64 results on '"Bacteria cytology"'
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2. An Ancient Riboswitch Class in Bacteria Regulates Purine Biosynthesis and One-Carbon Metabolism.
- Author
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Kim, Peter B., Nelson, James W., and Breaker, Ronald R.
- Subjects
- *
RIBOSWITCHES , *BACTERIA cytology , *PURINE synthesis , *BIOSYNTHESIS , *CARBON metabolism , *CELLULAR control mechanisms - Abstract
Summary Over 30 years ago, ZTP (5-aminoimidazole-4-carboxamide riboside 5′-triphosphate), a modified purine biosynthetic intermediate, was proposed to signal 10-formyl-tetrahydrofolate (10f-THF) deficiency in bacteria. However, the mechanisms by which this putative alarmone or its precursor ZMP (5-aminoimidazole-4-carboxamide ribonucleotide, also known as AICAR) brings about any metabolic changes remain unexplained. Herein, we report the existence of a widespread riboswitch class that is most commonly associated with genes related to de novo purine biosynthesis and one-carbon metabolism. Biochemical data confirm that members of this riboswitch class selectively bind ZMP and ZTP with nanomolar affinity while strongly rejecting numerous natural analogs. Indeed, increases in the ZMP/ZTP pool, caused by folate stress in bacterial cells, trigger changes in the expression of a reporter gene fused to representative ZTP riboswitches in vivo. The wide distribution of this riboswitch class suggests that ZMP/ZTP signaling is important for species in numerous bacterial lineages. [ABSTRACT FROM AUTHOR]
- Published
- 2015
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3. Constitutive Formation of Caveolae in a Bacterium
- Author
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Walser, Piers J., Ariotti, Nicholas, Howes, Mark, Ferguson, Charles, Webb, Richard, Schwudke, Dominik, Leneva, Natalya, Cho, Kwang-Jin, Cooper, Leanne, Rae, James, Floetenmeyer, Matthias, Oorschot, Viola M.J., Skoglund, Ulf, Simons, Kai, Hancock, John F., and Parton, Robert G.
- Subjects
- *
CAVEOLAE , *INTRACELLULAR membranes , *CELL membranes , *VESICLES (Cytology) , *OLIGOMERS , *BACTERIA cytology , *PERIPLASM - Abstract
Summary: Caveolin plays an essential role in the formation of characteristic surface pits, caveolae, which cover the surface of many animal cells. The fundamental principles of caveola formation are only slowly emerging. Here we show that caveolin expression in a prokaryotic host lacking any intracellular membrane system drives the formation of cytoplasmic vesicles containing polymeric caveolin. Vesicle formation is induced by expression of wild-type caveolins, but not caveolin mutants defective in caveola formation in mammalian systems. In addition, cryoelectron tomography shows that the induced membrane domains are equivalent in size and caveolin density to native caveolae and reveals a possible polyhedral arrangement of caveolin oligomers. The caveolin-induced vesicles or heterologous caveolae (h-caveolae) form by budding in from the cytoplasmic membrane, generating a membrane domain with distinct lipid composition. Periplasmic solutes are encapsulated in the budding h-caveola, and purified h-caveolae can be tailored to be targeted to specific cells of interest. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
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4. Erin Goley.
- Author
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Goley E
- Subjects
- Bacteriology history, Environment, History, 21st Century, Humans, Mentoring, Social Media, Bacteria cytology, Bacteria growth & development
- Abstract
Interview with Erin Goley, who studies the mechanisms governing bacterial morphogenesis and the regulation of bacterial growth in changing environments at Johns Hopkins University School of Medicine., (Copyright © 2021.)
- Published
- 2021
- Full Text
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5. Bacterial Growth Control Mechanisms Inferred from Multivariate Statistical Analysis of Single-Cell Measurements.
- Author
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Kohram M, Vashistha H, Leibler S, Xue B, and Salman H
- Subjects
- Cell Proliferation, Multivariate Analysis, Regression Analysis, Bacteria cytology, Bacteria growth & development, Single-Cell Analysis
- Abstract
Analysis of single-cell measurements of bacterial growth and division often relied on testing preconceived models of cell size control mechanisms. Such an approach could limit the scope of data analysis and prevent us from uncovering new information. Here, we take an "agnostic" approach by applying regression methods to multiple simultaneously measured cellular variables, which allow us to infer dependencies among those variables from their apparent correlations. Besides previously observed correlations attributed to particular cell size control mechanisms, we identify dependencies that point to potentially new mechanisms. In particular, cells born smaller than their sisters tend to grow faster and make up for the size difference acquired during division. We also find that sister cells are correlated beyond what single-cell, size-control models predict. These trends are consistently found in repeat experiments, although the dependencies vary quantitatively. Such variation highlights the sensitivity of cell growth to environmental variations and the limitation of currently used experimental setups., Competing Interests: Declaration of Interests The authors declare no competing interests., (Copyright © 2020 The Authors. Published by Elsevier Inc. All rights reserved.)
- Published
- 2021
- Full Text
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6. Signal Percolation within a Bacterial Community.
- Author
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Larkin JW, Zhai X, Kikuchi K, Redford SE, Prindle A, Liu J, Greenfield S, Walczak AM, Garcia-Ojalvo J, Mugler A, and Süel GM
- Subjects
- Bacteria cytology, Biofilms, Electrochemistry, Microbiota, Models, Biological, Phase Transition, Bacteria metabolism, Microbial Interactions, Single-Cell Analysis methods
- Abstract
Signal transmission among cells enables long-range coordination in biological systems. However, the scarcity of quantitative measurements hinders the development of theories that relate signal propagation to cellular heterogeneity and spatial organization. We address this problem in a bacterial community that employs electrochemical cell-to-cell communication. We developed a model based on percolation theory, which describes how signals propagate through a heterogeneous medium. Our model predicts that signal transmission becomes possible when the community is organized near a critical phase transition between a disconnected and a fully connected conduit of signaling cells. By measuring population-level signal transmission with single-cell resolution in wild-type and genetically modified communities, we confirm that the spatial distribution of signaling cells is organized at the predicted phase transition. Our findings suggest that at this critical point, the population-level benefit of signal transmission outweighs the single-cell level cost. The bacterial community thus appears to be organized according to a theoretically predicted spatial heterogeneity that promotes efficient signal transmission., (Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.)
- Published
- 2018
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7. Rediscovering Bacteria through Single-Molecule Imaging in Living Cells.
- Author
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Kapanidis AN, Lepore A, and El Karoui M
- Subjects
- Bacteria genetics, Microscopy, Photons, Bacteria cytology, Single Molecule Imaging methods
- Abstract
Bacteria are microorganisms central to health and disease, serving as important model systems for our understanding of molecular mechanisms and for developing new methodologies and vehicles for biotechnology. In the past few years, our understanding of bacterial cell functions has been enhanced substantially by powerful single-molecule imaging techniques. Using single fluorescent molecules as a means of breaking the optical microscopy limit, we can now reach resolutions of ∼20 nm inside single living cells, a spatial domain previously accessible only by electron microscopy. One can follow a single bacterial protein complex as it performs its functions and directly observe intricate cellular structures as they move and reorganize during the cell cycle. This toolbox enables the use of in vivo quantitative biology by counting molecules, characterizing their intracellular location and mobility, and identifying functionally distinct molecular distributions. Crucially, this can all be achieved while imaging large populations of cells, thus offering detailed views of the heterogeneity in bacterial communities. Here, we examine how this new scientific domain was born and discuss examples of applications to bacterial cellular mechanisms as well as emerging trends and applications., (Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.)
- Published
- 2018
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8. Cell Division: Symbiotic Bacteria Turn It Upside Down.
- Author
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Thanbichler M
- Subjects
- Animals, Bacteria cytology, Cell Division, Morphogenesis, Nematoda microbiology, Symbiosis
- Abstract
Symbiotic bacteria of the genus Thiosymbion attach to the surface of their nematode hosts using their poles and divide by longitudinal binary fission. A new study now sheds light on the molecular mechanisms that underlie this peculiar mode of proliferation., (Copyright © 2018 Elsevier Ltd. All rights reserved.)
- Published
- 2018
- Full Text
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9. Atomistic Scale Effects of Lipopolysaccharide Modifications on Bacterial Outer Membrane Defenses.
- Author
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Rice A and Wereszczynski J
- Subjects
- Arabinose analogs & derivatives, Arabinose metabolism, Bacteria metabolism, Calcium metabolism, Cell Membrane chemistry, Lipid Bilayers chemistry, Lipid Bilayers metabolism, Lipopolysaccharides chemistry, Molecular Conformation, Water metabolism, Bacteria cytology, Cell Membrane metabolism, Lipopolysaccharides metabolism, Molecular Dynamics Simulation
- Abstract
Lipopolysaccharides (LPS) are a main constituent of the outer membrane of Gram-negative bacteria. Salmonella enterica, like many other bacterial species, are able to chemically modify the structure of their LPS molecules through the PhoPQ pathway as a defense mechanism against the host immune response. These modifications make the outer membrane more resistant to antimicrobial peptides (AMPs), large lipophilic drugs, and cation depletion, and are crucial for survival within a host organism. It is believed that these LPS modifications prevent the penetration of large molecules and AMPs through a strengthening of lateral interactions between neighboring LPS molecules. Here, we performed a series of long-timescale molecular dynamics simulations to study how each of three key S. enterica lipid A modifications affect bilayer properties, with a focus on membrane structural characteristics, lateral interactions, and the divalent cation bridging network. Our results discern the unique impact each modification has on strengthening the bacterial outer membrane through effects such as increased hydrogen bonding and tighter lipid packing. Additionally, one of the modifications studied shifts Ca
2+ from the lipid A region, replacing it as a major cross-linking agent between adjacent lipids and potentially making bacteria less susceptible to AMPs that competitively displace cations from the membrane surface. These results further improve our understanding of outer membrane chemical properties and help elucidate how outer membrane modification systems, such as PhoPQ in S. enterica, are able to alter bacterial virulence., (Copyright © 2018 Biophysical Society. Published by Elsevier Inc. All rights reserved.)- Published
- 2018
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10. Subcellular Organization: A Critical Feature of Bacterial Cell Replication.
- Author
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Surovtsev IV and Jacobs-Wagner C
- Subjects
- Bacteria cytology, Bacteria metabolism, Bacterial Proteins genetics, Bacterial Proteins metabolism, Cell Division genetics, DNA Replication genetics, DNA, Bacterial genetics, Bacteria genetics, Chromosomes, Bacterial genetics, Gene Expression Regulation, Bacterial, Genome, Bacterial genetics
- Abstract
Spatial organization is a hallmark of all living systems. Even bacteria, the smallest forms of cellular life, display defined shapes and complex internal organization, showcasing a highly structured genome, cytoskeletal filaments, localized scaffolding structures, dynamic spatial patterns, active transport, and occasionally, intracellular organelles. Spatial order is required for faithful and efficient cellular replication and offers a powerful means for the development of unique biological properties. Here, we discuss organizational features of bacterial cells and highlight how bacteria have evolved diverse spatial mechanisms to overcome challenges cells face as self-replicating entities., (Copyright © 2018 Elsevier Inc. All rights reserved.)
- Published
- 2018
- Full Text
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11. Living in Their World.
- Subjects
- Animals, Archaea cytology, Archaea growth & development, Bacteria cytology, Bacteria genetics, Ecosystem, Eukaryota cytology, Eukaryota growth & development, Humans, Viruses genetics, Bacteria growth & development, Environmental Microbiology, Viruses growth & development
- Published
- 2018
- Full Text
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12. Radical Host-Specific Therapies for TB.
- Author
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van?Heijst, Jeroen?W.J. and Pamer, Eric?G.
- Subjects
- *
TUBERCULOSIS treatment , *INFLAMMATORY mediators , *PHYSIOLOGICAL effects of cytokines , *TUMOR necrosis factors , *REACTIVE oxygen species , *MACROPHAGES , *BACTERIA cytology , *HOST-bacteria relationships - Abstract
Although proinflammatory cytokines such as TNF are critical for containment of tuberculosis, they can also exacerbate disease when produced at high levels. In this issue of Cell, Roca and Ramakrishnan demonstrate that high TNF production induces reactive oxygen species in infected macrophages, ultimately leading to macrophage necrosis and bacterial dissemination. [ABSTRACT FROM AUTHOR]
- Published
- 2013
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13. Bacterial Border Fence
- Author
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Baldi, Sandro and Barral, Yves
- Subjects
- *
BACTERIA cytology , *EUKARYOTIC cells , *CELL compartmentation , *CAULOBACTER crescentus , *MEMBRANE proteins , *CELL membranes - Abstract
Bacteria lack many of the features that eukaryotic cells use to compartmentalize cytoplasm and membranes. In this issue, Schlimpert et al. describe a new mechanism of spatial confinment in the bacterium Caulobacter crescentus that prevents the exchange of soluble and membrane proteins between the stalk and cell body. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
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14. Flagellum Length Control: How Long Is Long Enough?
- Author
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Hughes KT
- Subjects
- Bacteria classification, Flagella chemistry, Flagellin metabolism, Bacteria cytology, Bacterial Physiological Phenomena, Flagella physiology
- Abstract
The bacterial flagellum is an organelle that self-assembles outside the cell body. Recent work has uncovered the mechanism for length control of this self-assembly process., (Copyright © 2017 Elsevier Ltd. All rights reserved.)
- Published
- 2017
- Full Text
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15. Visualizing Flagella while Tracking Bacteria.
- Author
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Turner L, Ping L, Neubauer M, and Berg HC
- Subjects
- Bacteria cytology, Cell Tracking, Flagella metabolism
- Abstract
A complete description of the swimming behavior of a bacterium requires measurement of the displacement and orientation of the cell body together with a description of the movement of the flagella. We rebuilt a tracking microscope so that we could visualize flagellar filaments of tracked cells by fluorescence. We studied Escherichia coli (cells of various lengths, including swarm cells), Bacillus subtilis (wild-type and a mutant with fewer flagella), and a motile Streptococcus (now Enterococcus). The run-and-tumble statistics were nearly the same regardless of cell shape, length, and flagellation; however, swarm cells rarely tumbled, and cells of Enterococcus tended to swim in loops when moving slowly. There were events in which filaments underwent polymorphic transformations but remained in bundles, leading to small deflections in direction of travel. Tumble speeds were ∼2/3 as large as run speeds, and the rates of change of swimming direction while running or tumbling were smaller when cells swam more rapidly. If a smaller fraction of filaments were involved in tumbles, the tumble intervals were shorter and the angles between runs were smaller., (Copyright © 2016 Biophysical Society. Published by Elsevier Inc. All rights reserved.)
- Published
- 2016
- Full Text
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16. SnapShot: The Bacterial Cytoskeleton.
- Author
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Fink G, Szewczak-Harris A, and Löwe J
- Subjects
- Archaea chemistry, Archaea cytology, Bacteria chemistry, Bacterial Proteins analysis, Bacteria cytology, Cytoskeleton chemistry
- Abstract
Most bacteria and archaea contain filamentous proteins and filament systems that are collectively known as the bacterial cytoskeleton, though not all of them are cytoskeletal, affect cell shape, or maintain intracellular organization. To view this SnapShot, open or download the PDF., (Copyright © 2016. Published by Elsevier Inc.)
- Published
- 2016
- Full Text
- View/download PDF
17. Size Regulation: Big Insights from Little Cells.
- Author
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Chen H and Good MC
- Subjects
- Caulobacter crescentus cytology, Escherichia coli cytology, Models, Biological, Bacteria cytology
- Abstract
Reporting in Cell, Harris and Theriot (2016) use modeling and quantitative imaging to analyze bacterial cell growth and division. By manipulating surface and volume growth rates, the authors provide insight into bacterial cell size regulation and propose that a threshold level of unincorporated cell wall material specifies when cells divide., (Copyright © 2016 Elsevier Inc. All rights reserved.)
- Published
- 2016
- Full Text
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18. SnapShot: Timescales in Cell Biology.
- Author
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Shamir M, Bar-On Y, Phillips R, and Milo R
- Subjects
- Animals, Bacteria cytology, Cell Physiological Phenomena, Humans, Mammals metabolism, Mammals physiology, Time
- Published
- 2016
- Full Text
- View/download PDF
19. Are We Really Vastly Outnumbered? Revisiting the Ratio of Bacterial to Host Cells in Humans.
- Author
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Sender R, Fuchs S, and Milo R
- Subjects
- Adult, Bacteria cytology, Body Weight, Cell Count, Colon microbiology, Female, Humans, Infant, Infant, Newborn, Male, Symbiosis, Bacterial Physiological Phenomena, Microbiota
- Abstract
It is often presented as common knowledge that, in the human body, bacteria outnumber human cells by a ratio of at least 10:1. Revisiting the question, we find that the ratio is much closer to 1:1., (Copyright © 2016 Elsevier Inc. All rights reserved.)
- Published
- 2016
- Full Text
- View/download PDF
20. Diffusion of Bacterial Cells in Porous Media.
- Author
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Licata NA, Mohari B, Fuqua C, and Setayeshgar S
- Subjects
- Agrobacterium tumefaciens cytology, Agrobacterium tumefaciens genetics, Bacterial Proteins genetics, Chemotaxis, Diffusion, Mutation, Porosity, Stochastic Processes, Bacteria cytology, Models, Biological
- Abstract
The chemotaxis signal transduction network regulates the biased random walk of many bacteria in favorable directions and away from harmful ones through modulating the frequency of directional reorientations. In mutants of diverse bacteria lacking the chemotaxis response, migration in classic motility agar, which constitutes a fluid-filled porous medium, is compromised; straight-swimming cells unable to tumble become trapped within the agar matrix. Spontaneous mutations that restore spreading have been previously observed in the enteric bacterium Escherichia coli, and recent work in other bacterial species has isolated and quantified different classes of nonchemotacting mutants exhibiting the same spreading phenotype. We present a theoretical description of bacterial diffusion in a porous medium-the natural habitat for many cell types-which elucidates how diverse modifications of the motility apparatus resulting in a nonzero tumbling frequency allows for unjamming of otherwise straight-swimming cells at internal boundaries and leads to net migration. A unique result of our analysis is increasing diffusive spread with increasing tumbling frequency in the small pore limit, consistent with earlier experimental observations but not captured by previous models. Our theoretical results, combined with a simple model of bacterial diffusion and growth in agar, are compared with our experimental measurements of swim ring expansion as a function of time, demonstrating good quantitative agreement. Our results suggest that the details of the cellular tumbling process may be adapted to enable bacteria to propagate efficiently through complex environments. For engineered, self-propelled microswimmers that navigate via alternating straight runs and changes in direction, these results suggest an optimal reorientation strategy for efficient migration in a porous environment with a given microarchitecture., (Copyright © 2016 Biophysical Society. Published by Elsevier Inc. All rights reserved.)
- Published
- 2016
- Full Text
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21. Bacterial actin and tubulin homologs in cell growth and division.
- Author
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Busiek KK and Margolin W
- Subjects
- Actins chemistry, Bacteria cytology, Bacteria growth & development, Bacterial Physiological Phenomena, Bacterial Proteins chemistry, Cell Division physiology, Cell Proliferation physiology, Cytoskeletal Proteins physiology, Escherichia coli cytology, Escherichia coli growth & development, Escherichia coli physiology, Escherichia coli Proteins chemistry, Escherichia coli Proteins physiology, Guanosine Triphosphate metabolism, Models, Biological, Models, Molecular, Tubulin chemistry, Actins physiology, Bacterial Proteins physiology, Tubulin physiology
- Abstract
In contrast to the elaborate cytoskeletal machines harbored by eukaryotic cells, such as mitotic spindles, cytoskeletal structures detectable by typical negative stain electron microscopy are generally absent from bacterial cells. As a result, for decades it was thought that bacteria lacked cytoskeletal machines. Revolutions in genomics and fluorescence microscopy have confirmed the existence not only of smaller-scale cytoskeletal structures in bacteria, but also of widespread functional homologs of eukaryotic cytoskeletal proteins. The presence of actin, tubulin, and intermediate filament homologs in these relatively simple cells suggests that primitive cytoskeletons first arose in bacteria. In bacteria such as Escherichia coli, homologs of tubulin and actin directly interact with each other and are crucial for coordinating cell growth and division. The function and direct interactions between these proteins will be the focus of this review., (Copyright © 2015 Elsevier Ltd. All rights reserved.)
- Published
- 2015
- Full Text
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22. Bacterial evolution: rewiring modules to get in shape.
- Author
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Persat A and Gitai Z
- Subjects
- Bacteria cytology, Bacteria metabolism, Bacterial Proteins metabolism, Biological Evolution, Cell Polarity
- Abstract
Bacterial species take on a wide variety of shapes, but the mechanisms by which specific shapes evolve have remained poorly understood. A recent study demonstrates that two Asticcacaulis species repurposed an ancestral regulatory protein to rewire the modules of stalk regulation, localization, and synthesis, thereby generating new shapes., (Copyright © 2014 Elsevier Ltd. All rights reserved.)
- Published
- 2014
- Full Text
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23. A 2H solid-state NMR study of lipid clustering by cationic antimicrobial and cell-penetrating peptides in model bacterial membranes.
- Author
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Kwon B, Waring AJ, and Hong M
- Subjects
- Amino Acid Sequence, Antimicrobial Cationic Peptides chemistry, Carrier Proteins chemistry, Carrier Proteins pharmacology, Cell-Penetrating Peptides chemistry, Magnetic Resonance Spectroscopy, Molecular Sequence Data, Temperature, tat Gene Products, Human Immunodeficiency Virus chemistry, tat Gene Products, Human Immunodeficiency Virus pharmacology, Antimicrobial Cationic Peptides pharmacology, Bacteria cytology, Cell Membrane chemistry, Cell Membrane drug effects, Cell-Penetrating Peptides pharmacology, Phosphatidylethanolamines chemistry, Phosphatidylglycerols chemistry
- Abstract
Domain formation in bacteria-mimetic membranes due to cationic peptide binding was recently proposed based on calorimetric data. We now use (2)H solid-state NMR to critically examine the presence and absence of domains in bacterial membranes containing zwitterionic 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylethanolamine (POPE) and anionic 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylglycerol (POPG) lipids. Chain-perdeuterated POPE and POPG are used in single-component membranes, binary POPE/POPG (3:1) membranes, and membranes containing one of four cationic peptides: two antimicrobial peptides (AMPs) of the β-hairpin family of protegrin-1 (PG-1), and two cell-penetrating peptides (CPPs), HIV TAT and penetratin. (2)H quadrupolar couplings were measured to determine the motional amplitudes of POPE and POPG acyl chains as a function of temperature. Homogeneously mixed POPE/POPG membranes should give the same quadrupolar couplings for the two lipids, whereas the presence of membrane domains enriched in one of the two lipids should cause distinct (2)H quadrupolar couplings that reflect different chain disorder. At physiological temperature (308 K), we observed no or only small coupling differences between POPE and POPG in the presence of any of the cationic peptides. However, around ambient temperature (293 K), at which gel- and liquid-crystalline phases coexist in the peptide-free POPE/POPG membrane, the peptides caused distinct quadrupolar couplings for the two lipids, indicating domain formation. The broad-spectrum antimicrobial peptide PG-1 ordered ∼40% of the POPE lipids while disordering POPG. The Gram-negative selective PG-1 mutant, IB549, caused even larger differences in the POPE and POPG disorder: ∼80% of POPE partitioned into the ordered phase, whereas all of the POPG remained in the disordered phase. In comparison, TAT rigidified POPE and POPG similarly in the binary membrane at ambient temperature, indicating that TAT does not cause dynamic heterogeneity but interacts with the membrane with a different mechanism. Penetratin maintained the POPE order but disordered POPG, suggesting moderate domain separation. These results provide insight into the extent of domain formation in bacterial membranes and the possible peptide structural requirements for this phenomenon., (Copyright © 2013 Biophysical Society. Published by Elsevier Inc. All rights reserved.)
- Published
- 2013
- Full Text
- View/download PDF
24. Elasticity and biochemistry of growth relate replication rate to cell length and cross-link density in rod-shaped bacteria.
- Author
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Belgrave AM and Wolgemuth CW
- Subjects
- Bacteria metabolism, Bacterial Physiological Phenomena, Cell Wall metabolism, Elasticity, Bacteria cytology, Cell Growth Processes, DNA Replication, Models, Biological
- Abstract
In rod-shaped bacteria, cell morphology is correlated with the replication rate. For a given species, cells that replicate faster are longer and have less cross-linked cell walls. Here, we propose a simple mechanochemical model that explains the dependence of cell length and cross-linking on the replication rate. Our model shows good agreement with existing experimental data and provides further evidence that cell wall synthesis is mediated by multienzyme complexes; however, our results suggest that these synthesis complexes only mediate glycan insertion and cross-link severing, whereas recross-linking is performed independently., (Copyright © 2013 Biophysical Society. Published by Elsevier Inc. All rights reserved.)
- Published
- 2013
- Full Text
- View/download PDF
25. Cell shape can mediate the spatial organization of the bacterial cytoskeleton.
- Author
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Wang S and Wingreen NS
- Subjects
- Bacteria cytology, Bacterial Proteins chemistry, Bacterial Proteins metabolism, Cell Membrane chemistry, Cell Membrane metabolism, Cytoskeletal Proteins chemistry, Cytoskeletal Proteins metabolism, Cytoskeleton metabolism, Kinetics, Protein Binding, Protein Conformation, Protein Multimerization, Bacteria chemistry, Cytoskeleton chemistry, Models, Chemical
- Abstract
The bacterial cytoskeleton guides the synthesis of cell wall and thus regulates cell shape. Because 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., (Copyright © 2013 Biophysical Society. Published by Elsevier Inc. All rights reserved.)
- Published
- 2013
- Full Text
- View/download PDF
26. The relation of signal transduction to the sensitivity and dynamic range of bacterial chemotaxis.
- Author
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Namba T, Nishikawa M, and Shibata T
- Subjects
- Adaptation, Physiological, Bacteria metabolism, Methylation, Bacteria cytology, Chemotaxis, Models, Biological, Signal Transduction
- Abstract
Complex networks of interacting molecular components of living cells are responsible for many important processes, such as signal processing and transduction. An important challenge is to understand how the individual properties of these molecular interactions and biochemical transformations determine the system-level properties of biological functions. Here, we address the issue of the accuracy of signal transduction performed by a bacterial chemotaxis system. The chemotaxis sensitivity of bacteria to a chemoattractant gradient has been measured experimentally from bacterial aggregation in a chemoattractant-containing capillary. The observed precision of the chemotaxis depended on environmental conditions such as the concentration and molecular makeup of the chemoattractant. In a quantitative model, we derived the chemotactic response function, which is essential to describing the signal transduction process involved in bacterial chemotaxis. In the presence of a gradient, an analytical solution is derived that reveals connections between the chemotaxis sensitivity and the characteristics of the signaling system, such as reaction rates. These biochemical parameters are integrated into two system-level parameters: one characterizes the efficiency of gradient sensing, and the other is related to the dynamic range of chemotaxis. Thus, our approach explains how a particular signal transduction property affects the system-level performance of bacterial chemotaxis. We further show that the two parameters can be derived from published experimental data from a capillary assay, which successfully characterizes the performance of bacterial chemotaxis., (Copyright © 2012 Biophysical Society. Published by Elsevier Inc. All rights reserved.)
- Published
- 2012
- Full Text
- View/download PDF
27. Membrane-active peptides and the clustering of anionic lipids.
- Author
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Wadhwani P, Epand RF, Heidenreich N, Bürck J, Ulrich AS, and Epand RM
- Subjects
- Amino Acid Sequence, Anions chemistry, Bacteria cytology, Bacteria drug effects, Calorimetry, Differential Scanning, Cell Membrane chemistry, Cell Membrane drug effects, Circular Dichroism, Microbial Sensitivity Tests, Molecular Sequence Data, Peptides chemistry, Peptides pharmacology, Transition Temperature drug effects, Cell Membrane metabolism, Lipids chemistry, Peptides metabolism
- Abstract
There is some overlap in the biological activities of cell-penetrating peptides (CPPs) and antimicrobial peptides (AMPs). We compared nine AMPs, seven CPPs, and a fusion peptide with regard to their ability to cluster anionic lipids in a mixture mimicking the cytoplasmic membrane of Gram-negative bacteria, as measured by differential scanning calorimetry. We also studied their bacteriostatic effect on several bacterial strains, and examined their conformational changes upon membrane binding using circular dichroism. A remarkable correlation was found between the net positive charge of the peptides and their capacity to induce anionic lipid clustering, which was independent of their secondary structure. Among the peptides studied, six AMPs and four CPPs were found to have strong anionic lipid clustering activity. These peptides also had bacteriostatic activity against several strains (particularly Gram-negative Escherichia coli) that are sensitive to lipid clustering agents. AMPs and CPPs that did not cluster anionic lipids were not toxic to E. coli. As shown previously for several types of AMPs, anionic lipid clustering likely contributes to the mechanism of antibacterial action of highly cationic CPPs. The same mechanism could explain the escape of CPPs from intracellular endosomes that are enriched with anionic lipids., (Copyright © 2012 Biophysical Society. Published by Elsevier Inc. All rights reserved.)
- Published
- 2012
- Full Text
- View/download PDF
28. Cell size control in bacteria.
- Author
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Chien AC, Hill NS, and Levin PA
- Subjects
- Bacteria cytology, Cell Size
- Abstract
Like eukaryotes, bacteria must coordinate division with growth to ensure cells are the appropriate size for a given environmental condition or developmental fate. As single-celled organisms, nutrient availability is one of the strongest influences on bacterial cell size. Classic physiological experiments conducted over four decades ago first demonstrated that cell size is directly correlated with nutrient source and growth rate in the Gram-negative bacterium Salmonella typhimurium. This observation subsequently served as the basis for studies revealing a role for cell size in cell cycle progression in a closely related organism, Escherichia coli. More recently, the development of powerful genetic, molecular, and imaging tools has allowed us to identify and characterize the nutrient-dependent pathway responsible for coordinating cell division and cell size with growth rate in the Gram-positive model organism Bacillus subtilis. Here, we discuss the role of cell size in bacterial growth and development and propose a broadly applicable model for cell size control in this important and highly divergent domain of life., (Copyright © 2012 Elsevier Ltd. All rights reserved.)
- Published
- 2012
- Full Text
- View/download PDF
29. Quantification of fluorophore copy number from intrinsic fluctuations during fluorescence photobleaching.
- Author
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Nayak CR and Rutenberg AD
- Subjects
- Bacteria cytology, Bacteria metabolism, Computer Simulation, Fluorescence, Fluorescence Polarization, Movement, Protein Biosynthesis, Fluorescent Dyes metabolism, Photobleaching
- Abstract
We present a theoretical technique for quantifying the cellular copy-number of fluorophores that relies on the random nature of the photobleaching process. Our approach does not require single-molecule sensitivity, and therefore can be used with commonly used epifluorescence microscopes. Fluctuations arising from photobleaching can be used to estimate the proportionality between fluorescence intensity and copy-number, which can then be used with subsequent intensity measurements to estimate copy-number. We calculate the statistical errors of our approach and verify them with stochastic simulations. By using fluctuations over the entire photobleaching process, we obtain significantly smaller errors than previous approaches that have used fluctuations arising from cytoplasmic proteins partitioning during cellular division. From the time-dependence of the fluctuations as photobleaching proceeds, we can discriminate between desired photobleach fluctuations and background noise or photon shot noise. Our approach does not require cellular division and the photobleaching rate sets a timescale that is adjustable with respect to cellular processes. We hope that our approach will now be applied experimentally., (Copyright © 2011 Biophysical Society. Published by Elsevier Inc. All rights reserved.)
- Published
- 2011
- Full Text
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30. Subcellular positioning: unstable filaments on the move.
- Author
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Graumann PL
- Subjects
- Actins physiology, Bacillus subtilis genetics, Bacillus subtilis physiology, Bacteria chemistry, Bacterial Proteins genetics, Bacterial Proteins physiology, Cell Wall physiology, Cytoskeleton physiology, DNA, Bacterial genetics, DNA, Bacterial physiology, Microtubule-Associated Proteins genetics, Microtubule-Associated Proteins physiology, Plasmids genetics, Protein Stability, Actin Cytoskeleton physiology, Bacteria cytology, Bacterial Physiological Phenomena, Models, Biological
- Abstract
A key question in cell biology is how proteins and entire protein complexes localize to defined subcellular positions in non-compartmentalized cells or within cell compartments. A recent report involving computational modeling and live-cell imaging suggests that dynamically unstable protein filaments provide an adaptable and versatile positioning system.
- Published
- 2011
- Full Text
- View/download PDF
31. Theoretical and computational investigation of flagellin translocation and bacterial flagellum growth.
- Author
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Tanner DE, Ma W, Chen Z, and Schulten K
- Subjects
- Kinetics, Pressure, Protein Conformation, Protein Transport, Protein Unfolding, Bacteria cytology, Flagella metabolism, Flagellin chemistry, Flagellin metabolism, Molecular Dynamics Simulation
- Abstract
The bacterial flagellum is a self-assembling filament, which bacteria use for swimming. It is built from tens of thousands of flagellin monomers in a self-assembly process that involves translocation of the monomers through the flagellar interior, a channel, to the growing tip. Flagellum monomers are pumped into the filament at the base, move unfolded along the channel and then bind to the tip of the filament, thereby extending the growing flagellum. The flagellin translocation process, due to the flagellum maximum length of 20 μm, is an extreme example of protein transport through channels. Here, we derive a model for flagellin transport through the long confining channel, testing the key assumptions of the model through molecular dynamics simulations that also furnish system parameters needed for quantitative description. Together, mathematical model and molecular dynamics simulations explain why the growth rate of flagellar filaments decays exponentially with filament length and why flagellum growth ceases at a certain maximum length., (Copyright © 2011 Biophysical Society. Published by Elsevier Inc. All rights reserved.)
- Published
- 2011
- Full Text
- View/download PDF
32. Cell division intersects with cell geometry.
- Author
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Moseley JB and Nurse P
- Subjects
- Bacteria genetics, Chromosome Segregation, Chromosomes, Bacterial, Chromosomes, Fungal, Mitosis, Yeasts genetics, Bacteria cytology, Cell Division, Yeasts cytology
- Abstract
Single-celled organisms monitor cell geometry and use this information to control cell division. Such geometry-sensing mechanisms control both the decision to enter into cell division and the physical orientation of the chromosome segregation machinery, suggesting that signals controlling cell division may be linked to the mechanisms that ensure proper chromosome segregation., (Copyright 2010 Elsevier Inc. All rights reserved.)
- Published
- 2010
- Full Text
- View/download PDF
33. Pushing and pulling in prokaryotic DNA segregation.
- Author
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Gerdes K, Howard M, and Szardenings F
- Subjects
- Actins metabolism, Bacteria cytology, Bacterial Proteins metabolism, Chromosomes, Bacterial metabolism, Plasmids metabolism, Tubulin metabolism, Bacteria metabolism, DNA, Bacterial metabolism
- Abstract
In prokaryotes, DNA can be segregated by three different types of cytoskeletal filaments. The best-understood type of partitioning (par) locus encodes an actin homolog called ParM, which forms dynamically unstable filaments that push plasmids apart in a process reminiscent of mitosis. However, the most common type of par locus, which is present on many plasmids and most bacterial chromosomes, encodes a P loop ATPase (ParA) that distributes plasmids equidistant from one another on the bacterial nucleoid. A third type of par locus encodes a tubulin homolog (TubZ) that forms cytoskeletal filaments that move rapidly with treadmill dynamics., (Copyright 2010 Elsevier Inc. All rights reserved.)
- Published
- 2010
- Full Text
- View/download PDF
34. Interplay between intrinsic noise and the stochasticity of the cell cycle in bacterial colonies.
- Author
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Canela-Xandri O, Sagués F, and Buceta J
- Subjects
- Algorithms, Bacterial Proteins metabolism, Cell Cycle, Cell Division, Gene Expression Regulation, Protein Biosynthesis, Stochastic Processes, Time Factors, Bacteria cytology, Models, Biological
- Abstract
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.)
- Published
- 2010
- Full Text
- View/download PDF
35. Cellular heterogeneity: do differences make a difference?
- Author
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Altschuler SJ and Wu LF
- Subjects
- Animals, Bacteria cytology, Cytological Techniques, Drosophila, Cells chemistry, Cells metabolism
- Abstract
A central challenge of biology is to understand how individual cells process information and respond to perturbations. Much of our knowledge is based on ensemble measurements. However, cell-to-cell differences are always present to some degree in any cell population, and the ensemble behaviors of a population may not represent the behaviors of any individual cell. Here, we discuss examples of when heterogeneity cannot be ignored and describe practical strategies for analyzing and interpreting cellular heterogeneity., (Copyright (c) 2010 Elsevier Inc. All rights reserved.)
- Published
- 2010
- Full Text
- View/download PDF
36. SnapShot: Bacterial Appendages I.
- Author
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Rego AT, Fronzes R, and Waksman G
- Subjects
- Bacterial Physiological Phenomena, Bacteria cytology, Fimbriae, Bacterial physiology
- Published
- 2010
- Full Text
- View/download PDF
37. Sculpting the bacterial cell.
- Author
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Margolin W
- Subjects
- Actins metabolism, Actins physiology, Bacteria classification, Bacteria growth & development, Bacterial Proteins metabolism, Bacterial Proteins physiology, Cell Polarity, Cell Wall metabolism, Cell Wall ultrastructure, Cytoskeleton metabolism, Cytoskeleton physiology, Cytoskeleton ultrastructure, Peptidoglycan metabolism, Phylogeny, Prokaryotic Cells physiology, Prokaryotic Cells ultrastructure, Bacteria cytology, Cell Shape, Prokaryotic Cells cytology
- Abstract
Prokaryotes come in a wide variety of shapes, determined largely by natural selection, physical constraints, and patterns of cell growth and division. Because of their relative simplicity, bacterial cells are excellent models for how genes and proteins can directly determine morphology. Recent advances in cytological methods for bacteria have shown that distinct cytoskeletal filaments composed of actin and tubulin homologs are important for guiding growth patterns of the cell wall in bacteria, and that the glycan strands that constitute the wall are generally perpendicular to the direction of growth. This cytoskeleton-directed cell wall patterning is strikingly reminiscent of how plant cell wall growth is regulated by microtubules. In rod-shaped bacilli, helical cables of actin-like MreB protein stretch along the cell length and orchestrate elongation of the cell wall, whereas the tubulin-like FtsZ protein directs formation of the division septum and the resulting cell poles. The overlap and interplay between these two systems and the peptidoglycan-synthesizing enzymes they recruit are the major driving forces of cylindrical shapes. Round cocci, on the other hand, have lost their MreB cables and instead must grow mainly via their division septum, giving them their characteristic round or ovoid shapes. Other bacteria that lack MreB homologs or even cell walls use distinct cytoskeletal systems to maintain their distinct shapes. Here I review what is known about the mechanisms that determine the shape of prokaryotic cells.
- Published
- 2009
- Full Text
- View/download PDF
38. Cell division: breaking up is easy to do.
- Author
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Chen IA
- Subjects
- Biological Evolution, Cell Cycle Proteins metabolism, Cell Membrane metabolism, Models, Biological, Bacteria cytology, Bacteria metabolism, Cell Division physiology
- Abstract
How did cells divide before protein machines evolved? A new study shows that bacteria can reproduce without the division machinery, supporting the idea that primordial cells could have divided using physical mechanisms alone.
- Published
- 2009
- Full Text
- View/download PDF
39. Networking opportunities for bacteria.
- Author
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Dwyer DJ, Kohanski MA, and Collins JJ
- Subjects
- Bacteria cytology, Bacteria genetics, Genomics, Bacteria metabolism, Systems Biology
- Abstract
In this post-genomic era, our capacity to explore biological networks and predict network architectures has been greatly expanded, accelerating interest in systems biology. Here, we highlight recent systems biology studies in prokaryotes, consider the challenges ahead, and suggest opportunities for future studies in bacterial models.
- Published
- 2008
- Full Text
- View/download PDF
40. Polarity and differential inheritance--universal attributes of life?
- Author
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Macara IG and Mili S
- Subjects
- Animals, Bacteria cytology, Eukaryotic Cells cytology, Fungi cytology, Cell Division, Cell Polarity
- Abstract
When and why did cell polarization arise? Recent work in bacteria and yeast suggests that polarization may have evolved to restrict senescence to one daughter during division by enabling the differential segregation of damaged material. In more complex organisms, polarity functions have diversified to permit the differential inheritance of centrosomes, RNAs, proteins, and membranes, which is essential for the generation of diverse cell types from stem cells and for morphogenesis.
- Published
- 2008
- Full Text
- View/download PDF
41. Origin of individuality of two daughter cells during the division process examined by the simultaneous measurement of growth and swimming property using an on-chip single-cell cultivation system.
- Author
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Umehara S, Inoue I, Wakamoto Y, and Yasuda K
- Subjects
- Bacteria cytology, Bacterial Physiological Phenomena, Cell Culture Techniques methods, Genes, Reporter, Green Fluorescent Proteins analysis, Models, Biological, Software, Cell Division physiology, Cell Movement physiology, Cells cytology
- Abstract
We examined the origin of individuality of two daughter cells born from an isolated single Escherichia coli mother cell during its cell division process by monitoring the change in its swimming behavior and tumbling frequency using an on-chip single-cell cultivation system. By keeping the isolated condition of an observed single cell, we compared its growth and swimming property within a generation and over up to seven generations. It revealed that running speed decreased as cell length smoothly increased within each generation, whereas tumbling frequency fluctuated among generations. Also found was an extraordinary tumbling mode characterized by the prolonged duration of pausing in predivisional cells after cell constriction. The observed prolonged pausing may imply the coexistence of two distinct control systems in a predivisional cell, indicating that individuality of daughter cells emerges after a mother cell initiates constriction and before it gets physically separated into two new cell bodies.
- Published
- 2007
- Full Text
- View/download PDF
42. Bacterial swarming: a re-examination of cell-movement patterns.
- Author
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Kaiser D
- Subjects
- Models, Biological, Myxococcales physiology, Bacteria cytology, Bacterial Physiological Phenomena, Flagella physiology, Locomotion physiology
- Abstract
Many bacteria simultaneously grow and spread rapidly over a surface that supplies them with nutrient. Called 'swarming', this pattern of movement directs new cells to the edge of the colony. Swarming reduces competition between cells for nutrients, speeding growth. Behind the swarm edge, where the cell density is higher, growth is limited by transport of nutrient from the subsurface to the overlying cells. Despite years of study, the choreography of swarm cell movement, the bacterial equivalent of dancing toward an exit in a very dense crowd of moving bodies, remains a mystery. Swarming can be propelled by rotating flagella, and either by pulling with type IV pili or by pushing with the secretion of slime. By identifying patterns of movement that are common to swarms making use of different engines, a model of swarm choreography can be proposed.
- Published
- 2007
- Full Text
- View/download PDF
43. Microbial biofilms: e pluribus unum.
- Author
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Nobile CJ and Mitchell AP
- Subjects
- Bacteria cytology, Bacteria genetics, Bacterial Adhesion, Biodiversity, Cell Adhesion, Extracellular Matrix physiology, Fungi cytology, Fungi genetics, Genetic Variation, Bacterial Physiological Phenomena, Biofilms growth & development, Fungi physiology
- Published
- 2007
- Full Text
- View/download PDF
44. Diverse paths to midcell: assembly of the bacterial cell division machinery.
- Author
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Goehring NW and Beckwith J
- Subjects
- Carrier Proteins metabolism, Cell Cycle Proteins metabolism, Cell Wall physiology, Escherichia coli Proteins metabolism, N-Acetylmuramoyl-L-alanine Amidase metabolism, Bacteria cytology, Bacterial Physiological Phenomena, Bacterial Proteins metabolism, Cell Division physiology, Cytoskeletal Proteins metabolism, Models, Biological, Multiprotein Complexes metabolism, Signal Transduction physiology
- Abstract
At the heart of bacterial cell division is a dynamic ring-like structure of polymers of the tubulin homologue FtsZ. This ring forms a scaffold for assembly of at least ten additional proteins at midcell, the majority of which are likely to be involved in remodeling the peptidoglycan cell wall at the division site. Together with FtsZ, these proteins are thought to form a cell division complex, or divisome. In Escherichia coli, the components of the divisome are recruited to midcell according to a strikingly linear hierarchy that predicts a step-wise assembly pathway. However, recent studies have revealed unexpected complexity in the assembly steps, indicating that the apparent linearity does not necessarily reflect a temporal order. The signals used to recruit cell division proteins to midcell are diverse and include regulated self-assembly, protein-protein interactions, and the recognition of specific septal peptidoglycan substrates. There is also evidence for a complex web of interactions among these proteins and at least one distinct subcomplex of cell division proteins has been defined, which is conserved among E. coli, Bacillus subtilis and Streptococcus pneumoniae.
- Published
- 2005
- Full Text
- View/download PDF
45. The real 'domains' of life.
- Author
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Walsh DA and Doolittle WF
- Subjects
- Archaea cytology, Archaea genetics, Bacteria cytology, Bacteria genetics, Eukaryotic Cells cytology, Genome Components genetics, RNA, Ribosomal genetics, Archaea classification, Bacteria classification, Classification methods, Phylogeny
- Published
- 2005
- Full Text
- View/download PDF
46. Chemically resolved imaging of biological cells and thin films by infrared scanning near-field optical microscopy.
- Author
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Cricenti A, Generosi R, Luce M, Perfetti P, Margaritondo G, Talley D, Sanghera JS, Aggarwal ID, Tolk NH, Congiu-Castellano A, Rizzo MA, and Piston DW
- Subjects
- Animals, Biofilms growth & development, Cell Line, Equipment Failure Analysis, Rats, Bacteria cytology, Bacteria metabolism, Islets of Langerhans cytology, Islets of Langerhans metabolism, Microscopy, Confocal instrumentation, Microscopy, Confocal methods, Spectrophotometry, Infrared instrumentation, Spectrophotometry, Infrared methods
- Abstract
The infrared (IR) absorption of a biological system can potentially report on fundamentally important microchemical properties. For example, molecular IR profiles are known to change during increases in metabolic flux, protein phosphorylation, or proteolytic cleavage. However, practical implementation of intracellular IR imaging has been problematic because the diffraction limit of conventional infrared microscopy results in low spatial resolution. We have overcome this limitation by using an IR spectroscopic version of scanning near-field optical microscopy (SNOM), in conjunction with a tunable free-electron laser source. The results presented here clearly reveal different chemical constituents in thin films and biological cells. The space distribution of specific chemical species was obtained by taking SNOM images at IR wavelengths (lambda) corresponding to stretch absorption bands of common biochemical bonds, such as the amide bond. In our SNOM implementation, this chemical sensitivity is combined with a lateral resolution of 0.1 micro m ( approximately lambda/70), well below the diffraction limit of standard infrared microscopy. The potential applications of this approach touch virtually every aspect of the life sciences and medical research, as well as problems in materials science, chemistry, physics, and environmental research.
- Published
- 2003
- Full Text
- View/download PDF
47. Bacterial division: the fellowship of the ring.
- Author
-
Margolin W
- Subjects
- Bacterial Proteins genetics, Bacterial Proteins metabolism, Cell Division physiology, Mutation, Bacteria cytology, Bacterial Proteins physiology, Cytoskeletal Proteins, Metalloendopeptidases physiology
- Abstract
The Z ring, composed of the tubulin homolog FtsZ, is essential for bacterial cell division. Recently a new protein, ZapA, has been discovered that localizes to the Z ring and stabilizes it, probably by promoting the bundling of FtsZ protofilaments.
- Published
- 2003
- Full Text
- View/download PDF
48. Small talk. Cell-to-cell communication in bacteria.
- Author
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Bassler BL
- Subjects
- Bacteria cytology, Bacteria genetics, Enzyme Induction genetics, Gene Expression Regulation, Enzymologic genetics, Lactones metabolism, Bacteria metabolism, Cell Communication physiology, Gene Expression Regulation, Bacterial genetics, Signal Transduction physiology, Symbiosis genetics
- Abstract
In a process called quorum sensing, groups of bacteria communicate with one another to coordinate their behavior and function like a multicellular organism. A diverse array of secreted chemical signal molecules and signal detection apparatuses facilitate highly productive intra- and interspecies relationships.
- Published
- 2002
- Full Text
- View/download PDF
49. Bacterial surface motility: slime trails, grappling hooks and nozzles.
- Author
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Merz AJ and Forest KT
- Subjects
- Bacteria cytology, Bacteria metabolism, Fimbriae Proteins, Fimbriae, Bacterial chemistry, Intercellular Junctions metabolism, Intercellular Junctions ultrastructure, Membrane Proteins chemistry, Membrane Proteins metabolism, Models, Molecular, Protein Conformation, Surface-Active Agents metabolism, Bacterial Physiological Phenomena, Fimbriae, Bacterial physiology, Locomotion
- Published
- 2002
- Full Text
- View/download PDF
50. Mesoscopic simulation of cell membrane damage, morphology change and rupture by nonionic surfactants.
- Author
-
Groot RD and Rabone KL
- Subjects
- Bacteria drug effects, Cell Membrane drug effects, Cell Membrane Permeability drug effects, Cell Size, Diffusion, Glycerol metabolism, Lipid Bilayers chemistry, Lipid Bilayers metabolism, Models, Biological, Phosphatidylethanolamines metabolism, Reproducibility of Results, Surface-Active Agents pharmacology, Thermodynamics, Water metabolism, Bacteria cytology, Cell Membrane chemistry, Cell Membrane metabolism, Computer Simulation, Surface-Active Agents chemistry, Surface-Active Agents metabolism
- Abstract
A new simulation method, dissipative particle dynamics, is applied to model biological membranes. In this method, several atoms are united into a single simulation particle. The solubility and compressibility of the various liquid components are reproduced by the simulation model. When applied to a bilayer of phosphatidylethanolamine, the membrane structure obtained matches quantitatively with full atomistic simulations and with experiments reported in the literature. The method is applied to investigate the cause of cell death when bacteria are exposed to nonionic surfactants. Mixed bilayers of lipid and nonionic surfactant were studied, and the diffusion of water through the bilayer was monitored. Small transient holes are seen to appear at 40% mole-fraction C(9)E(8), which become permanent holes between 60 and 70% surfactant. When C(12)E(6) is applied, permanent holes only arise at 90% mole-fraction surfactant. Some simulations have been carried out to determine the rupture properties of mixed bilayers of phosphatidylethanolamine and C(12)E(6). These simulations indicate that the area of a pure lipid bilayer can be increased by a factor 2. The inclusion of surfactant considerably reduces both the extensibility and the maximum stress that the bilayer can withstand. This may explain why dividing cells are more at risk than static cells.
- Published
- 2001
- Full Text
- View/download PDF
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