Finally, our data suggested that the inhibition of intestinal T cell proliferation could result via PGE2-mediated down-regulation of the T cell activation-signaling molecule P59fyn. These findings support a role of T cell-mediated immune defense against bacterial translocation in burn injury.

Streptococcus suis DivIVA Protein Is a Substrate of Ser/Thr Kinase STK and Involved in Cell Division Regulation

PubMed Central

Ni, Hua; Fan, Weiwei; Li, Chaolong; Wu, Qianqian; Hou, Hongfen; Hu, Dan; Zheng, Feng; Zhu, Xuhui; Wang, Changjun; Cao, Xiangrong; Shao, Zhu-Qing; Pan, Xiuzhen

2018-01-01

Streptococcus suis serotype 2 is an important swine pathogen and an emerging zoonotic agent that causes severe infections. Recent studies have reported a eukaryotic-like Ser/Thr protein kinase (STK) gene and characterized its role in the growth and virulence of different S. suis 2 strains. In the present study, phosphoproteomic analysis was adopted to identify substrates of the STK protein. Seven proteins that were annotated to participate in different cell processes were identified as potential substrates, which suggests the pleiotropic effects of stk on S. suis 2 by targeting multiple pathways. Among them, a protein characterized as cell division initiation protein (DivIVA) was further investigated. In vitro analysis demonstrated that the recombinant STK protein directly phosphorylates threonine at amino acid position 199 (Thr-199) of DivIVA. This effect could be completely abolished by the T199A mutation. To determine the specific role of DivIVA in growth and division, a divIVA mutant was constructed. The ΔdivIVA strain exhibited impaired growth and division, including lower viability, enlarged cell mass, asymmetrical division caused by aberrant septum, and extremely weak pathogenicity in a mouse infection model. Collectively, our results reveal that STK regulates the cell growth and virulence of S. suis 2 by targeting substrates that are involved in different biological pathways. The inactivation of DivIVA leads to severe defects in cell division and strongly attenuates pathogenicity, thereby indicating its potential as a molecular drug target against S. suis. PMID:29616196

Conventional CD4+ T cells present bacterial antigens to induce cytotoxic and memory CD8+ T cell responses.

PubMed

Cruz-Adalia, Aránzazu; Ramirez-Santiago, Guillermo; Osuna-Pérez, Jesús; Torres-Torresano, Mónica; Zorita, Virgina; Martínez-Riaño, Ana; Boccasavia, Viola; Borroto, Aldo; Martínez Del Hoyo, Gloria; González-Granado, José María; Alarcón, Balbino; Sánchez-Madrid, Francisco; Veiga, Esteban

2017-11-17

Bacterial phagocytosis and antigen cross-presentation to activate CD8 + T cells are principal functions of professional antigen presenting cells. However, conventional CD4 + T cells also capture and kill bacteria from infected dendritic cells in a process termed transphagocytosis (also known as transinfection). Here, we show that transphagocytic T cells present bacterial antigens to naive CD8 + T cells, which proliferate and become cytotoxic in response. CD4 + T-cell-mediated antigen presentation also occurs in vivo in the course of infection, and induces the generation of central memory CD8 + T cells with low PD-1 expression. Moreover, transphagocytic CD4 + T cells induce protective anti-tumour immune responses by priming CD8 + T cells, highlighting the potential of CD4 + T cells as a tool for cancer immunotherapy.

Osmotic Pressure, Bacterial Cell Walls, and Penicillin: A Demonstration.

ERIC Educational Resources Information Center

Lennox, John E.

1984-01-01

An easily constructed apparatus that models the effect of penicillin on the structure of bacterial cells is described. Background information and procedures for using the apparatus during a classroom demonstration are included. (JN)

From cell differentiation to cell collectives: Bacillus subtilis uses division of labor to migrate.

PubMed

van Gestel, Jordi; Vlamakis, Hera; Kolter, Roberto

2015-04-01

The organization of cells, emerging from cell-cell interactions, can give rise to collective properties. These properties are adaptive when together cells can face environmental challenges that they separately cannot. One particular challenge that is important for microorganisms is migration. In this study, we show how flagellum-independent migration is driven by the division of labor of two cell types that appear during Bacillus subtilis sliding motility. Cell collectives organize themselves into bundles (called "van Gogh bundles") of tightly aligned cell chains that form filamentous loops at the colony edge. We show, by time-course microscopy, that these loops migrate by pushing themselves away from the colony. The formation of van Gogh bundles depends critically on the synergistic interaction of surfactin-producing and matrix-producing cells. We propose that surfactin-producing cells reduce the friction between cells and their substrate, thereby facilitating matrix-producing cells to form bundles. The folding properties of these bundles determine the rate of colony expansion. Our study illustrates how the simple organization of cells within a community can yield a strong ecological advantage. This is a key factor underlying the diverse origins of multicellularity.

Genetic analysis of indefinite division in human cells: Evidence for a cell senescence-related gene(s) on human chromosome 4

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yi Ning; Ledbetter, D.H.; Smith, J.R.

1991-07-01

Earlier studies had demonstrated that fusion of normal with immortal human cells yielded hybrids having limited division potential. This indicated that the phenotype of limited proliferation (cellular senescence) is dominant and that immortal cells result from recessive changes in normal growth-regulatory genes. In additional studies, the authors exploited the fact that the immortal phenotype is recessive and, by fusing various immortal human cell lines with each other, identified four complementation groups for indefinite division. Assignment of cell lines to specific groups allowed us to take a focused approach to identify the chromosomes and genes involved in growth regulation that havemore » been modified in immortal cells. They report here that introduction of a normal human chromosome 4 into three immortal cell lines (HeLa, J82, T98G) assigned to complementation group B resulted in loss of proliferation and reversal of the immortal phenotype. No effect on the proliferation potential of cell lines representative of the other complementation groups was observed. This result suggests that a gene(s) involved in cellular senescence and normal growth regulation resides on chromosome 4.« less

The influence of GAP-43 on orientation of cell division through G proteins.

PubMed

Huang, Rui; Zhao, Junpeng; Ju, Lili; Wen, Yujun; Xu, Qunyuan

2015-12-01

Recent studies have shown that GAP-43 is highly expressed in horizontally dividing neural progenitor cells, and G protein complex are required for proper mitotic-spindle orientation of those progenitors in the mammalian developing cortex. In order to verify the hypothesis that GAP-43 may influence the orientation of cell division through interacting with G proteins during neurogenesis, the GAP-43 RNA from adult C57 mouse was cloned into the pEGFP-N1 vector, which was then transfected into Madin-Darby Canine Kidney (MDCK) cells cultured in a three-dimensional (3D) cell culture system. The interaction of GAP-43 with Gαi was detected by co-immunoprecipitation (co-IP), while cystogenesis of 3D morphogenesis of MDCK cells and expression of GAP-43 and Gαi were determined by immunofluorescence and Western blotting. The results showed are as follows: After being transfected by pEGFP-N1-GAP-43, GAP-43 was localized on the cell membrane and co-localized with Gαi, and this dramatically induced a defective cystogenesis in 3D morphogenesis of MDCK cells. The functional interaction between GAP-43 and Gαi proteins was proven by the co-IP assay. It can be considered from the results that the GAP-43 is involved in the orientation of cell division by interacting with Gαi and this should be an important mechanism for neurogenesis in the mammalian brain. Copyright © 2015 Elsevier Ltd. All rights reserved.

The polarity protein Baz forms a platform for the centrosome orientation during asymmetric stem cell division in the Drosophila male germline.

PubMed

Inaba, Mayu; Venkei, Zsolt G; Yamashita, Yukiko M

2015-03-20

Many stem cells divide asymmetrically in order to balance self-renewal with differentiation. The essence of asymmetric cell division (ACD) is the polarization of cells and subsequent division, leading to unequal compartmentalization of cellular/extracellular components that confer distinct cell fates to daughter cells. Because precocious cell division before establishing cell polarity would lead to failure in ACD, these two processes must be tightly coupled; however, the underlying mechanism is poorly understood. In Drosophila male germline stem cells, ACD is prepared by stereotypical centrosome positioning. The centrosome orientation checkpoint (COC) further serves to ensure ACD by preventing mitosis upon centrosome misorientation. In this study, we show that Bazooka (Baz) provides a platform for the correct centrosome orientation and that Baz-centrosome association is the key event that is monitored by the COC. Our work provides a foundation for understanding how the correct cell polarity may be recognized by the cell to ensure productive ACD.

From Cell Differentiation to Cell Collectives: Bacillus subtilis Uses Division of Labor to Migrate

PubMed Central

van Gestel, Jordi; Vlamakis, Hera; Kolter, Roberto

2015-01-01

The organization of cells, emerging from cell–cell interactions, can give rise to collective properties. These properties are adaptive when together cells can face environmental challenges that they separately cannot. One particular challenge that is important for microorganisms is migration. In this study, we show how flagellum-independent migration is driven by the division of labor of two cell types that appear during Bacillus subtilis sliding motility. Cell collectives organize themselves into bundles (called “van Gogh bundles”) of tightly aligned cell chains that form filamentous loops at the colony edge. We show, by time-course microscopy, that these loops migrate by pushing themselves away from the colony. The formation of van Gogh bundles depends critically on the synergistic interaction of surfactin-producing and matrix-producing cells. We propose that surfactin-producing cells reduce the friction between cells and their substrate, thereby facilitating matrix-producing cells to form bundles. The folding properties of these bundles determine the rate of colony expansion. Our study illustrates how the simple organization of cells within a community can yield a strong ecological advantage. This is a key factor underlying the diverse origins of multicellularity. PMID:25894589

In vitro bacterial cytotoxicity of CNTs: reactive oxygen species mediate cell damage edges over direct physical puncturing.

PubMed

Rajavel, Krishnamoorthy; Gomathi, Rajkumar; Manian, Sellamuthu; Rajendra Kumar, Ramasamy Thangavelu

2014-01-21

Understanding the bacterial cytotoxicity of CNTs is important for a wide variety of applications in the biomedical, environmental, and health sectors. A majority of the earlier reports attributed the bactericidal cytotoxicity of CNTs to bacterial cell membrane damage by direct physical puncturing. Our results reveal that bacterial cell death via bacterial cell membrane damage is induced by reactive oxygen species (ROS) produced from CNTs and is not due to direct physical puncturing by CNTs. To understand the actual mechanism of bacterial killing, we elucidated the bacterial cytotoxicity of SWCNTs and MWCNTs against Gram-negative human pathogenic bacterial species Escherichia coli, Shigella sonnei, Klebsiella pneumoniae, and Pseudomonas aeruginosa and its amelioration upon functionalizing the CNTs with antioxidant tannic acid (TA). Interestingly, the bacterial cells treated with CNTs exhibited severe cell damage under laboratory (ambient) and sunlight irradiation conditions. However, CNTs showed no cytotoxicity to the bacterial cells when incubated in the dark. The quantitative assessments carried out by us made it explicit that CNTs are effective generators of ROS such as (1)O2, O2(•-), and (•)OH in an aqueous medium under both ambient and sunlight-irradiated conditions. Both naked and TA-functionalized CNTs showed negligible ROS production in the dark. Furthermore, strong correlations were obtained between ROS produced by CNTs and the bacterial cell mortality (with the correlation coefficient varying between 0.7618 and 0.9891) for all four tested pathogens. The absence of bactericidal cytotoxicity in both naked and functionalized CNTs in the dark reveals that the presence of ROS is the major factor responsible for the bactericidal action compared to direct physical puncturing. This understanding of the bactericidal activity of the irradiated CNTs, mediated through the generation of ROS, could be interesting for novel applications such as regulated ROS delivery

Autologous tumor cells engineered to express bacterial antigens.

PubMed

Ramiya, Vijayakumar K; Jerald, Maya M; Lawman, Patricia D; Lawman, Michael J P

2014-01-01

Cancer immunotherapies are emerging as promising treatment modalities in the management of the disease. As a result, cancer vaccines are considered to be immensely crucial in preventing recurrence, a well-known nemesis in cancer patients because they have the potential to activate memory antitumor immunity. Due to poor antigenicity and self-tolerance, most tumor antigens require interventional vaccine therapies to provide an adequate "danger" signal to the immune system in order to activate a robust, clinically meaningful antitumor immunity. It has been postulated that this requirement may be achieved by providing bacterial and/or viral immunogens to prime this type of immune response. Briefly, we provide here a method of transfecting whole tumor cells with plasmid DNA encoding an immunogenic bacterial protein such as Emm55, which was derived from Streptococcus pyogenes (S. pyogenes). Subsequent inactivation of the transfected cells by irradiation (100 Gray) prevents replication. This type of whole-cell vaccine, e.g., ImmuneFx™, has demonstrated activity in a murine neuroblastoma model, in canine lymphoma patients with naturally occurring disease, and in many cancer types in companion animals. The protocols described in this chapter provide the necessary materials and methodologies to manufacture such a vaccine.

Dichromatic and monochromatic laser radiation effects on antibiotic resistance, biofilm formation, and division rate of Pantoea agglomerans

NASA Astrophysics Data System (ADS)

Thomé, A. M. C.; Souza, B. P.; Mendes, J. P. M.; Cardoso, A. F. R.; Soares, L. C.; Trajano, E. T. L.; Fonseca, A. S.

2018-06-01

Since infection is a common cause of delayed wound healing, it is important to understand the effect of low-level laser therapy (LLLT) in bacterial mechanisms. In this study we evaluated the effects of LLLT on antibiotic resistance, division rate, and biofilm formation of Pantoea agglomerans. P. agglomerans samples were isolated from human pressure injuries in humans and cultures were exposed to low-level monochromatic and simultaneous dichromatic laser radiation to study the susceptibility of an antimicrobial to ampicillin and piperacillin  +  tazobactam, quantification of areas of bacterial colonies, and biofilm formation of bacterial cells. Fluence, wavelength, and emission mode were used in the therapeutic protocols for wound healing. The data showed no changes in the areas of the colonies, but dichromatic laser radiation decreased biofilm formation, while a monochromatic red laser at low dose increased biofilm formation and infrared at high dose decreased antibiotic resistance to ampicillin. LLLT modulates antibiotic resistance and biofilm formation of P. agglomerans, but these depend on the laser irradiation parameters, since dichromatic laser radiation induces biological effects that differ from those induced by monochromatic laser radiation. Thus, simultaneous dichromatic low-level red and infrared lasers could be a new option for the treatment of infected wounds, reducing biofilm formation, without altering antibiotic resistance and the division rate of P. agglomerans cultures.

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

PubMed Central

Mathis, Roland; Ackermann, Martin

2016-01-01

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 bacterium Caulobacter crescentus and 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. PMID:26960998

How-to-Do-It: Hands-on Activities that Relate Mendelian Genetics to Cell Division.

ERIC Educational Resources Information Center

McKean, Heather R.; Gibson, Linda S.

1989-01-01

Presented is an activity designed to connect Mendelian laws with the physical processes of cell division. Included are materials production, procedures and worksheets for the meiosis-mitosis game and a genetics game. (CW)

Rumen Bacterial Degradation of Forage Cell Walls Investigated by Electron Microscopy

PubMed Central

Akin, Danny E.; Amos, Henry E.

1975-01-01

The association of rumen bacteria with specific leaf tissues of the forage grass Kentucky-31 tall fescue (Festuca arundinacea Schreb.) during in vitro degradation was investigated by transmission and scanning electron microscopy. Examination of degraded leaf cross-sections revealed differential rates of tissue degradation in that the cell walls of the mesophyll and pholem were degraded prior to those of the outer bundle sheath and epidermis. Rumen bacteria appeared to degrade the mesophyll, in some cases, and phloem without prior attachment to the plant cell walls. The degradation of bundle sheath and epidermal cell walls appeared to be preceded by attachment of bacteria to the plant cell wall. Ultrastructural features apparently involved in the adhesion of large cocci to plant cells were observed by transmission and scanning electron microscopy. The physical association between plant and rumen bacterial cells during degradation apparently varies with tissue types. Bacterial attachment, by extracellular features in some microorganisms, is required prior to degradation of the more resistant tissues. Images PMID:16350017

The coral core microbiome identifies rare bacterial taxa as ubiquitous endosymbionts

PubMed Central

D Ainsworth, Tracy; Krause, Lutz; Bridge, Thomas; Torda, Gergely; Raina, Jean-Baptise; Zakrzewski, Martha; Gates, Ruth D; Padilla-Gamiño, Jacqueline L; Spalding, Heather L; Smith, Celia; Woolsey, Erika S; Bourne, David G; Bongaerts, Pim; Hoegh-Guldberg, Ove; Leggat, William

2015-01-01

Despite being one of the simplest metazoans, corals harbor some of the most highly diverse and abundant microbial communities. Differentiating core, symbiotic bacteria from this diverse host-associated consortium is essential for characterizing the functional contributions of bacteria but has not been possible yet. Here we characterize the coral core microbiome and demonstrate clear phylogenetic and functional divisions between the micro-scale, niche habitats within the coral host. In doing so, we discover seven distinct bacterial phylotypes that are universal to the core microbiome of coral species, separated by thousands of kilometres of oceans. The two most abundant phylotypes are co-localized specifically with the corals' endosymbiotic algae and symbiont-containing host cells. These bacterial symbioses likely facilitate the success of the dinoflagellate endosymbiosis with corals in diverse environmental regimes. PMID:25885563

Evolution and tinkering: what do a protein kinase, a transcriptional regulator and chromosome segregation/cell division proteins have in common?

PubMed

Derouiche, Abderahmane; Shi, Lei; Kalantari, Aida; Mijakovic, Ivan

2016-02-01

In this study, we focus on functional interactions among multi-domain proteins which share a common evolutionary origin. The examples we develop are four Bacillus subtilis proteins, which all possess an ATP-binding Walker motif: the bacterial tyrosine kinase (BY-kinase) PtkA, the chromosome segregation protein Soj (ParA), the cell division protein MinD and a transcription regulator SalA. These proteins have arisen via duplication of the ancestral ATP-binding domain, which has undergone fusions with other functional domains in the process of divergent evolution. We point out that these four proteins, despite having very different physiological roles, engage in an unusually high number of binary functional interactions. Namely, MinD attracts Soj and PtkA to the cell pole, and in addition, activates the kinase function of PtkA. SalA also activates the kinase function of PtkA, and it gets phosphorylated by PtkA as well. The consequence of this phosphorylation is the activation of SalA as a transcriptional repressor. We hypothesize that these functional interactions remain preserved during divergent evolution and represent a constraint on the process of evolutionary "tinkering", brought about by fusions of different functional domains.

Differentiation of epithelial cells to M cells in response to bacterial colonization on the follicle-associated epithelium of Peyer's patch in rat small intestine.

PubMed

Chin, Keigi; Onishi, Sachiko; Yuji, Midori; Inamoto, Tetsurou; Qi, Wang-Mei; Warita, Katsuhiko; Yokoyama, Toshifumi; Hoshi, Nobuhiko; Kitagawa, Hiroshi

2006-10-01

To clarify the relationship between M cells and intestinal microflora, histoplanimetrical investigation into the bacterial colonization and the differentiation to M cells was carried out in rat Peyer's patch under physiological conditions. The follicle-associated epithelium (FAE), except for the narrow area of apical region, was closely covered with both neighboring intestinal villi and a thick mucous layer, the latter of which also filled the intervillous spaces as well as the space between the FAE and the neighboring intestinal villi. Indigenous bacteria adhered almost constantly to the narrow areas of apical regions of both intestinal villi and the FAE. Bacterial colonies were occasionally located on the basal to middle region of FAE, where M cells also appeared, forming large pockets. When bacterial colonies were located on the basal to middle region of FAE, bacteria with the same morphological characteristics also proliferated in the intervillous spaces neighboring the Peyer's patch. In cases with no bacterial colonies on the basal to middle region of FAE, however, M cells were rare in the FAE. Histoplanimetrical analysis showed the similar distribution pattern of bacterial colonies on the FAE and M cells in the FAE. M cells ultrastructurally engulfed indigenous bacteria, which were then transported to the pockets. These results suggest that indigenous bacterial colonization on the FAE stimulates the differentiation of M cells in the FAE under physiological conditions. The uptake of bacteria by M cells might contribute the regulation of the development of indigenous bacterial colonies in the small intestine.

New Application of Hyperspectral Imaging for Bacterial Cell Classification

USDA-ARS?s Scientific Manuscript database

Hyperspectral microscopy has shown potential as a method for rapid detection of foodborne pathogenic bacteria with spectral characteristics from bacterial cells. Hyperspectral microscope images (HMIs) are collected from broiler chicken isolates of Salmonella serotypes Enteritidis, Typhimurium, Infa...

Peptide promotes overcoming of the division limit in human somatic cell.

PubMed

Khavinson, V Kh; Bondarev, I E; Butyugov, A A; Smirnova, T D

2004-05-01

We previously showed that treatment of normal human diploid cells with Epithalon (Ala-Glu-Asp-Gly) induced expression of telomerase catalytic subunit, its enzymatic activity, and elongation of telomeres. Here we studied the effect of this peptide on proliferative potential of human fetal fibroblasts. Primary pulmonary fibroblasts derived from a 24-week fetus lost the proliferative potential at the 34th passage. The mean size of telomeres in these cells was appreciably lower than during early passages (passage 10). Addition of Epithalon to aging cells in culture induced elongation of telomeres to the size comparable to their length during early passages. Peptide-treated cells with elongated telomeres made 10 extra divisions (44 passages) in comparison with the control and continued dividing. Hence, Epithalon prolonged the vital cycle of normal human cells due to overcoming the Heyflick limit.

Division of labour in the yeast: Saccharomyces cerevisiae.

PubMed

Wloch-Salamon, Dominika M; Fisher, Roberta M; Regenberg, Birgitte

2017-10-01

Division of labour between different specialized cell types is a central part of how we describe complexity in multicellular organisms. However, it is increasingly being recognized that division of labour also plays an important role in the lives of predominantly unicellular organisms. Saccharomyces cerevisiae displays several phenotypes that could be considered a division of labour, including quiescence, apoptosis and biofilm formation, but they have not been explicitly treated as such. We discuss each of these examples, using a definition of division of labour that involves phenotypic variation between cells within a population, cooperation between cells performing different tasks and maximization of the inclusive fitness of all cells involved. We then propose future research directions and possible experimental tests using S. cerevisiae as a model organism for understanding the genetic mechanisms and selective pressures that can lead to the evolution of the very first stages of a division of labour. Copyright © 2017 John Wiley & Sons, Ltd. Copyright © 2017 John Wiley & Sons, Ltd.

Cell shape can mediate the spatial organization of the bacterial cytoskeleton

NASA Astrophysics Data System (ADS)

Wang, Siyuan; Wingreen, Ned

2013-03-01

The bacterial cytoskeleton guides the synthesis of cell wall and thus regulates cell shape. Since spatial patterning of the bacterial cytoskeleton is critical to the proper control of cell shape, it is important to ask how the cytoskeleton spatially self-organizes in the first place. In this work, we develop a quantitative model to account for the various spatial patterns adopted by bacterial cytoskeletal proteins, especially the orientation and length of cytoskeletal filaments such as FtsZ and MreB in rod-shaped cells. We show that the combined mechanical energy of membrane bending, membrane pinning, and filament bending of a membrane-attached cytoskeletal filament can be sufficient to prescribe orientation, e.g. circumferential for FtsZ or helical for MreB, with the accuracy of orientation increasing with the length of the cytoskeletal filament. Moreover, the mechanical energy can compete with the chemical energy of cytoskeletal polymerization to regulate filament length. Notably, we predict a conformational transition with increasing polymer length from smoothly curved to end-bent polymers. Finally, the mechanical energy also results in a mutual attraction among polymers on the same membrane, which could facilitate tight polymer spacing or bundling. The predictions of the model can be verified through genetic, microscopic, and microfluidic approaches.

Overly long centrioles and defective cell division upon excess of the SAS-4-related protein CPAP.

PubMed

Kohlmaier, Gregor; Loncarek, Jadranka; Meng, Xing; McEwen, Bruce F; Mogensen, Mette M; Spektor, Alexander; Dynlacht, Brian D; Khodjakov, Alexey; Gönczy, Pierre

2009-06-23

The centrosome is the principal microtubule organizing center (MTOC) of animal cells. Accurate centrosome duplication is fundamental for genome integrity and entails the formation of one procentriole next to each existing centriole, once per cell cycle. The procentriole then elongates to eventually reach the same size as the centriole. The mechanisms that govern elongation of the centriolar cylinder and their potential relevance for cell division are not known. Here, we show that the SAS-4-related protein CPAP is required for centrosome duplication in cycling human cells. Furthermore, we demonstrate that CPAP overexpression results in the formation of abnormally long centrioles. This also promotes formation of more than one procentriole in the vicinity of such overly long centrioles, eventually resulting in the presence of supernumerary MTOCs. This in turn leads to multipolar spindle assembly and cytokinesis defects. Overall, our findings suggest that centriole length must be carefully regulated to restrict procentriole number and thus ensure accurate cell division.

Cell directional migration and oriented division on three-dimensional laser-induced periodic surface structures on polystyrene.

PubMed

Wang, Xuefeng; Ohlin, Christian A; Lu, Qinghua; Hu, Jun

2008-05-01

The extracellular matrix in animal tissues usually provides a three-dimensional structural support to cells in addition to performing various other important functions. In the present study, wavy submicrometer laser-irradiated periodic surface structures (LIPSS) were produced on a smooth polystyrene film by polarized laser irradiation with a wavelength of 266 nm. Rat C6 glioma cells exhibited directional migration and oriented division on laser-irradiated polystyrene, which was parallel to the direction of LIPSS. However, rat C6 glioma cells on smooth polystyrene moved in a three-step invasion cycle, with faster migration speed than that on laser-irradiated polystyrene. In addition, focal adhesions examined by immunostaining focal adhesion kinase in human epithelial carcinoma HeLa cells were punctuated on smooth polystyrene, whereas dash-like on laser-irradiated polystyrene. We hypothesized that LIPSS on laser-irradiated polystyrene acted as an anisotropic and persistent mechanical stimulus to guide cell anisotropic spreading, migration and division through focal adhesions.

Morphology, Growth, and Size Limit of Bacterial Cells

NASA Astrophysics Data System (ADS)

Jiang, Hongyuan; Sun, Sean X.

2010-07-01

Bacterial cells utilize a living peptidoglycan network (PG) to separate the cell interior from the surroundings. The shape of the cell is controlled by PG synthesis and cytoskeletal proteins that form bundles and filaments underneath the cell wall. The PG layer also resists turgor pressure and protects the cell from osmotic shock. We argue that mechanical influences alter the chemical equilibrium of the reversible PG assembly and determine the cell shape and cell size. Using a mechanochemical approach, we show that the cell shape can be regarded as a steady state of a growing network under the influence of turgor pressure and mechanical stress. Using simple elastic models, we predict the size of common spherical and rodlike bacteria. The influence of cytoskeletal bundles such as crescentin and MreB are discussed within the context of our model.

Diversity in ATP concentrations in a single bacterial cell population revealed by quantitative single-cell imaging

PubMed Central

Yaginuma, Hideyuki; Kawai, Shinnosuke; Tabata, Kazuhito V.; Tomiyama, Keisuke; Kakizuka, Akira; Komatsuzaki, Tamiki; Noji, Hiroyuki; Imamura, Hiromi

2014-01-01

Recent advances in quantitative single-cell analysis revealed large diversity in gene expression levels between individual cells, which could affect the physiology and/or fate of each cell. In contrast, for most metabolites, the concentrations were only measureable as ensemble averages of many cells. In living cells, adenosine triphosphate (ATP) is a critically important metabolite that powers many intracellular reactions. Quantitative measurement of the absolute ATP concentration in individual cells has not been achieved because of the lack of reliable methods. In this study, we developed a new genetically-encoded ratiometric fluorescent ATP indicator “QUEEN”, which is composed of a single circularly-permuted fluorescent protein and a bacterial ATP binding protein. Unlike previous FRET-based indicators, QUEEN was apparently insensitive to bacteria growth rate changes. Importantly, intracellular ATP concentrations of numbers of bacterial cells calculated from QUEEN fluorescence were almost equal to those from firefly luciferase assay. Thus, QUEEN is suitable for quantifying the absolute ATP concentration inside bacteria cells. Finally, we found that, even for a genetically-identical Escherichia coli cell population, absolute concentrations of intracellular ATP were significantly diverse between individual cells from the same culture, by imaging QUEEN signals from single cells. PMID:25283467

The effect of antibacterial acting extracorporeal shockwaves on bacterial cell integrity.

PubMed

Horn, Carsten; Mengele, Karin; Gerdesmeyer, Ludger; Gradinger, Reiner; Gollwitzer, Hans

2009-12-01

Antibacterial effects of extracorporeal shockwaves (ESWs) have been demonstrated in vitro against bacteria under static and dynamic growth conditions. This study assessed the effects of ESWs on the cell wall integrity of bacteria. Standardized suspensions of Staphylococcus aureus were exposed to various shockwave impulses (2000-12,000) of different energy flux densities (EFD, 0.38-0.96 mJ/mm(2)). Bacterial suspensions of equal concentration that had been permeabilized (to >99%) with isopropanol were used as positive controls. The bacteria of all groups were stained with Sytox Green nucleic acid stain. The fluorescence of the shockwave-treated, permeabilized, and untreated suspensions was measured and compared for bacterial survival, quantified by colony-forming units after plating. Although ESWs showed a significant energy-dependent antibacterial effect that reduced CFUs in the treated suspensions by between 56% and 99%, only maximum energies (4000 impulses at 0.96 mJ/mm(2) and 12,000 impulses at 0.59 mJ/mm(2)) were followed by a significant increase in fluorescence compared with the untreated control (p<0.05). However, the fluorescence of these treated groups was still far less than that of the alcohol-permeabilized positive control groups (p<0.05). Lower energies and impulse rates did not show increased intracellular uptake of the fluorescent dye (p>0.05). This is the first study to assess bacterial cell wall permeability after ESW treatment. It was found that the permeabilization of bacterial cells after ESW treatment was far less than expected due to the corresponding antibacterial effect. Other mechanisms, such as intracellular effects, might be involved in bacterial killing after ESWs and still must be elucidated.

MinD and MinE Interact with Anionic Phospholipids and Regulate Division Plane Formation in Escherichia coli*

PubMed Central

Renner, Lars D.; Weibel, Douglas B.

2012-01-01

The Min proteins (MinC, MinD, and MinE) form a pole-to-pole oscillator that controls the spatial assembly of the division machinery in Escherichia coli cells. Previous studies identified that interactions of MinD with phospholipids positioned the Min machinery at the membrane. We extend these studies by measuring the affinity, kinetics, and ATPase activity of E. coli MinD, MinE, and MinDE binding to supported lipid bilayers containing varying compositions of anionic phospholipids. Using quartz crystal microbalance measurements, we found that the binding affinity (Kd) for the interaction of recombinant E. coli MinD and MinE with lipid bilayers increased with increasing concentration of the anionic phospholipids phosphatidylglycerol and cardiolipin. The Kd for MinD (1.8 μm) in the presence of ATP was smaller than for MinE (12.1 μm) binding to membranes consisting of 95:5 phosphatidylcholine/cardiolipin. The simultaneous binding of MinD and MinE to membranes revealed that increasing the concentration of anionic phospholipid stimulates the initial rate of adsorption (kon). The ATPase activity of MinD decreased in the presence of anionic phospholipids. These results indicate that anionic lipids, which are concentrated at the poles, increase the retention of MinD and MinE and explain its dwell time at this region of bacterial cells. These studies provide insight into interactions between MinD and MinE and between these proteins and membranes that are relevant to understanding the process of bacterial cell division, in which the interaction of proteins and membranes is essential. PMID:23012351