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Sample records for arcab two-component system

  1. Crystallization in two-component Coulomb systems.

    PubMed

    Bonitz, M; Filinov, V S; Fortov, V E; Levashov, P R; Fehske, H

    2005-12-01

    The analysis of Coulomb crystallization is extended from one-component to two-component plasmas. Critical parameters for the existence of Coulomb crystals are derived for both classical and quantum crystals. In the latter case, a critical mass ratio of the two charged components is found, which is of the order of 80. Thus, holes in semiconductors with sufficiently flat valence bands are predicted to spontaneously order into a regular lattice. Such hole crystals are intimately related to ion Coulomb crystals in white dwarf and neutron stars as well as to ion crystals produced in the laboratory. A unified phase diagram of two-component Coulomb crystals is presented and is verified by first-principles computer simulations. PMID:16384315

  2. Feedback Control of Two-Component Regulatory Systems.

    PubMed

    Groisman, Eduardo A

    2016-09-01

    Two-component systems are a dominant form of bacterial signal transduction. The prototypical two-component system consists of a sensor that responds to a specific input(s) by modifying the output of a cognate regulator. Because the output of a two-component system is the amount of phosphorylated regulator, feedback mechanisms may alter the amount of regulator, and/or modify the ability of a sensor or other proteins to alter the phosphorylation state of the regulator. Two-component systems may display intrinsic feedback whereby the amount of phosphorylated regulator changes under constant inducing conditions and without the participation of additional proteins. Feedback control allows a two-component system to achieve particular steady-state levels, to reach a given steady state with distinct dynamics, to express coregulated genes in a given order, and to activate a regulator to different extents, depending on the signal acting on the sensor. PMID:27607549

  3. A new two-component integrable system with peakon solutions

    PubMed Central

    Xia, Baoqiang; Qiao, Zhijun

    2015-01-01

    A new two-component system with cubic nonlinearity and linear dispersion: mt=bux+12[m(uv−uxvx)]x−12m(uvx−uxv),nt=bvx+12[n(uv−uxvx)]x+12n(uvx−uxv),m=u−uxx,n=v−vxx,where b is an arbitrary real constant, is proposed in this paper. This system is shown integrable with its Lax pair, bi-Hamiltonian structure and infinitely many conservation laws. Geometrically, this system describes a non-trivial one-parameter family of pseudo-spherical surfaces. In the case b=0, the peaked soliton (peakon) and multi-peakon solutions to this two-component system are derived. In particular, the two-peakon dynamical system is explicitly solved and their interactions are investigated in details. Moreover, a new integrable cubic nonlinear equation with linear dispersion mt=bux+12[m(|u|2−|ux|2)]x−12m(uux∗−uxu∗),m=u−uxx,is obtained by imposing the complex conjugate reduction v=u* to the two-component system. The complex-valued N-peakon solution and kink wave solution to this complex equation are also derived. PMID:25792956

  4. Interaction Analysis of a Two-Component System Using Nanodiscs

    PubMed Central

    Hörnschemeyer, Patrick; Liss, Viktoria; Heermann, Ralf; Jung, Kirsten; Hunke, Sabine

    2016-01-01

    Two-component systems are the major means by which bacteria couple adaptation to environmental changes. All utilize a phosphorylation cascade from a histidine kinase to a response regulator, and some also employ an accessory protein. The system-wide signaling fidelity of two-component systems is based on preferential binding between the signaling proteins. However, information on the interaction kinetics between membrane embedded histidine kinase and its partner proteins is lacking. Here, we report the first analysis of the interactions between the full-length membrane-bound histidine kinase CpxA, which was reconstituted in nanodiscs, and its cognate response regulator CpxR and accessory protein CpxP. Using surface plasmon resonance spectroscopy in combination with interaction map analysis, the affinity of membrane-embedded CpxA for CpxR was quantified, and found to increase by tenfold in the presence of ATP, suggesting that a considerable portion of phosphorylated CpxR might be stably associated with CpxA in vivo. Using microscale thermophoresis, the affinity between CpxA in nanodiscs and CpxP was determined to be substantially lower than that between CpxA and CpxR. Taken together, the quantitative interaction data extend our understanding of the signal transduction mechanism used by two-component systems. PMID:26882435

  5. Universality Classes in Two-Component Driven Diffusive Systems

    NASA Astrophysics Data System (ADS)

    Popkov, V.; Schmidt, J.; Schütz, G. M.

    2015-08-01

    We study time-dependent density fluctuations in the stationary state of driven diffusive systems with two conserved densities . Using Monte-Carlo simulations of two coupled single-lane asymmetric simple exclusion processes we present numerical evidence for universality classes with dynamical exponents and (but different from the Kardar-Parisi-Zhang (KPZ) universality class), which have not been reported yet for driven diffusive systems. The numerical asymmetry of the dynamical structure functions converges slowly for some of the non-KPZ superdiffusive modes for which mode coupling theory predicts maximally asymmetric -stable Lévy scaling functions. We show that all universality classes predicted by mode coupling theory for two conservation laws are generic: they occur in two-component systems with nonlinearities in the associated currents already of the minimal order . The macroscopic stationary current-density relation and the compressibility matrix determine completely all permissible universality classes through the mode coupling coefficients which we compute explicitly for general two-component systems.

  6. Theory of Ostwald ripening in a two-component system

    NASA Technical Reports Server (NTRS)

    Baird, J. K.; Lee, L. K.; Frazier, D. O.; Naumann, R. J.

    1986-01-01

    When a two-component system is cooled below the minimum temperature for its stability, it separates into two or more immiscible phases. The initial nucleation produces grains (if solid) or droplets (if liquid) of one of the phases dispersed in the other. The dynamics by which these nuclei proceed toward equilibrium is called Ostwald ripening. The dynamics of growth of the droplets depends upon the following factors: (1) The solubility of the droplet depends upon its radius and the interfacial energy between it and the surrounding (continuous) phase. There is a critical radius determined by the supersaturation in the continuous phase. Droplets with radii smaller than critical dissolve, while droplets with radii larger grow. (2) The droplets concentrate one component and reject the other. The rate at which this occurs is assumed to be determined by the interdiffusion of the two components in the continuous phase. (3) The Ostwald ripening is constrained by conservation of mass; e.g., the amount of materials in the droplet phase plus the remaining supersaturation in the continuous phase must equal the supersaturation available at the start. (4) There is a distribution of droplet sizes associated with a mean droplet radius, which grows continuously with time. This distribution function satisfies a continuity equation, which is solved asymptotically by a similarity transformation method.

  7. Efficient two-component relativistic method for large systems

    SciTech Connect

    Nakai, Hiromi

    2015-12-31

    This paper reviews a series of theoretical studies to develop efficient two-component (2c) relativistic method for large systems by the author’s group. The basic theory is the infinite-order Douglas-Kroll-Hess (IODKH) method for many-electron Dirac-Coulomb Hamiltonian. The local unitary transformation (LUT) scheme can effectively produce the 2c relativistic Hamiltonian, and the divide-and-conquer (DC) method can achieve linear-scaling of Hartree-Fock and electron correlation methods. The frozen core potential (FCP) theoretically connects model potential calculations with the all-electron ones. The accompanying coordinate expansion with a transfer recurrence relation (ACE-TRR) scheme accelerates the computations of electron repulsion integrals with high angular momenta and long contractions.

  8. Mitochondrial two-component signaling systems in Candida albicans.

    PubMed

    Mavrianos, John; Berkow, Elizabeth L; Desai, Chirayu; Pandey, Alok; Batish, Mona; Rabadi, Marissa J; Barker, Katherine S; Pain, Debkumar; Rogers, P David; Eugenin, Eliseo A; Chauhan, Neeraj

    2013-06-01

    Two-component signal transduction pathways are one of the primary means by which microorganisms respond to environmental signals. These signaling cascades originated in prokaryotes and were inherited by eukaryotes via endosymbiotic lateral gene transfer from ancestral cyanobacteria. We report here that the nuclear genome of the pathogenic fungus Candida albicans contains elements of a two-component signaling pathway that seem to be targeted to the mitochondria. The C. albicans two-component response regulator protein Srr1 (stress response regulator 1) contains a mitochondrial targeting sequence at the N terminus, and fluorescence microscopy reveals mitochondrial localization of green fluorescent protein-tagged Srr1. Moreover, phylogenetic analysis indicates that C. albicans Srr1 is more closely related to histidine kinases and response regulators found in marine bacteria than are other two-component proteins present in the fungi. These data suggest conservation of this protein during the evolutionary transition from endosymbiont to a subcellular organelle. We used microarray analysis to determine whether the phenotypes observed with a srr1Δ/Δ mutant could be correlated with gene transcriptional changes. The expression of mitochondrial genes was altered in the srr1Δ/Δ null mutant in comparison to their expression in the wild type. Furthermore, apoptosis increased significantly in the srr1Δ/Δ mutant strain compared to the level of apoptosis in the wild type, suggesting the activation of a mitochondrion-dependent apoptotic cell death pathway in the srr1Δ/Δ mutant. Collectively, this study shows for the first time that a lower eukaryote like C. albicans possesses a two-component response regulator protein that has survived in mitochondria and regulates a subset of genes whose functions are associated with the oxidative stress response and programmed cell death (apoptosis). PMID:23584995

  9. Mitochondrial Two-Component Signaling Systems in Candida albicans

    PubMed Central

    Mavrianos, John; Berkow, Elizabeth L.; Desai, Chirayu; Pandey, Alok; Batish, Mona; Rabadi, Marissa J.; Barker, Katherine S.; Pain, Debkumar; Rogers, P. David; Eugenin, Eliseo A.

    2013-01-01

    Two-component signal transduction pathways are one of the primary means by which microorganisms respond to environmental signals. These signaling cascades originated in prokaryotes and were inherited by eukaryotes via endosymbiotic lateral gene transfer from ancestral cyanobacteria. We report here that the nuclear genome of the pathogenic fungus Candida albicans contains elements of a two-component signaling pathway that seem to be targeted to the mitochondria. The C. albicans two-component response regulator protein Srr1 (stress response regulator 1) contains a mitochondrial targeting sequence at the N terminus, and fluorescence microscopy reveals mitochondrial localization of green fluorescent protein-tagged Srr1. Moreover, phylogenetic analysis indicates that C. albicans Srr1 is more closely related to histidine kinases and response regulators found in marine bacteria than are other two-component proteins present in the fungi. These data suggest conservation of this protein during the evolutionary transition from endosymbiont to a subcellular organelle. We used microarray analysis to determine whether the phenotypes observed with a srr1Δ/Δ mutant could be correlated with gene transcriptional changes. The expression of mitochondrial genes was altered in the srr1Δ/Δ null mutant in comparison to their expression in the wild type. Furthermore, apoptosis increased significantly in the srr1Δ/Δ mutant strain compared to the level of apoptosis in the wild type, suggesting the activation of a mitochondrion-dependent apoptotic cell death pathway in the srr1Δ/Δ mutant. Collectively, this study shows for the first time that a lower eukaryote like C. albicans possesses a two-component response regulator protein that has survived in mitochondria and regulates a subset of genes whose functions are associated with the oxidative stress response and programmed cell death (apoptosis). PMID:23584995

  10. Dissipative model for a two component gas system with friction

    SciTech Connect

    Lopez, G.; Murgia, M.; Sosa, M.

    1994-02-01

    For a mixture of small and large component of gases, the large component is treated as an ideal gas. A dissipative model is proposed for the small component, and the thermodynamic characteristics of the gas are derived through a statistical mechanical approach. The model requires for the small component to have a big dimension and its number of particles to be smaller than the large one. Using the associated partition function, the internal energy and the equation of state are calculated. The internal energy does not suffer any deviation from that of the two component ideal gas, but the equation of state deviates from that of the ideal gas for large values of the parameter which characterizes the dissipative model.

  11. Characterizing the regulon of the two-component system, PSPTO_3380 and PSPTO_3381

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The two-component system, PSPTO_3380 (3380) and PSPTO_3381 (3381) in Pseudomonas syringae pv. tomato DC3000 (Pst) is involved in pathogenicity. We have reported that addition of a number of divalent cations to the medium induces expression of this two-component system. 3380/3381 regulates transcrip...

  12. Comprehensive DNA Microarray Analysis of Bacillus subtilis Two-Component Regulatory Systems

    PubMed Central

    Kobayashi, Kazuo; Ogura, Mitsuo; Yamaguchi, Hirotake; Yoshida, Ken-Ichi; Ogasawara, Naotake; Tanaka, Teruo; Fujita, Yasutaro

    2001-01-01

    It has recently been shown through DNA microarray analysis of Bacillus subtilis two-component regulatory systems (DegS-DegU, ComP-ComA, and PhoR-PhoP) that overproduction of a response regulator of the two-component systems in the background of a deficiency of its cognate sensor kinase affects the regulation of genes, including its target ones. The genome-wide effect on gene expression caused by the overproduction was revealed by DNA microarray analysis. In the present work, we newly analyzed 24 two-component systems by means of this strategy, leaving out 8 systems to which it was unlikely to be applicable. This analysis revealed various target gene candidates for these two-component systems. It is especially notable that interesting interactions appeared to take place between several two-component systems. Moreover, the probable functions of some unknown two-component systems were deduced from the list of their target gene candidates. This work is heuristic but provides valuable information for further study toward a comprehensive understanding of the B. subtilis two-component regulatory systems. The DNA microarray data obtained in this work are available at the KEGG Expression Database website (http://www.genome.ad.jp/kegg/expression). PMID:11717295

  13. Methods of producing epoxides from alkenes using a two-component catalyst system

    DOEpatents

    Kung, Mayfair C.; Kung, Harold H.; Jiang, Jian

    2013-07-09

    Methods for the epoxidation of alkenes are provided. The methods include the steps of exposing the alkene to a two-component catalyst system in an aqueous solution in the presence of carbon monoxide and molecular oxygen under conditions in which the alkene is epoxidized. The two-component catalyst system comprises a first catalyst that generates peroxides or peroxy intermediates during oxidation of CO with molecular oxygen and a second catalyst that catalyzes the epoxidation of the alkene using the peroxides or peroxy intermediates. A catalyst system composed of particles of suspended gold and titanium silicalite is one example of a suitable two-component catalyst system.

  14. Perturbational Blowup Solutions to the Two-Component Dullin-Gottwald-Holm System

    PubMed Central

    2016-01-01

    We construct a family of nonradially symmetric exact solutions for the two-component DGH system by the perturbational method. Depending on the parameters, the class of solutions includes both blowup type and global existence type. PMID:27127801

  15. Autoamplification of a Two-Component Regulatory System Results in “Learning” Behavior

    PubMed Central

    Hoffer, Sally M.; Westerhoff, Hans V.; Hellingwerf, Klaas J.; Postma, Pieter W.; Tommassen, Jan

    2001-01-01

    We have tested the hypothesis that the autoamplification of two-component regulatory systems results in “learning” behavior, i.e., that bacteria respond faster or more extensively to a signal when a similar signal has been perceived in the past. Indeed, the induction of alkaline phosphatase activity upon phosphate limitation was faster if the cultures had been limited for phosphate previously, and this faster response correlated with the autoamplification of the cognate two-component system. PMID:11466297

  16. Comparative Analysis of Wolbachia Genomes Reveals Streamlining and Divergence of Minimalist Two-Component Systems

    PubMed Central

    Christensen, Steen; Serbus, Laura Renee

    2015-01-01

    Two-component regulatory systems are commonly used by bacteria to coordinate intracellular responses with environmental cues. These systems are composed of functional protein pairs consisting of a sensor histidine kinase and cognate response regulator. In contrast to the well-studied Caulobacter crescentus system, which carries dozens of these pairs, the streamlined bacterial endosymbiont Wolbachia pipientis encodes only two pairs: CckA/CtrA and PleC/PleD. Here, we used bioinformatic tools to compare characterized two-component system relays from C. crescentus, the related Anaplasmataceae species Anaplasma phagocytophilum and Ehrlichia chaffeensis, and 12 sequenced Wolbachia strains. We found the core protein pairs and a subset of interacting partners to be highly conserved within Wolbachia and these other Anaplasmataceae. Genes involved in two-component signaling were positioned differently within the various Wolbachia genomes, whereas the local context of each gene was conserved. Unlike Anaplasma and Ehrlichia, Wolbachia two-component genes were more consistently found clustered with metabolic genes. The domain architecture and key functional residues standard for two-component system proteins were well-conserved in Wolbachia, although residues that specify cognate pairing diverged substantially from other Anaplasmataceae. These findings indicate that Wolbachia two-component signaling pairs share considerable functional overlap with other α-proteobacterial systems, whereas their divergence suggests the potential for regulatory differences and cross-talk. PMID:25809075

  17. Transcriptome analysis of all two-component regulatory system mutants of Escherichia coli K-12.

    PubMed

    Oshima, Taku; Aiba, Hirofumi; Masuda, Yasushi; Kanaya, Shigehiko; Sugiura, Masahito; Wanner, Barry L; Mori, Hirotada; Mizuno, Takeshi

    2002-10-01

    We have systematically examined the mRNA profiles of 36 two-component deletion mutants, which include all two-component regulatory systems of Escherichia coli, under a single growth condition. DNA microarray results revealed that the mutants belong to one of three groups based on their gene expression profiles in Luria-Bertani broth under aerobic conditions: (i) those with no or little change; (ii) those with significant changes; and (iii) those with drastic changes. Under these conditions, the anaeroresponsive ArcB/ArcA system, the osmoresponsive EnvZ/OmpR system and the response regulator UvrY showed the most drastic changes. Cellular functions such as flagellar synthesis and expression of the RpoS regulon were affected by multiple two-component systems. A high correlation coefficient of expression profile was found between several two-component mutants. Together, these results support the view that a network of functional interactions, such as cross-regulation, exists between different two-component systems. The compiled data are avail-able at our website (http://ecoli.aist-nara.ac.jp/xp_analysis/ 2_components). PMID:12366850

  18. An intimate link: two-component signal transduction systems and metal transport systems in bacteria

    PubMed Central

    Singh, Kamna; Senadheera, Dilani B; Cvitkovitch, Dennis G

    2014-01-01

    Bacteria have evolved various strategies to contend with high concentrations of environmental heavy metal ions for rapid, adaptive responses to maintain cell viability. Evidence gathered in the past two decades suggests that bacterial two-component signal transduction systems (TCSTSs) are intimately involved in monitoring cation accumulation, and can regulate the expression of related metabolic and virulence genes to elicit adaptive responses to changes in the concentration of these ions. Using examples garnered from recent studies, we summarize the cross-regulatory relationships between metal ions and TCSTSs. We present evidence of how bacterial TCSTSs modulate metal ion homeostasis and also how metal ions, in turn, function to control the activities of these signaling systems linked with bacterial survival and virulence. PMID:25437189

  19. The Pseudomonas aeruginosa AlgZR two-component system coordinates multiple phenotypes

    PubMed Central

    Okkotsu, Yuta; Little, Alexander S.; Schurr, Michael J.

    2014-01-01

    Pseudomonas aeruginosa is an opportunistic pathogen that causes a multitude of infections. These infections can occur at almost any site in the body and are usually associated with a breach of the innate immune system. One of the prominent sites where P. aeruginosa causes chronic infections is within the lungs of cystic fibrosis patients. P. aeruginosa uses two-component systems that sense environmental changes to differentially express virulence factors that cause both acute and chronic infections. The P. aeruginosa AlgZR two component system is one of its global regulatory systems that affects the organism's fitness in a broad manner. This two-component system is absolutely required for two P. aeruginosa phenotypes: twitching motility and alginate production, indicating its importance in both chronic and acute infections. Additionally, global transcriptome analyses indicate that it regulates the expression of many different genes, including those associated with quorum sensing, type IV pili, type III secretion system, anaerobic metabolism, cyanide and rhamnolipid production. This review examines the complex AlgZR regulatory network, what is known about the structure and function of each protein, and how it relates to the organism's ability to cause infections. PMID:24999454

  20. The CpxRA Two-Component System Is Essential for Citrobacter rodentium Virulence

    PubMed Central

    Thomassin, Jenny-Lee; Giannakopoulou, Natalia; Zhu, Lei; Gross, Jeremy; Salmon, Kristiana; Leclerc, Jean-Mathieu; Daigle, France; Le Moual, Hervé

    2015-01-01

    Citrobacter rodentium is a murine intestinal pathogen used as a model for the foodborne human pathogens enterohemorrhagic Escherichia coli and enteropathogenic E. coli. During infection, these pathogens use two-component signal transduction systems to detect and adapt to changing environmental conditions. In E. coli, the CpxRA two-component signal transduction system responds to envelope stress by modulating the expression of a myriad of genes. Quantitative real-time PCR showed that cpxRA was expressed in the colon of C57BL/6J mice infected with C. rodentium. To determine whether CpxRA plays a role during C. rodentium infection, a cpxRA deletion strain was generated and found to have a colonization defect during infection. This defect was independent of an altered growth rate or a defective type III secretion system, and single-copy chromosomal complementation of cpxRA restored virulence. The C. rodentium strains were then tested in C3H/HeJ mice, a lethal intestinal infection model. Mice infected with the ΔcpxRA strain survived infection, whereas mice infected with the wild-type or complemented strains succumbed to infection. Furthermore, we found that the cpxRA expression level was higher during early infection than at a later time point. Taken together, these data demonstrate that the CpxRA two-component signal transduction system is essential for the in vivo virulence of C. rodentium. In addition, these data suggest that fine-tuned cpxRA expression is important for infection. This is the first study that identifies a C. rodentium two-component transduction system required for pathogenesis. This study further indicates that CpxRA is an interesting target for therapeutics against enteric pathogens. PMID:25712925

  1. Multistability in an optomechanical system with a two-component Bose-Einstein condensate

    SciTech Connect

    Dong Ying; Ye Jinwu; Pu Han

    2011-03-15

    We investigate a system consisting of a two-component Bose-Einstein condensate interacting dispersively with a Fabry-Perot optical cavity where the two components of the condensate are resonantly coupled to each other by another classical field. The key feature of this system is that the atomic motional degrees of freedom and the internal pseudospin degrees of freedom are coupled to the cavity field simultaneously, hence an effective spin-orbital coupling within the condensate is induced by the cavity. The interplay among the atomic center-of-mass motion, the atomic collective spin, and the cavity field leads to a strong nonlinearity, resulting in multistable behavior in both matter wave and light wave at the few-photon level.

  2. Theory of supramolecular co-polymerization in a two-component system

    NASA Astrophysics Data System (ADS)

    Jabbari-Farouji, S.; van der Schoot, Paul

    2012-08-01

    As a first step to understand the role of molecular or chemical polydispersity in self-assembly, we put forward a coarse-grained model that describes the spontaneous formation of quasi-linear polymers in solutions containing two self-assembling species. Our theoretical framework is based on a two-component self-assembled Ising model in which the chemical bidispersity, i.e., the presence of two distinct chemical entities, is parameterized in terms of the strengths of the binding free energies that depend on the monomer species involved in the pairing interaction. Depending upon the relative values of the binding free energies involved, different morphologies of assemblies that include both components are formed, exhibiting random, blocky or alternating ordering of the two components in the assemblies. Analyzing the model for the case of blocky ordering, which is of most practical interest, we find that the transition from conditions of minimal assembly to those characterized by strong polymerization can be described by a critical concentration that depends on the concentration ratio of the two species. Interestingly, the distribution of monomers in the assemblies is different from that in the original distribution, i.e., the ratio of the concentrations of the two components put into the system. The monomers with a smaller binding free energy are more abundant in short assemblies and monomers with a larger binding affinity are more abundant in longer assemblies. Under certain conditions the two components congregate into separate supramolecular polymeric species and in that sense phase separate. We find strong deviations from the expected growth law for supramolecular polymers even for modest amounts of a second component, provided it is chemically sufficiently distinct from the main one.

  3. Functional Analysis of the Mycobacterium tuberculosis MprAB Two-Component Signal Transduction System

    PubMed Central

    Zahrt, Thomas C.; Wozniak, Christopher; Jones, Denise; Trevett, Andrea

    2003-01-01

    The mechanisms utilized by Mycobacterium tuberculosis to establish, maintain, or reactivate from latent infection in the host are largely unknown but likely include genes that mediate adaptation to conditions encountered during persistence. Previously, a two-component signal transduction system, mprAB, was found to be required in M. tuberculosis for establishment and maintenance of persistent infection in a tissue- and stage-specific fashion. To begin to characterize the role of this system in M. tuberculosis physiology and virulence, a functional analysis of the mprA and mprB gene products was initiated. Here, evidence is presented demonstrating that sensor kinase MprB and response regulator MprA function as an intact signal-transducing pair in vitro and in vivo. Sensor kinase MprB can be autophosphorylated, can donate phosphate to MprA, and can act as a phospho-MprA phosphatase in vitro. Correspondingly, response regulator MprA can accept phosphate from MprB or from small phosphodonors including acetyl phosphate. Mutagenesis of residues His249 in MprB and Asp48 in MprA abolished the ability of these proteins to be phosphorylated in vitro. Introduction of these alleles into Mycobacterium bovis BCGattenuated virulence in macrophages in vivo. Together, these results support a role for the mprAB two-component system in M. tuberculosis physiology and pathogenesis. Characterization of two-component signal transduction systems will enhance our understanding of processes regulated by M. tuberculosis during acute and/or persistent infection in the host. PMID:14638785

  4. Two-component systems in Streptomyces: key regulators of antibiotic complex pathways

    PubMed Central

    2013-01-01

    Streptomyces, the main antibiotic-producing bacteria, responds to changing environmental conditions through a complex sensing mechanism and two-component systems (TCSs) play a crucial role in this extraordinary “sensing” device. Moreover, TCSs are involved in the biosynthetic control of a wide range of secondary metabolites, among them commercial antibiotics. Increased knowledge about TCSs can be a powerful asset in the manipulation of bacteria through genetic engineering with a view to obtaining higher efficiencies in secondary metabolite production. In this review we summarise the available information about Streptomyces TCSs, focusing specifically on their connections to antibiotic production. PMID:24354561

  5. The Two-Component Virial Theorem and the Physical Properties of Stellar Systems.

    PubMed

    Dantas; Ribeiro; Capelato; de Carvalho RR

    2000-01-01

    Motivated by present indirect evidence that galaxies are surrounded by dark matter halos, we investigate whether their physical properties can be described by a formulation of the virial theorem that explicitly takes into account the gravitational potential term representing the interaction of the dark halo with the baryonic or luminous component. Our analysis shows that the application of such a "two-component virial theorem" not only accounts for the scaling relations displayed by, in particular, elliptical galaxies, but also for the observed properties of all virialized stellar systems, ranging from globular clusters to galaxy clusters. PMID:10587482

  6. Characterization of a novel two-component system in Burkholderia cenocepacia.

    PubMed

    Merry, Callie R; Perkins, Michael; Mu, Lin; Peterson, Bridget K; Knackstedt, Rebecca W; Weingart, Christine L

    2015-04-01

    Two-component systems are important regulatory systems that allow bacteria to adjust to environmental conditions, and in some bacteria are used in pathogenesis. We identified a novel two-component system in Burkholderia cenocepacia, an opportunistic pathogen that causes pneumonia in cystic fibrosis (CF) patients. The putative operon encodes BceS, a sensor kinase, and BceR, a response regulator. Our studies indicated that the bceR mutant showed a statistically significant decrease in protease, swimming motility, and quorum sensing when compared to the wild-type, but there was no significant difference in phospholipase C activity, swarming, and biofilm formation. In addition, the mutant showed a statistically significant reduction in virulence compared to the wild-type using the alfalfa plant model. Examination of the Burkholderia cepacia complex (a group of organisms that are phenotypically similar, but genotypically distinct) revealed that this system is prevalent in B. ambifaria, B. multivorans, B. vietnamiensis and B. dolosa. Interestingly, all these organisms have been associated with CF patients. The collective results indicate that BceSR influences various activities important in Burkholderia physiology and possibly pathogenesis. This information could be important in the design of novel therapeutics for Burkholderia infections. PMID:25519693

  7. Characterization of a temperature-responsive two component regulatory system from the Antarctic archaeon, Methanococcoides burtonii

    PubMed Central

    Najnin, T.; Siddiqui, K. S.; Taha, T; Elkaid, N.; Kornfeld, G.; Curmi, P. M. G.; Cavicchioli, R.

    2016-01-01

    Cold environments dominate the Earth’s biosphere and the resident microorganisms play critical roles in fulfilling global biogeochemical cycles. However, only few studies have examined the molecular basis of thermosensing; an ability that microorganisms must possess in order to respond to environmental temperature and regulate cellular processes. Two component regulatory systems have been inferred to function in thermal regulation of gene expression, but biochemical studies assessing these systems in Bacteria are rare, and none have been performed in Archaea or psychrophiles. Here we examined the LtrK/LtrR two component regulatory system from the Antarctic archaeon, Methanococcoides burtonii, assessing kinase and phosphatase activities of wild-type and mutant proteins. LtrK was thermally unstable and had optimal phosphorylation activity at 10 °C (the lowest optimum activity for any psychrophilic enzyme), high activity at 0 °C and was rapidly thermally inactivated at 30 °C. These biochemical properties match well with normal environmental temperatures of M. burtonii (0–4 °C) and the temperature this psychrophile is capable of growing at in the laboratory (−2 to 28 °C). Our findings are consistent with a role for LtrK in performing phosphotransfer reactions with LtrR that could lead to temperature-dependent gene regulation. PMID:27052690

  8. Peptidoglycan Recognition Proteins kill bacteria by inducing suicide through protein-sensing two-component systems

    PubMed Central

    Kashyap, Des Raj; Wang, Minhui; Liu, Li-Hui; Boons, Geert-Jan; Gupta, Dipika; Dziarski, Roman

    2011-01-01

    Mammalian Peptidoglycan Recognition Proteins (PGRPs), similar to antimicrobial lectins, bind to bacterial cell wall and kill bacteria through an unknown mechanism. We show that PGRPs enter Gram-positive cell wall at the site of daughter cell separation during cell division. In Bacillus subtilis PGRPs activate the CssR-CssS two-component system that detects and disposes of misfolded proteins exported out of bacterial cells. This activation results in membrane depolarization, cessation of intracellular peptidoglycan, protein, RNA, and DNA synthesis, and production of hydroxyl radicals, which are responsible for bacterial death. PGRPs also bind to the outer membrane in Escherichia coli and activate functionally homologous CpxA-CpxR two-component system, which results in bacterial death. We excluded other potential bactericidal mechanisms (inhibition of extracellular peptidoglycan synthesis, hydrolysis of peptidoglycan, and membrane permeabilization). Thus we reveal a novel mechanism of bacterial killing by innate immunity proteins that bind to cell wall or outer membrane and exploit bacterial stress defense response to kill bacteria. PMID:21602801

  9. Novel Two-Component Systems Implied in Antibiotic Production in Streptomyces coelicolor

    PubMed Central

    Yepes, Ana; Rico, Sergio; Rodríguez-García, Antonio; Santamaría, Ramón I.; Díaz, Margarita

    2011-01-01

    The abundance of two-component systems (TCSs) in Streptomyces coelicolor A3(2) genome indicates their importance in the physiology of this soil bacteria. Currently, several TCSs have been related to antibiotic regulation, and the purpose in this study was the characterization of five TCSs, selected by sequence homology with the well-known absA1A2 system, that could also be associated with this important process. Null mutants of the five TCSs were obtained and two mutants (ΔSCO1744/1745 and ΔSCO4596/4597/4598) showed significant differences in both antibiotic production and morphological differentiation, and have been renamed as abr (antibiotic regulator). No detectable changes in antibiotic production were found in the mutants in the systems that include the ORFs SCO3638/3639, SCO3640/3641 and SCO2165/2166 in any of the culture conditions assayed. The system SCO1744/1745 (AbrA1/A2) was involved in negative regulation of antibiotic production, and acted also as a negative regulator of the morphological differentiation. By contrast, the system SCO4596/4597/4598 (AbrC1/C2/C3), composed of two histidine kinases and one response regulator, had positive effects on both morphological development and antibiotic production. Microarray analyses of the ΔabrC1/C2/C3 and wild-type transcriptomes revealed downregulation of actII-ORF4 and cdaR genes, the actinorhodin and calcium-dependent antibiotic pathway-specific regulators respectively. These results demonstrated the involvement of these new two-component systems in antibiotic production and morphological differentiation by different approaches. One is a pleiotropic negative regulator: abrA1/A2. The other one is a positive regulator composed of three elements, two histidine kinases and one response regulator: abrC1/C2/C3. PMID:21625497

  10. Spatial propagation for a two component reaction-diffusion system arising in population dynamics

    NASA Astrophysics Data System (ADS)

    Ducrot, Arnaud

    2016-06-01

    In this work a two component epidemic reaction-diffusion system posed on the whole space RN is considered. Uniform boundedness of the solutions is proved using suitable local Lp-estimates. The spatial invasion of a localized introduced amount of infective is studied yielding to the derivation of the asymptotic speed of spread for the infection. This part is achieved using uniform persistence ideas. The state of the population after the epidemic is further investigated using different Lyapunov like arguments. The solution is shown to converge the endemic equilibrium point behind the front in the equi-diffusional case. For general diffusion coefficient unique ergodicity of the tail of invasion is obtained by constructing a suitable sub-harmonic map.

  11. Addition Formulae of Discrete KP, q-KP and Two-Component BKP Systems

    NASA Astrophysics Data System (ADS)

    Gao, Xu; Li, Chuan-Zhong; He, Jing-Song

    2016-04-01

    In this paper, we construct the addition formulae for several integrable hierarchies, including the discrete KP, the q-deformed KP, the two-component BKP and the D type Drinfeld–Sokolov hierarchies. With the help of the Hirota bilinear equations and τ functions of different kinds of KP hierarchies, we prove that these addition formulae are equivalent to these hierarchies. These studies show that the addition formula in the research of the integrable systems has good universality. Supported by the Zhejiang Provincial Natural Science Foundation under Grant No. LY15A010004, the National Natural Science Foundation of China under Grant Nos. 11201251, 11571192 and the Natural Science Foundation of Ningbo under Grant No. 2015A610157. Jingsong He is supported by the National Natural Science Foundation of China under Grant No. 11271210, K.C. Wong Magna Fund in Ningbo University

  12. Luminescence kinetics of two-component molecular systems in porous glasses

    NASA Astrophysics Data System (ADS)

    Starokurov, Yu. V.; Letuta, S. N.; Pashkevich, S. N.; Antropova, T. V.; Gordeeva, Yu. A.; Saletsky, A. M.

    2013-01-01

    The kinetics of bimolecular photoreactions accompanied by a characteristic delayed emission of reactant molecules is studied in nanoporous silica glasses upon selective activation of a two-component luminophore system (erythrosine-anthracene) by a short (10 ns) pulse of a Nd3+:YAG laser (532 nm). Time-resolved luminescence signals with different shapes are recorded in different spectral regions. The emission at a wavelength of 430 nm is identified as the sensitized delayed annihilation fluorescence of anthracene. The long-time luminescence in the region of 570 nm consists of thermally induced delayed fluorescence of erythrosine and an emission resulting from heterogeneous annihilation of triplet excitations of erythrosine and anthracene. The effect of pore sizes on the triplet-triplet energy transfer efficiency is determined.

  13. Regulation of virulence by a two-component system in group B streptococcus.

    PubMed

    Jiang, Sheng-Mei; Cieslewicz, Michael J; Kasper, Dennis L; Wessels, Michael R

    2005-02-01

    Group B Streptococcus (GBS) is frequently carried in the gastrointestinal or genitourinary tract as a commensal organism, yet it has the potential to cause life-threatening infection in newborn infants, pregnant women, and individuals with chronic illness. Regulation of virulence factor expression may affect whether GBS behaves as an asymptomatic colonizer or an invasive pathogen, but little is known about how such factors are controlled in GBS. We now report the characterization of a GBS locus that encodes a two-component regulatory system similar to CsrRS (or CovRS) in Streptococcus pyogenes. Inactivation of csrR, encoding the putative response regulator, in two unrelated wild-type strains of GBS resulted in a marked increase in production of beta-hemolysin/cytolysin and a striking decrease in production of CAMP factor, an unrelated cytolytic toxin. Quantitative RNA hybridization experiments revealed that these two phenotypes were associated with a marked increase and decrease in expression of the corresponding genes, cylE and cfb, respectively. The CsrR mutant strains also displayed increased expression of scpB encoding C5a peptidase. Similar, but less marked, changes in gene expression were observed in CsrS (putative sensor component) mutants, evidence that CsrR and CsrS constitute a functional two-component system. Experimental infection studies in mice demonstrated reduced virulence of both CsrR and CsrS mutant strains relative to the wild type. Together, these results indicate that CsrRS regulates expression of multiple GBS virulence determinants and is likely to play an important role in GBS pathogenesis. PMID:15659687

  14. Mycobacterium tuberculosis two-component systems and implications in novel vaccines and drugs.

    PubMed

    Zhou, PeiFu; Long, QuanXin; Zhou, YeXin; Wang, HongHai; Xie, JianPing

    2012-01-01

    Communication is vital for nearly all organisms to survive and thrive. For some particularly successful intracellular pathogens, a robust and precise signal transduction system is imperative for handling the complex, volatile, and harsh niche. The communication network of the etiology of tuberculosis, Mycobacterium tuberculosis (M.tb), namely two-component system (TCS), the eukaryotic-like Ser/Thr protein kinases(STPKs) system, the protein tyrosine kinase(PTK) system and the extracytoplasmic function σ(ECF-σ) system, determine how the pathogen responds to environmental fluctuations. At least 12 pair TCSs and four orphan proteins (three response regulators, Rv2884, Rv0260c, Rv0818, and one putative sensory transduction protein, Rv3143) can be found in the M.tb H37Rv genome. They regulate various aspects of M.tb, including virulence, dormancy, persistence, and drug resistance. This review focuses on the physiological roles of TCSs and the network of M.tb TCSs from a systems biology perspective. The implications of TCSs for better vaccine and new drug targets against tuberculosis are also examined. PMID:22339658

  15. Investigation of in vivo cross-talk between key two-component systems of Escherichia coli.

    PubMed

    Verhamme, Daniël T; Arents, Jos C; Postma, Pieter W; Crielaard, Wim; Hellingwerf, Klaas J

    2002-01-01

    Intracellular signal transfer in bacteria is dominated by phosphoryl transfer between conserved transmitter and receiver domains in regulatory proteins of so-called two-component systems. Escherichia coli contains 30 such systems, which allow it to modulate gene expression, enzyme activity and the direction of flagellar rotation. The authors have investigated whether, and to what extent, these separate systems form (an) interacting network(s) in vivo, focussing on interactions between four major systems, involved in the responses to the availability of phosphorylated sugars (Uhp), phosphate (Pho), nitrogen (Ntr) and oxygen (Arc). Significant cross-talk was not detectable in wild-type cells. Decreasing expression levels of succinate dehydrogenase (reporting Arc activation), upon activation of the Pho system, appeared to be independent of signalling through PhoR. Cross-talk towards NtrC did occur, however, in a ntrB deletion strain, upon joint activation of Pho, Ntr and Uhp. UhpT expression was demonstrated when cells were grown on pyruvate, through non-cognate phosphorylation of UhpA by acetyl phosphate. PMID:11782500

  16. The CpxRA two-component system contributes to Legionella pneumophila virulence.

    PubMed

    Tanner, Jennifer R; Li, Laam; Faucher, Sébastien P; Brassinga, Ann Karen C

    2016-06-01

    The bacterium Legionella pneumophila is capable of intracellular replication within freshwater protozoa as well as human macrophages, the latter of which results in the serious pneumonia Legionnaires' disease. A primary factor involved in these host cell interactions is the Dot/Icm Type IV secretion system responsible for translocating effector proteins needed to establish and maintain the bacterial replicative niche. Several regulatory factors have been identified to control the expression of the Dot/Icm system and effectors, one of which is the CpxRA two-component system, suggesting essentiality for virulence. In this study, we generated cpxR, cpxA and cpxRA in-frame null mutant strains to further delineate the role of the CpxRA system in bacterial survival and virulence. We found that cpxR is essential for intracellular replication within Acanthamoeba castellanii, but not in U937-derived macrophages. Transcriptome analysis revealed that CpxRA regulates a large number of virulence-associated proteins including Dot/Icm effectors as well as Type II secreted substrates. Furthermore, the cpxR and cpxRA mutant strains were more sodium resistant than the parental strain Lp02, and cpxRA expression reaches maximal levels during postexponential phase. Taken together, our findings suggest the CpxRA system is a key contributor to L. pneumophila virulence in protozoa via virulence factor regulation. PMID:26934669

  17. P2CS: a two-component system resource for prokaryotic signal transduction research

    PubMed Central

    Barakat, Mohamed; Ortet, Philippe; Jourlin-Castelli, Cécile; Ansaldi, Mireille; Méjean, Vincent; Whitworth, David E

    2009-01-01

    Background With the escalation of high throughput prokaryotic genome sequencing, there is an ever-increasing need for databases that characterise, catalogue and present data relating to particular gene sets and genomes/metagenomes. Two-component system (TCS) signal transduction pathways are the dominant mechanisms by which micro-organisms sense and respond to external as well as internal environmental changes. These systems respond to a wide range of stimuli by triggering diverse physiological adjustments, including alterations in gene expression, enzymatic reactions, or protein-protein interactions. Description We present P2CS (Prokaryotic 2-Component Systems), an integrated and comprehensive database of TCS signal transduction proteins, which contains a compilation of the TCS genes within 755 completely sequenced prokaryotic genomes and 39 metagenomes. P2CS provides detailed annotation of each TCS gene including family classification, sequence features, functional domains, as well as genomic context visualization. To bypass the generic problem of gene underestimation during genome annotation, we also constituted and searched an ORFeome, which improves the recovery of TCS proteins compared to searches on the equivalent proteomes. Conclusion P2CS has been developed for computational analysis of the modular TCSs of prokaryotic genomes and metagenomes. It provides a complete overview of information on TCSs, including predicted candidate proteins and probable proteins, which need further curation/validation. The database can be browsed and queried with a user-friendly web interface at . PMID:19604365

  18. Photoisomerization-induced morphology and transparency transition in an azobenzene based two-component organogel system.

    PubMed

    Cao, Xinhua; Liu, Xue; Chen, Liming; Mao, Yueyuan; Lan, Haichuang; Yi, Tao

    2015-11-15

    A two-component gel containing long chain alkylated gallic acid (GA) and photochromic phenazopyridine (PAP) was prepared. The gel was thoroughly characterized by UV-visible and IR spectra, SEM and POM images, XRD diffraction and dynamic oscillatory measurements. The structure and transparency of the two-component gel can be reversibly changed by alternative UV light irradiation and warming in the palm of the hand. This kind of soft material has potential application in upscale surface functional materials. PMID:26218198

  19. The Evolution of Two-Component Systems in Bacteria RevealsDifferent Strategies for Niche Adaptation

    SciTech Connect

    Alm, Eric; Huang, Katherine; Arkin, Adam

    2006-09-13

    Two-component systems including histidine protein kinasesrepresent the primary signal transduction paradigm in prokaryoticorganisms. To understand how these systems adapt to allow organisms todetect niche-specific signals, we analyzed the phylogenetic distributionof nearly 5000 histidine protein kinases from 207 sequenced prokaryoticgenomes. We found that many genomes carry a large repertoire of recentlyevolved signaling genes, which may reflect selective pressure to adapt tonew environmental conditions. Both lineage-specific gene family expansionand horizontal gene transfer play major roles in the introduction of newhistidine kinases into genomes; however, there are differences in howthese two evolutionary forces act. Genes imported via horizontal transferare more likely to retain their original functionality as inferred from asimilar complement of signaling domains, while gene family expansionaccompanied by domain shuffling appears to be a major source of novelgenetic diversity. Family expansion is the dominantsource of newhistidine kinase genes in the genomes most enriched in signalingproteins, and detailed analysis reveals that divergence in domainstructure and changes in expression patterns are hallmarks of recentexpansions. Finally, while these two modes of gene acquisition arewidespread across bacterial taxa, there are clear species-specificpreferences for which mode is used.

  20. A Crp-Dependent Two-Component System Regulates Nitrate and Nitrite Respiration in Shewanella oneidensis

    PubMed Central

    Dong, Yangyang; Wang, Jixuan; Fu, Huihui; Zhou, Guangqi; Shi, Miaomiao; Gao, Haichun

    2012-01-01

    We have previously illustrated the nitrate/nitrite respiratory pathway of Shewanella oneidensis, which is renowned for its remarkable versatility in respiration. Here we investigated the systems regulating the pathway with a reliable approach which enables characterization of mutants impaired in nitrate/nitrite respiration by guaranteeing biomass. The S. oneidensis genome encodes an Escherichia coli NarQ/NarX homolog SO3981 and two E. coli NarP/NarL homologs SO1860 and SO3982. Results of physiological characterization and mutational analyses demonstrated that S. oneidensis possesses a single two-component system (TCS) for regulation of nitrate/nitrite respiration, consisting of the sensor kinase SO3981(NarQ) and the response regulator SO3982(NarP). The TCS directly controls the transcription of nap and nrfA (genes encoding nitrate and nitrite reductases, respectively) but regulates the former less tightly than the latter. Additionally, phosphorylation at residue 57 of SO3982 is essential for its DNA-binding capacity. At the global control level, Crp is found to regulate expression of narQP as well as nap and nrfA. In contrast to NarP-NarQ, Crp is more essential for nap rather than nrfA. PMID:23240049

  1. Gene Regulation by the LiaSR Two-Component System in Streptococcus mutans

    PubMed Central

    Shankar, Manoharan; Mohapatra, Saswat S.; Biswas, Saswati; Biswas, Indranil

    2015-01-01

    The LiaSR two-component signal transduction system regulates cellular responses to several environmental stresses, including those that induce cell envelope damages. Downstream regulons of the LiaSR system have been implicated in tolerance to acid, antibiotics and detergents. In the dental pathogen Streptococcus mutans, the LiaSR system is necessary for tolerance against acid, antibiotics, and cell wall damaging stresses during growth in the oral cavity. To understand the molecular mechanisms by which LiaSR regulates gene expression, we created a mutant LiaR in which the conserved aspartic acid residue (the phosphorylation site), was changed to alanine residue (D58A). As expected, the LiaR-D58A variant was unable to acquire the phosphate group and bind to target promoters. We also noted that the predicted LiaR-binding motif upstream of the lia operon does not appear to be well conserved. Consistent with this observation, we found that LiaR was unable to bind to the promoter region of lia; however, we showed that LiaR was able to bind to the promoters of SMU.753, SMU.2084 and SMU.1727. Based on sequence analysis and DNA binding studies we proposed a new 25-bp conserved motif essential for LiaR binding. Introducing alterations at fully conserved positions in the 25-bp motif affected LiaR binding, and the binding was dependent on the combination of positions that were altered. By scanning the S. mutans genome for the occurrence of the newly defined LiaR binding motif, we identified the promoter of hrcA (encoding a key regulator of the heat shock response) that contains a LiaR binding motif, and we showed that hrcA is negatively regulated by the LiaSR system. Taken together our results suggest a putative role of the LiaSR system in heat shock responses of S. mutans. PMID:26020679

  2. Transcriptome Analysis of the Brucella abortus BvrR/BvrS Two-Component Regulatory System

    PubMed Central

    Viadas, Cristina; Rodríguez, María C.; Sangari, Felix J.; Gorvel, Jean-Pierre; García-Lobo, Juan M.; López-Goñi, Ignacio

    2010-01-01

    Background The two-component BvrR/BvrS system is essential for Brucella abortus virulence. It was shown previously that its dysfunction alters the expression of some major outer membrane proteins and the pattern of lipid A acylation. To determine the genes regulated by BvrR/BvrS, we performed a whole-genome microarray analysis using B. abortus RNA obtained from wild type and bvrR mutant cells grown in the same conditions. Methodology/Principal Findings A total of 127 differentially expressed genes were found: 83 were over expressed and 44 were less expressed in the bvrR mutant. Two operons, the phosphotransferase system and the maltose transport system, were down-regulated. Several genes involved in cell envelope or outer membrane biogenesis were differentially expressed: genes for outer membrane proteins (omp25a, omp25d), lipoproteins, LPS and fatty acid biosynthesis, stress response proteins, chaperones, flagellar genes, and twelve genes encoding ABC transport systems. Ten genes related with carbon metabolism (pckA and fumB among others) were up-regulated in the bvrR mutant, and denitrification genes (nirK, norC and nosZ) were also regulated. Notably, seven transcriptional regulators were affected, including VjbR, ExoR and OmpR that were less expressed in the bvrR mutant. Finally, the expression of eleven genes which have been previously related with Brucella virulence was also altered. Conclusions/Significance All these data corroborate the impact of BvrR/BvrS on cell envelope modulation, confirm that this system controls the carbon and nitrogen metabolism, and suggest a cross-talk among some regulators to adjust the Brucella physiology to the shift expected to occur during the transit from the extracellular to the intracellular niche. PMID:20422049

  3. Functional characterization of WalRK: A two-component signal transduction system from Bacillus anthracis.

    PubMed

    Dhiman, Alisha; Bhatnagar, Sonika; Kulshreshtha, Parul; Bhatnagar, Rakesh

    2014-01-01

    Two-component signal transduction systems (TCS), consisting of a sensor histidine protein kinase and its cognate response regulator, are an important mode of environmental sensing in bacteria. Additionally, they have been found to regulate virulence determinants in several pathogens. Bacillus anthracis, the causative agent of anthrax and a bioterrorism agent, harbours 41 pairs of TCS. However, their role in its pathogenicity has remained largely unexplored. Here, we show that WalRK of B. anthracis forms a functional TCS which exhibits some species-specific functions. Biochemical studies showed that domain variants of WalK, the histidine kinase, exhibit classical properties of autophosphorylation and phosphotransfer to its cognate response regulator WalR. Interestingly, these domain variants also show phosphatase activity towards phosphorylated WalR, thereby making WalK a bifunctional histidine kinase/phosphatase. An in silico regulon determination approach, using a consensus binding sequence from Bacillus subtilis, provided a list of 30 genes that could form a putative WalR regulon in B. anthracis. Further, electrophoretic mobility shift assay was used to show direct binding of purified WalR to the upstream regions of three putative regulon candidates, an S-layer protein EA1, a cell division ABC transporter FtsE and a sporulation histidine kinase KinB3. Our work lends insight into the species-specific functions and mode of action of B. anthracis WalRK. PMID:24490131

  4. P2CS: updates of the prokaryotic two-component systems database

    PubMed Central

    Ortet, Philippe; Whitworth, David E.; Santaella, Catherine; Achouak, Wafa; Barakat, Mohamed

    2015-01-01

    The P2CS database (http://www.p2cs.org/) is a comprehensive resource for the analysis of Prokaryotic Two-Component Systems (TCSs). TCSs are comprised of a receptor histidine kinase (HK) and a partner response regulator (RR) and control important prokaryotic behaviors. The latest incarnation of P2CS includes 164 651 TCS proteins, from 2758 sequenced prokaryotic genomes. Several important new features have been added to P2CS since it was last described. Users can search P2CS via BLAST, adding hits to their cart, and homologous proteins can be aligned using MUSCLE and viewed using Jalview within P2CS. P2CS also provides phylogenetic trees based on the conserved signaling domains of the RRs and HKs from entire genomes. HK and RR trees are annotated with gene organization and domain architecture, providing insights into the evolutionary origin of the contemporary gene set. The majority of TCSs are encoded by adjacent HK and RR genes, however, ‘orphan’ unpaired TCS genes are also abundant and identifying their partner proteins is challenging. P2CS now provides paired HK and RR trees with proteins from the same genetic locus indicated. This allows the appraisal of evolutionary relationships across entire TCSs and in some cases the identification of candidate partners for orphan TCS proteins. PMID:25324303

  5. Intrinsic Negative Feedback Governs Activation Surge in Two-Component Regulatory Systems

    PubMed Central

    Yeo, Won-Sik; Zwir, Igor; Huang, Henry V.; Shin, Dongwoo; Kato, Akinori; Groisman, Eduardo A.

    2013-01-01

    SUMMARY PhoP and PhoQ comprise a two-component system in the bacterium Salmonella enterica. PhoQ is the sensor kinase/phosphatase that modifies the phosphorylation state of the regulator PhoP in response to stimuli. The amount of phosphorylated PhoP surges after activation, then declines to reach a steady-state level. We now recapitulate this surge in vitro by incubating PhoP and PhoQ with ATP and ADP. Mathematical modeling identified PhoQ’s affinity for ADP as the key parameter dictating phosphorylated PhoP levels, as ADP promotes PhoQ’s phosphatase activity toward phosphorylated PhoP. The lid covering the nucleotide-binding pocket of PhoQ governs the kinase to phosphatase switch because a lid mutation that decreased ADP binding compromised PhoQ’s phosphatase activity in vitro and resulted in sustained expression of PhoP-dependent mRNAs in vivo. This feedback mechanism may curtail futile ATP consumption because ADP not only stimulates PhoQ’s phosphatase activity but also inhibits ATP binding necessary for the kinase reaction. PMID:22325356

  6. Genome-Wide Identification and Expression Analysis of Two-Component System Genes in Tomato

    PubMed Central

    He, Yanjun; Liu, Xue; Ye, Lei; Pan, Changtian; Chen, Lifei; Zou, Tao; Lu, Gang

    2016-01-01

    The two-component system (TCS), which comprises histidine kinases (HKs), phosphotransfers (HPs), and response regulator proteins (RRs), plays pivotal roles in regulating plant growth, development, and responses to biotic and abiotic stresses. TCS genes have been comprehensively identified and investigated in various crops but poorly characterized in tomato. In this work, a total of 65 TCS genes consisting of 20 HK(L)s, six HPs, and 39 RRs were identified from tomato genome. The classification, gene structures, conserved domains, chromosome distribution, phylogenetic relationship, gene duplication events, and subcellular localization of the TCS gene family were predicted and analyzed in detail. The amino acid sequences of tomato TCS family members, except those of type-B RRs, are highly conserved. The gene duplication events of the TCS family mainly occurred in the RR family. Furthermore, the expansion of RRs was attributed to both segment and tandem duplication. The subcellular localizations of the selected green fluorescent protein (GFP) fusion proteins exhibited a diverse subcellular targeting, thereby confirming their predicted divergent functionality. The majority of TCS family members showed distinct organ- or development-specific expression patterns. In addition, most of TCS genes were induced by abiotic stresses and exogenous phytohormones. The full elucidation of TCS elements will be helpful for comprehensive analysis of the molecular biology and physiological role of the TCS superfamily. PMID:27472316

  7. Genome-Wide Identification and Expression Analysis of Two-Component System Genes in Tomato.

    PubMed

    He, Yanjun; Liu, Xue; Ye, Lei; Pan, Changtian; Chen, Lifei; Zou, Tao; Lu, Gang

    2016-01-01

    The two-component system (TCS), which comprises histidine kinases (HKs), phosphotransfers (HPs), and response regulator proteins (RRs), plays pivotal roles in regulating plant growth, development, and responses to biotic and abiotic stresses. TCS genes have been comprehensively identified and investigated in various crops but poorly characterized in tomato. In this work, a total of 65 TCS genes consisting of 20 HK(L)s, six HPs, and 39 RRs were identified from tomato genome. The classification, gene structures, conserved domains, chromosome distribution, phylogenetic relationship, gene duplication events, and subcellular localization of the TCS gene family were predicted and analyzed in detail. The amino acid sequences of tomato TCS family members, except those of type-B RRs, are highly conserved. The gene duplication events of the TCS family mainly occurred in the RR family. Furthermore, the expansion of RRs was attributed to both segment and tandem duplication. The subcellular localizations of the selected green fluorescent protein (GFP) fusion proteins exhibited a diverse subcellular targeting, thereby confirming their predicted divergent functionality. The majority of TCS family members showed distinct organ- or development-specific expression patterns. In addition, most of TCS genes were induced by abiotic stresses and exogenous phytohormones. The full elucidation of TCS elements will be helpful for comprehensive analysis of the molecular biology and physiological role of the TCS superfamily. PMID:27472316

  8. Adaptation to Environmental Stimuli within the Host: Two-Component Signal Transduction Systems of Mycobacterium tuberculosis

    PubMed Central

    Bretl, Daniel J.; Demetriadou, Chrystalla; Zahrt, Thomas C.

    2011-01-01

    Summary: Pathogenic microorganisms encounter a variety of environmental stresses following infection of their respective hosts. Mycobacterium tuberculosis, the etiological agent of tuberculosis, is an unusual bacterial pathogen in that it is able to establish lifelong infections in individuals within granulomatous lesions that are formed following a productive immune response. Adaptation to this highly dynamic environment is thought to be mediated primarily through transcriptional reprogramming initiated in response to recognition of stimuli, including low-oxygen tension, nutrient depletion, reactive oxygen and nitrogen species, altered pH, toxic lipid moieties, cell wall/cell membrane-perturbing agents, and other environmental cues. To survive continued exposure to these potentially adverse factors, M. tuberculosis encodes a variety of regulatory factors, including 11 complete two-component signal transduction systems (TCSSs) and several orphaned response regulators (RRs) and sensor kinases (SKs). This report reviews our current knowledge of the TCSSs present in M. tuberculosis. In particular, we discuss the biochemical and functional characteristics of individual RRs and SKs, the environmental stimuli regulating their activation, the regulons controlled by the various TCSSs, and the known or postulated role(s) of individual TCSSs in the context of M. tuberculosis physiology and/or pathogenesis. PMID:22126994

  9. Site-Directed Mutagenesis to Improve Sensitivity of a Synthetic Two-Component Signaling System.

    PubMed

    Olshefsky, Audrey; Shehata, Laila; Kuldell, Natalie

    2016-01-01

    Two-component signaling (2CS) systems enable bacterial cells to respond to changes in their local environment, often using a membrane-bound sensor protein and a cytoplasmic responder protein to regulate gene expression. Previous work has shown that Escherichia coli's natural EnvZ/OmpR 2CS could be modified to construct a light-sensing bacterial photography system. The resulting bacterial photographs, or "coliroids," rely on a phosphotransfer reaction between Cph8, a synthetic version of EnvZ that senses red light, and OmpR. Gene expression changes can be visualized through upregulation of a LacZ reporter gene by phosphorylated OmpR. Unfortunately, basal LacZ expression leads to a detectable reporter signal even when cells are grown in the light, diminishing the contrast of the coliroids. We performed site-directed mutagenesis near the phosphotransfer site of Cph8 to isolate mutants with potentially improved image contrast. Five mutants were examined, but only one of the mutants, T541S, increased the ratio of dark/light gene expression, as measured by β-galactosidase activity. The ratio changed from 2.57 fold in the starting strain to 5.59 in the T541S mutant. The ratio decreased in the four other mutant strains we examined. The phenotype observed in the T541S mutant strain may arise because the serine sidechain is chemically similar but physically smaller than the threonine sidechain. This may minimally change the protein's local structure, but may be less sterically constrained when compared to threonine, resulting in a higher probability of a phosphotransfer event. Our initial success pairing synthetic biology and site-directed mutagenesis to optimize the bacterial photography system's performance encourages us to imagine further improvements to the performance of this and other synthetic systems, especially those based on 2CS signaling. PMID:26799494

  10. Regulon Controlled by the GppX Hybrid Two Component system in Porphyromonas gingivalis

    PubMed Central

    Hirano, Takanori; Beck, David A. C.; Wright, Chris J.; Demuth, Donald R.; Hackett, Murray; Lamont, Richard J.

    2012-01-01

    Summary The periodontal pathogen Porphyromonas gingivalis experiences a number of environmental conditions in the oral cavity and must monitor and respond to a variety of environmental cues. However the organism possesses only five full two-component systems, one of which is the hybrid system GppX. To investigate the regulon controlled by GppX we performed RNA-Seq on a ΔgppX mutant. Fifty three genes were up-regulated and 37 genes were down-regulated in the ΔgppX mutant. Pathway analyses revealed no systemic function for GppX under nutrient replete conditions; however, over 40% of the differentially abundant genes were annotated as encoding hypothetical proteins indicating a novel role for GppX. Abundance of small (s)RNA was, in general, not affected by the absence of GppX. To further define the role of GppX with respect to regulation of a hypothetical protein observed with the greatest significant relative abundance change relative to a wild-type control, PGN_0151, we constructed a series of strains in which a ΔgppX mutation was complemented with GppX protein containing specific domain and phosphotransfer mutations. The transmembrane domains, the DNA binding domain and the phosphotransfer residues were all required for regulation of PGN_0151. In addition, binding of GppX to the PGN_0151 promoter regions was confirmed by an electrophoretic mobility shift assay (EMSA). Both the ΔgppX mutant and a ΔPGN_0151 mutant were deficient in monospecies biofilm formation, suggesting a role for the GppX-PGN_0151 regulon in colonization and survival of the organism. PMID:23194602

  11. Site-Directed Mutagenesis to Improve Sensitivity of a Synthetic Two-Component Signaling System

    PubMed Central

    Kuldell, Natalie

    2016-01-01

    Two-component signaling (2CS) systems enable bacterial cells to respond to changes in their local environment, often using a membrane-bound sensor protein and a cytoplasmic responder protein to regulate gene expression. Previous work has shown that Escherichia coli’s natural EnvZ/OmpR 2CS could be modified to construct a light-sensing bacterial photography system. The resulting bacterial photographs, or “coliroids,” rely on a phosphotransfer reaction between Cph8, a synthetic version of EnvZ that senses red light, and OmpR. Gene expression changes can be visualized through upregulation of a LacZ reporter gene by phosphorylated OmpR. Unfortunately, basal LacZ expression leads to a detectable reporter signal even when cells are grown in the light, diminishing the contrast of the coliroids. We performed site-directed mutagenesis near the phosphotransfer site of Cph8 to isolate mutants with potentially improved image contrast. Five mutants were examined, but only one of the mutants, T541S, increased the ratio of dark/light gene expression, as measured by β-galactosidase activity. The ratio changed from 2.57 fold in the starting strain to 5.59 in the T541S mutant. The ratio decreased in the four other mutant strains we examined. The phenotype observed in the T541S mutant strain may arise because the serine sidechain is chemically similar but physically smaller than the threonine sidechain. This may minimally change the protein’s local structure, but may be less sterically constrained when compared to threonine, resulting in a higher probability of a phosphotransfer event. Our initial success pairing synthetic biology and site-directed mutagenesis to optimize the bacterial photography system’s performance encourages us to imagine further improvements to the performance of this and other synthetic systems, especially those based on 2CS signaling. PMID:26799494

  12. A two-component high-affinity nitrate uptake system in barley.

    PubMed

    Tong, Yiping; Zhou, Jing-Jiang; Li, Zhensheng; Miller, Anthony J

    2005-02-01

    The analysis of genome databases for many different plants has identified a group of genes that are related to one part of a two-component nitrate transport system found in algae. Earlier work using mutants and heterologous expression has shown that a high-affinity nitrate transport system from the unicellular green algae, Chlamydomonas reinhardtii required two gene products for function. One gene encoded a typical carrier-type structure with 12 putative trans-membrane (TM) domains and the other gene, nar2 encoded a much smaller protein that had only one TM domain. As both gene families occur in plants we investigated whether this transport model has more general relevance among plants. The screening for nitrate transporter activity was greatly helped by a novel assay using (15)N-enriched nitrate uptake into Xenopus oocytes expressing the proteins. This assay enables many oocytes to be rapidly screened for nitrate transport activity. The functional activity of a barley nitrate transporter, HvNRT2.1, in oocytes required co-injection of a second mRNA. Although three very closely related nar2-like genes were cloned from barley, only one of these was able to give functional nitrate transport when co-injected into oocytes. The nitrate transport performed by this two-gene system was inhibited at more acidic external pH and by acidification of the cytoplasm. This specific requirement for two-gene products to give nitrate transport function has important implications for attempts to genetically manipulate this fundamental process in plants. PMID:15659102

  13. Transduction of envelope stress in Escherichia coli by the Cpx two-component system.

    PubMed Central

    Raivio, T L; Silhavy, T J

    1997-01-01

    Disruption of normal protein trafficking in the Escherichia coli cell envelope (inner membrane, periplasm, outer membrane) can activate two parallel, but distinct, signal transduction pathways. This activation stimulates the expression of a number of genes whose products function to fold or degrade the mislocalized proteins. One of these signal transduction pathways is a two-component regulatory system comprised of the histidine kinase CpxA and the response regulator, CpxR. In this study we characterized gain-of-function Cpx* mutants in order to learn more about Cpx signal transduction. Sequencing demonstrated that the cpx* mutations cluster in either the periplasmic, the transmembrane, or the H-box domain of CpxA. Intriguingly, most of the periplasmic cpx* gain-of-function mutations cluster in the central region of this domain, and one encodes a deletion of 32 amino acids. Strains harboring these mutations are rendered insensitive to a normally activating signal. In vivo and in vitro characterization of maltose-binding-protein fusions between the wild-type CpxA and a representative cpx* mutant, CpxA101, showed that the mutant CpxA is altered in phosphotransfer reactions with CpxR. Specifically, while both CpxA and CpxA101 function as autokinases and CpxR kinases, CpxA101 is devoid of a CpxR-P phosphatase activity normally present in the wild-type protein. Taken together, the data support a model for Cpx-mediated signal transduction in which the kinase/phosphatase ratio is elevated by stress. Further, the sequence and phenotypes of periplasmic cpx* mutations suggest that interactions with a periplasmic signaling molecule may normally dictate a decreased kinase/phosphatase ratio under nonstress conditions. PMID:9401031

  14. Characterization of an Archaeal Two-Component System That Regulates Methanogenesis in Methanosaeta harundinacea

    PubMed Central

    Guo, Xiaopeng; Qi, Lei; Dong, Xiuzhu

    2014-01-01

    Two-component signal transduction systems (TCSs) are a major mechanism used by bacteria in response to environmental changes. Although many sequenced archaeal genomes encode TCSs, they remain poorly understood. Previously, we reported that a methanogenic archaeon, Methanosaeta harundinacea, encodes FilI, which synthesizes carboxyl-acyl homoserine lactones, to regulate transitions of cellular morphology and carbon metabolic fluxes. Here, we report that filI, the cotranscribed filR2, and the adjacent filR1 constitute an archaeal TCS. FilI possesses a cytoplasmic kinase domain (histidine kinase A and histidine kinase-like ATPase) and its cognate response regulator. FilR1 carries a receiver (REC) domain coupled with an ArsR-related domain with potential DNA-binding ability, while FilR2 carries only a REC domain. In a phosphorelay assay, FilI was autophosphorylated and specifically transferred the phosphoryl group to FilR1 and FilR2, confirming that the three formed a cognate TCS. Through chromatin immunoprecipitation–quantitative polymerase chain reaction (ChIP-qPCR) using an anti-FilR1 antibody, FilR1 was shown to form in vivo associations with its own promoter and the promoter of the filI-filR2 operon, demonstrating a regulatory pattern common among TCSs. ChIP-qPCR also detected FilR1 associations with key genes involved in acetoclastic methanogenesis, acs4 and acs1. Electrophoretic mobility shift assays confirmed the in vitro tight binding of FilR1 to its own promoter and those of filI-filR2, acs4, and mtrABC. This also proves the DNA-binding ability of the ArsR-related domain, which is found primarily in Archaea. The archaeal promoters of acs4, filI, acs1, and mtrABC also initiated FilR1-modulated expression in an Escherichia coli lux reporter system, suggesting that FilR1 can up-regulate both archaeal and bacterial transcription. In conclusion, this work identifies an archaeal FilI/FilRs TCS that regulates the methanogenesis of M. harundinacea. PMID:24748383

  15. Phenotype microarray analysis of Escherichia coli K-12 mutants with deletions of all two-component systems.

    PubMed

    Zhou, Lu; Lei, Xiang-He; Bochner, Barry R; Wanner, Barry L

    2003-08-01

    Two-component systems are the most common mechanism of transmembrane signal transduction in bacteria. A typical system consists of a histidine kinase and a partner response regulator. The histidine kinase senses an environmental signal, which it transmits to its partner response regulator via a series of autophosphorylation, phosphotransfer, and dephosphorylation reactions. Much work has been done on particular systems, including several systems with regulatory roles in cellular physiology, communication, development, and, in the case of bacterial pathogens, the expression of genes important for virulence. We used two methods to investigate two-component regulatory systems in Escherichia coli K-12. First, we systematically constructed mutants with deletions of all two-component systems by using a now-standard technique of gene disruption (K. A. Datsenko and B. L. Wanner, Proc. Natl. Acad. Sci. USA 97:6640-6645, 2000). We then analyzed these deletion mutants with a new technology called Phenotype MicroArrays, which permits assays of nearly 2,000 growth phenotypes simultaneously. In this study we tested 100 mutants, including mutants with individual deletions of all two-component systems and several related genes, including creBC-regulated genes (cbrA and cbrBC), phoBR-regulated genes (phoA, phoH, phnCDEFGHIJKLMNOP, psiE, and ugpBAECQ), csgD, luxS, and rpoS. The results of this battery of nearly 200,000 tests provided a wealth of new information concerning many of these systems. Of 37 different two-component mutants, 22 showed altered phenotypes. Many phenotypes were expected, and several new phenotypes were also revealed. The results are discussed in terms of the biological roles and other information concerning these systems, including DNA microarray data for a large number of the same mutants. Other mutational effects are also discussed. PMID:12897016

  16. The Campylobacter jejuni CprRS two-component regulatory system regulates aspects of the cell envelope

    Technology Transfer Automated Retrieval System (TEKTRAN)

    As a leading cause of foodborne bacterial gastroenteritis, Campylobacter jejuni is a significant human pathogen. C. jejuni lives commensally in the gastrointestinal tract of animals, but tolerates variable environments during transit to a susceptible host. A two-component regulatory system, CprRS, w...

  17. Reciprocal Regulation of Resistance-Nodulation-Division Efflux Systems and the Cpx Two-Component System in Vibrio cholerae

    PubMed Central

    Taylor, Dawn L.; Bina, X. Renee; Slamti, Leyla; Waldor, Matthew K.

    2014-01-01

    The Cpx two-component regulatory system has been shown in Escherichia coli to alleviate stress caused by misfolded cell envelope proteins. The Vibrio cholerae Cpx system was previously found to respond to cues distinct from those in the E. coli system, suggesting that this system fulfills a different physiological role in the cholera pathogen. Here, we used microarrays to identify genes that were regulated by the V. cholerae Cpx system. Our observations suggest that the activation of the V. cholerae Cpx system does not induce expression of genes involved in the mitigation of stress generated by misfolded cell envelope proteins but promotes expression of genes involved in antimicrobial resistance. In particular, activation of the Cpx system induced expression of the genes encoding the VexAB and VexGH resistance-nodulation-division (RND) efflux systems and their cognate outer membrane pore protein TolC. The promoters for these loci contained putative CpxR consensus binding sites, and ectopic cpxR expression activated transcription from the promoters for the RND efflux systems. CpxR was not required for intrinsic antimicrobial resistance, but CpxR activation enhanced resistance to antimicrobial substrates of VexAB and VexGH. Mutations that inactivated VexAB or VexGH efflux activity resulted in the activation of the Cpx response, suggesting that vexAB and vexGH and the cpxP-cpxRA system are reciprocally regulated. We speculate that the reciprocal regulation of the V. cholerae RND efflux systems and the Cpx two-component system is mediated by the intracellular accumulation of an endogenously produced metabolic by-product that is normally extruded from the cell by the RND efflux systems. PMID:24799626

  18. Influence of two-component signal transduction systems of Lactobacillus casei BL23 on tolerance to stress conditions.

    PubMed

    Alcántara, Cristina; Revilla-Guarinos, Ainhoa; Zúñiga, Manuel

    2011-02-01

    Lactobacillus casei BL23 carries 17 two-component signal transduction systems. Insertional mutations were introduced into each gene encoding the cognate response regulators, and their effects on growth under different conditions were assayed. Inactivation of systems TC01, TC06, and TC12 (LCABL_02080-LCABL_02090, LCABL_12050-LCABL_12060, and LCABL_19600-LCABL_19610, respectively) led to major growth defects under the conditions assayed. PMID:21183633

  19. Two-Component Signal Transduction Pathways Regulating Growth and Cell Cycle Progression in a Bacterium: A System-Level Analysis

    PubMed Central

    2005-01-01

    Two-component signal transduction systems, comprised of histidine kinases and their response regulator substrates, are the predominant means by which bacteria sense and respond to extracellular signals. These systems allow cells to adapt to prevailing conditions by modifying cellular physiology, including initiating programs of gene expression, catalyzing reactions, or modifying protein–protein interactions. These signaling pathways have also been demonstrated to play a role in coordinating bacterial cell cycle progression and development. Here we report a system-level investigation of two-component pathways in the model organism Caulobacter crescentus. First, by a comprehensive deletion analysis we show that at least 39 of the 106 two-component genes are required for cell cycle progression, growth, or morphogenesis. These include nine genes essential for growth or viability of the organism. We then use a systematic biochemical approach, called phosphotransfer profiling, to map the connectivity of histidine kinases and response regulators. Combining these genetic and biochemical approaches, we identify a new, highly conserved essential signaling pathway from the histidine kinase CenK to the response regulator CenR, which plays a critical role in controlling cell envelope biogenesis and structure. Depletion of either cenK or cenR leads to an unusual, severe blebbing of cell envelope material, whereas constitutive activation of the pathway compromises cell envelope integrity, resulting in cell lysis and death. We propose that the CenK–CenR pathway may be a suitable target for new antibiotic development, given previous successes in targeting the bacterial cell wall. Finally, the ability of our in vitro phosphotransfer profiling method to identify signaling pathways that operate in vivo takes advantage of an observation that histidine kinases are endowed with a global kinetic preference for their cognate response regulators. We propose that this system

  20. The two-component system CpxAR is Essential for Virulence in the phytopathogen bacteria Dickeya dadantii EC3937

    PubMed Central

    Bontemps-Gallo, Sébastien; Madec, Edwige; Lacroix, Jean-Marie

    2015-01-01

    The CpxAR two-component system is present in many Proteobacteria. It controls expression of genes required to maintain envelope integrity in response to environmental injury. Consequently, this two-component system was shown to be required for virulence of several zoo-pathogens but it has never been investigated in phyto-pathogens. In this paper, we investigate the role of the CpxAR two-component system in vitro and in vivo in Dickeya dadantii, an enterobacterial phytopathogen that causes soft-rot disease in a large variety of plant species. cpxA null mutant displays a constitutively phosphorylated CpxR phenotype as shown by direct analysis of phosphorylation of CpxR by a Phos-Tag retardation gel approach. Virulence in plants is completely abolished in cpxA or cpxR mutants of D. dadantii. In planta, CpxAR is only activated at an early stage of the infection process as shown by Phos-Tag and gene fusion analyses. To our knowledge, this is the first time that the timing of CpxAR phosphorelay activation has been investigated during the infection process by direct monitoring of response regulator phosphorylation. PMID:25856505

  1. A scissor blade-like closing mechanism implicated in transmembrane signaling in a Bacteroides hybrid two-component system

    PubMed Central

    Lowe, Elisabeth C.; Baslé, Arnaud; Czjzek, Mirjam; Firbank, Susan J.; Bolam, David N.

    2012-01-01

    Signaling across the membrane in response to extracellular stimuli is essential for survival of all cells. In bacteria, responses to environmental changes are predominantly mediated by two-component systems, which are typically composed of a membrane-spanning sensor histidine kinase and a cytoplasmic response regulator. In the human gut symbiont Bacteroides thetaiotaomicron, hybrid two-component systems are a key part of the bacterium’s ability to sense and degrade complex carbohydrates in the gut. Here, we identify the activating ligand of the hybrid two-component system, BT4663, which controls heparin and heparan sulfate acquisition and degradation in this prominent gut microbe, and report the crystal structure of the extracellular sensor domain in both apo and ligand-bound forms. Current models for signal transduction across the membrane involve either a piston-like or rotational displacement of the transmembrane helices to modulate activity of the linked cytoplasmic kinases. The structures of the BT4663 sensor domain reveal a significant conformational change in the homodimer on ligand binding, which results in a scissor-like closing of the C-termini of each protomer. We propose this movement activates the attached intracellular kinase domains and represents an allosteric mechanism for bacterial transmembrane signaling distinct from previously described models, thus expanding our understanding of signal transduction across the membrane, a fundamental requirement in many important biological processes. PMID:22532667

  2. A global two component signal transduction system that integrates the control of photosynthesis, carbon dioxide assimilation, and nitrogen fixation

    PubMed Central

    Joshi, Hemalata M.; Tabita, F. Robert

    1996-01-01

    Photosynthesis, biological nitrogen fixation, and carbon dioxide assimilation are three fundamental biological processes catalyzed by photosynthetic bacteria. In the present study, it is shown that mutant strains of the nonsulfur purple photosynthetic bacteria Rhodospirillum rubrum and Rhodobacter sphaeroides, containing a blockage in the primary CO2 assimilatory pathway, derepress the synthesis of components of the nitrogen fixation enzyme complex and abrogate normal control mechanisms. The absence of the Calvin–Benson–Bassham (CBB) reductive pentose phosphate CO2 fixation pathway removes an important route for the dissipation of excess reducing power. Thus, the mutant strains develop alternative means to remove these reducing equivalents, resulting in the synthesis of large amounts of nitrogenase even in the presence of ammonia. This response is under the control of a global two-component signal transduction system previously found to regulate photosystem biosynthesis and the transcription of genes required for CO2 fixation through the CBB pathway and alternative routes. In addition, this two-component system directly controls the ability of these bacteria to grow under nitrogen-fixing conditions. These results indicate that there is a molecular link between the CBB and nitrogen fixation process, allowing the cell to overcome powerful control mechanisms to remove excess reducing power generated by photosynthesis and carbon metabolism. Furthermore, these results suggest that the two-component system integrates the expression of genes required for the three processes of photosynthesis, nitrogen fixation, and carbon dioxide fixation. PMID:8962083

  3. Stability of the train of N solitary waves for the two-component Camassa-Holm shallow water system

    NASA Astrophysics Data System (ADS)

    Liu, Xingxing

    2016-06-01

    Considered herein is the integrable two-component Camassa-Holm shallow water system derived in the context of shallow water theory, which admits blow-up solutions and the solitary waves interacting like solitons. Using modulation theory, and combining the almost monotonicity of a local version of energy with the argument on the stability of a single solitary wave, we prove that the train of N solitary waves, which are sufficiently decoupled, is orbitally stable in the energy space H1 (R) ×L2 (R).

  4. Bacillus subtilis Two-Component System Sensory Kinase DegS Is Regulated by Serine Phosphorylation in Its Input Domain

    PubMed Central

    Jers, Carsten; Kobir, Ahasanul; Søndergaard, Elsebeth Oline; Jensen, Peter Ruhdal; Mijakovic, Ivan

    2011-01-01

    Bacillus subtilis two-component system DegS/U is well known for the complexity of its regulation. The cytosolic sensory kinase DegS does not receive a single predominant input signal like most two-component kinases, instead it integrates a wide array of metabolic inputs that modulate its activity. The phosphorylation state of the response regulator DegU also does not confer a straightforward “on/off” response; it is fine-tuned and at different levels triggers different sub-regulons. Here we describe serine phosphorylation of the DegS sensing domain, which stimulates its kinase activity. We demonstrate that DegS phosphorylation can be carried out by at least two B. subtilis Hanks-type kinases in vitro, and this stimulates the phosphate transfer towards DegU. The consequences of this process were studied in vivo, using phosphomimetic (Ser76Asp) and non-phosphorylatable (Ser76Ala) mutants of DegS. In a number of physiological assays focused on different processes regulated by DegU, DegS S76D phosphomimetic mutant behaved like a strain with intermediate levels of DegU phosphorylation, whereas DegS S76A behaved like a strain with lower levels of DegU phophorylation. These findings suggest a link between DegS phosphorylation at serine 76 and the level of DegU phosphorylation, establishing this post-translational modification as an additional trigger for this two-component system. PMID:21304896

  5. Characterization of a two-component system in Streptococcus pyogenes which is involved in regulation of hyaluronic acid production.

    PubMed

    Bernish, B; van de Rijn, I

    1999-02-19

    Hyaluronic acid production by group A streptococci is regulated by transcriptional control. In this study, transposon mutagenesis of an unencapsulated strain yielded an encapsulated mutant. Two genes homologous to sensors and response regulators of bacterial two-component systems were identified downstream of the transposon insertion. Inactivation of the putative sensor gene, csrS, in three different unencapsulated strains yielded encapsulated mutant strains. Electrophoretic mobility shift assays determined factor(s) in a cytoplasmic extract of an unencapsulated group A streptococcal strain was binding to a double-stranded DNA fragment derived from the has operon promoter. In contrast, similarly prepared cytoplasmic extracts from a csrS deletion mutant did not shift the fragment. The putative response regulator, CsrR, was partially purified and was shown to bind the has operon promoter fragment. The affinity and specificity of CsrR for the fragment were increased significantly after incubation with acetyl phosphate. DNase I footprinting determined that the acetyl phosphate-treated CsrR was binding to key sequences in the promoter and the coding region of hasA. Therefore, a two-component system is repressing the production of hyaluronic acid in group A streptococci using a phosphorylation-dependent binding interaction between the response regulator CsrR and the promoter region of the has operon. PMID:9988717

  6. Origin and evolution of two-component debris discs and an application to the q1 Eridani system

    NASA Astrophysics Data System (ADS)

    Schüppler, Christian; Krivov, Alexander V.; Löhne, Torsten; Booth, Mark; Kirchschlager, Florian; Wolf, Sebastian

    2016-09-01

    Many debris discs reveal a two-component structure, with an outer Kuiper-belt analogue and a warm inner component whose origin is still a matter of debate. One possibility is that warm emission stems from an `asteroid belt' closer in to the star. We consider a scenario in which a set of giant planets is formed in an initially extended planetesimal disc. These planets carve a broad gap around their orbits, splitting up the disc into the outer and the inner belts. After the gas dispersal, both belts undergo collisional evolution in a steady-state regime. This scenario is explored with detailed collisional simulations involving realistic physics to describe a long-term collisional depletion of the two-component disc. We find that the inner disc may be able to retain larger amounts of material at older ages than thought before on the basis of simplified analytic models. We show that the proposed scenario is consistent with a suite of thermal emission and scattered light observational data for a bright two-temperature debris disc around a nearby solar-type star q1 Eridani. This implies a Solar system-like architecture of the system, with an outer massive `Kuiper belt', an inner `asteroid belt', and a few Neptune- to Jupiter-mass planets in between.

  7. A two-component system regulates the expression of an ABC transporter for xylo-oligosaccharides in Geobacillus stearothermophilus.

    PubMed

    Shulami, Smadar; Zaide, Galia; Zolotnitsky, Gennady; Langut, Yael; Feld, Geoff; Sonenshein, Abraham L; Shoham, Yuval

    2007-02-01

    Geobacillus stearothermophilus T-6 utilizes an extensive and highly regulated hemicellulolytic system. The genes comprising the xylanolytic system are clustered in a 39.7-kb chromosomal segment. This segment contains a 6-kb transcriptional unit (xynDCEFG) coding for a potential two-component system (xynDC) and an ATP-binding cassette (ABC) transport system (xynEFG). The xynD promoter region contains a 16-bp inverted repeat resembling the operator site for the xylose repressor, XylR. XylR was found to bind specifically to this sequence, and binding was efficiently prevented in vitro in the presence of xylose. The ABC transport system was shown to comprise an operon of three genes (xynEFG) that is transcribed from its own promoter. The nonphosphorylated fused response regulator, His6-XynC, bound to a 220-bp fragment corresponding to the xynE operator. DNase I footprinting analysis showed four protected zones that cover the -53 and the +34 regions and revealed direct repeat sequences of a GAAA-like motif. In vitro transcriptional assays and quantitative reverse transcription-PCR demonstrated that xynE transcription is activated 140-fold in the presence of 1.5 microM XynC. The His6-tagged sugar-binding lipoprotein (XynE) of the ABC transporter interacted with different xylosaccharides, as demonstrated by isothermal titration calorimetry. The change in the heat capacity of binding (DeltaCp) for XynE with xylotriose suggests a stacking interaction in the binding site that can be provided by a single Trp residue and a sugar moiety. Taken together, our data show that XynEFG constitutes an ABC transport system for xylo-oligosaccharides and that its transcription is negatively regulated by XylR and activated by the response regulator XynC, which is part of a two-component sensing system. PMID:17142383

  8. YycH regulates the activity of the essential YycFG two-component system in Bacillus subtilis.

    PubMed

    Szurmant, Hendrik; Nelson, Kristine; Kim, Eun-Ja; Perego, Marta; Hoch, James A

    2005-08-01

    Of the numerous two-component signal transduction systems found in bacteria, only a very few have proven to be essential for cell viability. Among these is the YycF (response regulator)-YycG (histidine kinase) system, which is highly conserved in and specific to the low-G+C content gram-positive bacteria. Given the pathogenic nature of several members of this class of bacteria, the YycF-YycG system has been suggested as a prime antimicrobial target. In an attempt to identify genes involved in regulation of this two-component system, a transposon mutagenesis study was designed to identify suppressors of a temperature-sensitive YycF mutant in Bacillus subtilis. Suppressors could be identified, and the prime target was the yycH gene located adjacent to yycG and within the same operon. A lacZ reporter assay revealed that YycF-regulated gene expression was elevated in a yycH strain, whereas disruption of any of the three downstream genes within the operon, yycI, yycJ, and yycK, showed no such effect. The concentrations of both YycG and YycF, assayed immunologically, remained unchanged between the wild-type and the yycH strain as determined by immunoassay. Alkaline phosphatase fusion studies showed that YycH is located external to the cell membrane, suggesting that it acts in the regulation of the sensor domain of the YycG sensor histidine kinase. The yycH strain showed a characteristic cell wall defect consistent with the previously suggested notion that the YycF-YycG system is involved in regulating cell wall homeostasis and indicating that either up- or down-regulation of YycF activity affects this homeostatic mechanism. PMID:16030236

  9. YycH Regulates the Activity of the Essential YycFG Two-Component System in Bacillus subtilis

    PubMed Central

    Szurmant, Hendrik; Nelson, Kristine; Kim, Eun-Ja; Perego, Marta; Hoch, James A.

    2005-01-01

    Of the numerous two-component signal transduction systems found in bacteria, only a very few have proven to be essential for cell viability. Among these is the YycF (response regulator)-YycG (histidine kinase) system, which is highly conserved in and specific to the low-G+C content gram-positive bacteria. Given the pathogenic nature of several members of this class of bacteria, the YycF-YycG system has been suggested as a prime antimicrobial target. In an attempt to identify genes involved in regulation of this two-component system, a transposon mutagenesis study was designed to identify suppressors of a temperature-sensitive YycF mutant in Bacillus subtilis. Suppressors could be identified, and the prime target was the yycH gene located adjacent to yycG and within the same operon. A lacZ reporter assay revealed that YycF-regulated gene expression was elevated in a yycH strain, whereas disruption of any of the three downstream genes within the operon, yycI, yycJ, and yycK, showed no such effect. The concentrations of both YycG and YycF, assayed immunologically, remained unchanged between the wild-type and the yycH strain as determined by immunoassay. Alkaline phosphatase fusion studies showed that YycH is located external to the cell membrane, suggesting that it acts in the regulation of the sensor domain of the YycG sensor histidine kinase. The yycH strain showed a characteristic cell wall defect consistent with the previously suggested notion that the YycF-YycG system is involved in regulating cell wall homeostasis and indicating that either up- or down-regulation of YycF activity affects this homeostatic mechanism. PMID:16030236

  10. Mutational Activation of the AmgRS Two-Component System in Aminoglycoside-Resistant Pseudomonas aeruginosa

    PubMed Central

    Lau, Calvin Ho-Fung; Fraud, Sebastien; Jones, Marcus; Peterson, Scott N.; Poole, Keith

    2013-01-01

    The amgRS operon encodes a presumed membrane stress-responsive two-component system linked to intrinsic aminoglycoside resistance in Pseudomonas aeruginosa. Genome sequencing of a lab isolate showing modest pan-aminoglycoside resistance, strain K2979, revealed a number of mutations, including a substitution in amgS that produced an R182C change in the AmgS sensor kinase product of this gene. Introduction of this mutation into an otherwise wild-type strain recapitulated the resistance phenotype, while correcting the mutation in the resistant mutant abrogated the resistant phenotype, confirming that the amgS mutation is responsible for the aminoglycoside resistance of strain K2979. The amgSR182 mutation promoted an AmgR-dependent, 2- to 3-fold increase in expression of the AmgRS target genes htpX and PA5528, mirroring the impact of aminoglycoside exposure of wild-type cells on htpX and PA5528 expression. This suggests that amgSR182 is a gain-of-function mutation that activates AmgS and the AmgRS two-component system in promoting modest resistance to aminoglycosides. Screening of several pan-aminoglycoside-resistant clinical isolates of P. aeruginosa revealed three that showed elevated htpX and PA5528 expression and harbored single amino acid-altering mutations in amgS (V121G or D106N) and no mutations in amgR. Introduction of the amgSV121G mutation into wild-type P. aeruginosa generated a resistance phenotype reminiscent of the amgSR182 mutant and produced a 2- to 3-fold increase in htpX and PA5528 expression, confirming that it, too, is a gain-of-function aminoglycoside resistance-promoting mutation. These results highlight the contribution of amgS mutations and activation of the AmgRS two-component system to acquired aminoglycoside resistance in lab and clinical isolates of P. aeruginosa. PMID:23459488

  11. 5S Clavam Biosynthesis Is Controlled by an Atypical Two-Component Regulatory System in Streptomyces clavuligerus

    PubMed Central

    Kwong, Thomas; Zelyas, Nathan J.; Cai, Hui; Tahlan, Kapil; Wong, Annie

    2012-01-01

    Streptomyces clavuligerus produces a collection of five clavam metabolites, including the clinically important β-lactamase inhibitor clavulanic acid, as well as four structurally related metabolites called 5S clavams. The paralogue gene cluster of S. clavuligerus is one of three clusters of genes for the production of these clavam metabolites. A region downstream of the cluster was analyzed, and snk, res1, and res2, encoding elements of an atypical two-component regulatory system, were located. Mutation of any one of the three genes had no effect on clavulanic acid production, but snk and res2 mutants produced no 5S clavams, whereas res1 mutants overproduced 5S clavams. Reverse transcriptase PCR analyses showed that transcription of cvm7p (which encodes a transcriptional activator of 5S clavam biosynthesis) and 5S clavam biosynthetic genes was eliminated in snk and in res2 mutants but that snk and res2 transcription was unaffected in a cvm7p mutant. Both snk and res2 mutants could be complemented by introduction of cvm7p under the control of an independently regulated promoter. In vitro assays showed that Snk can autophosphorylate and transfer its phosphate group to both Res1 and Res2, and Snk-H365, Res1-D52, and Res2-D52 were identified as the phosphorylation sites for the system. Dephosphorylation assays indicated that Res1 stimulates dephosphorylation of Res2∼P. These results suggest a regulatory cascade in which Snk and Res2 form a two-component system controlling cvm7p transcription, with Res1 serving as a checkpoint to modulate phosphorylation levels. Cvm7P then activates transcription of 5S clavam biosynthetic genes. PMID:22751548

  12. Two-Component Signal Transduction Systems of Desulfovibrio Vulgaris: Structural and Phylogenetic Analysis and Deduction of Putative Cognate Pairs

    SciTech Connect

    Zhang, Weiwen; Culley, David E.; Wu, Gang; Brockman, Fred J.

    2006-01-20

    ABSTRACT-Two-component signal transduction systems (TCSTS) composed of sensory histidine kinases (HK) and response regulators (RR), constitute a key element of the mechanism by which bacteria sense and respond to changes in environments. A large number of TCSTSs including 59 putative HKs and 55 RRs were identified from the Desulfovibrio vulgaris genome, indicating their important roles in regulation of cellular metabolism. In this study, the structural and phylogenetic analysis of all putative TCSTSs in D. vulgaris was performed. The results showed D. vulgaris contained an unexpectedly large number of hybrid-type HKs, implying that multiple-step phosphorelay may be a common signal transduction mechanism in D. vulgaris. Most TCSTS components of D. vulgaris were found clustered into several subfamilies previously recognized in other bacteria and extensive co-evolution between D. vulgaris HKs and RRs was observed, suggesting that the concordance of HKs and RRs in cognate phylogenetic groups could be indicative of cognate TCSTSs...

  13. Effects of the global regulator CsrA on the BarA/UvrY two-component signaling system.

    PubMed

    Camacho, Martha I; Alvarez, Adrian F; Chavez, Ricardo Gonzalez; Romeo, Tony; Merino, Enrique; Georgellis, Dimitris

    2015-03-01

    The hybrid sensor kinase BarA and its cognate response regulator UvrY, members of the two-component signal transduction family, activate transcription of CsrB and CsrC noncoding RNAs. These two small RNAs act by sequestering the RNA binding protein CsrA, which posttranscriptionally regulates translation and/or stability of its target mRNAs. Here, we provide evidence that CsrA positively affects, although indirectly, uvrY expression, at both the transcriptional and translational levels. We also demonstrate that CsrA is required for properly switching BarA from its phosphatase to its kinase activity. Thus, the existence of a feedback loop mechanism that involves the Csr and BarA/UvrY global regulatory systems is exposed. PMID:25535275

  14. Two-component signal transduction system SaeRS is involved in competence and penicillin susceptibility in Staphylococcus epidermidis.

    PubMed

    Lou, Qiang; Ma, Yuanfang; Qu, Di

    2016-04-01

    Staphylococcus epidermidis, which is a causative pathogen of nosocomial infection, expresses its virulent traits such as biofilm and autolysis regulated by two-component signal transduction system SaeRS. In this study, the S. epidermidis SaeRS was identified to negatively regulate the expression of genes involved in competence (comF, murF), cytolysis (lrgA), and autolysis (lytS) by DNA microarray or real-time RT-PCR analysis. In addition, saeRS mutant showed increased competence and higher susceptibility to antibiotics such as penicillin and oxacillin than the wild-type strain. The study will be helpful for understanding the characterization of the SaeRS in S. epidermidis. PMID:26898187

  15. A plasmid-encoded two-component regulatory system involved in copper-inducible transcription in Lactococcus lactis.

    PubMed

    Khunajakr, N; Liu, C Q; Charoenchai, P; Dunn, N W

    1999-03-18

    Two regulatory genes (lcoR and lcoS) were identified from a plasmid-borne lactococcal copper resistance determinant and characterized by transcriptional fusion to the promoterless chloramphenicol acetyltransferase gene (cat). RT-PCR analysis indicates that lcoR and lcoS are organized within an operon, controlling the transcription of cat in a copper-inducible manner. The amino acid sequences deduced from lcoR and lcoS show homology to the response and sensor proteins of known two-component regulatory systems. Deletion within either lcoS or both genes inactivated the copper-dependent activity, suggesting the presence of no trans-acting lcoR and lcoS homologs in the lactococcal host chromosome. The transcription start site involved in copper induction was mapped by primer extension. PMID:10095123

  16. Modulation of virulence genes by the two-component system PhoP-PhoQ in avian pathogenic Escherichia coli.

    PubMed

    Tu, Jian; Huang, Boyan; Zhang, Yu; Zhang, Yuxi; Xue, Ting; Li, Shaocan; Qi, Kezong

    2016-01-01

    Avian pathogenic Escherichia coli (APEC) infections are a very important problem in the poultry industry. PhoP-PhoQ is a two-component system that regulates virulence genes in APEC. In this study, we constructed strains that lacked the PhoP or PhoQ genes to assess regulation of APEC pathogenicity by the PhoP-PhoQ two-component system. The PhoP mutant strain AE18, PhoQ mutant strain AE19, and PhoP/PhoQ mutant strain AE20 were constructed by the Red homologous recombination method. Swim plates were used to evaluate the motility of the APEC strains, viable bacteria counting was used to assess adhesion and invasion of chick embryo fibroblasts, and Real-Time PCR was used to measure mRNA expression of virulence genes. We first confirmed that AE18, AE19, and AE20 were successfully constructed from the wild-type AE17 strain. AE18, AE19, and AE20 showed significant decreases in motility of 70.97%, 83.87%, and 37.1%, respectively, in comparison with AE17. Moreover, in comparison with AE17, AE18, AE19, and AE20 showed significant decreases of 63.11%, 65.42%, and 30.26%, respectively, in CEF cell adhesion, and significant decreases of 59.83%, 57.82%, and 37.90%, respectively, in CEF cell invasion. In comparison with AE17, transcript levels of sodA, polA, and iss were significantly decreased in AE18, while transcript levels of fimC and iss were significantly decreased in AE19. Our results demonstrate that deletion of PhoP or PhoQ inhibits invasion and adhesion of APEC to CEF cells and significantly reduces APEC virulence by regulating transcription of virulence genes. PMID:27096785

  17. BqsR/BqsS Constitute a Two-Component System That Senses Extracellular Fe(II) in Pseudomonas aeruginosa

    PubMed Central

    Kreamer, Naomi N. K.; Wilks, Jessica C.; Marlow, Jeffrey J.; Coleman, Maureen L.

    2012-01-01

    Pseudomonas aeruginosa is a ubiquitous Gram-negative bacterium best known as the predominant opportunistic pathogen infecting the lungs of cystic fibrosis patients. In this context, it is thought to form biofilms, within which locally reducing and acidic conditions can develop that favor the stability of ferrous iron [Fe(II)]. Because iron is a signal that stimulates biofilm formation, we performed a microarray study to determine whether P. aeruginosa strain PA14 exhibits a specific transcriptional response to extracellular Fe(II). Among the genes that were most upregulated in response to Fe(II) were those encoding the two-component system BqsR/BqsS, previously identified for its role in P. aeruginosa strain PAO1 biofilm decay (13); here, we demonstrate its role in extracellular Fe(II) sensing. bqsS and bqsR form an operon together with two small upstream genes, bqsP and bqsQ, and one downstream gene, bqsT. BqsR/BqsS sense extracellular Fe(II) at physiologically relevant concentrations (>10 μM) and elicit a specific transcriptional response, including its autoregulation. The sensor distinguishes between Fe(II), Fe(III), and other dipositive cations [Ca(II), Cu(II), Mg(II), Mn(II), Zn(II)] under aerobic or anaerobic conditions. The gene that is most upregulated by BqsR/BqsS, as measured by quantitative reverse transcription-PCR (qRT-PCR), is PA14_04180, which is predicted to encode a periplasmic oligonucleotide/oligosaccharide-binding domain (OB-fold) protein. Coincident with phenazine production during batch culture growth, Fe(II) becomes the majority of the total iron pool and bqsS is upregulated. The existence of a two-component system that senses Fe(II) indicates that extracellular Fe(II) is an important environmental signal for P. aeruginosa. PMID:22194456

  18. On mechanics and thermodynamics of a stellar galaxy in a two-component virial system and the Fundamental Plane

    NASA Astrophysics Data System (ADS)

    Secco, L.

    2005-06-01

    The paper confirms the existence of a special configuration (among the infinitive number of a priori possible virial states) which a B stellar (Baryonic) component may assume inside a given D dark halo potential well. This satisfies the d'Alembert Principle of virtual works and its typical dimension works as a scale length (we call tidal radius) induced on the gravitational field of the bright component by the dark one. Its dynamic and thermodynamic properties are here analyzed in connection with the physical reason for the existence of the Fundamental Plane (FP) for ellipticals and, in general, for two-component virialized systems. The analysis is performed by using two-component models with two power-law density profiles and two homogeneous cores. The outputs of this kind of models, at the special configuration, are summarized and compared with some observable scaling relations for pressure supported ellipticals. The problem of extending the results to a general class of models with Zhao (1996) [MNRAS 278, 488] profiles, which are more suitable for an elliptical galaxy system, is also taken into account. The virial equilibrium stages of the two-component system have to occur after a previous violent relaxation phase. If the stellar B component is allowed to cool slowly its virial evolution consists of a sequence of contractions with enough time to rearrange the virial equilibrium after any step. The thermodynamic process during the dynamical evolution is so divided into a sequence of transformations which are irreversible but occur between two quasi-equilibrium stages. Then, it is possible to assign: a mean temperature to the whole B component during this quasi-static sequence and the entropy variation between two consecutive virial steps. The analysis allows the conclusion that the induced scale length is a real confinement for the stellar system. This follows from the application of the Io Thermodynamics Principle under the virial equilibrium constraint, by

  19. A modified two-component regulatory system is involved in temperature-dependent biosynthesis of the Pseudomonas syringae phytotoxin coronatine.

    PubMed Central

    Ullrich, M; Peñaloza-Vázquez, A; Bailey, A M; Bender, C L

    1995-01-01

    Biosynthesis of the phytotoxin coronatine (COR) in Pseudomonas syringae pv. glycinea PG4180 is regulated by temperature at the transcriptional level. A 3.4-kb DNA fragment from the COR biosynthetic gene cluster restored temperature-regulated phytotoxin production to Tn5 mutants defective in COR production. Nucleotide sequence analysis of this fragment revealed three genes, corS, corP, and corR, which encode a modified two-component regulatory system consisting of one sensor protein, CorS, and two response regulator proteins, CorP and CorR. Although only one response regulator, CorR, had a DNA-binding domain, the phosphate-receiving domains of both response regulator proteins were highly conserved. Transcriptional fusions of the corP and corR promoters to a promoterless glucuronidase gene (uidA) indicated that these two genes are expressed constitutively at 18 and 28 degrees C. In contrast, a corS::uidA fusion exhibited the temperature dependence previously observed for COR biosynthetic promoters and exhibited maximal transcriptional activity at 18 degrees C and low activity at 28 degrees C. Furthermore, glucuronidase activity for corS::uidA was decreased in corP, corR, and corS mutants relative to the levels observed for PG4180(corS::uidA). This difference was not observed for corP::uidA and corR::uidA transcriptional fusions since expression of these fusions remained low and constitutive regardless of the genetic background. The three regulatory genes functioned in a P. syringae strain lacking the COR gene cluster to achieve temperature-dependent activation of an introduced COR biosynthetic promoter, indicating that this triad of genes is the primary control for COR biosynthesis and responsible for thermoregulation. Our data suggest that the modified two-component regulatory system described in this study might transduce and amplify a temperature signal which results in transcriptional activation of COR biosynthetic genes. PMID:7592381

  20. A Conserved Two-Component Signal Transduction System Controls the Response to Phosphate Starvation in Bifidobacterium breve UCC2003

    PubMed Central

    Alvarez-Martin, Pablo; Fernández, Matilde; O'Connell-Motherway, Mary; O'Connell, Kerry Joan; Sauvageot, Nicolas; Fitzgerald, Gerald F.; MacSharry, John; Zomer, Aldert

    2012-01-01

    This work reports on the identification and molecular characterization of the two-component regulatory system (2CRS) PhoRP, which controls the response to inorganic phosphate (Pi) starvation in Bifidobacterium breve UCC2003. The response regulator PhoP was shown to bind to the promoter region of pstSCAB, specifying a predicted Pi transporter system, as well as that of phoU, which encodes a putative Pi-responsive regulatory protein. This interaction is assumed to cause transcriptional modulation under conditions of Pi limitation. Our data suggest that the phoRP genes are subject to positive autoregulation and, together with pstSCAB and presumably phoU, represent the complete regulon controlled by the phoRP-encoded 2CRS in B. breve UCC2003. Determination of the minimal PhoP binding region combined with bioinformatic analysis revealed the probable recognition sequence of PhoP, designated here as the PHO box, which together with phoRP is conserved among many high-GC-content Gram-positive bacteria. The importance of the phoRP 2CRS in the response of B. breve to Pi starvation conditions was confirmed by analysis of a B. breve phoP insertion mutant which exhibited decreased growth under phosphate-limiting conditions compared to its parent strain UCC2003. PMID:22635988

  1. DNA-affinity-purified Chip (DAP-chip) Method to Determine Gene Targets for Bacterial Two component Regulatory Systems

    PubMed Central

    Rajeev, Lara; Luning, Eric G.; Mukhopadhyay, Aindrila

    2014-01-01

    In vivo methods such as ChIP-chip are well-established techniques used to determine global gene targets for transcription factors. However, they are of limited use in exploring bacterial two component regulatory systems with uncharacterized activation conditions. Such systems regulate transcription only when activated in the presence of unique signals. Since these signals are often unknown, the in vitro microarray based method described in this video article can be used to determine gene targets and binding sites for response regulators. This DNA-affinity-purified-chip method may be used for any purified regulator in any organism with a sequenced genome. The protocol involves allowing the purified tagged protein to bind to sheared genomic DNA and then affinity purifying the protein-bound DNA, followed by fluorescent labeling of the DNA and hybridization to a custom tiling array. Preceding steps that may be used to optimize the assay for specific regulators are also described. The peaks generated by the array data analysis are used to predict binding site motifs, which are then experimentally validated. The motif predictions can be further used to determine gene targets of orthologous response regulators in closely related species. We demonstrate the applicability of this method by determining the gene targets and binding site motifs and thus predicting the function for a sigma54-dependent response regulator DVU3023 in the environmental bacterium Desulfovibrio vulgaris Hildenborough. PMID:25079303

  2. Structure and mechanism of the essential two-component signal-transduction system WalKR in Staphylococcus aureus

    PubMed Central

    Ji, Quanjiang; Chen, Peter J.; Qin, Guangrong; Deng, Xin; Hao, Ziyang; Wawrzak, Zdzislaw; Yeo, Won-Sik; Quang, Jenny Winjing; Cho, Hoonsik; Luo, Guan-Zheng; Weng, Xiaocheng; You, Qiancheng; Luan, Chi-Hao; Yang, Xiaojing; Bae, Taeok; Yu, Kunqian; Jiang, Hualiang; He, Chuan

    2016-01-01

    Most low GC Gram-positive bacteria possess an essential walKR two-component system (TCS) for signal transduction involved in regulating cell wall homoeostasis. Despite the well-established intracellular regulatory mechanism, the role of this TCS in extracellular signal recognition and factors that modulate the activity of this TCS remain largely unknown. Here we identify the extracellular receptor of the kinase ‘WalK' (erWalK) as a key hub for bridging extracellular signal input and intracellular kinase activity modulation in Staphylococcus aureus. Characterization of the crystal structure of erWalK revealed a canonical Per-Arnt-Sim (PAS) domain for signal sensing. Single amino-acid mutation of potential signal-transduction residues resulted in severely impaired function of WalKR. A small molecule derived from structure-based virtual screening against erWalK is capable of selectively activating the walKR TCS. The molecular level characterization of erWalK will not only facilitate exploration of natural signal(s) but also provide a template for rational design of erWalK inhibitors. PMID:26987594

  3. Structure and mechanism of the essential two-component signal-transduction system WalKR in Staphylococcus aureus

    DOE PAGESBeta

    Ji, Quanjiang; Chen, Peter J.; Qin, Guangrong; Deng, Xin; Hao, Ziyang; Wawrzak, Zdzislaw; Yeo, Won -Sik; Quang, Jenny Winjing; Cho, Hoonsik; Luo, Guan -Zheng; et al

    2016-03-18

    Most low GC Gram-positive bacteria possess an essential walKR two-component system (TCS) for signal transduction involved in regulating cell wall homoeostasis. Despite the well-established intracellular regulatory mechanism, the role of this TCS in extracellular signal recognition and factors that modulate the activity of this TCS remain largely unknown. Here we identify the extracellular receptor of the kinase ‘WalK’ (erWalK) as a key hub for bridging extracellular signal input and intracellular kinase activity modulation in Staphylococcus aureus. Characterization of the crystal structure of erWalK revealed a canonical Per-Arnt-Sim (PAS) domain for signal sensing. Single amino-acid mutation of potential signal-transduction residues resultedmore » in severely impaired function of WalKR. A small molecule derived from structure-based virtual screening against erWalK is capable of selectively activating the walKR TCS. Lastly, the molecular level characterization of erWalK will not only facilitate exploration of natural signal(s) but also provide a template for rational design of erWalK inhibitors.« less

  4. A Blue Light Inducible Two-Component Signal Transduction System in the Plant Pathogen Pseudomonas syringae pv. tomato☆

    PubMed Central

    Cao, Z.; Buttani, V.; Losi, A.; Gärtner, W.

    2008-01-01

    Abstract The open reading frame PSPTO2896 from the plant pathogen Pseudomonas syringae pv. tomato encodes a protein of 534 amino acids showing all salient features of a blue light-driven two-component system. The N-terminal LOV (light, oxygen, voltage) domain, potentially binding a flavin chromophore, is followed by a histidine kinase (HK) motif and a response regulator (RR). The full-length protein (PST-LOV) and, separately, the RR and the LOV+HK part (PST-LOVΔRR) were heterologously expressed and functionally characterized. The two LOV proteins showed typical LOV-like spectra and photochemical reactions, with the blue light-driven, reversible formation of a covalent flavin-cysteine bond. The fluorescence changes in the lit state of full-length PST-LOV, but not in PST-LOVΔRR, indicating a direct interaction between the LOV core and the RR module. Experiments performed with radioactive ATP uncover the light-driven kinase activity. For both PST-LOV and PST-LOVΔRR, much more radioactivity is incorporated when the protein is in the lit state. Furthermore, addition of the RR domain to the fully phosphorylated PST-LOVΔRR leads to a very fast transfer of radioactivity, indicating a highly efficient HK activity and a tight interaction between PST-LOVΔRR and RR, possibly facilitated by the LOV core itself. PMID:17905842

  5. The Two-Component System GrvRS (EtaRS) Regulates ace Expression in Enterococcus faecalis OG1RF

    PubMed Central

    Singh, Kavindra V.; La Rosa, Sabina Leanti; Cohen, Ana Luisa V.; Murray, Barbara E.

    2014-01-01

    Expression of ace (adhesin to collagen of Enterococcus faecalis), encoding a virulence factor in endocarditis and urinary tract infection models, has been shown to increase under certain conditions, such as in the presence of serum, bile salts, urine, and collagen and at 46°C. However, the mechanism of ace/Ace regulation under different conditions is still unknown. In this study, we identified a two-component regulatory system GrvRS as the main regulator of ace expression under these stress conditions. Using Northern hybridization and β-galactosidase assays of an ace promoter-lacZ fusion, we found transcription of ace to be virtually absent in a grvR deletion mutant under the conditions that increase ace expression in wild-type OG1RF and in the complemented strain. Moreover, a grvR mutant revealed decreased collagen binding and biofilm formation as well as attenuation in a murine urinary tract infection model. Here we show that GrvR plays a major role in control of ace expression and E. faecalis virulence. PMID:25385790

  6. The Role of CzcRS Two-Component Systems in the Heavy Metal Resistance of Pseudomonas putida X4

    PubMed Central

    Liu, Pulin; Chen, Xi; Huang, Qiaoyun; Chen, Wenli

    2015-01-01

    The role of different czcRS genes in metal resistance and the cross-link between czcRS and czcCBA in Pseudomonas putida X4 were studied to advance understanding of the mechanisms by which P. putida copes with metal stress. Similar to P. putida KT2440, two complete czcRS1 and czcRS2 two-component systems, as well as a czcR3 without the corresponding sensing component were amplified in P. putida X4. The histidine kinase genes czcS1 and czcS2 were inactivated and fused to lacZ by homologous recombination. The lacZ fusion assay revealed that Cd2+ and Zn2+ caused a decrease in the transcription of czcRS1, whereas Cd2+ treatment enhanced the transcription of czcRS2. The mutation of different czcRSs showed that all czcRSs are necessary to facilitate full metal resistance in P. putida X4. A putative gene just downstream of czcR3 is related to metal ion resistance, and its transcription was activated by Zn2+. Data from quantitative real-time polymerase chain reaction (qRT-PCR) strongly suggested that czcRSs regulate the expression of czcCBA, and a cross-link exists between different czcRSs. PMID:26225958

  7. Two-Component Systems Are Involved in the Regulation of Botulinum Neurotoxin Synthesis in Clostridium botulinum Type A Strain Hall

    PubMed Central

    Connan, Chloé; Brueggemann, Holger; Mazuet, Christelle; Raffestin, Stéphanie; Cayet, Nadège; Popoff, Michel R.

    2012-01-01

    Clostridium botulinum synthesizes a potent neurotoxin (BoNT) which associates with non-toxic proteins (ANTPs) to form complexes of various sizes. The bont and antp genes are clustered in two operons. In C. botulinum type A, bont/A and antp genes are expressed during the end of the exponential growth phase and the beginning of the stationary phase under the control of an alternative sigma factor encoded by botR/A, which is located between the two operons. In the genome of C. botulinum type A strain Hall, 30 gene pairs predicted to encode two-component systems (TCSs) and 9 orphan regulatory genes have been identified. Therefore, 34 Hall isogenic antisense strains on predicted regulatory genes (29 TCSs and 5 orphan regulatory genes) have been obtained by a mRNA antisense procedure. Two TCS isogenic antisense strains showed more rapid growth kinetics and reduced BoNT/A production than the control strain, as well as increased bacterial lysis and impairment of the bacterial cell wall structure. Three other TCS isogenic antisense strains induced a low level of BoNT/A and ANTP production. Interestingly, reduced expression of bont/A and antp genes was shown to be independent of botR/A. These results indicate that BoNT/A synthesis is under the control of a complex network of regulation including directly at least three TCSs. PMID:22848632

  8. The YvqE two-component system controls biofilm formation and acid production in Streptococcus pyogenes.

    PubMed

    Isaka, Masanori; Tatsuno, Ichiro; Maeyama, Jun-Ichi; Matsui, Hideyuki; Zhang, Yan; Hasegawa, Tadao

    2016-07-01

    In Streptococcus pyogenes, proteins involved in determining virulence are controlled by stand-alone response regulators and by two-component regulatory systems. Previous studies reported that, compared to the parental strain, the yvqE sensor knockout strain showed significantly reduced growth and lower virulence. To determine the function of YvqE, we performed biofilm analysis and pH assays on yvqE mutants, and site-directed mutagenesis of YvqE. The yvqE deletion mutant showed a slower acid production rate, indicating that YvqE regulates acid production from sugar fermentation. The mutant strain, in which the Asp(26) residue in YvqE was replaced with Asn, affected biofilm formation, suggesting that this amino acid senses hydrogen ions produced by fermentative sugar metabolism. Signals received by YvqE were directly or indirectly responsible for inducing pilus expression. This study shows that at low environmental pH, biofilm formation in S. pyogenes is mediated by YvqE and suggests that regulation of pilus expression by environmental acidification could be directly under the control of YvqE. PMID:27061781

  9. Two-Component System Response Regulators Involved in Virulence of Streptococcus pneumoniae TIGR4 in Infective Endocarditis

    PubMed Central

    Trihn, My; Ge, Xiuchun; Dobson, Alleson; Kitten, Todd; Munro, Cindy L.; Xu, Ping

    2013-01-01

    Streptococci resident in the oral cavity have been linked to infective endocarditis (IE). While other viridans streptococci are commonly studied in relation to IE, less research has been focused on Streptococcus pneumoniae. We established for the first time an animal model of S. pneumoniae IE, and examined the virulence of the TIGR4 strain in this model. We hypothesized that two-component systems (TCS) may mediate S. pneumoniae TIGR4 strain virulence in IE and examined TCS response regulator (RR) mutants of TIGR4 in vivo with the IE model. Thirteen of the 14 RR protein genes were mutagenized, excluding only the essential gene SP_1227. The requirement of the 13 RRs for S. pneumoniae competitiveness in the IE model was assessed in vivo through use of quantitative real-time PCR (qPCR) and competitive index assays. Using real-time PCR, several RR mutants were detected at significantly lower levels in infected heart valves compared with a control strain suggesting the respective RRs are candidate virulence factors for IE. The virulence reduction of the ΔciaR mutant was further confirmed by competitive index assay. Our data suggest that CiaR is a virulence factor of S. pneumoniae strain TIGR4 for IE. PMID:23342132

  10. Two-component system response regulators involved in virulence of Streptococcus pneumoniae TIGR4 in infective endocarditis.

    PubMed

    Trihn, My; Ge, Xiuchun; Dobson, Alleson; Kitten, Todd; Munro, Cindy L; Xu, Ping

    2013-01-01

    Streptococci resident in the oral cavity have been linked to infective endocarditis (IE). While other viridans streptococci are commonly studied in relation to IE, less research has been focused on Streptococcus pneumoniae. We established for the first time an animal model of S. pneumoniae IE, and examined the virulence of the TIGR4 strain in this model. We hypothesized that two-component systems (TCS) may mediate S. pneumoniae TIGR4 strain virulence in IE and examined TCS response regulator (RR) mutants of TIGR4 in vivo with the IE model. Thirteen of the 14 RR protein genes were mutagenized, excluding only the essential gene SP_1227. The requirement of the 13 RRs for S. pneumoniae competitiveness in the IE model was assessed in vivo through use of quantitative real-time PCR (qPCR) and competitive index assays. Using real-time PCR, several RR mutants were detected at significantly lower levels in infected heart valves compared with a control strain suggesting the respective RRs are candidate virulence factors for IE. The virulence reduction of the ΔciaR mutant was further confirmed by competitive index assay. Our data suggest that CiaR is a virulence factor of S. pneumoniae strain TIGR4 for IE. PMID:23342132

  11. Characterization of a novel bile-inducible operon encoding a two-component regulatory system in Lactobacillus acidophilus.

    PubMed

    Pfeiler, Erika A; Azcarate-Peril, M Andrea; Klaenhammer, Todd R

    2007-07-01

    Lactobacillus acidophilus NCFM is an industrially important strain used extensively as a probiotic culture. Tolerance of the presence of bile is an attribute important to microbial survival in the intestinal tract. A whole-genome microarray was employed to examine the effects of bile on the global transcriptional profile of this strain, with the intention of elucidating genes contributing to bile tolerance. Genes involved in carbohydrate metabolism were generally induced, while genes involved in other aspects of cellular growth were mostly repressed. A 7-kb eight-gene operon encoding a two-component regulatory system (2CRS), a transporter, an oxidoreductase, and four hypothetical proteins was significantly upregulated in the presence of bile. Deletion mutations were constructed in six genes of the operon. Transcriptional analysis of the 2CRS mutants showed that mutation of the histidine protein kinase (HPK) had no effect on the induction of the operon, whereas the mutated response regulator (RR) showed enhanced induction when the cells were exposed to bile. These results indicate that the 2CRS plays a role in bile tolerance and that the operon it resides in is negatively controlled by the RR. Mutations in the transporter, the HPK, the RR, and a hypothetical protein each resulted in loss of tolerance of bile. Mutations in genes encoding another hypothetical protein and a putative oxidoreductase resulted in significant increases in bile tolerance. This functional analysis showed that the operon encoded proteins involved in both bile tolerance and bile sensitivity. PMID:17449631

  12. Gene expression of a two-component regulatory system associated with sunscreen biosynthesis in the cyanobacterium Nostoc punctiforme ATCC 29133.

    PubMed

    Janssen, Jacob; Soule, Tanya

    2016-01-01

    Long-wavelength ultraviolet radiation (UVA) can damage cells through photooxidative stress, leading to harmful photosensitized proteins and pigments in cyanobacteria. To mitigate damage, some cyanobacteria secrete the UVA-absorbing pigment scytonemin into their extracellular sheath. Comparative genomic analyses suggest that scytonemin biosynthesis is regulated by the two-component regulatory system (TCRS) proteins encoded by Npun_F1277 and Npun_F1278 in the cyanobacterium Nostoc punctiforme ATCC 29133. To understand the dynamics of these genes, their expression was measured following exposure to UVA, UVB, high visible (VIS) irradiance and oxidative stress for 20, 40 and 60 min. Overall, both genes had statistically similar patterns of expression for all four conditions and were generally upregulated, except for those exposed to UVB by 60 min and for the cells under oxidative stress. The greatest UVA response was an upregulation by 20 min, while the response to UVB was the most dramatic and persisted through 40 min. High VIS irradiance resulted in a modest upregulation, while oxidative stress caused a slight downregulation. Both genes were also found to occur on the same transcript. These results demonstrate that these genes are positively responding to several light-associated conditions, which suggests that this TCRS may regulate more than just scytonemin biosynthesis under UVA stress. PMID:26656542

  13. The Two-Component System PhoPR of Clostridium acetobutylicum Is Involved in Phosphate-Dependent Gene Regulation ▿

    PubMed Central

    Fiedler, Tomas; Mix, Maren; Meyer, Uta; Mikkat, Stefan; Glocker, Michael O.; Bahl, Hubert; Fischer, Ralf-Jörg

    2008-01-01

    The phoPR gene locus of Clostridium acetobutylicum ATCC 824 comprises two genes, phoP and phoR. Deduced proteins are predicted to represent a response regulator and sensor kinase of a phosphate-dependent two-component regulatory system. We analyzed the expression patterns of phoPR in Pi-limited chemostat cultures and in response to Pi pulses. A basic transcription level under high-phosphate conditions was shown, and a significant increase in mRNA transcript levels was found when external Pi concentrations dropped below 0.3 mM. In two-dimensional gel electrophoresis experiments, a 2.5-fold increase in PhoP was observed under Pi-limiting growth conditions compared to growth with an excess of Pi. At least three different transcription start points for phoP were determined by primer extension analyses. Proteins PhoP and an N-terminally truncated *PhoR were individually expressed heterologously in Escherichia coli and purified. Autophosphorylation of *PhoR and phosphorylation of PhoP were shown in vitro. Electromobility shift assays proved that there was a specific binding of PhoP to the promoter region of the phosphate-regulated pst operon of C. acetobutylicum. PMID:18689481

  14. Involvement of two-component signalling systems in the regulation of stomatal aperture by light in Arabidopsis thaliana.

    PubMed

    Marchadier, Elodie; Hetherington, Alistair M

    2014-07-01

    Two-component signalling (TCS) systems play important roles in cytokinin and ethylene signalling in Arabidopsis thaliana. Although the involvement of histidine kinases (AHKs) in drought stress responses has been described, their role and that of histidine phosphotransferases (AHPs) in guard cell signalling remain to be fully elucidated. Here, we investigated the roles of TCS genes, the histidine phosphotransferase AHP2 and the histidine kinases AHK2 and AHK3, previously reported to play roles in cytokinin and abscisic acid (ABA) signalling. We show that AHP2 is present in the nucleus and the cytoplasm, and is involved in light-induced opening. We also present evidence that there is some redistribution of AHP2 from the nucleus to the cytoplasm on addition of ABA. In addition, we provide data to support a role for the cytokinin receptors AHK2 and AHK3 in light-induced stomatal opening and, by inference, in controlling the stomatal sensitivity to ABA. Our results provide new insights into the operation of TCS in plants, cross-talk in stomatal signalling and, in particular, the process of light-induced stomatal opening. PMID:24758561

  15. The RpfCG two-component system negatively regulates the colonization of sugar cane stalks by Xanthomonas albilineans.

    PubMed

    Rott, Philippe; Fleites, Laura A; Mensi, Imène; Sheppard, Lauren; Daugrois, Jean-Heinrich; Dow, J Maxwell; Gabriel, Dean W

    2013-06-01

    The genome of Xanthomonas albilineans, the causal agent of sugar cane leaf scald, carries a gene cluster encoding a predicted quorum sensing system that is highly related to the diffusible signalling factor (DSF) systems of the plant pathogens Xylella fastidiosa and Xanthomonas campestris. In these latter pathogens, a cluster of regulation of pathogenicity factors (rpf) genes encodes the DSF system and is involved in control of various cellular processes. Mutation of Xanthomonas albilineans rpfF, encoding a predicted DSF synthase, in Florida strain XaFL07-1 resulted in a small reduction of disease severity (DS). Single-knockout mutations of rpfC and rpfG (encoding a predicted DSF sensor and regulator, respectively) had no effect on DS or swimming motility of the pathogen. However, capacity of the pathogen to cause disease was slightly reduced and swimming motility was severely affected when rpfG and rpfC were both deleted. Similar results were obtained when the entire rpfGCF region was deleted. Surprisingly, when the pathogen was mutated in rpfG or rpfC (single or double mutations) it was able to colonize sugar cane spatially more efficiently than the wild-type. Mutation in rpfF alone did not affect the degree of spatial invasion. We conclude that the DSF signal contributes to symptom expression but not to invasion of sugar cane stalks by Xanthomonas albilineans strain XaFL07-1, which is mainly controlled by the RpfCG two-component system. PMID:23538716

  16. A two-component system regulates gene expression of the type IX secretion component proteins via an ECF sigma factor

    PubMed Central

    Kadowaki, Tomoko; Yukitake, Hideharu; Naito, Mariko; Sato, Keiko; Kikuchi, Yuichiro; Kondo, Yoshio; Shoji, Mikio; Nakayama, Koji

    2016-01-01

    The periodontopathogen Porphyromonas gingivalis secretes potent pathogenic proteases, gingipains, via the type IX secretion system (T9SS). This system comprises at least 11 components; however, the regulatory mechanism of their expression has not yet been elucidated. Here, we found that the PorY (PGN_2001)-PorX (PGN_1019)-SigP (PGN_0274) cascade is involved in the regulation of T9SS. Surface plasmon resonance (SPR) analysis revealed a direct interaction between a recombinant PorY (rPorY) and a recombinant PorX (rPorX). rPorY autophosphorylated and transferred a phosphoryl group to rPorX in the presence of Mn2+. These results demonstrate that PorX and PorY act as a response regulator and a histidine kinase, respectively, of a two component system (TCS), although they are separately encoded on the chromosome. T9SS component-encoding genes were down-regulated in a mutant deficient in a putative extracytoplasmic function (ECF) sigma factor, PGN_0274 (SigP), similar to the porX mutant. Electrophoretic gel shift assays showed that rSigP bound to the putative promoter regions of T9SS component-encoding genes. The SigP protein was lacking in the porX mutant. Co-immunoprecipitation and SPR analysis revealed the direct interaction between SigP and PorX. Together, these results indicate that the PorXY TCS regulates T9SS-mediated protein secretion via the SigP ECF sigma factor. PMID:26996145

  17. CovS/CovR of group B streptococcus: a two-component global regulatory system involved in virulence.

    PubMed

    Lamy, Marie-Cécile; Zouine, Mohammed; Fert, Juliette; Vergassola, Massimo; Couve, Elisabeth; Pellegrini, Elisabeth; Glaser, Philippe; Kunst, Frank; Msadek, Tarek; Trieu-Cuot, Patrick; Poyart, Claire

    2004-12-01

    In this study, we carried out a detailed structural and functional analysis of a Streptococcus agalactiae (GBS) two-component system which is orthologous to the CovS/CovR (CsrS/CsrR) regulatory system of Streptococcus pyogenes. In GBS, covR and covS are part of a seven gene operon transcribed from two promoters that are not regulated by CovR. A DeltacovSR mutant was found to display dramatic phenotypic changes such as increased haemolytic activity and reduced CAMP activity on blood agar. Adherence of the DeltacovSR mutant to epithelial cells was greatly increased and analysis by transmission electron microscopy revealed the presence at its surface of a fibrous extracellular matrix that might be involved in these intercellular interactions. However, the DeltacovSR mutant was unable to initiate growth in RPMI and its viability in human normal serum was greatly impaired. A major finding of this phenotypic analysis was that the CovS/CovR system is important for GBS virulence, as a 3 log increase of the LD(50) of the mutant strain was observed in the neonate rat sepsis model. The pleiotropic phenotype of the DeltacovSR mutant is in full agreement with the large number of genes controlled by CovS/CovR as seen by expression profiling analysis, many of which encode potentially secreted or cell surface-associated proteins: 76 genes are repressed whereas 63 were positively regulated. CovR was shown to bind directly to the regulatory regions of several of these genes and a consensus CovR recognition sequence was proposed using both DNase I footprinting and computational analyses. PMID:15554966

  18. A two-component system regulates gene expression of the type IX secretion component proteins via an ECF sigma factor.

    PubMed

    Kadowaki, Tomoko; Yukitake, Hideharu; Naito, Mariko; Sato, Keiko; Kikuchi, Yuichiro; Kondo, Yoshio; Shoji, Mikio; Nakayama, Koji

    2016-01-01

    The periodontopathogen Porphyromonas gingivalis secretes potent pathogenic proteases, gingipains, via the type IX secretion system (T9SS). This system comprises at least 11 components; however, the regulatory mechanism of their expression has not yet been elucidated. Here, we found that the PorY (PGN_2001)-PorX (PGN_1019)-SigP (PGN_0274) cascade is involved in the regulation of T9SS. Surface plasmon resonance (SPR) analysis revealed a direct interaction between a recombinant PorY (rPorY) and a recombinant PorX (rPorX). rPorY autophosphorylated and transferred a phosphoryl group to rPorX in the presence of Mn(2+). These results demonstrate that PorX and PorY act as a response regulator and a histidine kinase, respectively, of a two component system (TCS), although they are separately encoded on the chromosome. T9SS component-encoding genes were down-regulated in a mutant deficient in a putative extracytoplasmic function (ECF) sigma factor, PGN_0274 (SigP), similar to the porX mutant. Electrophoretic gel shift assays showed that rSigP bound to the putative promoter regions of T9SS component-encoding genes. The SigP protein was lacking in the porX mutant. Co-immunoprecipitation and SPR analysis revealed the direct interaction between SigP and PorX. Together, these results indicate that the PorXY TCS regulates T9SS-mediated protein secretion via the SigP ECF sigma factor. PMID:26996145

  19. A Copper-Activated Two-Component System Interacts with Zinc and Imipenem Resistance in Pseudomonas aeruginosa▿

    PubMed Central

    Caille, Olivier; Rossier, Claude; Perron, Karl

    2007-01-01

    The effects of copper (Cu) on trace metal and antibiotic resistance of Pseudomonas aeruginosa have been investigated. Cu treatments induced resistance not only to this metal but also, surprisingly, to zinc (Zn). Quantitative reverse transcription-PCR (qRT-PCR) revealed that after Cu treatment the transcription of the czcRS two-component system (TCS) operon was enhanced as well as that of the czcCBA operon encoding an efflux pump specific for zinc, cadmium, and cobalt. Cu treatments at the same time caused a decrease in the production of OprD porin, resulting in resistance to the carbapenem antibiotic imipenem. The CzcR regulator was known to repress oprD. However, Cu was still able to decrease the production of OprD and induce imipenem resistance in a czcRS knockout mutant. This strongly suggested that another Cu-dependent regulatory system was acting negatively on oprD expression. TCS regulator genes copR-copS have been shown to be involved in Cu tolerance in P. aeruginosa. qRT-PCR showed that overproduction of the CopR or of the CzcR regulator resulted in increased transcription of the czcC gene as well as in a decrease in oprD gene transcription, either in the wild-type strain or in the czcRS knockout mutant. Overproduction experiments suggest that a metal-dependent mechanism operates at the posttranscriptional level to control the production of the CzcCBA efflux pump. This study shows that CopR is a new negative regulator of OprD porin and that it links Zn, Cu, and imipenem resistances by interacting with the CzcRS TCS. PMID:17449606

  20. Regulation of arsenite oxidation by the phosphate two-component system PhoBR in Halomonas sp. HAL1.

    PubMed

    Chen, Fang; Cao, Yajing; Wei, Sha; Li, Yanzhi; Li, Xiangyang; Wang, Qian; Wang, Gejiao

    2015-01-01

    Previously, the expression of arsenite [As(III)] oxidase genes aioBA was reported to be regulated by a three-component regulatory system, AioXSR, in a number of As(III)-oxidizing bacterial strains. However, the regulation mechanism is still unknown when aioXSR genes are absent in some As(III)-oxidizing bacterial genomes, such as in Halomonas sp. HAL1. In this study, transposon mutagenesis and gene knock-out mutation were performed, and two mutants, HAL1-phoR 931 and HAL1-▵phoB, were obtained in strain HAL1. The phoR and phoB constitute a two-component system which is responsible for phosphate (Pi) acquisition and assimilation. Both of the mutants showed negative As(III)-oxidation phenotypes in low Pi condition (0.1 mM) but not under normal Pi condition (1 mM). The phoBR complementation strain HAL1-▵phoB-C reversed the mutants' null phenotypes back to wild type status. Meanwhile, lacZ reporter fusions using pCM-lacZ showed that the expression of phoBR and aioBA were both induced by As(III) but were not induced in HAL1-phoR 931 and HAL1-▵phoB. Using 15 consensus Pho box sequences, a putative Pho box was found in the aioBA regulation region. PhoB was able to bind to the putative Pho box in vivo (bacterial one-hybrid detection) and in vitro (electrophoretic mobility gel shift assay), and an 18-bp binding sequence containing nine conserved bases were determined. This study provided the evidence that PhoBR regulates the expression of aioBA in Halomonas sp. HAL1 under low Pi condition. The new regulation model further implies the close metabolic connection between As and Pi. PMID:26441863

  1. Two-Component System Cross-Regulation Integrates Bacillus anthracis Response to Heme and Cell Envelope Stress

    PubMed Central

    Mike, Laura A.; Choby, Jacob E.; Brinkman, Paul R.; Olive, Lorenzo Q.; Dutter, Brendan F.; Ivan, Samuel J.; Gibbs, Christopher M.; Sulikowski, Gary A.; Stauff, Devin L.; Skaar, Eric P.

    2014-01-01

    Two-component signaling systems (TCSs) are one of the mechanisms that bacteria employ to sense and adapt to changes in the environment. A prototypical TCS functions as a phosphorelay from a membrane-bound sensor histidine kinase (HK) to a cytoplasmic response regulator (RR) that controls target gene expression. Despite significant homology in the signaling domains of HKs and RRs, TCSs are thought to typically function as linear systems with little to no cross-talk between non-cognate HK-RR pairs. Here we have identified several cell envelope acting compounds that stimulate a previously uncharacterized Bacillus anthracis TCS. Furthermore, this TCS cross-signals with the heme sensing TCS HssRS; therefore, we have named it HssRS interfacing TCS (HitRS). HssRS reciprocates cross-talk to HitRS, suggesting a link between heme toxicity and cell envelope stress. The signaling between HssRS and HitRS occurs in the parental B. anthracis strain; therefore, we classify HssRS-HitRS interactions as cross-regulation. Cross-talk between HssRS and HitRS occurs at both HK-RR and post-RR signaling junctions. Finally, HitRS also regulates a previously unstudied ABC transporter implicating this transporter in the response to cell envelope stress. This chemical biology approach to probing TCS signaling provides a new model for understanding how bacterial signaling networks are integrated to enable adaptation to complex environments such as those encountered during colonization of the vertebrate host. PMID:24675902

  2. Genome-Wide Identification of Two-Component System Genes in Cucurbitaceae Crops and Expression Profiling Analyses in Cucumber

    PubMed Central

    He, Yanjun; Liu, Xue; Zou, Tao; Pan, Changtian; Qin, Li; Chen, Lifei; Lu, Gang

    2016-01-01

    Cucumber and watermelon, which belong to Cucurbitaceae family, are economically important cultivated crops worldwide. However, these crops are vulnerable to various adverse environments. Two-component system (TCS), consisting of histidine kinases (HKs), phosphotransfers (HPs), and response regulator proteins (RRs), plays important roles in various plant developmental processes and signaling transduction in responses to a wide range of biotic and abiotic stresses. No systematic investigation has been conducted on TCS genes in Cucurbitaceae species. Based on the completion of the cucumber and watermelon genome draft, we identified 46 and 49 TCS genes in cucumber and watermelon, respectively. The cucumber TCS members included 18 HK(L)s, 7 HPs, and 21 RRs, whereas the watermelon TCS system consisted of 19 HK(L)s, 6 HPs, and 24 RRs. The sequences and domains of TCS members from these two species were highly conserved. Gene duplication events occurred rarely, which might have resulted from the absence of recent whole-genome duplication event in these two Cucurbitaceae crops. Numerous stress- and hormone-responsive cis-elements were detected in the putative promoter regions of the cucumber TCS genes. Meanwhile, quantitative real-time PCR indicated that most of the TCS genes in cucumber were specifically or preferentially expressed in certain tissues or organs, especially in the early developing fruit. Some TCS genes exhibited diverse patterns of gene expression in response to abiotic stresses as well as exogenous trans-zeatin (ZT) and abscisic acid (ABA) treatment, suggesting that TCS genes might play significant roles in responses to various abiotic stresses and hormones in Cucurbitaceae crops. PMID:27446129

  3. Genome-Wide Identification of Two-Component System Genes in Cucurbitaceae Crops and Expression Profiling Analyses in Cucumber.

    PubMed

    He, Yanjun; Liu, Xue; Zou, Tao; Pan, Changtian; Qin, Li; Chen, Lifei; Lu, Gang

    2016-01-01

    Cucumber and watermelon, which belong to Cucurbitaceae family, are economically important cultivated crops worldwide. However, these crops are vulnerable to various adverse environments. Two-component system (TCS), consisting of histidine kinases (HKs), phosphotransfers (HPs), and response regulator proteins (RRs), plays important roles in various plant developmental processes and signaling transduction in responses to a wide range of biotic and abiotic stresses. No systematic investigation has been conducted on TCS genes in Cucurbitaceae species. Based on the completion of the cucumber and watermelon genome draft, we identified 46 and 49 TCS genes in cucumber and watermelon, respectively. The cucumber TCS members included 18 HK(L)s, 7 HPs, and 21 RRs, whereas the watermelon TCS system consisted of 19 HK(L)s, 6 HPs, and 24 RRs. The sequences and domains of TCS members from these two species were highly conserved. Gene duplication events occurred rarely, which might have resulted from the absence of recent whole-genome duplication event in these two Cucurbitaceae crops. Numerous stress- and hormone-responsive cis-elements were detected in the putative promoter regions of the cucumber TCS genes. Meanwhile, quantitative real-time PCR indicated that most of the TCS genes in cucumber were specifically or preferentially expressed in certain tissues or organs, especially in the early developing fruit. Some TCS genes exhibited diverse patterns of gene expression in response to abiotic stresses as well as exogenous trans-zeatin (ZT) and abscisic acid (ABA) treatment, suggesting that TCS genes might play significant roles in responses to various abiotic stresses and hormones in Cucurbitaceae crops. PMID:27446129

  4. Regulation of arsenite oxidation by the phosphate two-component system PhoBR in Halomonas sp. HAL1

    PubMed Central

    Chen, Fang; Cao, Yajing; Wei, Sha; Li, Yanzhi; Li, Xiangyang; Wang, Qian; Wang, Gejiao

    2015-01-01

    Previously, the expression of arsenite [As(III)] oxidase genes aioBA was reported to be regulated by a three-component regulatory system, AioXSR, in a number of As(III)-oxidizing bacterial strains. However, the regulation mechanism is still unknown when aioXSR genes are absent in some As(III)-oxidizing bacterial genomes, such as in Halomonas sp. HAL1. In this study, transposon mutagenesis and gene knock-out mutation were performed, and two mutants, HAL1-phoR931 and HAL1-▵phoB, were obtained in strain HAL1. The phoR and phoB constitute a two-component system which is responsible for phosphate (Pi) acquisition and assimilation. Both of the mutants showed negative As(III)-oxidation phenotypes in low Pi condition (0.1 mM) but not under normal Pi condition (1 mM). The phoBR complementation strain HAL1-▵phoB-C reversed the mutants' null phenotypes back to wild type status. Meanwhile, lacZ reporter fusions using pCM-lacZ showed that the expression of phoBR and aioBA were both induced by As(III) but were not induced in HAL1-phoR931 and HAL1-▵phoB. Using 15 consensus Pho box sequences, a putative Pho box was found in the aioBA regulation region. PhoB was able to bind to the putative Pho box in vivo (bacterial one-hybrid detection) and in vitro (electrophoretic mobility gel shift assay), and an 18-bp binding sequence containing nine conserved bases were determined. This study provided the evidence that PhoBR regulates the expression of aioBA in Halomonas sp. HAL1 under low Pi condition. The new regulation model further implies the close metabolic connection between As and Pi. PMID:26441863

  5. The MprB Extracytoplasmic Domain Negatively Regulates Activation of the Mycobacterium tuberculosis MprAB Two-Component System

    PubMed Central

    Bretl, Daniel J.; Bigley, Tarin M.; Terhune, Scott S.

    2014-01-01

    Mycobacterium tuberculosis is an acid-fast pathogen of humans and the etiological agent of tuberculosis (TB). It is estimated that one-third of the world's population is latently (persistently) infected with M. tuberculosis. M. tuberculosis persistence is regulated, in part, by the MprAB two-component signal transduction system, which is activated by and mediates resistance to cell envelope stress. Here we identify MprAB as part of an evolutionarily conserved cell envelope stress response network and demonstrate that MprAB-mediated signal transduction is negatively regulated by the MprB extracytoplasmic domain (ECD). In particular, we report that deregulated production of the MprB sensor kinase, or of derivatives of this protein, negatively impacts M. tuberculosis growth. The observed growth attenuation is dependent on MprAB-mediated signal transduction and is exacerbated in strains of M. tuberculosis producing an MprB variant lacking its ECD. Interestingly, full-length MprB, and the ECD of MprB specifically, immunoprecipitates the Hsp70 chaperone DnaK in vivo, while overexpression of dnaK inhibits MprAB-mediated signal transduction in M. tuberculosis grown in the absence or presence of cell envelope stress. We propose that under nonstress conditions, or under conditions in which proteins present in the extracytoplasmic space are properly folded, signaling through the MprAB system is inhibited by the MprB ECD. Following exposure to cell envelope stress, proteins present in the extracytoplasmic space become unfolded or misfolded, leading to removal of the ECD-mediated negative regulation of MprB and subsequent activation of MprAB. PMID:24187094

  6. The CsrR/CsrS two-component system of group A Streptococcus responds to environmental Mg2+.

    PubMed

    Gryllos, Ioannis; Levin, James C; Wessels, Michael R

    2003-04-01

    Group A streptococci control expression of key virulence determinants via the two-component sensorregulator system CsrRCsrS. The membrane-bound sensor CsrS is thought to respond to previously unknown environmental signal(s) by controlling phosphorylation of its cognate regulator component CsrR. Phosphorylation of CsrR increases its affinity for binding to the promoter regions of Csr-regulated genes to repress transcription. Here we show that environmental Mg(2+) concentration is a potent and specific stimulus for CsrRCsrS-mediated regulation. We studied the effect of divalent cations on expression of the Csr-regulated hyaluronic acid capsule genes (hasABC) by measuring chloramphenicol acetyltransferase (CAT) activity in a reporter strain of group A Streptococcus carrying a has operon promoter-cat fusion. Addition of Mg(2+), but not of Ca(2+), Mn(2+), or Zn(2+), repressed capsule gene expression by up to 80% in a dose-dependent fashion. The decrease in capsule gene transcription was associated with a marked reduction in cell-associated capsular polysaccharide. RNA hybridization analysis demonstrated reduced expression of the Csr-regulated hasABC operon, streptokinase (ska), and streptolysin S (sagA) during growth in the presence of 15 mM Mg(2+) for the wild-type strain 003CAT but not for an isogenic csrS mutant. We propose that Mg(2+) binds to CsrS to induce phosphorylation of CsrR and subsequent repression of virulence gene expression. The low concentration of Mg(2+) in extracellular body fluids predicts that the CsrRCsrS system is maintained in the inactive state during infection, thereby allowing maximal expression of critical virulence determinants in the human host. PMID:12646707

  7. A multi-step phosphorelay two-component system impacts on tolerance against dehydration stress in common wheat.

    PubMed

    Gahlaut, Vijay; Mathur, Saloni; Dhariwal, Raman; Khurana, Jitendra P; Tyagi, Akhilesh K; Balyan, Harindra S; Gupta, Pushpendra K

    2014-12-01

    Wheat is an important staple crop, and its productivity is severely constrained by drought stress (DS). An understanding of the molecular basis of drought tolerance is necessary for genetic improvement of wheat for tolerance to DS. The two-component system (TCS) serves as a common sensor-regulator coupling mechanism implicated in the regulation of diverse biological processes (including response to DS) not only in prokaryotes, but also in higher plants. In the latter, TCS generally consists of two signalling elements, a histidine kinase (HK) and a response regulator (RR) associated with an intermediate element called histidine phosphotransferase (HPT). Keeping in view the possible utility of TCS in developing water use efficient (WUE) wheat cultivars, we identified and characterized 62 wheat genes encoding TCS elements in a silico study; these included 7 HKs, 45 RRs along with 10 HPTs. Twelve of the 62 genes showed relatively higher alterations in the expression under drought. The quantitative RT-PCR (qRT-PCR)-based expression analysis of these 12 TCS genes was carried out in wheat seedlings of a drought sensitive (HD2967) and a tolerant (Dharwar Dry) cultivar subjected to either dehydration stress or cytokinin treatment. The expression of these 12 genes under dehydration stress differed in sensitive and tolerant genotypes, even though for individual genes, both showed either up-regulation or down-regulation. In response to the treatment of cytokinin, the expression of type-A RR genes was higher in the tolerant genotype, relative to that in the sensitive genotype, the situation being reverse for the type-B RRs. These results have been discussed in the context of the role of TCS elements in drought tolerance in wheat. PMID:25228409

  8. Two-Component System VicRK Regulates Functions Associated with Establishment of Streptococcus sanguinis in Biofilms

    PubMed Central

    Moraes, Julianna J.; Stipp, Rafael N.; Harth-Chu, Erika N.; Camargo, Tarsila M.; Höfling, José F.

    2014-01-01

    Streptococcus sanguinis is a commensal pioneer colonizer of teeth and an opportunistic pathogen of infectious endocarditis. The establishment of S. sanguinis in host sites likely requires dynamic fitting of the cell wall in response to local stimuli. In this study, we investigated the two-component system (TCS) VicRK in S. sanguinis (VicRKSs), which regulates genes of cell wall biogenesis, biofilm formation, and virulence in opportunistic pathogens. A vicK knockout mutant obtained from strain SK36 (SKvic) showed slight reductions in aerobic growth and resistance to oxidative stress but an impaired ability to form biofilms, a phenotype restored in the complemented mutant. The biofilm-defective phenotype was associated with reduced amounts of extracellular DNA during aerobic growth, with reduced production of H2O2, a metabolic product associated with DNA release, and with inhibitory capacity of S. sanguinis competitor species. No changes in autolysis or cell surface hydrophobicity were detected in SKvic. Reverse transcription-quantitative PCR (RT-qPCR), electrophoretic mobility shift assays (EMSA), and promoter sequence analyses revealed that VicR directly regulates genes encoding murein hydrolases (SSA_0094, cwdP, and gbpB) and spxB, which encodes pyruvate oxidase for H2O2 production. Genes previously associated with spxB expression (spxR, ccpA, ackA, and tpK) were not transcriptionally affected in SKvic. RT-qPCR analyses of S. sanguinis biofilm cells further showed upregulation of VicRK targets (spxB, gbpB, and SSA_0094) and other genes for biofilm formation (gtfP and comE) compared to expression in planktonic cells. This study provides evidence that VicRKSs regulates functions crucial for S. sanguinis establishment in biofilms and identifies novel VicRK targets potentially involved in hydrolytic activities of the cell wall required for these functions. PMID:25183732

  9. Extrusion foaming of thermoplastic cellulose acetate from renewable resources using a two-component physical blowing agent system

    NASA Astrophysics Data System (ADS)

    Hopmann, Ch.; Windeck, C.; Hendriks, S.; Zepnik, S.; Wodke, T.

    2014-05-01

    Thermoplastic cellulose acetate (CA) is a bio-based polymer with optical, mechanical and thermal properties comparable to those of polystyrene (PS). The substitution of the predominant petrol-based PS in applications like foamed food trays can lead to a more sustainable economic practice. However, CA is also suitable for more durable applications as the biodegradability rate can be controlled by adjusting the degree of substitutions. The extrusion foaming of CA still has to overcome certain challenges. CA is highly hydrophilic and can suffer from hydrolytic degradation if not dried properly. Therefore, the influence of residual moisture on the melt viscosity is rather high. Beyond, the surface quality of foam CA sheets is below those of PS due to the particular foaming behaviour. This paper presents results of a recent study on extrusion foamed CA, using a two-component physical blowing agent system compromising HFO 1234ze as blowing agent and organic solvents as co-propellant. Samples with different co-propellants are processed on a laboratory single screw extruder at IKV. Morphology and surface topography are investigated with respect to the blowing agent composition and the die pressure. In addition, relationships between foam density, foam morphology and the propellants are analysed. The choice of the co-propellant has a significant influence on melt-strength, foaming behaviour and the possible blow-up ratio of the sheet. Furthermore, a positive influence of the co-propellant on the surface quality can be observed. In addition, the focus is laid on the effect of external contact cooling of the foamed sheets after the die exit.

  10. Two-Component-System Histidine Kinases Involved in Growth of Listeria monocytogenes EGD-e at Low Temperatures.

    PubMed

    Pöntinen, Anna; Markkula, Annukka; Lindström, Miia; Korkeala, Hannu

    2015-06-15

    Two-component systems (TCSs) aid bacteria in adapting to a wide variety of stress conditions. While the role of TCS response regulators in the cold tolerance of the psychrotrophic foodborne pathogen Listeria monocytogenes has been demonstrated previously, no comprehensive studies showing the role of TCS histidine kinases of L. monocytogenes at low temperature have been performed. We compared the expression levels of each histidine kinase-encoding gene of L. monocytogenes EGD-e in logarithmic growth phase at 3°C and 37°C, as well as the expression levels 30 min, 3 h, and 7 h after cold shock at 5°C and preceding cold shock (at 37°C). We constructed a deletion mutation in each TCS histidine kinase gene, monitored the growth of the EGD-e wild-type and mutant strains at 3°C and 37°C, and measured the minimum growth temperature of each strain. Two genes, yycG and lisK, proved significant in regard to induced relative expression levels under cold conditions and cold-sensitive mutant phenotypes. Moreover, the ΔresE mutant showed a lower growth rate than that of wild-type EGD-e at 3°C. Eleven other genes showed upregulated gene expression but revealed no cold-sensitive phenotypes. The results show that the histidine kinases encoded by yycG and lisK are important for the growth and adaptation of L. monocytogenes EGD-e at low temperature. PMID:25841007

  11. Association between polymorphisms in the csrRS two-component regulatory system and invasive group A streptococcal infection.

    PubMed

    Lin, J-N; Chang, L-L; Lai, C-H; Lin, H-H; Chen, Y-H

    2014-05-01

    The csrRS two-component regulatory system is an important element in the pathogenesis of group A Streptococcus (GAS). The main goal of this study is to understand the association between csrRS polymorphisms and GAS infection. We sequenced the csrRS genes from 172 clinical isolates, including 81 invasive and 91 noninvasive isolates, and then employed phylogenetic analyses to determine the consequences of the csrRS polymorphisms. In total, 13 and 26 polymorphic loci were detected in the csrR and csrS genes, respectively. These polymorphisms constituted 14 csrR and 25 csrS alleles, producing two CsrR and seven CsrS variants, respectively. Three invasive isolates contained an indel in csrS, but no indel was identified in csrR. The frequency and distribution of polymorphisms in csrR and csrS was significantly different between the invasive and noninvasive infection isolates (p < 0.001). For CsrR, only one noninvasive isolate was identified to have a V29I mutation. The amino acid substitutions in CsrS included S32P (0.6 %), E265G (0.6 %), E265K (0.6 %), I332V (1.7 %), and N498K (82.6 %). Isolates with an N498K single mutation were more likely to be associated with invasive infections (p < 0.001). The dN/dS ratio indicated that both csrR and csrS were under purifying selection. The fixation index suggested a moderate evolutionary differentiation of the csrR and csrS alleles between invasive and noninvasive isolates. The identification of these genetic differences within the csrRS loci will provide a better understanding of the pathogenesis of GAS. PMID:24158687

  12. BarA-UvrY Two-Component System Regulates Virulence of Uropathogenic E. coli CFT073

    PubMed Central

    Palaniyandi, Senthilkumar; Mitra, Arindam; Herren, Christopher D.; Lockatell, C. Virginia; Johnson, David E.; Zhu, Xiaoping; Mukhopadhyay, Suman

    2012-01-01

    Uropathogenic Escherichia coli (UPEC), a member of extraintestinal pathogenic E. coli, cause ∼80% of community-acquired urinary tract infections (UTI) in humans. UPEC initiates its colonization in epithelial cells lining the urinary tract with a complicated life cycle, replicating and persisting in intracellular and extracellular niches. Consequently, UPEC causes cystitis and more severe form of pyelonephritis. To further understand the virulence characteristics of UPEC, we investigated the roles of BarA-UvrY two-component system (TCS) in regulating UPEC virulence. Our results showed that mutation of BarA-UvrY TCS significantly decreased the virulence of UPEC CFT073, as assessed by mouse urinary tract infection, chicken embryo killing assay, and cytotoxicity assay on human kidney and uroepithelial cell lines. Furthermore, mutation of either barA or uvrY gene reduced the production of hemolysin, lipopolysaccharide (LPS), proinflammatory cytokines (TNF-α and IL-6) and chemokine (IL-8). The virulence phenotype was restored similar to that of wild-type by complementation of either barA or uvrY gene in trans. In addition, we discussed a possible link between the BarA-UvrY TCS and CsrA in positively and negatively controlling virulence in UPEC. Overall, this study provides the evidences for BarA-UvrY TCS regulates the virulence of UPEC CFT073 and may point to mechanisms by which virulence regulations are observed in different ways may control the long-term survival of UPEC in the urinary tract. PMID:22363626

  13. A New Two-Component Regulatory System Involved in Adhesion, Autolysis, and Extracellular Proteolytic Activity of Staphylococcus aureus

    PubMed Central

    Fournier, Bénédicte; Hooper, David C.

    2000-01-01

    A transposition mutant of Staphylococcus aureus was selected from the parent strain MT23142, a derivative of strain 8325. The site of transposition was near the 5′ terminus of the gene arlS. ArlS exhibits strong similarities with histidine protein kinases. Sequence analysis suggested that arlS forms an operon with upstream gene arlR. The predicted product of arlR is a member of the OmpR-PhoB family of response regulators. The arlS mutant formed a biofilm on a polystyrene surface unlike the parent strain and the complemented mutant. Biofilm formation was associated with increased primary adherence to polystyrene, whereas cellular adhesion was only slightly decreased. In addition, the arlS mutant exhibited increased autolysis and altered peptidoglycan hydrolase activity compared to the parental strain and to the complemented mutant. As it has been shown for coagulase-negative staphylococci that some autolysins are able to bind polymer surfaces, these data suggest that the two-component regulatory system ArlS-ArlR may control attachment to polymer surfaces by affecting secreted peptidoglycan hydrolase activity. Finally, the arlS mutant showed a dramatic decrease of extracellular proteolytic activity, including serine protease activity, in comparison to the wild-type strain and the complemented mutant, and cells grown in the presence of phenylmethylsulfonyl fluoride (a serine protease inhibitor) showed an increased autolysin activity. Since the locus arlR-arlS strikingly modifies extracellular proteolytic activity, this locus might also be involved in the virulence of S. aureus. PMID:10869073

  14. Polymyxin Resistance of Pseudomonas aeruginosa phoQ Mutants Is Dependent on Additional Two-Component Regulatory Systems

    PubMed Central

    Gutu, Alina D.; Sgambati, Nicole; Strasbourger, Pnina; Brannon, Mark K.; Jacobs, Michael A.; Haugen, Eric; Kaul, Rajinder K.; Johansen, Helle Krogh; Høiby, Niels

    2013-01-01

    Pseudomonas aeruginosa can develop resistance to polymyxin as a consequence of mutations in the PhoPQ regulatory system, mediated by covalent lipid A modification. Transposon mutagenesis of a polymyxin-resistant phoQ mutant defined 41 novel loci required for resistance, including two regulatory systems, ColRS and CprRS. Deletion of the colRS genes, individually or in tandem, abrogated the polymyxin resistance of a ΔphoQ mutant, as did individual or tandem deletion of cprRS. Individual deletion of colR or colS in a ΔphoQ mutant also suppressed 4-amino-l-arabinose addition to lipid A, consistent with the known role of this modification in polymyxin resistance. Surprisingly, tandem deletion of colRS or cprRS in the ΔphoQ mutant or individual deletion of cprR or cprS failed to suppress 4-amino-l-arabinose addition to lipid A, indicating that this modification alone is not sufficient for PhoPQ-mediated polymyxin resistance in P. aeruginosa. Episomal expression of colRS or cprRS in tandem or of cprR individually complemented the Pm resistance phenotype in the ΔphoQ mutant, while episomal expression of colR, colS, or cprS individually did not. Highly polymyxin-resistant phoQ mutants of P. aeruginosa isolated from polymyxin-treated cystic fibrosis patients harbored mutant alleles of colRS and cprS; when expressed in a ΔphoQ background, these mutant alleles enhanced polymyxin resistance. These results define ColRS and CprRS as two-component systems regulating polymyxin resistance in P. aeruginosa, indicate that addition of 4-amino-l-arabinose to lipid A is not the only PhoPQ-regulated biochemical mechanism required for resistance, and demonstrate that colRS and cprS mutations can contribute to high-level clinical resistance. PMID:23459479

  15. Identification, Functional Characterization and Regulon Prediction of a Novel Two Component System Comprising BAS0540-BAS0541 of Bacillus anthracis

    PubMed Central

    Gopalani, Monisha; Kandari, Divya; Bhatnagar, Rakesh

    2016-01-01

    Two component systems (TCSs) can be envisaged as complex molecular devices that help the bacteria to sense its environment and respond aptly. 41 TCSs are predicted in Bacillus anthracis, a potential bioterrorism agent, of which only four have been studied so far. Thus, the intricate signaling network contributed by TCSs remains largely unmapped in B. anthracis and needs comprehensive exploration. In this study, we functionally characterized one such system composed of BAS0540 (Response regulator) and BAS0541 (Histidine kinase). BAS0540-BAS0541, the closest homolog of CiaRH of Streptococcus in B. anthracis, forms a functional TCS with BAS0541 displaying autophosphorylation and subsequent phosphotransfer to BAS0540. BAS0540 was also found to accept phosphate from physiologically relevant small molecule phosphodonors like acetyl phosphate and carbamoyl phosphate. Results of qRT-PCR and immunoblotting demonstrated that BAS0540 exhibits a constitutive expression throughout the growth of B. anthracis. Regulon prediction for BAS0540 in B. anthracis was done in silico using the consensus DNA binding sequence of CiaR of Streptococcus. The predicted regulon of BAS0540 comprised of 23 genes, which could be classified into 8 functionally diverse categories. None of the proven virulence factors were a part of the predicted regulon, an observation contrasting with the regulon of CiaRH in Streptococci. Electrophoretic mobility shift assay was used to show direct binding of purified BAS0540 to the upstream regions of 5 putative regulon candidates- BAS0540 gene itself; a gene predicted to encode cell division protein FtsA; a self–immunity gene; a RND family transporter gene and a gene encoding stress (heat) responsive protein. A significant enhancement in the DNA binding ability of BAS0540 was observed upon phosphorylation. Overexpression of response regulator BAS0540 in B. anthracis led to a prodigious increase of ~6 folds in the cell length, thereby conferring it a filamentous

  16. Identification, Functional Characterization and Regulon Prediction of a Novel Two Component System Comprising BAS0540-BAS0541 of Bacillus anthracis.

    PubMed

    Gopalani, Monisha; Dhiman, Alisha; Rahi, Amit; Kandari, Divya; Bhatnagar, Rakesh

    2016-01-01

    Two component systems (TCSs) can be envisaged as complex molecular devices that help the bacteria to sense its environment and respond aptly. 41 TCSs are predicted in Bacillus anthracis, a potential bioterrorism agent, of which only four have been studied so far. Thus, the intricate signaling network contributed by TCSs remains largely unmapped in B. anthracis and needs comprehensive exploration. In this study, we functionally characterized one such system composed of BAS0540 (Response regulator) and BAS0541 (Histidine kinase). BAS0540-BAS0541, the closest homolog of CiaRH of Streptococcus in B. anthracis, forms a functional TCS with BAS0541 displaying autophosphorylation and subsequent phosphotransfer to BAS0540. BAS0540 was also found to accept phosphate from physiologically relevant small molecule phosphodonors like acetyl phosphate and carbamoyl phosphate. Results of qRT-PCR and immunoblotting demonstrated that BAS0540 exhibits a constitutive expression throughout the growth of B. anthracis. Regulon prediction for BAS0540 in B. anthracis was done in silico using the consensus DNA binding sequence of CiaR of Streptococcus. The predicted regulon of BAS0540 comprised of 23 genes, which could be classified into 8 functionally diverse categories. None of the proven virulence factors were a part of the predicted regulon, an observation contrasting with the regulon of CiaRH in Streptococci. Electrophoretic mobility shift assay was used to show direct binding of purified BAS0540 to the upstream regions of 5 putative regulon candidates- BAS0540 gene itself; a gene predicted to encode cell division protein FtsA; a self-immunity gene; a RND family transporter gene and a gene encoding stress (heat) responsive protein. A significant enhancement in the DNA binding ability of BAS0540 was observed upon phosphorylation. Overexpression of response regulator BAS0540 in B. anthracis led to a prodigious increase of ~6 folds in the cell length, thereby conferring it a filamentous

  17. Pseudomonas aeruginosa MifS-MifR Two-Component System Is Specific for α-Ketoglutarate Utilization

    PubMed Central

    Tatke, Gorakh; Kumari, Hansi; Silva-Herzog, Eugenia; Ramirez, Lourdes; Mathee, Kalai

    2015-01-01

    Pseudomonas aeruginosa is a Gram-negative, metabolically versatile opportunistic pathogen that elaborates a multitude of virulence factors, and is extraordinarily resistant to a gamut of clinically significant antibiotics. This ability, in part, is mediated by two-component regulatory systems (TCS) that play a crucial role in modulating virulence mechanisms and metabolism. MifS (PA5512) and MifR (PA5511) form one such TCS implicated in biofilm formation. MifS is a sensor kinase whereas MifR belongs to the NtrC superfamily of transcriptional regulators that interact with RpoN (σ54). In this study we demonstrate that the mifS and mifR genes form a two-gene operon. The close proximity of mifSR operon to poxB (PA5514) encoding a ß-lactamase hinted at the role of MifSR TCS in regulating antibiotic resistance. To better understand this TCS, clean in-frame deletions were made in P. aeruginosa PAO1 creating PAO∆mifS, PAO∆mifR and PAO∆mifSR. The loss of mifSR had no effect on the antibiotic resistance profile. Phenotypic microarray (BioLOG) analyses of PAO∆mifS and PAO∆mifR revealed that these mutants were unable to utilize C5-dicarboxylate α-ketoglutarate (α-KG), a key tricarboxylic acid cycle intermediate. This finding was confirmed using growth analyses, and the defect can be rescued by mifR or mifSR expressed in trans. These mifSR mutants were able to utilize all the other TCA cycle intermediates (citrate, succinate, fumarate, oxaloacetate or malate) and sugars (glucose or sucrose) except α-KG as the sole carbon source. We confirmed that the mifSR mutants have functional dehydrogenase complex suggesting a possible defect in α-KG transport. The inability of the mutants to utilize α-KG was rescued by expressing PA5530, encoding C5-dicarboxylate transporter, under a regulatable promoter. In addition, we demonstrate that besides MifSR and PA5530, α-KG utilization requires functional RpoN. These data clearly suggests that P. aeruginosa MifSR TCS is involved

  18. The Ferrous Iron-Responsive BqsRS Two-Component System Activates Genes That Promote Cationic Stress Tolerance

    PubMed Central

    Kreamer, Naomi N.; Costa, Flavia

    2015-01-01

    ABSTRACT The physiological resistance of pathogens to antimicrobial treatment is a severe problem in the context of chronic infections. For example, the mucus-filled lungs of cystic fibrosis (CF) patients are readily colonized by diverse antibiotic-resistant microorganisms, including Pseudomonas aeruginosa. Previously, we showed that bioavailable ferrous iron [Fe(II)] is present in CF sputum at all stages of infection and constitutes a significant portion of the iron pool at advanced stages of lung function decline [R. C. Hunter et al., mBio 4(4):e00557-13, 2013]. P. aeruginosa, a dominant CF pathogen, senses Fe(II) using a two-component signal transduction system, BqsRS, which is transcriptionally active in CF sputum [R. C. Hunter et al., mBio 4(4):e00557-13, 2013; N. N. Kreamer, J. C. Wilks, J. J. Marlow, M. L. Coleman, and D. K. Newman, J Bacteriol 194:1195–1204, 2012]. Here, we show that an RExxE motif in BqsS is required for BqsRS activation. Once Fe(II) is sensed, BqsR binds a tandem repeat DNA sequence, activating transcription. The BqsR regulon—defined through iterative bioinformatic predictions and experimental validation—includes several genes whose products are known to drive antibiotic resistance to aminoglycosides and polymyxins. Among them are genes encoding predicted determinants of polyamine transport and biosynthesis. Compared to the wild type, bqsS and bqsR deletion mutants are sensitive to high levels of Fe(II), produce less spermidine in high Fe(II), and are more sensitive to tobramycin and polymyxin B but not arsenate, chromate, or cefsulodin. BqsRS thus mediates a physiological response to Fe(II) that guards the cell against positively charged molecules but not negatively charged stressors. These results suggest Fe(II) is an important environmental signal that, via BqsRS, bolsters tolerance of a variety of cationic stressors, including clinically important antimicrobial agents. PMID:25714721

  19. PSPTO_3380 and PSPTO_3381: A two-component system that influences the virulence of Pseudomonas syringae pv. tomato DC3000

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A major factor in pathogenesis is the ability of the pathogen to respond and react to the host environment during the infection cycle. For bacteria, external stimuli are mainly sensed by two-component systems (TCS) composed of histidine kinases with external recognition domains and cytoplasmic respo...

  20. Mechanisms underlying zoonotic success of Campylobacter jejuni: the CprRS two-component regulatory system influences essential processes, biofilm formation, and pathogenesis

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Mechanisms underlying zoonotic success of Campylobacter jejuni: the CprRS two-component regulatory system influences essential processes, biofilm formation, and pathogenesis Campylobacter jejuni is a leading cause of food- and waterbourne bacterial gastroenteritis in the developed world. Although il...

  1. Analysis of the activity and regulon of the two-component regulatory system encoded by Cjj1484 and Cjj1483 of Campylobacter jejuni

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Campylobacter jejuni is a leading cause of bacterial diarrheal disease throughout the world and a frequent commensal in the intestinal tract of poultry and many other animals. For maintaining optimal growth and ability to colonize various hosts, C. jejuni depends upon two-component regulatory system...

  2. The KdpD/KdpE two-component system of Photorhabdus asymbiotica promotes bacterial survival within M. sexta hemocytes.

    PubMed

    Vlisidou, Isabella; Eleftherianos, Ioannis; Dorus, Steve; Yang, Guowei; ffrench-Constant, Richard H; Reynolds, Stuart E; Waterfield, Nick R

    2010-11-01

    Many bacteria persist within phagocytes, deploying complex sets of tightly regulated virulence factors to manipulate and survive within host cells. So far, no single factor has been identified that is sufficient to allow intracellular persistence of an otherwise non-pathogenic bacterium. Here we report that the two-component KdpD/KdpE sensor kinase/response regulator of the insect and human pathogen Photorhabdus asymbiotica (Pa) is sufficient to allow a harmless laboratory strain of E. coli to resist phagocytic killing and persist within insect hemocytes, ultimately killing the insect. Screening of a cosmid library of Pa in E. coli by injection into the moth Manduca sexta, previously identified three overlapping clones which caused the insect to cease feeding and subsequently die. Transposon mutagenesis revealed a cosmid encoded kdp high affinity potassium pump regulon was responsible for this phenotype. Gentamycin protection assays and confocal microscopy revealed the cosmid clones were persisting inside insect hemocytes far longer than control bacteria. Cloning and expression of PakdpD/kdpE alone into E. coli recapitulated the phenotype. Bioassay results and transcriptional analysis of various E. coli kdp mutants harboring the Pa kdp genes confirmed that Pa KdpD/KdpE was able to induce the E. coli kdp pump structural genes in response to exposure to insect hemocytes but not blood plasma alone. The finding that Pa KdpD/KdpE can facilitate resistance of E. coli to phagocytic killing suggests a central role for potassium in this process, supporting previous work implicating potassium sensing in virulence of other bacteria and also in the normal process of protease killing of engulfed bacteria by neutrophils. PMID:20932844

  3. The prrAB Two-Component System Is Essential for Mycobacterium tuberculosis Viability and Is Induced under Nitrogen-Limiting Conditions

    PubMed Central

    Malhotra, Vandana; Cornelison, Garrett L.; Clark-Curtiss, Josephine E.

    2012-01-01

    The Mycobacterium tuberculosis prrA-prrB (Rv0903c-Rv0902c) two-component regulatory system is expressed during intracellular growth in human macrophages and is required for early intracellular multiplication in murine macrophages, suggesting its importance in establishing infection. To better understand the function of the prrA-prrB two-component system, we defined the transcriptional characteristics of the prrA and prrB genes during exponential and stationary growth and upon exposure to different environmental stresses and attempted to generate a prrA-prrB deletion mutant. The prrA and prrB genes constitute an operon and are cotranscribed during logarithmic growth, with transcriptional levels decreasing in stationary phase and during hypoxia. Despite the transcriptional differences, PrrA protein levels remained relatively stable throughout growth and in hypoxia. Under conditions of nitrogen limitation, prrAB transcription was induced, while acidic pH stress and carbon starvation did not significantly alter transcript levels. Deletion of the prrAB operon on the chromosome of M. tuberculosis H37Rv occurred only in the presence of an episomal copy of the prrAB genes, indicating that this two-component system is essential for viability. Characterization of the prrAB locus in M. tuberculosis Mt21D3, a previously described prrA transposon mutant, revealed that this strain is not a true prrA knockout mutant. Rather, Tn5367 transposon insertion into the prrA promoter only decreased prrA and prrB transcription and PrrA levels in Mt21D3 compared to those in the parental Mt103 clinical strain. These data provide the first report describing the essentiality of the M. tuberculosis prrAB two-component system and reveal insights into its potential role in mycobacterial growth and metabolism. PMID:22081401

  4. The prrAB two-component system is essential for Mycobacterium tuberculosis viability and is induced under nitrogen-limiting conditions.

    PubMed

    Haydel, Shelley E; Malhotra, Vandana; Cornelison, Garrett L; Clark-Curtiss, Josephine E

    2012-01-01

    The Mycobacterium tuberculosis prrA-prrB (Rv0903c-Rv0902c) two-component regulatory system is expressed during intracellular growth in human macrophages and is required for early intracellular multiplication in murine macrophages, suggesting its importance in establishing infection. To better understand the function of the prrA-prrB two-component system, we defined the transcriptional characteristics of the prrA and prrB genes during exponential and stationary growth and upon exposure to different environmental stresses and attempted to generate a prrA-prrB deletion mutant. The prrA and prrB genes constitute an operon and are cotranscribed during logarithmic growth, with transcriptional levels decreasing in stationary phase and during hypoxia. Despite the transcriptional differences, PrrA protein levels remained relatively stable throughout growth and in hypoxia. Under conditions of nitrogen limitation, prrAB transcription was induced, while acidic pH stress and carbon starvation did not significantly alter transcript levels. Deletion of the prrAB operon on the chromosome of M. tuberculosis H37Rv occurred only in the presence of an episomal copy of the prrAB genes, indicating that this two-component system is essential for viability. Characterization of the prrAB locus in M. tuberculosis Mt21D3, a previously described prrA transposon mutant, revealed that this strain is not a true prrA knockout mutant. Rather, Tn5367 transposon insertion into the prrA promoter only decreased prrA and prrB transcription and PrrA levels in Mt21D3 compared to those in the parental Mt103 clinical strain. These data provide the first report describing the essentiality of the M. tuberculosis prrAB two-component system and reveal insights into its potential role in mycobacterial growth and metabolism. PMID:22081401

  5. Virulence control in group A Streptococcus by a two-component gene regulatory system: global expression profiling and in vivo infection modeling.

    PubMed

    Graham, Morag R; Smoot, Laura M; Migliaccio, Cristi A Lux; Virtaneva, Kimmo; Sturdevant, Daniel E; Porcella, Stephen F; Federle, Michael J; Adams, Gerald J; Scott, June R; Musser, James M

    2002-10-15

    Two-component gene regulatory systems composed of a membrane-bound sensor and cytoplasmic response regulator are important mechanisms used by bacteria to sense and respond to environmental stimuli. Group A Streptococcus, the causative agent of mild infections and life-threatening invasive diseases, produces many virulence factors that promote survival in humans. A two-component regulatory system, designated covRS (cov, control of virulence; csrRS), negatively controls expression of five proven or putative virulence factors (capsule, cysteine protease, streptokinase, streptolysin S, and streptodornase). Inactivation of covRS results in enhanced virulence in mouse models of invasive disease. Using DNA microarrays and quantitative RT-PCR, we found that CovR influences transcription of 15% (n = 271) of all chromosomal genes, including many that encode surface and secreted proteins mediating host-pathogen interactions. CovR also plays a central role in gene regulatory networks by influencing expression of genes encoding transcriptional regulators, including other two-component systems. Differential transcription of genes influenced by covR also was identified in mouse soft-tissue infection. This analysis provides a genome-scale overview of a virulence gene network in an important human pathogen and adds insight into the molecular mechanisms used by group A Streptococcus to interact with the host, promote survival, and cause disease. PMID:12370433

  6. The development of a two-component force dynamometer and tool control system for dynamic machine tool research

    NASA Technical Reports Server (NTRS)

    Sutherland, I. A.

    1973-01-01

    The development is presented of a tooling system that makes a controlled sinusoidal oscillation simulating a dynamic chip removal condition. It also measures the machining forces in two mutually perpendicular directions without any cross sensitivity.

  7. A Simple Theory to Predict Small Changes in Volume and Refractivity During Mixing of a Two-Component Liquid System.

    ERIC Educational Resources Information Center

    Aminabhavi, Tejraj M.

    1983-01-01

    Discusses a set of relations (addressing changes in volume and refractivity) for use in the study of binary systems. Suggests including such an experiment in undergraduate physical chemistry courses (measuring density/refractive index of pure compounds and their mixtures) to predict even small changes occurring during mixing process. (Author/JN)

  8. A two-component enhancer-inhibitor transposon mutagenesis system for functional analysis of the Arabidopsis genome.

    PubMed Central

    Speulman, E; Metz, P L; van Arkel, G; te Lintel Hekkert, B; Stiekema, W J; Pereira, A

    1999-01-01

    A modified Enhancer-Inhibitor transposon system was used to generate a series of mutant lines by single-seed descent such that multiple I insertions occurred per plant. The distribution of original insertions in the population was assessed by isolating transposon-flanking DNA, and a database of insertion sites was created. Approximately three-quarters of the identified insertion sites show similarity to sequences stored in public databases, which demonstrates the power of this regimen of insertional mutagenesis. To isolate insertions in specific genes, we developed three-dimensional pooling and polymerase chain reaction strategies that we then validated by identifying mutants for the regulator genes APETALA1 and SHOOT MERISTEMLESS. The system then was used to identify inserts in a class of uncharacterized genes involved in lipid biosynthesis; one such insertion conferred a fiddlehead mutant phenotype. PMID:10521517

  9. A model system for pathogen detection using a two-component bacteriophage/bioluminescent signal amplification assay

    NASA Astrophysics Data System (ADS)

    Bright, Nathan G.; Carroll, Richard J.; Applegate, Bruce M.

    2004-03-01

    Microbial contamination has become a mounting concern the last decade due to an increased emphasis of minimally processed food products specifically produce, and the recognition of foodborne pathogens such as Campylobacter jejuni, Escherichia coli O157:H7, and Listeria monocytogenes. This research investigates a detection approach utilizing bacteriophage pathogen specificity coupled with a bacterial bioluminescent bioreporter utilizing the quorum sensing molecule from Vibrio fischeri, N-(3-oxohexanoyl)-homoserine lactone (3-oxo-C6-HSL). The 3-oxo-C6-HSL molecules diffuse out of the target cell after infection and induce bioluminescence from a population of 3-oxo-C6-HSL bioreporters (ROLux). E. coli phage M13, a well-characterized bacteriophage, offers a model system testing the use of bacteriophage for pathogen detection through cell-to-cell communication via a LuxR/3-oxo-C6-HSL system. Simulated temperate phage assays tested functionality of the ROLux reporter and production of 3-oxo-C6-HSL by various test strains. These assays showed detection limits of 102cfu after 24 hours in a varietry of detection formats. Assays incorporating the bacteriophage M13-luxI with the ROLux reporter and a known population of target cells were subsequently developed and have shown consistent detection limits of 105cfu target organisms. Measurable light response from high concentrations of target cells was almost immediate, suggesting an enrichment step to further improve detection limits and reduce assay time.

  10. The IRF5-TNPO3 association with systemic lupus erythematosus has two components that other autoimmune disorders variably share.

    PubMed

    Kottyan, Leah C; Zoller, Erin E; Bene, Jessica; Lu, Xiaoming; Kelly, Jennifer A; Rupert, Andrew M; Lessard, Christopher J; Vaughn, Samuel E; Marion, Miranda; Weirauch, Matthew T; Namjou, Bahram; Adler, Adam; Rasmussen, Astrid; Glenn, Stuart; Montgomery, Courtney G; Hirschfield, Gideon M; Xie, Gang; Coltescu, Catalina; Amos, Chris; Li, He; Ice, John A; Nath, Swapan K; Mariette, Xavier; Bowman, Simon; Rischmueller, Maureen; Lester, Sue; Brun, Johan G; Gøransson, Lasse G; Harboe, Erna; Omdal, Roald; Cunninghame-Graham, Deborah S; Vyse, Tim; Miceli-Richard, Corinne; Brennan, Michael T; Lessard, James A; Wahren-Herlenius, Marie; Kvarnström, Marika; Illei, Gabor G; Witte, Torsten; Jonsson, Roland; Eriksson, Per; Nordmark, Gunnel; Ng, Wan-Fai; Anaya, Juan-Manuel; Rhodus, Nelson L; Segal, Barbara M; Merrill, Joan T; James, Judith A; Guthridge, Joel M; Scofield, R Hal; Alarcon-Riquelme, Marta; Bae, Sang-Cheol; Boackle, Susan A; Criswell, Lindsey A; Gilkeson, Gary; Kamen, Diane L; Jacob, Chaim O; Kimberly, Robert; Brown, Elizabeth; Edberg, Jeffrey; Alarcón, Graciela S; Reveille, John D; Vilá, Luis M; Petri, Michelle; Ramsey-Goldman, Rosalind; Freedman, Barry I; Niewold, Timothy; Stevens, Anne M; Tsao, Betty P; Ying, Jun; Mayes, Maureen D; Gorlova, Olga Y; Wakeland, Ward; Radstake, Timothy; Martin, Ezequiel; Martin, Javier; Siminovitch, Katherine; Moser Sivils, Kathy L; Gaffney, Patrick M; Langefeld, Carl D; Harley, John B; Kaufman, Kenneth M

    2015-01-15

    Exploiting genotyping, DNA sequencing, imputation and trans-ancestral mapping, we used Bayesian and frequentist approaches to model the IRF5-TNPO3 locus association, now implicated in two immunotherapies and seven autoimmune diseases. Specifically, in systemic lupus erythematosus (SLE), we resolved separate associations in the IRF5 promoter (all ancestries) and with an extended European haplotype. We captured 3230 IRF5-TNPO3 high-quality, common variants across 5 ethnicities in 8395 SLE cases and 7367 controls. The genetic effect from the IRF5 promoter can be explained by any one of four variants in 5.7 kb (P-valuemeta = 6 × 10(-49); OR = 1.38-1.97). The second genetic effect spanned an 85.5-kb, 24-variant haplotype that included the genes IRF5 and TNPO3 (P-valuesEU = 10(-27)-10(-32), OR = 1.7-1.81). Many variants at the IRF5 locus with previously assigned biological function are not members of either final credible set of potential causal variants identified herein. In addition to the known biologically functional variants, we demonstrated that the risk allele of rs4728142, a variant in the promoter among the lowest frequentist probability and highest Bayesian posterior probability, was correlated with IRF5 expression and differentially binds the transcription factor ZBTB3. Our analytical strategy provides a novel framework for future studies aimed at dissecting etiological genetic effects. Finally, both SLE elements of the statistical model appear to operate in Sjögren's syndrome and systemic sclerosis whereas only the IRF5-TNPO3 gene-spanning haplotype is associated with primary biliary cirrhosis, demonstrating the nuance of similarity and difference in autoimmune disease risk mechanisms at IRF5-TNPO3. PMID:25205108

  11. Mutation of the Thiol-Disulfide Oxidoreductase SdbA Activates the CiaRH Two-Component System, Leading to Bacteriocin Expression Shutdown in Streptococcus gordonii

    PubMed Central

    Davey, Lauren; Halperin, Scott A.

    2015-01-01

    ABSTRACT Streptococcus gordonii is a commensal inhabitant of the human oral cavity. To maintain its presence as a major component of oral biofilms, S. gordonii secretes inhibitory molecules such as hydrogen peroxide and bacteriocins to inhibit competitors. S. gordonii produces two nonmodified bacteriocins (i.e., Sth1 and Sth2) that are regulated by the Com two-component regulatory system, which also regulates genetic competence. Previously we found that the thiol-disulfide oxidoreductase SdbA was required for bacteriocin activity; however, the role of SdbA in Com signaling was not clear. Here we demonstrate that ΔsdbA mutants lacked bacteriocin activity because the bacteriocin gene sthA was strongly repressed and the peptides were not secreted. Addition of synthetic competence-stimulating peptide to the medium reversed the phenotype, indicating that the Com pathway was functional but was not activated in the ΔsdbA mutant. Repression of bacteriocin production was mediated by the CiaRH two-component system, which was strongly upregulated in the ΔsdbA mutant, and inactivation of CiaRH restored bacteriocin production. The CiaRH-induced protease DegP was also upregulated in the ΔsdbA mutant, although it was not required for inhibition of bacteriocin production. This establishes CiaRH as a regulator of Sth bacteriocin activity and links the CiaRH and Com systems in S. gordonii. It also suggests that either SdbA or one of its substrates is an important factor in regulating activation of the CiaRH system. IMPORTANCE Streptococcus gordonii is a noncariogenic colonizer of the human oral cavity. To be competitive in the oral biofilm, S. gordonii secretes antimicrobial peptides called bacteriocins, which inhibit closely related species. Our previous data showed that mutation of the disulfide oxidoreductase SdbA abolished bacteriocin production. In this study, we show that mutation of SdbA generates a signal that upregulates the CiaRH two-component system, which in turn

  12. Using Two-Component Systems and other Bacterial Regulatory Factors for the Fabrication of Synthetic Genetic Devices

    PubMed Central

    Ninfa, Alexander J.; Selinsky, Stephen; Perry, Nicolas; Atkins, Stephen; Song, Qi Xiu; Mayo, Avi; Arps, David; Woolf, Peter; Atkinson, Mariette R.

    2011-01-01

    Synthetic biology is an emerging field in which the procedures and methods of engineering are extended to living organisms, with the long-term goal of producing novel cell types that aid human society. For example, engineered cell types may sense a particular environment and express gene products that serve as an indicator of that environment, or effect a change in that environment. While we are still some way from producing cells with significant practical applications, the immediate goals of synthetic biology are to develop a quantitative understanding of genetic circuitry and its interactions with the environment and to develop modular genetic circuitry derived from standard, interoperable, parts, that can be introduced into cells and results in some desired input/output function. Using an engineering approach, the input/output function of each modular element is characterized independently, providing a toolkit of elements that can be linked in different ways to provide various circuit topologies. The principle of modularity, yet largely unproven for biological systems, suggests that modules will function appropriately based on their design characteristics when combined into larger synthetic genetic devices. This modularity concept is similar to that used to develop large computer programs, where inpendent software modules can be independently developed and later combined into the final program. PMID:17628156

  13. The two-component system CprRS senses cationic peptides and triggers adaptive resistance in Pseudomonas aeruginosa independently of ParRS.

    PubMed

    Fernández, Lucía; Jenssen, Håvard; Bains, Manjeet; Wiegand, Irith; Gooderham, W James; Hancock, Robert E W

    2012-12-01

    Cationic antimicrobial peptides pass across the outer membrane by interacting with negatively charged lipopolysaccharide (LPS), leading to outer membrane permeabilization in a process termed self-promoted uptake. Resistance can be mediated by the addition of positively charged arabinosamine through the action of the arnBCADTEF operon. We recently described a series of two-component regulators that lead to the activation of the arn operon after recognizing environmental signals, including low-Mg(2+) (PhoPQ, PmrAB) or cationic (ParRS) peptides. However, some peptides did not activate the arn operon through ParRS. Here, we report the identification of a new two-component system, CprRS, which, upon exposure to a wide range of antimicrobial peptides, triggered the expression of the LPS modification operon. Thus, mutations in the cprRS operon blocked the induction of the arn operon in response to several antimicrobial peptides independently of ParRS but did not affect the response to low Mg(2+). Distinct patterns of arn induction were identified. Thus, the responses to polymyxins were abrogated by either parR or cprR mutations, while responses to other peptides, including indolicidin, showed differential dependency on the CprRS and ParRS systems in a concentration-dependent manner. It was further demonstrated that, following exposure to inducing antimicrobial peptides, cprRS mutants did not become adaptively resistant to polymyxins as was observed for wild-type cells. Our microarray studies demonstrated that the CprRS system controlled a quite modest regulon, indicating that it was quite specific to adaptive peptide resistance. These findings provide greater insight into the complex regulation of LPS modification in Pseudomonas aeruginosa, which involves the participation of at least 4 two-component systems. PMID:23006746

  14. Serotype- and strain- dependent contribution of the sensor kinase CovS of the CovRS two-component system to Streptococcus pyogenes pathogenesis

    PubMed Central

    2010-01-01

    Background The Streptococcus pyogenes (group A streptococci, GAS) two-component signal transduction system CovRS has been described to be important for pathogenesis of this exclusively human bacterial species. If this system acts uniquely in all serotypes is currently unclear. Presence of serotype- or strain-dependent regulatory circuits and polarity is an emerging scheme in Streptococcus pyogenes pathogenesis. Thus, the contribution of the sensor kinase (CovS) of the global regulatory two-component signal transduction system CovRS on pathogenesis of several M serotypes was investigated. Results CovS mutation uniformly repressed capsule expression and hampered keratinocyte adherence in all tested serotypes. However, a serotype- and even strain-dependent contribution on survival in whole human blood and biofilm formation was noted, respectively. Conclusions These data provide new information on the action of the CovS sensor kinase and revealed that its activity on capsule expression and keratinocyte adherence is uniform across serotypes, whereas the influence on biofilm formation and blood survival is serotype or even strain dependent. This adds the CovRS system to a growing list of serotype-specific acting regulatory loci in S. pyogenes. PMID:20113532

  15. The Role of the Two-Component System BaeSR in Disposing Chemicals through Regulating Transporter Systems in Acinetobacter baumannii.

    PubMed

    Lin, Ming-Feng; Lin, Yun-You; Lan, Chung-Yu

    2015-01-01

    Bacterial two-component regulatory systems (TCSs) facilitate changes in gene expression in response to environmental stimuli. TCS BaeR regulons influence tigecycline susceptibility in Acinetobacter baumannii through positively regulating the pump genes adeA and adeB. In this study, we demonstrate that an additional two transport systems, AdeIJK and MacAB-TolC, are also regulated by BaeSR. In the wild type and clinical tigecycline-resistant A. baumannii strains, gene expression of AdeIJK and MacAB-TolC increased after tigecycline induction, implicating their importance to tigecycline resistance in addition to AdeABC. Phenotypic microarray results showed that A. baumannii is vulnerable to certain chemicals, especially tannic acid, after deleting baeR, which was confirmed using the spot assay. The wild-type strain of A. baumannii also exhibited 1.6-fold and 4.4-fold increase in gene expression of adeJ and macB in the medium with 100 μg/mL tannic acid, but the increase was fully inhibited by baeR deletion. An electrophoretic motility shift assay based on an interaction between His-BaeR and the adeA, adeI and macA promoter regions did not demonstrate direct binding. In conclusion, A. baumannii can use the TCS BaeSR in disposing chemicals, such as tannic acid and tigecycline, through regulating the efflux pumps. PMID:26161744

  16. The Role of the Two-Component System BaeSR in Disposing Chemicals through Regulating Transporter Systems in Acinetobacter baumannii

    PubMed Central

    Lin, Ming-Feng; Lin, Yun-You; Lan, Chung-Yu

    2015-01-01

    Bacterial two-component regulatory systems (TCSs) facilitate changes in gene expression in response to environmental stimuli. TCS BaeR regulons influence tigecycline susceptibility in Acinetobacter baumannii through positively regulating the pump genes adeA and adeB. In this study, we demonstrate that an additional two transport systems, AdeIJK and MacAB-TolC, are also regulated by BaeSR. In the wild type and clinical tigecycline-resistant A. baumannii strains, gene expression of AdeIJK and MacAB-TolC increased after tigecycline induction, implicating their importance to tigecycline resistance in addition to AdeABC. Phenotypic microarray results showed that A. baumannii is vulnerable to certain chemicals, especially tannic acid, after deleting baeR, which was confirmed using the spot assay. The wild-type strain of A. baumannii also exhibited 1.6-fold and 4.4-fold increase in gene expression of adeJ and macB in the medium with 100 μg/mL tannic acid, but the increase was fully inhibited by baeR deletion. An electrophoretic motility shift assay based on an interaction between His-BaeR and the adeA, adeI and macA promoter regions did not demonstrate direct binding. In conclusion, A. baumannii can use the TCS BaeSR in disposing chemicals, such as tannic acid and tigecycline, through regulating the efflux pumps. PMID:26161744

  17. Control of CydB and GltA1 Expression by the SenX3 RegX3 Two Component Regulatory System of Mycobacterium tuberculosis

    PubMed Central

    Roberts, Gretta; Vadrevu, Indumathi S.; Madiraju, Murty V.; Parish, Tanya

    2011-01-01

    Two component regulatory systems are used widely by bacteria to coordinate changes in global gene expression profiles in response to environmental signals. The SenX3-RegX3 two component system of Mycobacterium tuberculosis has previously been shown to play a role in virulence and phosphate-responsive control of gene expression. We demonstrate that expression of SenX3-RegX3 is controlled in response to growth conditions, although the absolute changes are small. Global gene expression profiling of a RegX3 deletion strain and wild-type strain in different culture conditions (static, microaerobic, anaerobic), as well as in an over-expressing strain identified a number of genes with changed expression patterns. Among those were genes previously identified as differentially regulated in aerobic culture, including ald (encoding alanine dehydrogenase) cyd,encoding a subunit of the cytochrome D ubiquinol oxidase, and gltA1, encoding a citrate synthase. Promoter activity in the upstream regions of both cydB and gltA1 was altered in the RegX3 deletion strain. DNA-binding assays confirmed that RegX3 binds to the promoter regions of ald, cydB and gltA1 in a phosphorylation-dependent manner. Taken together these data suggest a direct role for the SenX-RegX3 system in modulating expression of aerobic respiration, in addition to its role during phosphate limitation. PMID:21698211

  18. The VarS/VarA two-component system modulates the activity of the Vibrio cholerae quorum-sensing transcriptional regulator HapR

    PubMed Central

    Tsou, Amy M.; Liu, Zhi; Cai, Tao

    2011-01-01

    The human pathogen Vibrio cholerae uses quorum sensing to regulate the expression of a number of phenotypes, including virulence factor production, in response to changes in cell density. It produces small molecules called autoinducers that increase in concentration as cell density increases, and these autoinducers bind to membrane sensors once they reach a certain threshold. This binding leads to signalling through a downstream phosphorelay pathway to alter the expression of the transcriptional regulator HapR. Previously, it was shown that the VarS/VarA two-component system acts on a component of the phosphorelay pathway upstream of HapR to regulate HapR expression levels. Here, we show that in addition to this mechanism of regulation, VarS and VarA also indirectly modulate HapR protein activity. This modulation is mediated by the small RNA CsrB but is independent of the known quorum-sensing system that links the autoinducers to HapR. Thus, the VarS/VarA two-component system intersects with the quorum-sensing network at two levels. In both cases, the effect of VarS and VarA on quorum sensing is dependent on the Csr small RNAs, which regulate carbon metabolism, suggesting that V. cholerae may integrate nutrient status and cell density sensory inputs to tailor its gene expression profile more precisely to surrounding conditions. PMID:21393367

  19. The BatR/BatS Two-Component Regulatory System Controls the Adaptive Response of Bartonella henselae during Human Endothelial Cell Infection ▿ † ‡

    PubMed Central

    Quebatte, Maxime; Dehio, Michaela; Tropel, David; Basler, Andrea; Toller, Isabella; Raddatz, Guenter; Engel, Philipp; Huser, Sonja; Schein, Hermine; Lindroos, Hillevi L.; Andersson, Siv G. E.; Dehio, Christoph

    2010-01-01

    Here, we report the first comprehensive study of Bartonella henselae gene expression during infection of human endothelial cells. Expression of the main cluster of upregulated genes, comprising the VirB type IV secretion system and its secreted protein substrates, is shown to be under the positive control of the transcriptional regulator BatR. We demonstrate binding of BatR to the promoters of the virB operon and a substrate-encoding gene and provide biochemical evidence that BatR and BatS constitute a functional two-component regulatory system. Moreover, in contrast to the acid-inducible (pH 5.5) homologs ChvG/ChvI of Agrobacterium tumefaciens, BatR/BatS are optimally activated at the physiological pH of blood (pH 7.4). By conservation analysis of the BatR regulon, we show that BatR/BatS are uniquely adapted to upregulate a genus-specific virulence regulon during hemotropic infection in mammals. Thus, we propose that BatR/BatS two-component system homologs represent vertically inherited pH sensors that control the expression of horizontally transmitted gene sets critical for the diverse host-associated life styles of the alphaproteobacteria. PMID:20418395

  20. A subfamily of putative cytokinin receptors is revealed by an analysis of the evolution of the two-component signaling system of plants.

    PubMed

    Gruhn, Nijuscha; Halawa, Mhyeddeen; Snel, Berend; Seidl, Michael F; Heyl, Alexander

    2014-05-01

    The two-component signaling system--the major signaling pathway of bacteria--is found among higher eukaryotes only in plants, where it regulates diverse processes, such as the signaling of the phytohormone cytokinin. Cytokinin is perceived by a hybrid histidine (His) kinase receptor, and the signal is transduced by a multistep phosphorelay system of His phosphotransfer proteins and different classes of response regulators (RRs). To shed light on the origin and evolution of the two-component signaling system members in plants, we conducted a comprehensive domain-based phylogenetic study across the relevant kingdoms, including Charophyceae algae, the group of green algae giving rise to land plants. Surprisingly, we identified a subfamily of cytokinin receptors with members only from the early diverging land plants Marchantia polymorpha and Physcomitrella patens and then experimentally characterized two members of this subfamily. His phosphotransfer proteins of Charophyceae seemed to be more closely related to land plants than to other groups of green algae. Farther down the signaling pathway, the type-B RRs were found across all plant clades, but many members lack either the canonical Asp residue or the DNA binding domain. In contrast, the type-A RRs seemed to be limited to land plants. Finally, the analysis provided hints that one additional group of RRs, the type-C RRs, might be degenerated receptors and thus, of a different evolutionary origin than bona fide RRs. PMID:24520157

  1. A Two-Component Alkyne Metathesis Catalyst System with an Improved Substrate Scope and Functional Group Tolerance: Development and Applications to Natural Product Synthesis.

    PubMed

    Schaubach, Sebastian; Gebauer, Konrad; Ungeheuer, Felix; Hoffmeister, Laura; Ilg, Marina K; Wirtz, Conny; Fürstner, Alois

    2016-06-13

    Although molybdenum alkylidyne complexes such as 1 endowed with triarylsilanolate ligands are excellent catalysts for alkyne metathesis, they can encounter limitations when (multiple) protic sites are present in a given substrate and/or when forcing conditions are necessary. In such cases, a catalyst formed in situ upon mixing of the trisamidomolybenum alkylidyne complex 3 and the readily available trisilanol derivatives 8 or 11 shows significantly better performance. This two-component system worked well for a series of model compounds comprising primary, secondary or phenolic -OH groups, as well as for a set of challenging (bis)propargylic substrates. Its remarkable efficiency is also evident from applications to the total syntheses of manshurolide, a highly strained sesquiterpene lactone with kinase inhibitory activity, and the structurally demanding immunosuppressive cyclodiyne ivorenolide A; in either case, the standard catalyst 1 largely failed to effect the critical macrocyclization, whereas the two-component system was fully operative. A study directed toward the quinolizidine alkaloid lythrancepine I features yet another instructive example, in that a triyne substrate was metathesized with the help of 3/11 such that two of the triple bonds participated in ring closure, while the third one passed uncompromised. As a spin-off of this project, a much improved ruthenium catalyst for the redox isomerization of propargyl alcohols to the corresponding enones was developed. PMID:27203803

  2. A two-component covRS regulatory system regulates expression of fructosyltransferase and a novel extracellular carbohydrate in Streptococcus mutans.

    PubMed

    Lee, Song F; Delaney, Gillian D; Elkhateeb, Mohammad

    2004-07-01

    The expression of fructosyltransferase (FTF), the enzyme that synthesizes fructan from sucrose, is regulated in the cariogenic bacterium Streptococcus mutans. However, the exact mechanism of FTF regulation is unknown. In this study, the role of a two-component regulatory system (covRS) in FTF expression was investigated. A CovR-defective mutant of S. mutans NG8 was constructed by homologous recombination. By use of immunoblotting, the mutant was shown to overexpress FTF in the absence of sucrose, while the wild type and a covRS-complemented mutant showed sucrose-inducible FTF expression. Reverse transcription-PCR showed that the ftf transcript levels were increased in the covR mutant, suggesting regulation at the transcriptional level. The covR mutant was also found to overproduce extracellular carbohydrate, and this phenotype was reversed by covRS complementation. Paper chromatographic studies and chemical tests showed that the extracellular carbohydrate contained glucose and glucuronic acid but not fructose. These results suggest that the extracellular carbohydrate was not fructan. The production of a glucose- and glucuronic acid-containing extracellular carbohydrate has not been reported for S. mutans and may be considered novel. In conclusion, the results indicate that the expression of FTF and a glucose- and glucuronic acid-containing carbohydrate was negatively regulated by the covRS two-component regulatory system in S. mutans. PMID:15213141

  3. A Subfamily of Putative Cytokinin Receptors Is Revealed by an Analysis of the Evolution of the Two-Component Signaling System of Plants1[W][OPEN

    PubMed Central

    Gruhn, Nijuscha; Halawa, Mhyeddeen; Snel, Berend; Seidl, Michael F.; Heyl, Alexander

    2014-01-01

    The two-component signaling system—the major signaling pathway of bacteria—is found among higher eukaryotes only in plants, where it regulates diverse processes, such as the signaling of the phytohormone cytokinin. Cytokinin is perceived by a hybrid histidine (His) kinase receptor, and the signal is transduced by a multistep phosphorelay system of His phosphotransfer proteins and different classes of response regulators (RRs). To shed light on the origin and evolution of the two-component signaling system members in plants, we conducted a comprehensive domain-based phylogenetic study across the relevant kingdoms, including Charophyceae algae, the group of green algae giving rise to land plants. Surprisingly, we identified a subfamily of cytokinin receptors with members only from the early diverging land plants Marchantia polymorpha and Physcomitrella patens and then experimentally characterized two members of this subfamily. His phosphotransfer proteins of Charophyceae seemed to be more closely related to land plants than to other groups of green algae. Farther down the signaling pathway, the type-B RRs were found across all plant clades, but many members lack either the canonical Asp residue or the DNA binding domain. In contrast, the type-A RRs seemed to be limited to land plants. Finally, the analysis provided hints that one additional group of RRs, the type-C RRs, might be degenerated receptors and thus, of a different evolutionary origin than bona fide RRs. PMID:24520157

  4. A Two-Component covRS Regulatory System Regulates Expression of Fructosyltransferase and a Novel Extracellular Carbohydrate in Streptococcus mutans

    PubMed Central

    Lee, Song F.; Delaney, Gillian D.; Elkhateeb, Mohammad

    2004-01-01

    The expression of fructosyltransferase (FTF), the enzyme that synthesizes fructan from sucrose, is regulated in the cariogenic bacterium Streptococcus mutans. However, the exact mechanism of FTF regulation is unknown. In this study, the role of a two-component regulatory system (covRS) in FTF expression was investigated. A CovR-defective mutant of S. mutans NG8 was constructed by homologous recombination. By use of immunoblotting, the mutant was shown to overexpress FTF in the absence of sucrose, while the wild type and a covRS-complemented mutant showed sucrose-inducible FTF expression. Reverse transcription-PCR showed that the ftf transcript levels were increased in the covR mutant, suggesting regulation at the transcriptional level. The covR mutant was also found to overproduce extracellular carbohydrate, and this phenotype was reversed by covRS complementation. Paper chromatographic studies and chemical tests showed that the extracellular carbohydrate contained glucose and glucuronic acid but not fructose. These results suggest that the extracellular carbohydrate was not fructan. The production of a glucose- and glucuronic acid-containing extracellular carbohydrate has not been reported for S. mutans and may be considered novel. In conclusion, the results indicate that the expression of FTF and a glucose- and glucuronic acid-containing carbohydrate was negatively regulated by the covRS two-component regulatory system in S. mutans. PMID:15213141

  5. The VirS/VirR two-component system regulates the anaerobic cytotoxicity, intestinal pathogenicity, and enterotoxemic lethality of Clostridium perfringens type C isolate CN3685.

    PubMed

    Ma, Menglin; Vidal, Jorge; Saputo, Juliann; McClane, Bruce A; Uzal, Francisco

    2011-01-01

    Clostridium perfringens vegetative cells cause both histotoxic infections (e.g., gas gangrene) and diseases originating in the intestines (e.g., hemorrhagic necrotizing enteritis or lethal enterotoxemia). Despite their medical and veterinary importance, the molecular pathogenicity of C. perfringens vegetative cells causing diseases of intestinal origin remains poorly understood. However, C. perfringens beta toxin (CPB) was recently shown to be important when vegetative cells of C. perfringens type C strain CN3685 induce hemorrhagic necrotizing enteritis and lethal enterotoxemia. Additionally, the VirS/VirR two-component regulatory system was found to control CPB production by CN3685 vegetative cells during aerobic infection of cultured enterocyte-like Caco-2 cells. Using an isogenic virR null mutant, the current study now reports that the VirS/VirR system also regulates CN3685 cytotoxicity during infection of Caco-2 cells under anaerobic conditions, as found in the intestines. More importantly, the virR mutant lost the ability to cause hemorrhagic necrotic enteritis in rabbit small intestinal loops. Western blot analyses demonstrated that the VirS/VirR system mediates necrotizing enteritis, at least in part, by controlling in vivo CPB production. In addition, vegetative cells of the isogenic virR null mutant were, relative to wild-type vegetative cells, strongly attenuated in their lethality in a mouse enterotoxemia model. Collectively, these results identify the first regulator of in vivo pathogenicity for C. perfringens vegetative cells causing disease originating in the complex intestinal environment. Since VirS/VirR also mediates histotoxic infections, this two-component regulatory system now assumes a global role in regulating a spectrum of infections caused by C. perfringens vegetative cells. PMID:21264065

  6. The VirS/VirR Two-Component System Regulates the Anaerobic Cytotoxicity, Intestinal Pathogenicity, and Enterotoxemic Lethality of Clostridium perfringens Type C Isolate CN3685

    PubMed Central

    Ma, Menglin; Vidal, Jorge; Saputo, Juliann; McClane, Bruce A.; Uzal, Francisco

    2011-01-01

    Clostridium perfringens vegetative cells cause both histotoxic infections (e.g., gas gangrene) and diseases originating in the intestines (e.g., hemorrhagic necrotizing enteritis or lethal enterotoxemia). Despite their medical and veterinary importance, the molecular pathogenicity of C. perfringens vegetative cells causing diseases of intestinal origin remains poorly understood. However, C. perfringens beta toxin (CPB) was recently shown to be important when vegetative cells of C. perfringens type C strain CN3685 induce hemorrhagic necrotizing enteritis and lethal enterotoxemia. Additionally, the VirS/VirR two-component regulatory system was found to control CPB production by CN3685 vegetative cells during aerobic infection of cultured enterocyte-like Caco-2 cells. Using an isogenic virR null mutant, the current study now reports that the VirS/VirR system also regulates CN3685 cytotoxicity during infection of Caco-2 cells under anaerobic conditions, as found in the intestines. More importantly, the virR mutant lost the ability to cause hemorrhagic necrotic enteritis in rabbit small intestinal loops. Western blot analyses demonstrated that the VirS/VirR system mediates necrotizing enteritis, at least in part, by controlling in vivo CPB production. In addition, vegetative cells of the isogenic virR null mutant were, relative to wild-type vegetative cells, strongly attenuated in their lethality in a mouse enterotoxemia model. Collectively, these results identify the first regulator of in vivo pathogenicity for C. perfringens vegetative cells causing disease originating in the complex intestinal environment. Since VirS/VirR also mediates histotoxic infections, this two-component regulatory system now assumes a global role in regulating a spectrum of infections caused by C. perfringens vegetative cells. PMID:21264065

  7. The Eukaryotic-Like Ser/Thr Kinase PrkC Regulates the Essential WalRK Two-Component System in Bacillus subtilis

    PubMed Central

    Dworkin, Jonathan

    2015-01-01

    Most bacteria contain both eukaryotic-like Ser/Thr kinases (eSTKs) and eukaryotic-like Ser/Thr phosphatases (eSTPs). Their role in bacterial physiology is not currently well understood in large part because the conditions where the eSTKs are active are generally not known. However, all sequenced Gram-positive bacteria have a highly conserved eSTK with extracellular PASTA repeats that bind cell wall derived muropeptides. Here, we report that in the Gram-positive bacterium Bacillus subtilis, the PASTA-containing eSTK PrkC and its cognate eSTP PrpC converge with the essential WalRK two-component system to regulate WalR regulon genes involved in cell wall metabolism. By continuously monitoring gene expression throughout growth, we consistently find a large PrkC-dependent effect on expression of several different WalR regulon genes in early stationary phase, including both those that are activated by WalR (yocH) as well as those that are repressed (iseA, pdaC). We demonstrate that PrkC phosphorylates WalR in vitro and in vivo on a single Thr residue located in the receiver domain. Although the phosphorylated region of the receiver domain is highly conserved among several B. subtilis response regulators, PrkC displays specificity for WalR in vitro. Consistently, strains expressing a nonphosphorylatable WalR point mutant strongly reduce both PrkC dependent activation and repression of yocH, iseA, and pdaC. This suggests a model where the eSTK PrkC regulates the essential WalRK two-component signaling system by direct phosphorylation of WalR Thr101, resulting in the regulation of WalR regulon genes involved in cell wall metabolism in stationary phase. As both the eSTK PrkC and the essential WalRK two-component system are highly conserved in Gram-positive bacteria, these results may be applicable to further understanding the role of eSTKs in Gram-positive physiology and cell wall metabolism. PMID:26102633

  8. The Eukaryotic-Like Ser/Thr Kinase PrkC Regulates the Essential WalRK Two-Component System in Bacillus subtilis.

    PubMed

    Libby, Elizabeth A; Goss, Lindsie A; Dworkin, Jonathan

    2015-06-01

    Most bacteria contain both eukaryotic-like Ser/Thr kinases (eSTKs) and eukaryotic-like Ser/Thr phosphatases (eSTPs). Their role in bacterial physiology is not currently well understood in large part because the conditions where the eSTKs are active are generally not known. However, all sequenced Gram-positive bacteria have a highly conserved eSTK with extracellular PASTA repeats that bind cell wall derived muropeptides. Here, we report that in the Gram-positive bacterium Bacillus subtilis, the PASTA-containing eSTK PrkC and its cognate eSTP PrpC converge with the essential WalRK two-component system to regulate WalR regulon genes involved in cell wall metabolism. By continuously monitoring gene expression throughout growth, we consistently find a large PrkC-dependent effect on expression of several different WalR regulon genes in early stationary phase, including both those that are activated by WalR (yocH) as well as those that are repressed (iseA, pdaC). We demonstrate that PrkC phosphorylates WalR in vitro and in vivo on a single Thr residue located in the receiver domain. Although the phosphorylated region of the receiver domain is highly conserved among several B. subtilis response regulators, PrkC displays specificity for WalR in vitro. Consistently, strains expressing a nonphosphorylatable WalR point mutant strongly reduce both PrkC dependent activation and repression of yocH, iseA, and pdaC. This suggests a model where the eSTK PrkC regulates the essential WalRK two-component signaling system by direct phosphorylation of WalR Thr101, resulting in the regulation of WalR regulon genes involved in cell wall metabolism in stationary phase. As both the eSTK PrkC and the essential WalRK two-component system are highly conserved in Gram-positive bacteria, these results may be applicable to further understanding the role of eSTKs in Gram-positive physiology and cell wall metabolism. PMID:26102633

  9. The two-component PhoR-PhoP system controls both primary metabolism and secondary metabolite biosynthesis in Streptomyces lividans

    PubMed Central

    Sola-Landa, A.; Moura, R. S.; Martín, J. F.

    2003-01-01

    The biosynthesis of most secondary metabolites in different bacteria is strongly depressed by inorganic phosphate. The two-component phoR-phoP system of Streptomyces lividans has been cloned and characterized. PhoR showed all of the characteristics of the membrane-bound sensor proteins, whereas PhoP is a member of the DNA-binding OmpR family. Deletion mutants lacking phoP or phoR-phoP, were unable to grow in minimal medium at low phosphate concentration (10 μM). Growth was fully restored by complementation with the phoR-phoP genes. Both S. lividans ΔphoP and ΔphoR-phoP deletion mutants were unable to synthesize extracellular alkaline phosphatase (AP) as shown by immunodetection with anti-AP antibodies and by enzymatic analysis, suggesting that the PhoR-PhoP system is required for expression of the AP gene (phoA). Synthesis of AP was restored by complementation of the deletion mutants with phoR-phoP. The biosynthesis of two secondary metabolites, actinorhodin and undecylprodigiosin, was significantly increased in both solid and liquid medium in the ΔphoP or ΔphoR-phoP deletion mutants. Negative phosphate control of both secondary metabolites was restored by complementation with the phoR-phoP cluster. These results prove that expression of both phoA and genes implicated in the biosynthesis of secondary metabolites in S. lividans is regulated by a mechanism involving the two-component PhoR-PhoP system. PMID:12730372

  10. Development and validation of a high-throughput cell-based screen to identify activators of a bacterial two-component signal transduction system.

    PubMed

    van Rensburg, Julia J; Fortney, Kate R; Chen, Lan; Krieger, Andrew J; Lima, Bruno P; Wolfe, Alan J; Katz, Barry P; Zhang, Zhong-Yin; Spinola, Stanley M

    2015-07-01

    CpxRA is a two-component signal transduction system (2CSTS) found in many drug-resistant Gram-negative bacteria. In response to periplasmic stress, CpxA autophosphorylates and donates a phosphoryl group to its cognate response regulator, CpxR. Phosphorylated CpxR (CpxR-P) upregulates genes involved in membrane repair and downregulates multiple genes that encode virulence factors, which are trafficked across the cell membrane. Mutants that constitutively activate CpxRA in Salmonella enterica serovar Typhimurium and Haemophilus ducreyi are avirulent in mice and humans, respectively. Thus, the activation of CpxRA has high potential as a novel antimicrobial/antivirulence strategy. Using a series of Escherichia coli strains containing a CpxR-P-responsive lacZ reporter and deletions in genes encoding CpxRA system components, we developed and validated a novel cell-based high-throughput screen (HTS) for CpxRA activators. A screen of 36,000 compounds yielded one hit compound that increased reporter activity in wild-type cells. This is the first report of a compound that activates, rather than inhibits, a 2CSTS. The activity profile of the compound against CpxRA pathway mutants in the presence of glucose suggested that the compound inhibits CpxA phosphatase activity. We confirmed that the compound induced the accumulation of CpxR-P in treated cells. Although the hit compound contained a nitro group, a derivative lacking this group retained activity in serum and had lower cytotoxicity than that of the initial hit. This HTS is amenable for the screening of larger libraries to find compounds that activate CpxRA by other mechanisms, and it could be adapted to find activators of other two-component systems. PMID:25870061

  11. Expression of the RND-type efflux pump AdeABC in Acinetobacter baumannii is regulated by the AdeRS two-component system.

    PubMed

    Marchand, Isabelle; Damier-Piolle, Laurence; Courvalin, Patrice; Lambert, Thierry

    2004-09-01

    The AdeABC pump of Acinetobacter baumannii BM4454, which confers resistance to various antibiotic classes including aminoglycosides, is composed of the AdeA, AdeB, and AdeC proteins; AdeB is a member of the RND superfamily. The adeA, adeB, and adeC genes are contiguous and adjacent to adeS and adeR, which are transcribed in the opposite direction and which specify proteins homologous to sensors and regulators of two-component systems, respectively (S. Magnet, P. Courvalin, and T. Lambert, Antimicrob. Agents Chemother. 45:3375-3380, 2001). Analysis by Northern hybridization indicated that the three genes were cotranscribed, although mRNAs corresponding to adeAB and adeC were also present. Cotranscription of the two regulatory genes was demonstrated by reverse transcription-PCR. Inactivation of adeS led to aminoglycoside susceptibility. Transcripts corresponding to adeAB were not detected in susceptible A. baumannii CIP 70-10 but were present in spontaneous gentamicin-resistant mutants obtained in vitro. Analysis of these mutants revealed the substitutions Thr153-->Met in AdeS downstream from the putative His-149 site of autophosphorylation, which is presumably responsible for the loss of phosphorylase activity by the sensor, and Pro116-->Leu in AdeR at the first residue of the alpha(5) helix of the receiver domain, which is involved in interactions that control the output domain of response regulators. These mutations led to constitutive expression of the pump and, thus, to antibiotic resistance. These data indicate that the AdeABC pump is cryptic in wild A. baumannii due to stringent control by the AdeRS two-component system. PMID:15328088

  12. Expression of the RND-Type Efflux Pump AdeABC in Acinetobacter baumannii Is Regulated by the AdeRS Two-Component System

    PubMed Central

    Marchand, Isabelle; Damier-Piolle, Laurence; Courvalin, Patrice; Lambert, Thierry

    2004-01-01

    The AdeABC pump of Acinetobacter baumannii BM4454, which confers resistance to various antibiotic classes including aminoglycosides, is composed of the AdeA, AdeB, and AdeC proteins; AdeB is a member of the RND superfamily. The adeA, adeB, and adeC genes are contiguous and adjacent to adeS and adeR, which are transcribed in the opposite direction and which specify proteins homologous to sensors and regulators of two-component systems, respectively (S. Magnet, P. Courvalin, and T. Lambert, Antimicrob. Agents Chemother. 45:3375-3380, 2001). Analysis by Northern hybridization indicated that the three genes were cotranscribed, although mRNAs corresponding to adeAB and adeC were also present. Cotranscription of the two regulatory genes was demonstrated by reverse transcription-PCR. Inactivation of adeS led to aminoglycoside susceptibility. Transcripts corresponding to adeAB were not detected in susceptible A. baumannii CIP 70-10 but were present in spontaneous gentamicin-resistant mutants obtained in vitro. Analysis of these mutants revealed the substitutions Thr153→Met in AdeS downstream from the putative His-149 site of autophosphorylation, which is presumably responsible for the loss of phosphorylase activity by the sensor, and Pro116→Leu in AdeR at the first residue of the α5 helix of the receiver domain, which is involved in interactions that control the output domain of response regulators. These mutations led to constitutive expression of the pump and, thus, to antibiotic resistance. These data indicate that the AdeABC pump is cryptic in wild A. baumannii due to stringent control by the AdeRS two-component system. PMID:15328088

  13. Impact of the Staphylococcus epidermidis LytSR two-component regulatory system on murein hydrolase activity, pyruvate utilization and global transcriptional profile

    PubMed Central

    2010-01-01

    Background Staphylococcus epidermidis has emerged as one of the most important nosocomial pathogens, mainly because of its ability to colonize implanted biomaterials by forming a biofilm. Extensive studies are focused on the molecular mechanisms involved in biofilm formation. The LytSR two-component regulatory system regulates autolysis and biofilm formation in Staphylococcus aureus. However, the role of LytSR played in S. epidermidis remained unknown. Results In the present study, we demonstrated that lytSR knock-out in S. epidermidis did not alter susceptibility to Triton X-100 induced autolysis. Quantitative murein hydrolase assay indicated that disruption of lytSR in S. epidermidis resulted in decreased activities of extracellular murein hydrolases, although zymogram showed no apparent differences in murein hydrolase patterns between S. epidermidis strain 1457 and its lytSR mutant. Compared to the wild-type counterpart, 1457ΔlytSR produced slightly more biofilm, with significantly decreased dead cells inside. Microarray analysis showed that lytSR mutation affected the transcription of 164 genes (123 genes were upregulated and 41 genes were downregulated). Specifically, genes encoding proteins responsible for protein synthesis, energy metabolism were downregulated, while genes involved in amino acid and nucleotide biosynthesis, amino acid transporters were upregulated. Impaired ability to utilize pyruvate and reduced activity of arginine deiminase was observed in 1457ΔlytSR, which is consistent with the microarray data. Conclusions The preliminary results suggest that in S. epidermidis LytSR two-component system regulates extracellular murein hydrolase activity, bacterial cell death and pyruvate utilization. Based on the microarray data, it appears that lytSR inactivation induces a stringent response. In addition, LytSR may indirectly enhance biofilm formation by altering the metabolic status of the bacteria. PMID:21073699

  14. A Two-Component System (XydS/R) Controls the Expression of Genes Encoding CBM6-Containing Proteins in Response to Straw in Clostridium cellulolyticum

    PubMed Central

    Celik, Hamza; Blouzard, Jean-Charles; Voigt, Birgit; Becher, Dörte; Trotter, Valentine; Fierobe, Henri-Pierre; Tardif, Chantal; Pagès, Sandrine; de Philip, Pascale

    2013-01-01

    The composition of the cellulosomes (multi enzymatic complexes involved in the degradation of plant cell wall polysaccharides) produced by Clostridium cellulolyticum differs according to the growth substrate. In particular, the expression of a cluster of 14 hemicellulase-encoding genes (called xyl-doc) seems to be induced by the presence of straw and not of cellulose. Genes encoding a putative two-component regulation system (XydS/R) were found upstream of xyl-doc. First evidence for the involvement of the response regulator, XydR, part of this two-component system, in the expression of xyl-doc genes was given by the analysis of the cellulosomes produced by a regulator overproducing strain when grown on cellulose. Nano-LC MS/MS analysis allowed the detection of the products of all xyl-doc genes and of the product of the gene at locus Ccel_1656 predicted to bear a carbohydrate binding domain targeting hemicellulose. RT-PCR experiments further demonstrated that the regulation occurs at the transcriptional level and that all xyl-doc genes are transcriptionally linked. mRNA quantification in a regulator knock-out strain and in its complemented derivative confirmed the involvement of the regulator in the expression of xyl-doc genes and of the gene at locus Ccel_1656 in response to straw. Electrophoretic mobility shift assays using the purified regulator further demonstrated that the regulator binds to DNA regions located upstream of the first gene of the xyl-doc gene cluster and upstream of the gene at locus Ccel_1656. PMID:23418511

  15. The Hybrid Histidine Kinase LadS Forms a Multicomponent Signal Transduction System with the GacS/GacA Two-Component System in Pseudomonas aeruginosa

    PubMed Central

    Redelberger, David; Fadel, Firas; Filloux, Alain; Sivaneson, Melissa; de Bentzmann, Sophie; Bordi, Christophe

    2016-01-01

    In response to environmental changes, Pseudomonas aeruginosa is able to switch from a planktonic (free swimming) to a sessile (biofilm) lifestyle. The two-component system (TCS) GacS/GacA activates the production of two small non-coding RNAs, RsmY and RsmZ, but four histidine kinases (HKs), RetS, GacS, LadS and PA1611, are instrumental in this process. RetS hybrid HK blocks GacS unorthodox HK autophosphorylation through the formation of a heterodimer. PA1611 hybrid HK, which is structurally related to GacS, interacts with RetS in P. aeruginosa in a very similar manner to GacS. LadS hybrid HK phenotypically antagonizes the function of RetS by a mechanism that has never been investigated. The four sensors are found in most Pseudomonas species but their characteristics and mode of signaling may differ from one species to another. Here, we demonstrated in P. aeruginosa that LadS controls both rsmY and rsmZ gene expression and that this regulation occurs through the GacS/GacA TCS. We additionally evidenced that in contrast to RetS, LadS signals through GacS/GacA without forming heterodimers, either with GacS or with RetS. Instead, we demonstrated that LadS is involved in a genuine phosphorelay, which requires both transmitter and receiver LadS domains. LadS signaling ultimately requires the alternative histidine-phosphotransfer domain of GacS, which is here used as an Hpt relay by the hybrid kinase. LadS HK thus forms, with the GacS/GacA TCS, a multicomponent signal transduction system with an original phosphorelay cascade, i.e. H1LadS→D1LadS→H2GacS→D2GacA. This highlights an original strategy in which a unique output, i.e. the modulation of sRNA levels, is controlled by a complex multi-sensing network to fine-tune an adapted biofilm and virulence response. PMID:27176226

  16. The Staphylococcus aureus KdpDE Two-Component System Couples Extracellular K+ Sensing and Agr Signaling to Infection Programming ▿ † ‡

    PubMed Central

    Xue, Ting; You, Yibo; Hong, De; Sun, Haipeng; Sun, Baolin

    2011-01-01

    The Kdp system is widely distributed among bacteria. In Escherichia coli, the Kdp-ATPase is a high-affinity K+ uptake system and its expression is activated by the KdpDE two-component system in response to K+ limitation or salt stress. However, information about the role of this system in many bacteria still remains obscure. Here we demonstrate that KdpFABC in Staphylococcus aureus is not a major K+ transporter and that the main function of KdpDE is not associated with K+ transport but that instead it regulates transcription for a series of virulence factors through sensing external K+ concentrations, indicating that this bacterium might modulate its infectious status through sensing specific external K+ stimuli in different environments. Our results further reveal that S. aureus KdpDE is upregulated by the Agr/RNAIII system, which suggests that KdpDE may be an important virulence regulator coordinating the external K+ sensing and Agr signaling during pathogenesis in this bacterium. PMID:21422185

  17. Brillouin spectroscopy studies of two-component polymerizable liquid system: 2,2-bis[4-(2-hydroxymethacryloxypropoxy)phenyl]propane/benzyl methacrylate.

    PubMed

    Łapsa, K; Marcinkowska, A; Andrzejewska, E; Drozdowski, M

    2011-08-15

    Brillouin spectroscopy was used to investigate viscoelastic properties of a two-component system consisting of a high viscosity liquid (HVL) and a low viscosity liquid (LVL), both able to polymerize. The model liquids were: 2,2-bis[4-(2-hydroxymethacryloxypropoxy)phenyl]propane (abbreviated as bis-GMA, HVL) and benzyl methacrylate (BzMA, LVL). The viscosity of the system was regulated by changing the monomer ratio. Hypersonic velocity and attenuation coefficient were investigated in a temperature range covering viscoelastic relaxation process. The dependence of the longitudinal viscosity on the system composition was determined. Additionally, the Brillouin studies were accompanied by some supplementary experimental methods, like low frequency shear viscosity measurements and observations of phase transitions by differential scanning calorimetry (DSC). The investigated monomer mixtures were then polymerized in a light-induced process and the polymerization kinetic curves were measured to find the possible correlation between the viscoelastic properties of the monomer mixture (as observed by Brillouin spectroscopy) and the polymerization course. PMID:20934905

  18. Brillouin spectroscopy studies of two-component polymerizable liquid system: 2,2-Bis[4-(2-hydroxymethacryloxypropoxy)phenyl]propane/benzyl methacrylate

    NASA Astrophysics Data System (ADS)

    Łapsa, K.; Marcinkowska, A.; Andrzejewska, E.; Drozdowski, M.

    2011-08-01

    Brillouin spectroscopy was used to investigate viscoelastic properties of a two-component system consisting of a high viscosity liquid (HVL) and a low viscosity liquid (LVL), both able to polymerize. The model liquids were: 2,2-bis[4-(2-hydroxymethacryloxypropoxy)phenyl]propane (abbreviated as bis-GMA, HVL) and benzyl methacrylate (BzMA, LVL). The viscosity of the system was regulated by changing the monomer ratio. Hypersonic velocity and attenuation coefficient were investigated in a temperature range covering viscoelastic relaxation process. The dependence of the longitudinal viscosity on the system composition was determined. Additionally, the Brillouin studies were accompanied by some supplementary experimental methods, like low frequency shear viscosity measurements and observations of phase transitions by differential scanning calorimetry (DSC). The investigated monomer mixtures were then polymerized in a light-induced process and the polymerization kinetic curves were measured to find the possible correlation between the viscoelastic properties of the monomer mixture (as observed by Brillouin spectroscopy) and the polymerization course.

  19. The Pseudomonas aeruginosa CreBC two-component system plays a major role in the response to β-lactams, fitness, biofilm growth, and global regulation.

    PubMed

    Zamorano, Laura; Moyà, Bartolomé; Juan, Carlos; Mulet, Xavier; Blázquez, Jesús; Oliver, Antonio

    2014-09-01

    Pseudomonas aeruginosa is a ubiquitous versatile environmental microorganism with a remarkable ability to grow under diverse environmental conditions. Moreover, P. aeruginosa is responsible for life-threatening infections in immunocompromised and cystic fibrosis patients, as the extraordinary capacity of this pathogen to develop antimicrobial resistance dramatically limits our therapeutic arsenal. Its large genome carries an outstanding number of genes belonging to regulatory systems, including multiple two-component sensor-regulator systems that modulate the response to the different environmental stimuli. Here, we show that one of two systems, designated CreBC (carbon source responsive) and BlrAB (β-lactam resistance), might be of particular relevance. We first identified the stimuli triggering the activation of the CreBC system, which specifically responds to penicillin-binding protein 4 (PBP4) inhibition by certain β-lactam antibiotics. Second, through an analysis of a large comprehensive collection of mutants, we demonstrate an intricate interconnection between the CreBC system, the peptidoglycan recycling pathway, and the expression of the concerning chromosomal β-lactamase AmpC. Third, we show that the CreBC system, and particularly its effector inner membrane protein CreD, plays a major role in bacterial fitness and biofilm development, especially in the presence of subinhibitory concentrations of β-lactams. Finally, global transcriptomics reveals broad regulatory functions of CreBC in basic physiological aspects, particularly anaerobic respiration, in both the presence and absence of antibiotics. Therefore, the CreBC system is envisaged as a potentially interesting target for improving the efficacy of β-lactams against P. aeruginosa infections. PMID:24936599

  20. Analysis of the Activity and Regulon of the Two-Component Regulatory System Composed by Cjj81176_1484 and Cjj81176_1483 of Campylobacter jejuni

    PubMed Central

    Luethy, Paul M.; Huynh, Steven; Parker, Craig T.

    2015-01-01

    ABSTRACT Campylobacter jejuni is a leading cause of bacterial diarrheal disease and a frequent commensal of the intestinal tract in poultry and other animals. For optimal growth and colonization of hosts, C. jejuni employs two-component regulatory systems (TCSs) to monitor environmental conditions and promote proper expression of specific genes. We analyzed the potential of C. jejuni Cjj81176_1484 (Cjj1484) and Cjj81176_1483 (Cjj1483) to encode proteins of a cognate TCS that influences expression of genes possibly important for C. jejuni growth and colonization. Transcriptome analysis revealed that the regulons of the Cjj81176_1484 (Cjj1484) histidine kinase and the Cjj81176_1483 (Cjj1483) response regulator contain many common genes, suggesting that these proteins likely form a cognate TCS. We found that this TCS generally functions to repress expression of specific proteins with roles in metabolism, iron/heme acquisition, and respiration. Furthermore, the TCS repressed expression of Cjj81176_0438 and Cjj81176_0439, which had previously been found to encode a gluconate dehydrogenase complex required for commensal colonization of the chick intestinal tract. However, the TCS and other specific genes whose expression is repressed by the TCS were not required for colonization of chicks. We observed that the Cjj1483 response regulator binds target promoters in both unphosphorylated and phosphorylated forms and influences expression of some specific genes independently of the Cjj1484 histidine kinase. This work further expands the signaling mechanisms of C. jejuni and provides additional insights regarding the complex and multifactorial regulation of many genes involved in basic metabolism, respiration, and nutrient acquisition that the bacterium requires for optimal growth in different environments. IMPORTANCE Bacterial two-component regulatory systems (TCSs) link environmental cues to expression of specific genes that enable optimal bacterial growth or colonization of

  1. Expanding the regulatory network that controls nitrogen fixation in Sinorhizobium meliloti: elucidating the role of the two-component system hFixL-FxkR.

    PubMed

    Reyes-González, Alma; Talbi, Chouhra; Rodríguez, Susana; Rivera, Patricia; Zamorano-Sánchez, David; Girard, Lourdes

    2016-06-01

    In Sinorhizobium meliloti, nitrogen fixation is regulated in response to oxygen concentration through the FixL-FixJ two-component system (TCS). Besides this conserved TCS, the field isolate SM11 also encodes the hFixL-FxkR TCS, which is responsible for the microoxic response in Rhizobium etli. Through genetic and physiological assays, we evaluated the role of the hFixL-FxkR TCS in S. meliloti SM11. Our results revealed that this regulatory system activates the expression of a fixKf orthologue (fixKa), in response to low oxygen concentration. Null mutations in either hFixL or FxkR promote upregulation of fixK1, a direct target of FixJ. Furthermore, the absence of this TCS translates into higher nitrogen fixation values as well as higher expression of fixN1 in nodules. Individual mutations in each of the fixK-like regulators encoded in the S. meliloti SM11 genome do not completely restrict fixN1 or fixN2 expression, pointing towards redundancy among these regulators. Both copies of fixN are necessary to achieve optimal levels of nitrogen fixation. This work provides evidence that the hFixL-FxkR TCS is activated in response to low oxygen concentration in S. meliloti SM11 and that it negatively regulates the expression of fixK1, fixN1 and nitrogen fixation. PMID:27010660

  2. The CasKR Two-Component System Is Required for the Growth of Mesophilic and Psychrotolerant Bacillus cereus Strains at Low Temperatures

    PubMed Central

    Diomandé, Sara Esther; Chamot, Stéphanie; Antolinos, Vera; Vasai, Florian; Guinebretière, Marie-Hélène; Bornard, Isabelle; Nguyen-the, Christophe; Broussolle, Véronique

    2014-01-01

    The different strains of Bacillus cereus can grow at temperatures covering a very diverse range. Some B. cereus strains can grow in chilled food and consequently cause food poisoning. We have identified a new sensor/regulator mechanism involved in low-temperature B. cereus growth. Construction of a mutant of this two-component system enabled us to show that this system, called CasKR, is required for growth at the minimal temperature (Tmin). CasKR was also involved in optimal cold growth above Tmin and in cell survival below Tmin. Microscopic observation showed that CasKR plays a key role in cell shape during cold growth. Introducing the casKR genes in a ΔcasKR mutant restored its ability to grow at Tmin. Although it was first identified in the ATCC 14579 model strain, this mechanism has been conserved in most strains of the B. cereus group. We show that the role of CasKR in cold growth is similar in other B. cereus sensu lato strains with different growth temperature ranges, including psychrotolerant strains. PMID:24509924

  3. The Acinetobacter baumannii Two-Component System AdeRS Regulates Genes Required for Multidrug Efflux, Biofilm Formation, and Virulence in a Strain-Specific Manner

    PubMed Central

    Richmond, Grace E.; Evans, Laura P.; Anderson, Michele J.; Wand, Matthew E.; Bonney, Laura C.; Ivens, Alasdair; Chua, Kim Lee; Webber, Mark A.; Sutton, J. Mark; Peterson, Marnie L.

    2016-01-01

    ABSTRACT The opportunistic pathogen Acinetobacter baumannii is able to persist in the environment and is often multidrug resistant (MDR), causing difficulties in the treatment of infections. Here, we show that the two-component system AdeRS, which regulates the production of the AdeABC multidrug resistance efflux pump, is required for the formation of a protective biofilm in an ex vivo porcine mucosal model, which mimics a natural infection of the human epithelium. Interestingly, deletion of adeB impacted only on the ability of strain AYE to form a biofilm on plastic and only on the virulence of strain Singapore 1 for Galleria mellonella. RNA-Seq revealed that loss of AdeRS or AdeB significantly altered the transcriptional landscape, resulting in the changed expression of many genes, notably those associated with antimicrobial resistance and virulence interactions. For example, A. baumannii lacking AdeRS displayed decreased expression of adeABC, pil genes, com genes, and a pgaC-like gene, whereas loss of AdeB resulted in increased expression of pil and com genes and decreased expression of ferric acinetobactin transport system genes. These data define the scope of AdeRS-mediated regulation, show that changes in the production of AdeABC mediate important phenotypes controlled by AdeRS, and suggest that AdeABC is a viable target for antimicrobial drug and antibiofilm discovery. PMID:27094331

  4. Analysis of Two-Component Systems in Group B Streptococcus Shows That RgfAC and the Novel FspSR Modulate Virulence and Bacterial Fitness

    PubMed Central

    Faralla, Cristina; Metruccio, Matteo M.; De Chiara, Matteo; Mu, Rong; Patras, Kathryn A.; Muzzi, Alessandro; Grandi, Guido; Margarit, Immaculada; Doran, Kelly S.

    2014-01-01

    ABSTRACT Group B Streptococcus (GBS), in the transition from commensal organisms to pathogens, will encounter diverse host environments and, thus, require coordinated control of the transcriptional responses to these changes. This work was aimed at better understanding the role of two-component signal transduction systems (TCS) in GBS pathophysiology through a systematic screening procedure. We first performed a complete inventory and sensory mechanism classification of all putative GBS TCS by genomic analysis. Five TCS were further investigated by the generation of knockout strains, and in vitro transcriptome analysis identified genes regulated by these systems, ranging from 0.1% to 3% of the genome. Interestingly, two sugar phosphotransferase systems appeared to be differentially regulated in the TCS-16 knockout strain (TCS loci were numbered in order of their appearance on the chromosome), suggesting an involvement in monitoring carbon source availability. High-throughput analysis of bacterial growth on different carbon sources showed that TCS-16 was necessary for the growth of GBS on fructose-6-phosphate. Additional transcriptional analysis provided further evidence for a stimulus-response circuit where extracellular fructose-6-phosphate leads to autoinduction of TCS-16, with concomitant dramatic upregulation of the adjacent operon, which encodes a phosphotransferase system. The TCS-16-deficient strain exhibited decreased persistence in a model of vaginal colonization. All mutant strains were also characterized in a murine model of systemic infection, and inactivation of TCS-17 (also known as RgfAC) resulted in hypervirulence. Our data suggest a role for the previously unknown TCS-16, here named FspSR, in bacterial fitness and carbon metabolism during host colonization, and the data also provide experimental evidence for TCS-17/RgfAC involvement in virulence. PMID:24846378

  5. A Sensory Complex Consisting of an ATP-binding Cassette Transporter and a Two-component Regulatory System Controls Bacitracin Resistance in Bacillus subtilis*

    PubMed Central

    Dintner, Sebastian; Heermann, Ralf; Fang, Chong; Jung, Kirsten; Gebhard, Susanne

    2014-01-01

    Resistance against antimicrobial peptides in many Firmicutes bacteria is mediated by detoxification systems that are composed of a two-component regulatory system (TCS) and an ATP-binding cassette (ABC) transporter. The histidine kinases of these systems depend entirely on the transporter for sensing of antimicrobial peptides, suggesting a novel mode of signal transduction where the transporter constitutes the actual sensor. The aim of this study was to investigate the molecular mechanisms of this unusual signaling pathway in more detail, using the bacitracin resistance system BceRS-BceAB of Bacillus subtilis as an example. To analyze the proposed communication between TCS and the ABC transporter, we characterized their interactions by bacterial two-hybrid analyses and could show that the permease BceB and the histidine kinase BceS interact directly. In vitro pulldown assays confirmed this interaction, which was found to be independent of bacitracin. Because it was unknown whether BceAB-type transporters could detect their substrate peptides directly or instead recognized the peptide-target complex in the cell envelope, we next analyzed substrate binding by the transport permease, BceB. Direct and specific binding of bacitracin by BceB was demonstrated by surface plasmon resonance spectroscopy. Finally, in vitro signal transduction assays indicated that complex formation with the transporter influenced the autophosphorylation activity of the histidine kinase. Taken together, our findings clearly show the existence of a sensory complex composed of TCS and ABC transporters and provide the first functional insights into the mechanisms of stimulus perception, signal transduction, and antimicrobial resistance employed by Bce-like detoxification systems. PMID:25118291

  6. Regulation of natural competence by the orphan two-component system sensor kinase ChiS involves a non-canonical transmembrane regulator in Vibrio cholerae.

    PubMed

    Yamamoto, Shouji; Mitobe, Jiro; Ishikawa, Takahiko; Wai, Sun Nyunt; Ohnishi, Makoto; Watanabe, Haruo; Izumiya, Hidemasa

    2014-01-01

    In Vibrio cholerae, 41 chitin-inducible genes, including the genes involved in natural competence for DNA uptake, are governed by the orphan two-component system (TCS) sensor kinase ChiS. However, the mechanism by which ChiS controls the expression of these genes is currently unknown. Here, we report the involvement of a novel transcription factor termed 'TfoS' in this process. TfoS is a transmembrane protein that contains a large periplasmic domain and a cytoplasmic AraC-type DNA-binding domain, but lacks TCS signature domains. Inactivation of tfoS abolished natural competence as well as transcription of the tfoR gene encoding a chitin-induced small RNA essential for competence gene expression. A TfoS fragment containing the DNA-binding domain specifically bound to and activated transcription from the tfoR promoter. Intracellular TfoS levels were unaffected by disruption of chiS and coexpression of TfoS and ChiS in Escherichia coli recovered transcription of the chromosomally integrated tfoR::lacZ gene, suggesting that TfoS is post-translationally modulated by ChiS during transcriptional activation; however, this regulation persisted when the canonical phosphorelay residues of ChiS were mutated. The results presented here suggest that ChiS operates a chitin-induced non-canonical signal transduction cascade through TfoS, leading to transcriptional activation of tfoR. PMID:24236404

  7. Roles of two-component system AfsQ1/Q2 in regulating biosynthesis of the yellow-pigmented coelimycin P2 in Streptomyces coelicolor.

    PubMed

    Chen, Shuangshuang; Zheng, Guosong; Zhu, Hong; He, Huiqi; Chen, Lei; Zhang, Weiwen; Jiang, Weihong; Lu, Yinhua

    2016-08-01

    We previously demonstrated that in Streptomyces coelicolor two-component system AfsQ1/Q2 activates the production of the yellow-colored coelimycin P2 (also named as yCPK) on glutamate-supplemented minimal medium, and the response regulator AfsQ1 could specifically bind to the intergenic region between two structural genes, cpkA and cpkD Here, a more in-depth investigation was performed to elucidate the mechanism underlying the role of AfsQ1/Q2 in regulating coelimycin P2 biosynthesis. Deletion of afsQ1/Q2 resulted in markedly decreased expression of the whole coelimycin P2 biosynthetic gene cluster. Electrophoretic mobility shift assays revealed that AfsQ1 bound only to the target site identified previously, but not to any other promoters in the gene cluster. Mutations of AfsQ1-binding motif only resulted in drastically reduced transcription of the cpkA/B/C operon (encoding three type I polyketide synthases) and intriguingly, led to enhanced expression of some coelimcyin P2 genes, particularly accA1 and scF These results suggested the direct role of AfsQ1/Q2 in regulating coelimycin production, which is directly mediated by the structural genes, but not the cluster-situated regulatory genes, and also implied that other unknown mechanisms may be involved in AfsQ1/Q2-mediated regulation of coelimycin P2 biosynthesis. PMID:27313101

  8. Expression of the genes encoding the CasK/R two-component system and the DesA desaturase during Bacillus cereus cold adaptation.

    PubMed

    Diomandé, Sara Esther; Doublet, Bénédicte; Vasaï, Florian; Guinebretière, Marie-Hélène; Broussolle, Véronique; Brillard, Julien

    2016-08-01

    Two-component systems (TCS) allow a cell to elaborate a variety of adaptive responses to environment changes. The recently discovered CasK/R TCS plays a role in the optimal unsaturation of fatty acids necessary for cold adaptation of the foodborne-pathogen Bacillus cereus Here, we showed that the promoter activity of the operon encoding this TCS was repressed during growth at low temperature in the stationary phase in the parental strain when compared to the casK/R mutant, suggesting that CasR negatively regulates the activity of its own promoter in these conditions. The promoter activity of the desA gene encoding the Δ5 fatty acid desaturase, providing unsaturated fatty acids (UFAs) required for low temperature adaptation, was repressed in the casK/R mutant grown at 12°C versus 37°C. This result suggests that CasK/R activates desA expression during B. cereus growth at low temperature, allowing an optimal unsaturation of the fatty acids. In contrast, desA expression was repressed during the lag phase at low temperature in presence of UFAs, in a CasK/R-independent manner. Our findings confirm that the involvement of this major TCS in B. cereus cold adaptation is linked to the upregulation of a fatty acid desaturase. PMID:27435329

  9. Genome-Wide Expression Profiling of Soybean Two-Component System Genes in Soybean Root and Shoot Tissues under Dehydration Stress

    PubMed Central

    Le, Dung Tien; Nishiyama, Rie; Watanabe, Yasuko; Mochida, Keiichi; Yamaguchi-Shinozaki, Kazuko; Shinozaki, Kazuo; Tran, Lam-Son Phan

    2011-01-01

    Two-component systems (TCSs) play vital functions in the adaptation of plants to environmental stresses. To identify soybean TCS genes involved in the regulation of drought stress response, we performed tissue-specific expression profiling of all 83 putative TCS genes in plants subjected to dehydration. Under well-watered conditions, the majority of soybean TCS genes were expressed higher in the root tissues. Additionally, a high variability in transcript abundance was observed for the TCS genes in both roots and shoots. Under dehydration, TCS genes were more responsive in shoots than in roots. Further analysis indicated that 50% more TCS genes were repressed by dehydration than induced. Specifically, 18 genes were induced by 2-fold or more, whereas 33 genes were down-regulated at least 2-fold by dehydration. TCS genes putatively involved in cytokinin and ethylene signallings strongly responded to dehydration, suggesting that crosstalk exists between different hormonal and stress pathways. Our study provides the first glance into the complex regulatory roles of soybean TCSs underlying their functions in response to dehydration. Additionally, these systematic expression analyses identified excellent dehydration-responsive candidate genes to further clarify soybean TCS functions in drought response and to enable the development of improved drought tolerance in transgenic soybeans. PMID:21208938

  10. Genome-wide identification, phylogeny, duplication, and expression analyses of two-component system genes in Chinese cabbage (Brassica rapa ssp. pekinensis).

    PubMed

    Liu, Zhenning; Zhang, Mei; Kong, Lijun; Lv, Yanxia; Zou, Minghua; Lu, Gang; Cao, Jiashu; Yu, Xiaolin

    2014-08-01

    In plants, a two component system (TCS) composed of sensor histidine kinases (HKs), histidine phosphotransfer proteins (HPs), and response regulators (RRs) has been employed in cytokinin signal transduction. A TCS exhibits important functions in diverse biological processes, including plant growth, development, and response to environmental stimuli. Conducting an exhaustive search of the Chinese cabbage genome, a total of 20 HK(L) (11 HKs and 9 HKLs), 8 HP (7 authentic and 1 pseudo), and 57 RR (21 Type-A, 17 Type-B, 4 Type-C, and 15 pseudo) proteins were identified. The structures, conserved domains, and phylogenetic relationships of these protein-coding genes were analysed in detail. The duplications, evolutionary patterns, and divergence of the TCS genes were investigated. The transcription levels of TCS genes in various tissues, organs, and developmental stages were further analysed to obtain information of the functions of these genes. Cytokinin-related binding elements were found in the putative promoter regions of Type-A BrRR genes. Furthermore, gene expression patterns to adverse environmental stresses (drought and high salinity) and exogenous phytohormones (tZ and ABA) were investigated. Numerous stress-responsive candidate genes were obtained. Our systematic analyses provided insights into the characterization of the TCS genes in Chinese cabbage and basis for further functional studies of such genes. PMID:24585003

  11. Two overlapping two-component systems in Xanthomonas oryzae pv. oryzae contribute to full fitness in rice by regulating virulence factors expression

    PubMed Central

    Zheng, Dehong; Yao, Xiaoyan; Duan, Meng; Luo, Yufeng; Liu, Biao; Qi, Pengyuan; Sun, Ming; Ruan, Lifang

    2016-01-01

    Two-component signal transduction systems (TCSs) are widely used by bacteria to adapt to the environment. In the present study, StoS (stress tolerance-related oxygen sensor) and SreKRS (salt response kinase, regulator, and sensor) were found to positively regulate extracellular polysaccharide (EPS) production and swarming in the rice pathogen Xanthomonas oryzae pv. oryzae (Xoo). Surprisingly, the absence of stoS or sreKRS did not attenuate virulence. To better understand the intrinsic functions of StoS and SreKRS, quantitative proteomics isobaric tags for relative and absolute quantitation (iTRAQ) was employed. Consistent with stoS and sreK mutants exhibiting a similar phenotype, the signalling circuits of StoS and SreKRS overlapped. Carbohydrate metabolism proteins and chemotaxis proteins, which could be responsible for EPS and swarming regulation, respectively, were reprogrammed in stoS and sreK mutants. Moreover, StoS and SreKRS demonstrated moderate expression of the major virulence factor, hypersensitive response and pathogenicity (Hrp) proteins through the HrpG-HrpX circuit. Most importantly, Xoo equipped with StoS and SreKRS outcompetes strains without StoS or SreKRS in co-infected rice and grows outside the host. Therefore, we propose that StoS and SreKRS adopt a novel strategy involving the moderation of Hrp protein expression and the promotion of EPS and motility to adapt to the environment. PMID:26957113

  12. Characterization of the role of the RadS/RadR two-component system in the radiation resistance of Deinococcus radiodurans.

    PubMed

    Desai, Shruti S; Rajpurohit, Yogendra S; Misra, Hari S; Deobagkar, Dileep N

    2011-10-01

    Deinococcus radiodurans shows extraordinary tolerance to DNA damage, and exhibits differential gene expression and protein recycling. A putative response regulator, the DRB0091 (RadR) ORF, was identified from a pool of DNA-binding proteins induced in response to gamma radiation in this bacterium. radR is located upstream of drB0090, which encodes a putative sensor histidine kinase (RadS) on the megaplasmid. Deletion of these genes both individually and together resulted in hypersensitivity to DNA-damaging agents and a delayed or altered double-strand break repair. A ΔradRradS double mutant and a ΔradR single mutant showed nearly identical responses to gamma radiation and UVC. Wild-type RadR and RadS complemented the corresponding mutant strains, but also exhibited significant cross-complementation, albeit at lower doses of gamma radiation. The radS transcript was not detected in the ΔradR mutant, suggesting the existence of a radRS operon. Recombinant RadS was autophosphorylated and could catalyse the transfer of γ phosphate from ATP to RadR in vitro. These results indicated the functional interaction of RadS and RadR, and suggested a role for the RadS/RadR two-component system in the radiation resistance of this bacterium. PMID:21737498

  13. Requirement of the Lactobacillus casei MaeKR two-component system for L-malic acid utilization via a malic enzyme pathway.

    PubMed

    Landete, José María; García-Haro, Luisa; Blasco, Amalia; Manzanares, Paloma; Berbegal, Carmen; Monedero, Vicente; Zúñiga, Manuel

    2010-01-01

    Lactobacillus casei can metabolize L-malic acid via malolactic enzyme (malolactic fermentation [MLF]) or malic enzyme (ME). Whereas utilization of L-malic acid via MLF does not support growth, the ME pathway enables L. casei to grow on L-malic acid. In this work, we have identified in the genomes of L. casei strains BL23 and ATCC 334 a cluster consisting of two diverging operons, maePE and maeKR, encoding a putative malate transporter (maeP), an ME (maeE), and a two-component (TC) system belonging to the citrate family (maeK and maeR). Homologous clusters were identified in Enterococcus faecalis, Streptococcus agalactiae, Streptococcus pyogenes, and Streptococcus uberis. Our results show that ME is essential for L-malic acid utilization in L. casei. Furthermore, deletion of either the gene encoding the histidine kinase or the response regulator of the TC system resulted in the loss of the ability to grow on L-malic acid, thus indicating that the cognate TC system regulates and is essential for the expression of ME. Transcriptional analyses showed that expression of maeE is induced in the presence of L-malic acid and repressed by glucose, whereas TC system expression was induced by L-malic acid and was not repressed by glucose. DNase I footprinting analysis showed that MaeR binds specifically to a set of direct repeats [5'-TTATT(A/T)AA-3'] in the mae promoter region. The location of the repeats strongly suggests that MaeR activates the expression of the diverging operons maePE and maeKR where the first one is also subjected to carbon catabolite repression. PMID:19897756

  14. Molecular Characterization of a Theta Replication Plasmid and Its Use for Development of a Two-Component Food-Grade Cloning System for Lactococcus lactis

    PubMed Central

    Émond, Éric; Lavallée, Richard; Drolet, Geneviève; Moineau, Sylvain; LaPointe, Gisèle

    2001-01-01

    pCD4, a small, highly stable theta-replicating lactococcal plasmid, was used to develop a food-grade cloning system. Sequence analysis revealed five open reading frames and two putative cis-acting regions. None appears to code for undesirable phenotypes with regard to food applications. Functional analysis of the replication module showed that only the cis-acting ori region and the repB gene coding for the replication initiator protein were needed for the stable replication and maintenance of pCD4 derivatives in Lactococcus lactis. A two-component food-grade cloning system was derived from the pCD4 replicon. The vector pVEC1, which carries the functional pCD4 replicon, is entirely made up of L. lactis DNA and has no selection marker. The companion pCOM1 is a repB-deficient pCD4 derivative that carries an erythromycin resistance gene as a dominant selection marker. The pCOM1 construct can only replicate in L. lactis if trans complemented by the RepB initiator provided by pVEC1. Since only the cotransformants that carry both pVEC1 and pCOM1 can survive on plates containing erythromycin, pCOM1 can be used transiently to select cells that have acquired pVEC1. Due to the intrinsic incompatibility between these plasmids, pCOM1 can be readily cured from the cells grown on an antibiotic-free medium after the selection step. The system was used to introduce a phage resistance mechanism into the laboratory strain MG1363 of L. lactis and two industrial strains. The introduction of the antiphage barrier did not alter the wild-type plasmid profile of the industrial strains. The phenotype was stable after 100 generations and conferred an effective resistance phenotype against phages of the 936 and c2 species. PMID:11282624

  15. Regulation of hrp genes and type III protein secretion in Erwinia amylovora by HrpX/HrpY, a novel two-component system, and HrpS.

    PubMed

    Wei, Z; Kim, J F; Beer, S V

    2000-11-01

    Two novel regulatory components, hrpX and hrpY, of the hrp system of Erwinia amylovora were identified. The hrpXY operon is expressed in rich media, but its transcription is increased threefold by low pH, nutrient, and temperature levels--conditions that mimic the plant apoplast. hrpXY is autoregulated and directs the expression of hrpL; hrpL, in turn, activates transcription of other loci in the hrp gene cluster (Z.-M. Wei and S. V. Beer, J. Bacteriol. 177:6201-6210, 1995). The deduced amino -acid sequences of hrpX and hrpY are similar to bacterial two-component regulators including VsrA/VsrD of Pseudomonas (Ralstonia) solanacearum, DegS/DegU of Bacillus subtilis, and UhpB/UhpA and NarX/NarP, NarL of Escherichia coli. The N-terminal signal-input domain of HrpX contains PAS domain repeats. hrpS, located downstream of hrpXY, encodes a protein with homology to WtsA (HrpS) of Erwinia (Pantoea) stewartii, HrpR and HrpS of Pseudomonas syringae, and other delta54-dependent, enhancer-binding proteins. Transcription of hrpS also is induced under conditions that mimic the plant apoplast. However, hrpS is not autoregulated, and its expression is not affected by hrpXY. When hrpS or hrpL were provided on multicopy plasmids, both hrpX and hrpY mutants recovered the ability to elicit the hypersensitive reaction in tobacco. This confirms that hrpS and hrpL are not epistatic to hrpXY. A model of the regulatory cascades leading to the induction of the E. amylovora type III system is proposed. PMID:11059492

  16. The Two-Component Signal Transduction System CopRS of Corynebacterium glutamicum Is Required for Adaptation to Copper-Excess Stress

    PubMed Central

    Schelder, Stephanie; Zaade, Daniela; Litsanov, Boris; Bott, Michael; Brocker, Melanie

    2011-01-01

    Copper is an essential cofactor for many enzymes but at high concentrations it is toxic for the cell. Copper ion concentrations ≥50 µM inhibited growth of Corynebacterium glutamicum. The transcriptional response to 20 µM Cu2+ was studied using DNA microarrays and revealed 20 genes that showed a ≥ 3-fold increased mRNA level, including cg3281-cg3289. Several genes in this genomic region code for proteins presumably involved in the adaption to copper-induced stress, e. g. a multicopper oxidase (CopO) and a copper-transport ATPase (CopB). In addition, this region includes the copRS genes (previously named cgtRS9) which encode a two-component signal transduction system composed of the histidine kinase CopS and the response regulator CopR. Deletion of the copRS genes increased the sensitivity of C. glutamicum towards copper ions, but not to other heavy metal ions. Using comparative transcriptome analysis of the ΔcopRS mutant and the wild type in combination with electrophoretic mobility shift assays and reporter gene studies the CopR regulon and the DNA-binding motif of CopR were identified. Evidence was obtained that CopR binds only to the intergenic region between cg3285 (copR) and cg3286 in the genome of C. glutamicum and activates expression of the divergently oriented gene clusters cg3285-cg3281 and cg3286-cg3289. Altogether, our data suggest that CopRS is the key regulatory system in C. glutamicum for the extracytoplasmic sensing of elevated copper ion concentrations and for induction of a set of genes capable of diminishing copper stress. PMID:21799779

  17. Potentiation of Aminoglycoside Activity in Pseudomonas aeruginosa by Targeting the AmgRS Envelope Stress-Responsive Two-Component System.

    PubMed

    Poole, Keith; Gilmour, Christie; Farha, Maya A; Mullen, Erin; Lau, Calvin Ho-Fung; Brown, Eric D

    2016-06-01

    A screen for agents that potentiated the activity of paromomycin (PAR), a 4,5-linked aminoglycoside (AG), against wild-type Pseudomonas aeruginosa identified the RNA polymerase inhibitor rifampin (RIF). RIF potentiated additional 4,5-linked AGs, such as neomycin and ribostamycin, but not the clinically important 4,6-linked AGs amikacin and gentamicin. Potentiation was absent in a mutant lacking the AmgRS envelope stress response two-component system (TCS), which protects the organism from AG-generated membrane-damaging aberrant polypeptides and, thus, promotes AG resistance, an indication that RIF was acting via this TCS in potentiating 4,5-linked AG activity. Potentiation was also absent in a RIF-resistant RNA polymerase mutant, consistent with its potentiation of AG activity being dependent on RNA polymerase perturbation. PAR-inducible expression of the AmgRS-dependent genes htpX and yccA was reduced by RIF, suggesting that AG activation of this TCS was compromised by this agent. Still, RIF did not compromise the membrane-protective activity of AmgRS, an indication that it impacted some other function of this TCS. RIF potentiated the activities of 4,5-linked AGs against several AG-resistant clinical isolates, in two cases also potentiating the activity of the 4,6-linked AGs. These cases were, in one instance, explained by an observed AmgRS-dependent expression of the MexXY multidrug efflux system, which accommodates a range of AGs, with RIF targeting of AmgRS undermining mexXY expression and its promotion of resistance to 4,5- and 4,6-linked AGs. Given this link between AmgRS, MexXY expression, and pan-AG resistance in P. aeruginosa, RIF might be a useful adjuvant in the AG treatment of P. aeruginosa infections. PMID:27021319

  18. Expression of Uptake Hydrogenase and Molybdenum Nitrogenase in Rhodobacter capsulatus Is Coregulated by the RegB-RegA Two-Component Regulatory System

    PubMed Central

    Elsen, Sylvie; Dischert, Wanda; Colbeau, Annette; Bauer, Carl E.

    2000-01-01

    Purple photosynthetic bacteria are capable of generating cellular energy from several sources, including photosynthesis, respiration, and H2 oxidation. Under nutrient-limiting conditions, cellular energy can be used to assimilate carbon and nitrogen. This study provides the first evidence of a molecular link for the coregulation of nitrogenase and hydrogenase biosynthesis in an anoxygenic photosynthetic bacterium. We demonstrated that molybdenum nitrogenase biosynthesis is under the control of the RegB-RegA two-component regulatory system in Rhodobacter capsulatus. Footprint analyses and in vivo transcription studies showed that RegA indirectly activates nitrogenase synthesis by binding to and activating the expression of nifA2, which encodes one of the two functional copies of the nif-specific transcriptional activator, NifA. Expression of nifA2 but not nifA1 is reduced in the reg mutants up to eightfold under derepressing conditions and is also reduced under repressing conditions. Thus, although NtrC is absolutely required for nifA2 expression, RegA acts as a coactivator of nifA2. We also demonstrated that in reg mutants, [NiFe]hydrogenase synthesis and activity are increased up to sixfold. RegA binds to the promoter of the hydrogenase gene operon and therefore directly represses its expression. Thus, the RegB-RegA system controls such diverse processes as energy-generating photosynthesis and H2 oxidation, as well as the energy-demanding processes of N2 fixation and CO2 assimilation. PMID:10781552

  19. The Essential yhcSR Two-Component Signal Transduction System Directly Regulates the lac and opuCABCD Operons of Staphylococcus aureus

    PubMed Central

    Yan, Meiying; Hall, Jeffrey W.; Yang, Junshu; Ji, Yinduo

    2012-01-01

    Our previous studies suggested that the essential two-component signal transduction system, YhcSR, regulates the opuCABCD operon at the transcriptional level, and the Pspac-driven opuCABCD partially complements the lethal effects of yhcS antisense RNA expression in Staphylococcus aureus. However, the reason why yhcSR regulon is required for growth is still unclear. In this report, we present that the lac and opuC operons are directly transcriptionally regulated by YhcSR. Using real-time RT-PCR we showed that the down-regulation of yhcSR expression affected the transcription of lacA encoding galactose-6-phosphotase isomerase subunit LacA, and opuCA encoding a subunit of a glycine betaine/carnitine/choline ABC transporter. Promoter-lux reporter fusion studies further confirmed the transcriptional regulation of lac by YhcSR. Gel shift assays revealed that YhcR binds to the promoter regions of the lac and opuC operons. Moreover, the Pspac-driven lacABC expression in trans was able to partially complement the lethal effect of induced yhcS antisense RNA. Likewise, the Pspac-driven opuCABCD expression in trans complemented the growth defect of S. aureus in a high osmotic strength medium during the depletion of YhcSR. Taken together, the above data indicate that the yhcSR system directly regulates the expression of lac and opuC operons, which, in turn, may be partially associated with the essentiality of yhcSR in S. aureus. These results provide a new insight into the biological functions of the yhcSR, a global regulator. PMID:23226327

  20. Unique Biofilm Signature, Drug Susceptibility and Decreased Virulence in Drosophila through the Pseudomonas aeruginosa Two-Component System PprAB

    PubMed Central

    Giraud, Caroline; Bernard, Christophe S.; Calderon, Virginie; Ewald, Friederike; Plésiat, Patrick; Nguyen, Cathy; Grunwald, Didier; Attree, Ina; Jeannot, Katy; Fauvarque, Marie-Odile

    2012-01-01

    Bacterial biofilm is considered as a particular lifestyle helping cells to survive hostile environments triggered by a variety of signals sensed and integrated through adequate regulatory pathways. Pseudomonas aeruginosa, a Gram-negative bacterium causing severe infections in humans, forms biofilms and is a fantastic example for fine-tuning of the transition between planktonic and community lifestyles through two-component systems (TCS). Here we decipher the regulon of the P. aeruginosa response regulator PprB of the TCS PprAB. We identified genes under the control of this TCS and once this pathway is activated, analyzed and dissected at the molecular level the PprB-dependent phenotypes in various models. The TCS PprAB triggers a hyper-biofilm phenotype with a unique adhesive signature made of BapA adhesin, a Type 1 secretion system (T1SS) substrate, CupE CU fimbriae, Flp Type IVb pili and eDNA without EPS involvement. This unique signature is associated with drug hyper-susceptibility, decreased virulence in acutely infected flies and cytotoxicity toward various cell types linked to decreased Type III secretion (T3SS). Moreover, once the PprB pathway is activated, decreased virulence in orally infected flies associated with enhanced biofilm formation and dissemination defect from the intestinal lumen toward the hemolymph compartment is reported. PprB may thus represent a key bacterial adaptation checkpoint of multicellular and aggregative behavior triggering the production of a unique matrix associated with peculiar antibiotic susceptibility and attenuated virulence, a particular interesting breach for therapeutic intervention to consider in view of possible eradication of P. aeruginosa biofilm-associated infections. PMID:23209420

  1. Two-component auroral electrojet

    SciTech Connect

    Kamide, Y.

    1982-10-01

    By using the AL index for one year as well as some of the IMS meridian chain records, the longitudinal center of the substorm westward electrojet is examined. Although on the average AL is most often dominated by stations located near 0300 MLT, the westward electrojet during the expansion and maximum phase of substorms tends to be centered in the premidnight to early morning sector, and, during the recovery phase, it is most intense in morning hours. It is suggested that the substorm-associated westward electrojet consists of two components which have different characteristic times; one produced mainly by Hall condutivity enhancements which dominate in the midnight sector and the other one by southward electric fields in the morning sector.

  2. Signaling mechanism by the Staphylococcus aureus two-component system LytSR: role of acetyl phosphate in bypassing the cell membrane electrical potential sensor LytS

    PubMed Central

    Patel, Kevin; Golemi-Kotra, Dasantila

    2016-01-01

    The two-component system LytSR has been linked to the signal transduction of cell membrane electrical potential perturbation and is involved in the adaptation of Staphylococcus aureus to cationic antimicrobial peptides. It consists of a membrane-bound histidine kinase, LytS, which belongs to the family of multiple transmembrane-spanning domains receptors, and a response regulator, LytR, which belongs to the novel family of non-helix-turn-helix DNA-binding domain proteins. LytR regulates the expression of cidABC and lrgAB operons, the gene products of which are involved in programmed cell death and lysis. In vivo studies have demonstrated involvement of two overlapping regulatory networks in regulating the lrgAB operon, both depending on LytR. One regulatory network responds to glucose metabolism and the other responds to changes in the cell membrane potential. Herein, we show that LytS has autokinase activity and can catalyze a fast phosphotransfer reaction, with 50% of its phosphoryl group lost within 1 minute of incubation with LytR. LytS has also phosphatase activity. Notably, LytR undergoes phosphorylation by acetyl phosphate at a rate that is 2-fold faster than the phosphorylation by LytS. This observation is significant in lieu of the in vivo observations that regulation of the lrgAB operon is LytR-dependent in the presence of excess glucose in the medium. The latter condition does not lead to perturbation of the cell membrane potential but rather to the accumulation of acetate in the cell. Our study provides insights into the molecular basis for regulation of lrgAB in a LytR-dependent manner under conditions that do not involve sensing by LytS. PMID:27127614

  3. Signaling mechanism by the Staphylococcus aureus two-component system LytSR: role of acetyl phosphate in bypassing the cell membrane electrical potential sensor LytS.

    PubMed

    Patel, Kevin; Golemi-Kotra, Dasantila

    2015-01-01

    The two-component system LytSR has been linked to the signal transduction of cell membrane electrical potential perturbation and is involved in the adaptation of Staphylococcus aureus to cationic antimicrobial peptides. It consists of a membrane-bound histidine kinase, LytS, which belongs to the family of multiple transmembrane-spanning domains receptors, and a response regulator, LytR, which belongs to the novel family of non-helix-turn-helix DNA-binding domain proteins. LytR regulates the expression of cidABC and lrgAB operons, the gene products of which are involved in programmed cell death and lysis. In vivo studies have demonstrated involvement of two overlapping regulatory networks in regulating the lrgAB operon, both depending on LytR. One regulatory network responds to glucose metabolism and the other responds to changes in the cell membrane potential. Herein, we show that LytS has autokinase activity and can catalyze a fast phosphotransfer reaction, with 50% of its phosphoryl group lost within 1 minute of incubation with LytR. LytS has also phosphatase activity. Notably, LytR undergoes phosphorylation by acetyl phosphate at a rate that is 2-fold faster than the phosphorylation by LytS. This observation is significant in lieu of the in vivo observations that regulation of the lrgAB operon is LytR-dependent in the presence of excess glucose in the medium. The latter condition does not lead to perturbation of the cell membrane potential but rather to the accumulation of acetate in the cell. Our study provides insights into the molecular basis for regulation of lrgAB in a LytR-dependent manner under conditions that do not involve sensing by LytS. PMID:27127614

  4. Involvement of the CasK/R two-component system in optimal unsaturation of the Bacillus cereus fatty acids during low-temperature growth.

    PubMed

    Diomandé, Sara Esther; Nguyen-the, Christophe; Abee, Tjakko; Tempelaars, Marcel H; Broussolle, Véronique; Brillard, Julien

    2015-11-20

    Bacillus cereus sensu lato is composed of a set of ubiquitous strains including human pathogens that can survive a range of food processing conditions, grow in refrigerated food, and sometimes cause food poisoning. We previously identified the two-component system CasK/R that plays a key role in cold adaptation. To better understand the CasK/R-controlled mechanisms that support low-temperature adaptation, we performed a transcriptomic analysis on the ATCC 14579 strain and its isogenic ∆casK/R mutant grown at 12°C. Several genes involved in fatty acid (FA) metabolism were downregulated in the mutant, including desA and desB encoding FA acyl-lipid desaturases that catalyze the formation of a double-bond on the FA chain in positions ∆5 and ∆10, respectively. A lower proportion of FAs presumably unsaturated by DesA was observed in the ΔcasK/R strain compared to the parental strain while no difference was found for FAs presumably unsaturated by DesB. Addition of phospholipids from egg yolk lecithin rich in unsaturated FAs, to growth medium, abolished the cold-growth impairment of ΔcasK/R suggesting that exogenous unsaturated FAs can support membrane-level modifications and thus compensate for the decreased production of these FAs in the B. cereus ∆casK/R mutant during growth at low temperature. Our findings indicate that CasK/R is involved in the regulation of FA metabolism, and is necessary for cold adaptation of B. cereus unless an exogenous source of unsaturated FAs is available. PMID:25987542

  5. A survey of HK, HPt, and RR domains and their organization in two-component systems and phosphorelay proteins of organisms with fully sequenced genomes

    PubMed Central

    Salvado, Baldiri; Vilaprinyo, Ester; Sorribas, Albert

    2015-01-01

    Two Component Systems and Phosphorelays (TCS/PR) are environmental signal transduction cascades in prokaryotes and, less frequently, in eukaryotes. The internal domain organization of proteins and the topology of TCS/PR cascades play an important role in shaping the responses of the circuits. It is thus important to maintain updated censuses of TCS/PR proteins in order to identify the various topologies used by nature and enable a systematic study of the dynamics associated with those topologies. To create such a census, we analyzed the proteomes of 7,609 organisms from all domains of life with fully sequenced and annotated genomes. To begin, we survey each proteome searching for proteins containing domains that are associated with internal signal transmission within TCS/PR: Histidine Kinase (HK), Response Regulator (RR) and Histidine Phosphotranfer (HPt) domains, and analyze how these domains are arranged in the individual proteins. Then, we find all types of operon organization and calculate how much more likely are proteins that contain TCS/PR domains to be coded by neighboring genes than one would expect from the genome background of each organism. Finally, we analyze if the fusion of domains into single TCS/PR proteins is more frequently observed than one might expect from the background of each proteome. We find 50 alternative ways in which the HK, HPt, and RR domains are observed to organize into single proteins. In prokaryotes, TCS/PR coding genes tend to be clustered in operons. 90% of all proteins identified in this study contain just one of the three domains, while 8% of the remaining proteins combine one copy of an HK, a RR, and/or an HPt domain. In eukaryotes, 25% of all TCS/PR proteins have more than one domain. These results might have implications for how signals are internally transmitted within TCS/PR cascades. These implications could explain the selection of the various designs in alternative circumstances. PMID:26339559

  6. Manipulation of the anoxic metabolism in Escherichia coli by ArcB deletion variants in the ArcBA two-component system.

    PubMed

    Bidart, Gonzalo N; Ruiz, Jimena A; de Almeida, Alejandra; Méndez, Beatriz S; Nikel, Pablo I

    2012-12-01

    Bioprocesses conducted under conditions with restricted O(2) supply are increasingly exploited for the synthesis of reduced biochemicals using different biocatalysts. The model facultative anaerobe Escherichia coli has elaborate sensing and signal transduction mechanisms for redox control in response to the availability of O(2) and other electron acceptors. The ArcBA two-component system consists of ArcB, a membrane-associated sensor kinase, and ArcA, the cognate response regulator. The tripartite hybrid kinase ArcB possesses a transmembrane, a PAS, a primary transmitter (H1), a receiver (D1), and a phosphotransfer (H2) domain. Metabolic fluxes were compared under anoxic conditions in a wild-type E. coli strain, its ΔarcB derivative, and two partial arcB deletion mutants in which ArcB lacked either the H1 domain or the PAS-H1-D1 domains. These analyses revealed that elimination of different segments in ArcB determines a distinctive distribution of d-glucose catabolic fluxes, different from that observed in the ΔarcB background. Metabolite profiles, enzyme activity levels, and gene expression patterns were also investigated in these strains. Relevant alterations were observed at the P-enol-pyruvate/pyruvate and acetyl coenzyme A metabolic nodes, and the formation of reduced fermentation metabolites, such as succinate, d-lactate, and ethanol, was favored in the mutant strains to different extents compared to the wild-type strain. These phenotypic traits were associated with altered levels of the enzymatic activities operating at these nodes, as well as with elevated NADH/NAD(+) ratios. Thus, targeted modification of global regulators to obtain different metabolic flux distributions under anoxic conditions is emerging as an attractive tool for metabolic engineering purposes. PMID:23064346

  7. Manipulation of the Anoxic Metabolism in Escherichia coli by ArcB Deletion Variants in the ArcBA Two-Component System

    PubMed Central

    Bidart, Gonzalo N.; Ruiz, Jimena A.; de Almeida, Alejandra; Méndez, Beatriz S.

    2012-01-01

    Bioprocesses conducted under conditions with restricted O2 supply are increasingly exploited for the synthesis of reduced biochemicals using different biocatalysts. The model facultative anaerobe Escherichia coli has elaborate sensing and signal transduction mechanisms for redox control in response to the availability of O2 and other electron acceptors. The ArcBA two-component system consists of ArcB, a membrane-associated sensor kinase, and ArcA, the cognate response regulator. The tripartite hybrid kinase ArcB possesses a transmembrane, a PAS, a primary transmitter (H1), a receiver (D1), and a phosphotransfer (H2) domain. Metabolic fluxes were compared under anoxic conditions in a wild-type E. coli strain, its ΔarcB derivative, and two partial arcB deletion mutants in which ArcB lacked either the H1 domain or the PAS-H1-D1 domains. These analyses revealed that elimination of different segments in ArcB determines a distinctive distribution of d-glucose catabolic fluxes, different from that observed in the ΔarcB background. Metabolite profiles, enzyme activity levels, and gene expression patterns were also investigated in these strains. Relevant alterations were observed at the P-enol-pyruvate/pyruvate and acetyl coenzyme A metabolic nodes, and the formation of reduced fermentation metabolites, such as succinate, d-lactate, and ethanol, was favored in the mutant strains to different extents compared to the wild-type strain. These phenotypic traits were associated with altered levels of the enzymatic activities operating at these nodes, as well as with elevated NADH/NAD+ ratios. Thus, targeted modification of global regulators to obtain different metabolic flux distributions under anoxic conditions is emerging as an attractive tool for metabolic engineering purposes. PMID:23064346

  8. Peptidoglycan metabolism is controlled by the WalRK (YycFG) and PhoPR two-component systems in phosphate-limited Bacillus subtilis cells.

    PubMed

    Bisicchia, Paola; Lioliou, Efthimia; Noone, David; Salzberg, Letal I; Botella, Eric; Hübner, Sebastian; Devine, Kevin M

    2010-02-01

    In Bacillus subtilis, the WalRK (YycFG) two-component system controls peptidoglycan metabolism in exponentially growing cells while PhoPR controls the response to phosphate limitation. Here we examine the roles of WalRK and PhoPR in peptidoglycan metabolism in phosphate-limited cells. We show that B. subtilis cells remain viable in a phosphate-limited state for an extended period and resume growth rapidly upon phosphate addition, even in the absence of a PhoPR-mediated response. Peptidoglycan synthesis occurs in phosphate-limited wild-type cells at approximately 27% the rate of exponentially growing cells, and at approximately 18% the rate of exponentially growing cells in the absence of PhoPR. In phosphate-limited cells, the WalRK regulon genes yocH, cwlO(yvcE), lytE and ydjM are expressed in a manner that is dependent on the WalR recognition sequence and deleting these genes individually reduces the rate of peptidoglycan synthesis. We show that ydjM expression can be activated by PhoP approximately P in vitro and that PhoP occupies its promoter in phosphate-limited cells. However, iseA(yoeB) expression cannot be repressed by PhoP approximately P in vitro, but can be repressed by non-phosphorylated WalR in vitro. Therefore, we conclude that peptidoglycan metabolism is controlled by both WalRK and PhoPR in phosphate-limited B. subtilis cells. PMID:20487291

  9. A Two-Component Regulatory System, CsrR-CsrS, Represses Expression of Three Streptococcus pyogenes Virulence Factors, Hyaluronic Acid Capsule, Streptolysin S, and Pyrogenic Exotoxin B

    PubMed Central

    Heath, Andrew; DiRita, Victor J.; Barg, Neil L.; Engleberg, N. Cary

    1999-01-01

    Certain Tn916 insertions in the chromosome of an M1-type, nonmucoid Streptococcus pyogenes isolate (MGAS166) were previously shown to result in stable mucoidy with increased expression of the capsular synthetic genes. The transposon insertions in these strains are directly upstream of an apparent operon encoding a two-component regulatory system, designated csrR-csrS. Compared with MGAS166, these mucoid mutants are more hemolytic and cause significantly more tissue damage in a murine model of skin infection. To extend these observations, we constructed an in-frame deletion in the gene encoding the response regulator, csrR, and we evaluated the expression of other known S. pyogenes virulence factors. We discovered that csrR mutants have enhanced transcription of sagA, a gene associated with streptolysin S (SLS) and speB, the gene encoding pyrogenic exotoxin B (SpeB). The mutants also express substantially higher SLS activity and SpeB antigen in late-exponential-phase cultures. There is no change in expression of emm, scpA, sic, or cpa (genes encoding other S. pyogenes virulence factors). CsrR− strains but not the wild-type parental strain produce necrotizing lesions in a mouse model of subcutaneous infection. A double mutant with deletions in both csrR and the capsular synthesis genes caused fewer and smaller necrotic skin lesions than the csrR mutants. However, this nonmucoid csrR strain was more likely than the wild type to yield necrotic lesions, suggesting that mucoidy contributes to virulence in this model of infection but that there are other csrR-regulated factors involved in the production of necrotic lesions. PMID:10496909

  10. A Moraxella catarrhalis Two-Component Signal Transduction System Necessary for Growth in Liquid Media Affects Production of Two Lysozyme Inhibitors

    PubMed Central

    Joslin, Stephanie N.; Pybus, Christine; Labandeira-Rey, Maria; Evans, Amanda S.; Attia, Ahmed S.; Brautigam, Chad A.

    2014-01-01

    There are a paucity of data concerning gene products that could contribute to the ability of Moraxella catarrhalis to colonize the human nasopharynx. Inactivation of a gene (mesR) encoding a predicted response regulator of a two-component signal transduction system in M. catarrhalis yielded a mutant unable to grow in liquid media. This mesR mutant also exhibited increased sensitivity to certain stressors, including polymyxin B, SDS, and hydrogen peroxide. Inactivation of the gene (mesS) encoding the predicted cognate sensor (histidine) kinase yielded a mutant with the same inability to grow in liquid media as the mesR mutant. DNA microarray and real-time reverse transcriptase PCR analyses indicated that several genes previously shown to be involved in the ability of M. catarrhalis to persist in the chinchilla nasopharynx were upregulated in the mesR mutant. Two other open reading frames upregulated in the mesR mutant were shown to encode small proteins (LipA and LipB) that had amino acid sequence homology to bacterial adhesins and structural homology to bacterial lysozyme inhibitors. Inactivation of both lipA and lipB did not affect the ability of M. catarrhalis O35E to attach to a human bronchial epithelial cell line in vitro. Purified recombinant LipA and LipB fusion proteins were each shown to inhibit human lysozyme activity in vitro and in saliva. A lipA lipB deletion mutant was more sensitive than the wild-type parent strain to killing by human lysozyme in the presence of human apolactoferrin. This is the first report of the production of lysozyme inhibitors by M. catarrhalis. PMID:25312959

  11. Two-Component Signal Transduction System CBO0787/CBO0786 Represses Transcription from Botulinum Neurotoxin Promoters in Clostridium botulinum ATCC 3502

    PubMed Central

    Zhang, Zhen; Korkeala, Hannu; Dahlsten, Elias; Sahala, Elina; Heap, John T.; Minton, Nigel P.; Lindström, Miia

    2013-01-01

    Blocking neurotransmission, botulinum neurotoxin is the most poisonous biological substance known to mankind. Despite its infamy as the scourge of the food industry, the neurotoxin is increasingly used as a pharmaceutical to treat an expanding range of muscle disorders. Whilst neurotoxin expression by the spore-forming bacterium Clostridium botulinum appears tightly regulated, to date only positive regulatory elements, such as the alternative sigma factor BotR, have been implicated in this control. The identification of negative regulators has proven to be elusive. Here, we show that the two-component signal transduction system CBO0787/CBO0786 negatively regulates botulinum neurotoxin expression. Single insertional inactivation of cbo0787 encoding a sensor histidine kinase, or of cbo0786 encoding a response regulator, resulted in significantly elevated neurotoxin gene expression levels and increased neurotoxin production. Recombinant CBO0786 regulator was shown to bind to the conserved −10 site of the core promoters of the ha and ntnh-botA operons, which encode the toxin structural and accessory proteins. Increasing concentration of CBO0786 inhibited BotR-directed transcription from the ha and ntnh-botA promoters, demonstrating direct transcriptional repression of the ha and ntnh-botA operons by CBO0786. Thus, we propose that CBO0786 represses neurotoxin gene expression by blocking BotR-directed transcription from the neurotoxin promoters. This is the first evidence of a negative regulator controlling botulinum neurotoxin production. Understanding the neurotoxin regulatory mechanisms is a major target of the food and pharmaceutical industries alike. PMID:23555260

  12. A two-component regulatory system, CsrR-CsrS, represses expression of three Streptococcus pyogenes virulence factors, hyaluronic acid capsule, streptolysin S, and pyrogenic exotoxin B.

    PubMed

    Heath, A; DiRita, V J; Barg, N L; Engleberg, N C

    1999-10-01

    Certain Tn916 insertions in the chromosome of an M1-type, nonmucoid Streptococcus pyogenes isolate (MGAS166) were previously shown to result in stable mucoidy with increased expression of the capsular synthetic genes. The transposon insertions in these strains are directly upstream of an apparent operon encoding a two-component regulatory system, designated csrR-csrS. Compared with MGAS166, these mucoid mutants are more hemolytic and cause significantly more tissue damage in a murine model of skin infection. To extend these observations, we constructed an in-frame deletion in the gene encoding the response regulator, csrR, and we evaluated the expression of other known S. pyogenes virulence factors. We discovered that csrR mutants have enhanced transcription of sagA, a gene associated with streptolysin S (SLS) and speB, the gene encoding pyrogenic exotoxin B (SpeB). The mutants also express substantially higher SLS activity and SpeB antigen in late-exponential-phase cultures. There is no change in expression of emm, scpA, sic, or cpa (genes encoding other S. pyogenes virulence factors). CsrR- strains but not the wild-type parental strain produce necrotizing lesions in a mouse model of subcutaneous infection. A double mutant with deletions in both csrR and the capsular synthesis genes caused fewer and smaller necrotic skin lesions than the csrR mutants. However, this nonmucoid csrR strain was more likely than the wild type to yield necrotic lesions, suggesting that mucoidy contributes to virulence in this model of infection but that there are other csrR-regulated factors involved in the production of necrotic lesions. PMID:10496909

  13. Regulation of Inhibition of Neutrophil Infiltration by the Two-Component Regulatory System CovRS in Subcutaneous Murine Infection with Group A Streptococcus

    PubMed Central

    Li, Jinquan; Zhu, Hui; Feng, Wenchao; Liu, Mengyao; Song, Yingli; Zhang, Xiaolan; Zhou, Yang; Bei, Weicheng

    2013-01-01

    Hypervirulent invasive group A streptococcus (GAS) isolates inhibit neutrophil infiltration more than pharyngitis isolates do, and the molecular basis of this difference is not well understood. This study was designed to first determine whether natural null mutation of the two-component regulatory system CovRS is responsible for the enhancement of the inhibition of neutrophil recruitment seen in hypervirulent GAS. Next, we examined the role of CovRS-regulated interleukin-8/CXC chemokine peptidase (SpyCEP), C5a peptidase (ScpA), and platelet-activating factor acetylhydrolase (SsE) in the enhanced innate immune evasion. Invasive isolate MGAS5005 induces less neutrophil infiltration and produced a greater lesion area than pharyngitis isolate MGAS2221 in subcutaneous infections of mice. It is known that MGAS5005, but not MGAS2221, has a natural 1-bp deletion in the covS gene. Replacement of covSΔ1bp in MGAS5005 with wild-type covS resulted in the MGAS2221 phenotype. Deletion of covS from MGAS2221 resulted in the MGAS5005 phenotype. Tests of single, double, and triple deletion mutants of the MGAS5005 sse, spyCEP, and scpA genes found that SsE plays a more important role than SpyCEP and ScpA in the inhibition of neutrophil recruitment and that SsE, SpyCEP, and ScpA do not have synergistic effects on innate immune evasion by MGAS5005. Deletion of sse, but not spyCEP or scpA, of MGAS2221 enhances neutrophil recruitment. Thus, covS null mutations can cause substantial inhibition of neutrophil recruitment by enhancing the expression of the chemoattractant-degrading virulence factors, and SsE, but not SpyCEP or ScpA, is required for CovRS-regulated GAS inhibition of neutrophil infiltration. PMID:23319556

  14. Role of the Two Component Signal Transduction System CpxAR in Conferring Cefepime and Chloramphenicol Resistance in Klebsiella pneumoniae NTUH-K2044

    PubMed Central

    Srinivasan, Vijaya Bharathi; Vaidyanathan, Vasanth; Mondal, Amitabha; Rajamohan, Govindan

    2012-01-01

    Background Klebsiella pneumoniae is a Gram-negative, non-motile, facultative anaerobe belonging to the Enterobacteriaceae family of the γ-Proteobacteria class in the phylum Proteobacteria. Multidrug resistant K. pneumoniae have caused major therapeutic problems worldwide due to emergence of extended-spectrum β-lactamase producing strains. Two-component systems serve as a basic stimulus-response coupling mechanism to allow organisms to sense and respond to changes in many different environmental conditions including antibiotic stress. Principal Findings In the present study, we investigated the role of an uncharacterized cpxAR operon in bacterial physiology and antimicrobial resistance by generating isogenic mutant (ΔcpxAR) deficient in the CpxA/CpxR component derived from the hyper mucoidal K1 strain K. pneumoniae NTUH-K2044. The behaviour of ΔcpxAR was determined under hostile conditions, reproducing stresses encountered in the gastrointestinal environment and deletion resulted in higher sensitivity to bile, osmotic and acid stresses. The ΔcpxAR was more susceptible to β-lactams and chloramphenicol than the wild-type strain, and complementation restored the altered phenotypes. The relative change in expression of acrB, acrD, eefB efflux genes were decreased in cpxAR mutant as evidenced by qRT-PCR. Comparison of outer membrane protein profiles indicated a conspicuous difference in the knock out background. Gel shift assays demonstrated direct binding of CpxRKP to promoter region of ompCKP in a concentration dependent manner. Conclusions and Significance The Cpx envelope stress response system is known to be activated by alterations in pH, membrane composition and misfolded proteins, and this systematic investigation reveals its direct involvement in conferring antimicrobial resistance against clinically significant antibiotics for the very first time. Overall results displayed in this report reflect the pleiotropic role of the CpxAR signaling system and

  15. Involvement of the HP0165-HP0166 Two-Component System in Expression of Some Acidic-pH-Upregulated Genes of Helicobacter pylori†

    PubMed Central

    Wen, Yi; Feng, Jing; Scott, David R.; Marcus, Elizabeth A.; Sachs, George

    2006-01-01

    About 200 genes of the gastric pathogen Helicobacter pylori increase expression at medium pHs of 6.2, 5.5, and 4.5, an increase that is abolished or much reduced by the buffering action of urease. Genes up-regulated by a low pH include the two-component system HP0165-HP0166, suggesting a role in the regulation of some of the pH-sensitive genes. To identify targets of HP0165-HP0166, the promoter regions of genes up-regulated by a low pH were grouped based on sequence similarity. Probes for promoter sequences representing each group were subjected to electrophoretic mobility shift assays (EMSA) with recombinant HP0166-His6 or a mutated response regulator, HP0166-D52N-His6, that can specifically determine the role of phosphorylation of HP0166 in binding (including a control EMSA with in-vitro-phosphorylated HP0166-His6). Nineteen of 45 promoter-regulatory regions were found to interact with HP0166-His6. Seven promoters for genes encoding α-carbonic anhydrase, omp11, fecD, lpp20, hypA, and two with unknown function (pHP1397-1396 and pHP0654-0675) were clustered in gene group A, which may respond to changes in the periplasmic pH at a constant cytoplasmic pH and showed phosphorylation-dependent binding in EMSA with HP0166-D52N-His6. Twelve promoters were clustered in groups B and C whose up-regulation likely also depends on a reduction of the cytoplasmic pH at a medium pH of 5.5 or 4.5. Most of the target promoters in groups B and C showed phosphorylation-dependent binding with HP0166-D52N-His6, but promoters for ompR (pHP0166-0162), pHP0682-0681, and pHP1288-1289 showed phosphorylation-independent binding. These findings, combined with DNase I footprinting, suggest that HP0165-0166 is an acid-responsive signaling system affecting the expression of pH-sensitive genes. Regulation of these genes responds either to a decrease in the periplasmic pH alone (HP0165 dependent) or also to a decrease in the cytoplasmic pH (HP0165 independent). PMID:16484186

  16. The two-component system CpxR/A represses the expression of Salmonella virulence genes by affecting the stability of the transcriptional regulator HilD

    PubMed Central

    De la Cruz, Miguel A.; Pérez-Morales, Deyanira; Palacios, Irene J.; Fernández-Mora, Marcos; Calva, Edmundo; Bustamante, Víctor H.

    2015-01-01

    Salmonella enterica can cause intestinal or systemic infections in humans and animals mainly by the presence of pathogenicity islands SPI-1 and SPI-2, containing 39 and 44 genes, respectively. The AraC-like regulator HilD positively controls the expression of the SPI-1 genes, as well as many other Salmonella virulence genes including those located in SPI-2. A previous report indicates that the two-component system CpxR/A regulates the SPI-1 genes: the absence of the sensor kinase CpxA, but not the absence of its cognate response regulator CpxR, reduces their expression. The presence and absence of cell envelope stress activates kinase and phosphatase activities of CpxA, respectively, which in turn controls the level of phosphorylated CpxR (CpxR-P). In this work, we further define the mechanism for the CpxR/A-mediated regulation of SPI-1 genes. The negative effect exerted by the absence of CpxA on the expression of SPI-1 genes was counteracted by the absence of CpxR or by the absence of the two enzymes, AckA and Pta, which render acetyl-phosphate that phosphorylates CpxR. Furthermore, overexpression of the lipoprotein NlpE, which activates CpxA kinase activity on CpxR, or overexpression of CpxR, repressed the expression of SPI-1 genes. Thus, our results provide several lines of evidence strongly supporting that the absence of CpxA leads to the phosphorylation of CpxR via the AckA/Pta enzymes, which represses both the SPI-1 and SPI-2 genes. Additionally, we show that in the absence of the Lon protease, which degrades HilD, the CpxR-P-mediated repression of the SPI-1 genes is mostly lost; moreover, we demonstrate that CpxR-P negatively affects the stability of HilD and thus decreases the expression of HilD-target genes, such as hilD itself and hilA, located in SPI-1. Our data further expand the insight on the different regulatory pathways for gene expression involving CpxR/A and on the complex regulatory network governing virulence in Salmonella. PMID:26300871

  17. Functional Characterization of a Novel Outer Membrane Porin KpnO, Regulated by PhoBR Two-Component System in Klebsiella pneumoniae NTUH-K2044

    PubMed Central

    Srinivasan, Vijaya Bharathi; Venkataramaiah, Manjunath; Mondal, Amitabha; Vaidyanathan, Vasanth; Govil, Tanvi; Rajamohan, Govindan

    2012-01-01

    Background The diffusion of antibiotics through the outer membrane is primarily affected by the porin super family, changes contribute to antibiotic resistance. Recently we demonstrated that the CpxAR two-component signaling system alters the expression of an uncharacterized porin OmpCKP, to mediate antimicrobial resistance in K. pneumoniae. Principal Findings In this study, functional characterization of the putative porin OmpCKP (denoted kpnO) with respect to antimicrobial susceptibility and virulence was evaluated by generating an isogenic mutant, ΔkpnO in a clinical isolate of K. pneumoniae. Estimation of uronic acid content confirmed that ΔkpnO produced ∼2.0 fold lesser capsular polysaccharide than the wild-type. The ΔkpnO displayed higher sensitivity to hyper osmotic and bile conditions. Disruption of kpnO increased the susceptibility of K. pneumoniae to oxidative and nitrostative stress by ∼1.6 fold and >7 fold respectively. The loss of the Klebsiella porin led to an increase in the minimum inhibitory concentration of tetracycline (3-fold), nalidixic acid (4-fold), tobramycin (4-fold), streptomycin (10-fold), and spectinomycin (10-fold), which could be restored following complementation. The single deletion of kpnO reduced the survival of the pathogen by 50% when exposed to disinfectants. In Caenorhabditis elegans model, the kpnO mutant exhibited significantly (P<0.01) lower virulence. To dissect the role of PhoBR signaling system in regulating the expression of the kpnO, a phoBKP isogenic mutant was constructed. The phoBKP mutant exhibited impaired gastrointestinal stress response and decreased antimicrobial susceptibility. The mRNA levels of kpnO were found to be 4-fold less in phoBKP mutant compared to wild type. A regulatory role of PhoBKP for the expression of kpnO was further supported by the specific binding of PhoBKP to the putative promoter of kpnO. Conclusions and Significance Loss of PhoBR regulated porin KpnO resulted in increased

  18. High temperature two component explosive

    DOEpatents

    Mars, James E.; Poole, Donald R.; Schmidt, Eckart W.; Wang, Charles

    1981-01-01

    A two component, high temperature, thermally stable explosive composition comprises a liquid or low melting oxidizer and a liquid or low melting organic fuel. The oxidizer and fuel in admixture are incapable of substantial spontaneous exothermic reaction at temperatures on the order of 475.degree. K. At temperatures on the order of 475.degree. K., the oxidizer and fuel in admixture have an activation energy of at least about 40 kcal/mol. As a result of the high activation energy, the preferred explosive compositions are nondetonable as solids at ambient temperature, and become detonable only when heated beyond the melting point. Preferable oxidizers are selected from alkali or alkaline earth metal nitrates, nitrites, perchlorates, and/or mixtures thereof. Preferred fuels are organic compounds having polar hydrophilic groups. The most preferred fuels are guanidinium nitrate, acetamide and mixtures of the two. Most preferred oxidizers are eutectic mixtures of lithium nitrate, potassium nitrate and sodium nitrate, of sodium nitrite, sodium nitrate and potassium nitrate, and of potassium nitrate, calcium nitrate and sodium nitrate.

  19. The Two-Component System CpxRA Negatively Regulates the Locus of Enterocyte Effacement of Enterohemorrhagic Escherichia coli Involving σ32 and Lon protease

    PubMed Central

    De la Cruz, Miguel A.; Morgan, Jason K.; Ares, Miguel A.; Yáñez-Santos, Jorge A.; Riordan, James T.; Girón, Jorge A.

    2016-01-01

    Enterohemorrhagic Escherichia coli (EHEC) is a significant cause of serious human gastrointestinal disease worldwide. EHEC strains contain a pathogenicity island called the locus of enterocyte effacement (LEE), which encodes virulence factors responsible for damaging the gut mucosa. The Cpx envelope stress response of E. coli is controlled by a two-component system (TCS) consisting of a sensor histidine kinase (CpxA) and a cytoplasmic response regulator (CpxR). In this study, we investigated the role of CpxRA in the expression of LEE-encoded virulence factors of EHEC. We found that a mutation in cpxA significantly affected adherence of EHEC to human epithelial cells. Analysis of this mutant revealed the presence of high levels of CpxR which repressed transcription of grlA and ler, the main positive virulence regulators of the LEE, and influenced negatively the production of the type 3 secretion system–associated EspABD translocator proteins. It is known that CpxR activates rpoH (Sigma factor 32), which in turns activates transcription of the lon protease gene. We found that transcription levels of ler and grlA were significantly increased in the lon and cpxA lon mutants suggesting that lon is involved in down-regulating LEE genes. In addition, the Galleria mellonella model of infection was used to analyze the effect of the loss of the cpx and lon genes in EHEC's ability to kill the larvae. We found that the cpxA mutant was significantly deficient at killing the larvae however, the cpxA lon mutant which overexpresses LEE genes in vitro, was unable to kill the larvae, suggesting that virulence in the G. mellonella model is T3SS independent and that CpxA modulates virulence through a yet unknown EHEC-specific factor. Our data provides new insights and broadens our scope into the complex regulatory network of the LEE in which the CpxA sensor kinase plays an important role in a cascade involving both global and virulence regulators. PMID:26904510

  20. Role of the BaeSR two-component system in the regulation of Acinetobacter baumannii adeAB genes and its correlation with tigecycline susceptibility

    PubMed Central

    2014-01-01

    Background Tigecycline resistance in Acinetobacter baumannii is primarily acquired through overexpression of the AdeABC efflux pump. Besides AdeRS, other two-component regulatory systems (TCSs) involving the regulation of this transporter have not been clarified. Results In this study, we found that the TCS genes baeR and baeS are co-transcribed and function as stress responders under high osmotic conditions. The baeSR and adeAB genes showed increased transcription in both the laboratory-induced and clinical tigecycline-resistant strains compared with the wild-type strain. The deletion of baeR in the ATCC 17978 strain led to 67–73% and 68% reduction in adeA and adeB expression, respectively, with a resultant 2-fold decrease in the tigecycline minimal inhibition concentration (MIC). In contrast, the overexpression of baeR resulted in a doubled tigecycline MIC, with a more than 2-fold increase in adeA and adeB expression. The influence of baeR knockout on adeAB gene expression can also be observed in the laboratory-induced tigecycline-resistant strain. A time-kill assay showed that the baeR deletion mutant showed an approximate 1-log10 reduction in colony forming units (CFUs) relative to the wild-type strain when the tigecycline concentration was 0.25 μg/mL throughout the assay period. The wild-type phenotype could be restored by trans-complementation with pWH1266-kan r -baeR. Increasing the tigecycline concentration to 0.5 μg/mL produced an even more marked 4.7-log10 reduction in CFUs of the baeR deletion mutant at 8 h, while only a 2.1-log10 reduction was observed for the wild-type strain. Conclusions Taken together, these data show for the first time that the BaeSR TCS influences the tigecycline susceptibility of A. baumannii through the positive regulation of the resistance-nodulation-division efflux pump genes adeA and adeB. PMID:24885279

  1. Crosstalk between the HpArsRS two-component system and HpNikR is necessary for maximal activation of urease transcription.

    PubMed

    Carpenter, Beth M; West, Abby L; Gancz, Hanan; Servetas, Stephanie L; Pich, Oscar Q; Gilbreath, Jeremy J; Hallinger, Daniel R; Forsyth, Mark H; Merrell, D Scott; Michel, Sarah L J

    2015-01-01

    Helicobacter pylori NikR (HpNikR) is a nickel dependent transcription factor that directly regulates a number of genes in this important gastric pathogen. One key gene that is regulated by HpNikR is ureA, which encodes for the urease enzyme. In vitro DNA binding studies of HpNikR with the ureA promoter (PureA ) previously identified a recognition site that is required for high affinity protein/DNA binding. As a means to determine the in vivo significance of this recognition site and to identify the key DNA sequence determinants required for ureA transcription, herein, we have translated these in vitro results to analysis directly within H. pylori. Using a series of GFP reporter constructs in which the PureA DNA target was altered, in combination with mutant H. pylori strains deficient in key regulatory proteins, we confirmed the importance of the previously identified HpNikR recognition sequence for HpNikR-dependent ureA transcription. Moreover, we identified a second factor, the HpArsRS two-component system that was required for maximum transcription of ureA. While HpArsRS is known to regulate ureA in response to acid shock, it was previously thought to function independently of HpNikR and to have no role at neutral pH. However, our qPCR analysis of ureA expression in wildtype, ΔnikR and ΔarsS single mutants as well as a ΔarsS/nikR double mutant strain background showed reduced basal level expression of ureA when arsS was absent. Additionally, we determined that both HpNikR and HpArsRS were necessary for maximal expression of ureA under nickel, low pH and combined nickel and low pH stresses. In vitro studies of HpArsR-P with the PureA DNA target using florescence anisotropy confirmed a direct protein/DNA binding interaction. Together, these data support a model in which HpArsRS and HpNikR cooperatively interact to regulate ureA transcription under various environmental conditions. This is the first time that direct "cross-talk" between HpArsRS and HpNikR at

  2. Crosstalk between the HpArsRS two-component system and HpNikR is necessary for maximal activation of urease transcription

    PubMed Central

    Carpenter, Beth M.; West, Abby L.; Gancz, Hanan; Servetas, Stephanie L.; Pich, Oscar Q.; Gilbreath, Jeremy J.; Hallinger, Daniel R.; Forsyth, Mark H.; Merrell, D. Scott; Michel, Sarah L. J.

    2015-01-01

    Helicobacter pylori NikR (HpNikR) is a nickel dependent transcription factor that directly regulates a number of genes in this important gastric pathogen. One key gene that is regulated by HpNikR is ureA, which encodes for the urease enzyme. In vitro DNA binding studies of HpNikR with the ureA promoter (PureA) previously identified a recognition site that is required for high affinity protein/DNA binding. As a means to determine the in vivo significance of this recognition site and to identify the key DNA sequence determinants required for ureA transcription, herein, we have translated these in vitro results to analysis directly within H. pylori. Using a series of GFP reporter constructs in which the PureA DNA target was altered, in combination with mutant H. pylori strains deficient in key regulatory proteins, we confirmed the importance of the previously identified HpNikR recognition sequence for HpNikR-dependent ureA transcription. Moreover, we identified a second factor, the HpArsRS two-component system that was required for maximum transcription of ureA. While HpArsRS is known to regulate ureA in response to acid shock, it was previously thought to function independently of HpNikR and to have no role at neutral pH. However, our qPCR analysis of ureA expression in wildtype, ΔnikR and ΔarsS single mutants as well as a ΔarsS/nikR double mutant strain background showed reduced basal level expression of ureA when arsS was absent. Additionally, we determined that both HpNikR and HpArsRS were necessary for maximal expression of ureA under nickel, low pH and combined nickel and low pH stresses. In vitro studies of HpArsR-P with the PureA DNA target using florescence anisotropy confirmed a direct protein/DNA binding interaction. Together, these data support a model in which HpArsRS and HpNikR cooperatively interact to regulate ureA transcription under various environmental conditions. This is the first time that direct “cross-talk” between HpArsRS and HpNikR at

  3. Transcriptional profiling of the two-component regulatory system VraSR in Staphylococcus aureus with low-level vancomycin resistance.

    PubMed

    Chen, Hongbin; Xiong, Zhujia; Liu, Kuoyue; Li, Shuguang; Wang, Ruobing; Wang, Xiaojuan; Zhang, Yawei; Wang, Hui

    2016-05-01

    The objective of this study was to comprehensively identify the target genes regulated by the two-component regulatory system VraSR in Staphylococcus aureus and to clarify the role of VraSR in low-level vancomycin resistance. Expression of vraS was determined by real-time quantitative reverse transcriptase PCR (qRT-PCR). A clinical heterogeneous vancomycin-intermediate S. aureus (hVISA) strain B6D and a vancomycin-intermediate S. aureus (VISA) strain D7 that was induced from a meticillin-resistant S. aureus strain were selected to construct vraSR null mutants by allelic replacement. The vraSR-complemented strain B6D_c was also constructed by allelic replacement. Genes differentially expressed in the wild-type, vraSR null mutant and complemented strains were detected using RNA-Seq and were validated by qRT-PCR. Compared with vancomycin-susceptible S. aureus strains, expression of vraS was upregulated in all four isogenic hVISA strains. Vancomycin minimum inhibitory concentrations (MICs) in the vraSR null mutants B6D-ΔvraSR and D7-ΔvraSR were significantly lower than in the wild-type strains B6D and D7 and the complemented strain B6D_c. RNA-Seq and qRT-PCR data showed that expression of genes encoding FmtA protein, foldase protein PrsA, capsular polysaccharide biosynthesis glycosyltransferase, TcaA, a putative membrane protein, and six hypothetical proteins was down regulated in both vraSR-null mutants B6D-ΔvraSR and D7-ΔvraSR. Most of these differentially expressed proteins are involved in cell wall biosynthesis, which is associated with vancomycin resistance in S. aureus. In conclusion, VraSR plays an important role in S. aureus strains with low-level vancomycin resistance. PrsA, FmtA, glycosyltransferase and TcaA are regulated directly or indirectly by VraSR. PMID:27084050

  4. Inactivation of SmeSyRy Two-Component Regulatory System Inversely Regulates the Expression of SmeYZ and SmeDEF Efflux Pumps in Stenotrophomonas maltophilia

    PubMed Central

    Lin, Yi-Tsung; Ning, Hsiao-Chen; Yang, Tsuey-Ching

    2016-01-01

    SmeYZ efflux pump is a critical pump responsible for aminoglycosides resistance, virulence-related characteristics (oxidative stress susceptibility, motility, and secreted protease activity), and virulence in Stenotrophomonas maltophilia. However, the regulatory circuit involved in SmeYZ expression is little known. A two-component regulatory system (TCS), smeRySy, transcribed divergently from the smeYZ operon is the first candidate to be considered. To assess the role of SmeRySy in smeYZ expression, the smeRySy isogenic deletion mutant, KJΔRSy, was constructed by gene replacement strategy. Inactivation of smeSyRy correlated with a higher susceptibility to aminoglycosides concomitant with an increased resistance to chloramphenicol, ciprofloxacin, tetracycline, and macrolides. To elucidate the underlying mechanism responsible for the antimicrobials susceptibility profiles, the SmeRySy regulon was firstly revealed by transcriptome analysis and further confirmed by quantitative real-time polymerase chain reaction (qRT-PCR) and promoter transcription fusion constructs assay. The results demonstrate that inactivation of smeRySy decreased the expression of SmeYZ pump and increased the expression of SmeDEF pump, which underlies the ΔsmeSyRy-mediated antimicrobials susceptibility profile. To elucidate the cognate relationship between SmeSy and SmeRy, a single mutant, KJΔRy, was constructed and the complementation assay of KJΔRSy with smeRy were performed. The results support that SmeSy-SmeRy TCS is responsible for the regulation of smeYZ operon; whereas SmeSy may be cognate with another unidentified response regulator for the regulation of smeDEF operon. The impact of inverse expression of SmeYZ and SmeDEF pumps on physiological functions was evaluated by mutants construction, H2O2 susceptibility test, swimming, and secreted protease activity assay. The increased expression of SmeDEF pump in KJΔRSy may compensate, to some extents, the SmeYZ downexpression

  5. Markov random fields reveal an N-terminal double beta-propeller motif as part of a bacterial hybrid two-component sensor system

    PubMed Central

    Menke, Matt; Berger, Bonnie; Cowen, Lenore

    2010-01-01

    The recent explosion in newly sequenced bacterial genomes is outpacing the capacity of researchers to try to assign functional annotation to all the new proteins. Hence, computational methods that can help predict structural motifs provide increasingly important clues in helping to determine how these proteins might function. We introduce a Markov Random Field approach tailored for recognizing proteins that fold into mainly β-structural motifs, and apply it to build recognizers for the β-propeller shapes. As an application, we identify a potential class of hybrid two-component sensor proteins, that we predict contain a double-propeller domain. PMID:20147619

  6. Ab initio two-component Ehrenfest dynamics

    NASA Astrophysics Data System (ADS)

    Ding, Feizhi; Goings, Joshua J.; Liu, Hongbin; Lingerfelt, David B.; Li, Xiaosong

    2015-09-01

    We present an ab initio two-component Ehrenfest-based mixed quantum/classical molecular dynamics method to describe the effect of nuclear motion on the electron spin dynamics (and vice versa) in molecular systems. The two-component time-dependent non-collinear density functional theory is used for the propagation of spin-polarized electrons while the nuclei are treated classically. We use a three-time-step algorithm for the numerical integration of the coupled equations of motion, namely, the velocity Verlet for nuclear motion, the nuclear-position-dependent midpoint Fock update, and the modified midpoint and unitary transformation method for electronic propagation. As a test case, the method is applied to the dissociation of H2 and O2. In contrast to conventional Ehrenfest dynamics, this two-component approach provides a first principles description of the dynamics of non-collinear (e.g., spin-frustrated) magnetic materials, as well as the proper description of spin-state crossover, spin-rotation, and spin-flip dynamics by relaxing the constraint on spin configuration. This method also holds potential for applications to spin transport in molecular or even nanoscale magnetic devices.

  7. Ab initio two-component Ehrenfest dynamics

    SciTech Connect

    Ding, Feizhi; Goings, Joshua J.; Liu, Hongbin; Lingerfelt, David B.; Li, Xiaosong

    2015-09-21

    We present an ab initio two-component Ehrenfest-based mixed quantum/classical molecular dynamics method to describe the effect of nuclear motion on the electron spin dynamics (and vice versa) in molecular systems. The two-component time-dependent non-collinear density functional theory is used for the propagation of spin-polarized electrons while the nuclei are treated classically. We use a three-time-step algorithm for the numerical integration of the coupled equations of motion, namely, the velocity Verlet for nuclear motion, the nuclear-position-dependent midpoint Fock update, and the modified midpoint and unitary transformation method for electronic propagation. As a test case, the method is applied to the dissociation of H{sub 2} and O{sub 2}. In contrast to conventional Ehrenfest dynamics, this two-component approach provides a first principles description of the dynamics of non-collinear (e.g., spin-frustrated) magnetic materials, as well as the proper description of spin-state crossover, spin-rotation, and spin-flip dynamics by relaxing the constraint on spin configuration. This method also holds potential for applications to spin transport in molecular or even nanoscale magnetic devices.

  8. Derivatives of Plant Phenolic Compound Affect the Type III Secretion System of Pseudomonas aeruginosa via a GacS-GacA Two-Component Signal Transduction System

    PubMed Central

    Yamazaki, Akihiro; Li, Jin; Zeng, Quan; Khokhani, Devanshi; Hutchins, William C.; Yost, Angela C.; Biddle, Eulandria; Toone, Eric J.

    2012-01-01

    Antibiotic therapy is the most commonly used strategy to control pathogenic infections; however, it has contributed to the generation of antibiotic-resistant bacteria. To circumvent this emerging problem, we are searching for compounds that target bacterial virulence factors rather than their viability. Pseudomonas aeruginosa, an opportunistic human pathogen, possesses a type III secretion system (T3SS) as one of the major virulence factors by which it secretes and translocates T3 effector proteins into human host cells. The fact that this human pathogen also is able to infect several plant species led us to screen a library of phenolic compounds involved in plant defense signaling and their derivatives for novel T3 inhibitors. Promoter activity screening of exoS, which encodes a T3-secreted toxin, identified two T3 inhibitors and two T3 inducers of P. aeruginosa PAO1. These compounds alter exoS transcription by affecting the expression levels of the regulatory small RNAs RsmY and RsmZ. These two small RNAs are known to control the activity of carbon storage regulator RsmA, which is responsible for the regulation of the key T3SS regulator ExsA. As RsmY and RsmZ are the only targets directly regulated by GacA, our results suggest that these phenolic compounds affect the expression of exoS through the GacSA-RsmYZ-RsmA-ExsA regulatory pathway. PMID:21968370

  9. Vancomycin susceptibility in methicillin-resistant Staphylococcus aureus is mediated by YycHI activation of the WalRK essential two-component regulatory system

    PubMed Central

    Cameron, David R.; Jiang, Jhih-Hang; Kostoulias, Xenia; Foxwell, Daniel J.; Peleg, Anton Y.

    2016-01-01

    The treatment of infections caused by methicillin-resistant Staphylococcus aureus is complicated by the emergence of strains with intermediate-level resistance to vancomycin (termed VISA). We have characterised a molecular pathway involved in the in vivo evolution of VISA mediated by the regulatory proteins YycH and YycI. In contrast to their function in other bacterial species, we report a positive role for these auxiliary proteins in regulation of the two-component regulator WalRK. Transcriptional profiling of yycH and yycI deletion mutants revealed downregulation of the ‘WalRK regulon’ including cell wall hydrolase genes atlA and sle1, with functional autolysis assays supporting these data by showing an impaired autolytic phenotype for each deletion strain. Using bacterial-two hybrid assays, we showed that YycH and YycI interact, and that YycHI also interacts with the sensor kinase WalK, forming a ternary protein complex. Mutation to YycH or YycI associated with clinical VISA strains had a deleterious impact on the YycHI/WalK complex, suggesting that the interaction is important for the regulation of WalRK. Taken together, we have described a novel antibiotic resistance strategy for the human pathogen S. aureus, whereby YycHI mutations are selected for in vivo leading to reduced WalRK activation, impaired cell wall turnover and ultimately reduced vancomycin efficacy. PMID:27600558

  10. Vancomycin susceptibility in methicillin-resistant Staphylococcus aureus is mediated by YycHI activation of the WalRK essential two-component regulatory system.

    PubMed

    Cameron, David R; Jiang, Jhih-Hang; Kostoulias, Xenia; Foxwell, Daniel J; Peleg, Anton Y

    2016-01-01

    The treatment of infections caused by methicillin-resistant Staphylococcus aureus is complicated by the emergence of strains with intermediate-level resistance to vancomycin (termed VISA). We have characterised a molecular pathway involved in the in vivo evolution of VISA mediated by the regulatory proteins YycH and YycI. In contrast to their function in other bacterial species, we report a positive role for these auxiliary proteins in regulation of the two-component regulator WalRK. Transcriptional profiling of yycH and yycI deletion mutants revealed downregulation of the 'WalRK regulon' including cell wall hydrolase genes atlA and sle1, with functional autolysis assays supporting these data by showing an impaired autolytic phenotype for each deletion strain. Using bacterial-two hybrid assays, we showed that YycH and YycI interact, and that YycHI also interacts with the sensor kinase WalK, forming a ternary protein complex. Mutation to YycH or YycI associated with clinical VISA strains had a deleterious impact on the YycHI/WalK complex, suggesting that the interaction is important for the regulation of WalRK. Taken together, we have described a novel antibiotic resistance strategy for the human pathogen S. aureus, whereby YycHI mutations are selected for in vivo leading to reduced WalRK activation, impaired cell wall turnover and ultimately reduced vancomycin efficacy. PMID:27600558

  11. Txc, a new type II secretion system of Pseudomonas aeruginosa strain PA7, is regulated by the TtsS/TtsR two-component system and directs specific secretion of the CbpE chitin-binding protein.

    PubMed

    Cadoret, Frédéric; Ball, Geneviève; Douzi, Badreddine; Voulhoux, Romé

    2014-07-01

    We present here the functional characterization of a third complete type II secretion system (T2SS) found in newly sequenced Pseudomonas aeruginosa strain PA7. We call this system Txc (third Xcp homolog). This system is encoded by the RGP69 region of genome plasticity found uniquely in strain PA7. In addition to the 11 txc genes, RGP69 contains two additional genes encoding a possible T2SS substrate and a predicted unorthodox sensor protein, TtsS (type II secretion sensor). We also identified a gene encoding a two-component response regulator called TtsR (type II secretion regulator), which is located upstream of the ttsS gene and just outside RGP69. We show that TtsS and TtsR constitute a new and functional two-component system that controls the production and secretion of the RGP69-encoded T2SS substrate in a Txc-dependent manner. Finally, we demonstrate that this Txc-secreted substrate binds chitin, and we therefore name it CbpE (chitin-binding protein E). PMID:24748613

  12. Txc, a New Type II Secretion System of Pseudomonas aeruginosa Strain PA7, Is Regulated by the TtsS/TtsR Two-Component System and Directs Specific Secretion of the CbpE Chitin-Binding Protein

    PubMed Central

    Cadoret, Frédéric; Ball, Geneviève; Douzi, Badreddine

    2014-01-01

    We present here the functional characterization of a third complete type II secretion system (T2SS) found in newly sequenced Pseudomonas aeruginosa strain PA7. We call this system Txc (third Xcp homolog). This system is encoded by the RGP69 region of genome plasticity found uniquely in strain PA7. In addition to the 11 txc genes, RGP69 contains two additional genes encoding a possible T2SS substrate and a predicted unorthodox sensor protein, TtsS (type II secretion sensor). We also identified a gene encoding a two-component response regulator called TtsR (type II secretion regulator), which is located upstream of the ttsS gene and just outside RGP69. We show that TtsS and TtsR constitute a new and functional two-component system that controls the production and secretion of the RGP69-encoded T2SS substrate in a Txc-dependent manner. Finally, we demonstrate that this Txc-secreted substrate binds chitin, and we therefore name it CbpE (chitin-binding protein E). PMID:24748613

  13. Two Component Signal Transduction in Desulfovibrio Species

    SciTech Connect

    Luning, Eric; Rajeev, Lara; Ray, Jayashree; Mukhopadhyay, Aindrila

    2010-05-17

    The environmentally relevant Desulfovibrio species are sulfate-reducing bacteria that are of interest in the bioremediation of heavy metal contaminated water. Among these, the genome of D. vulgaris Hildenborough encodes a large number of two component systems consisting of 72 putative response regulators (RR) and 64 putative histidinekinases (HK), the majority of which are uncharacterized. We classified the D. vulgaris Hildenborough RRs based on their output domains and compared the distribution of RRs in other sequenced Desulfovibrio species. We have successfully purified most RRs and several HKs as His-tagged proteins. We performed phospho-transfer experiments to verify relationships between cognate pairs of HK and RR, and we have also mapped a few non-cognate HK-RR pairs. Presented here are our discoveries from the Desulfovibrio RR categorization and results from the in vitro studies using purified His tagged D. vulgaris HKs and RRs.

  14. Complete solution of the problem of one-dimensional non-covalent non-cooperative self-assembly in two-component systems.

    PubMed

    Evstigneev, V P; Mosunov, A A; Buchelnikov, A S; Hernandez Santiago, A A; Evstigneev, M P

    2011-05-21

    Equations for the mass conservation law and the molecular parameters observed in spectroscopic experiments have been derived for non-covalent, non-cooperative, one-dimensional self-assembly in systems containing two types of interacting molecules (hetero-association), taking into account "reflected" complexes and "edge effects." PMID:21599083

  15. The CpxR/CpxA two-component regulatory system up-regulates the multidrug resistance cascade to facilitate Escherichia coli resistance to a model antimicrobial peptide.

    PubMed

    Weatherspoon-Griffin, Natasha; Yang, Dezhi; Kong, Wei; Hua, Zichun; Shi, Yixin

    2014-11-21

    A genome-wide susceptibility assay was used to identify specific CpxR-dependent genes that facilitate Escherichia coli resistance to a model cationic antimicrobial peptide, protamine. A total of 115 strains from the Keio Collection, each of which contained a deletion at a demonstrated or predicted CpxR/CpxA-dependent locus, were tested for protamine susceptibility. One strain that exhibited high susceptibility carried a deletion of tolC, a gene that encodes the outer membrane component of multiple tripartite multidrug transporters. Concomitantly, two of these efflux systems, AcrAB/TolC and EmrAB/TolC, play major roles in protamine resistance. Activation of the CpxR/CpxA system stimulates mar transcription, suggesting a new regulatory circuit that enhances the multidrug resistance cascade. Tripartite multidrug efflux systems contribute to bacterial resistance to protamine differently from the Tat system. DNase I footprinting analysis demonstrated that the CpxR protein binds to a sequence located in the -35 and -10 regions of mar promoter. This sequence resembles the consensus CpxR binding site, however, on the opposite strand. aroK, a CpxR-dependent gene that encodes a shikimate kinase in the tryptophan biosynthesis pathway, was also found to facilitate protamine resistance. Specific aromatic metabolites from this pathway, such as indole, can stimulate expression of well studied CpxR-dependent genes degP and cpxP, which are not components of the tripartite multidrug transporters. Thus, we propose a novel mechanism for E. coli to modulate resistance to protamine and likely other cationic antimicrobial peptides in which the CpxR/CpxA system up-regulates mar transcription in response to specific aromatic metabolites, subsequently stimulating the multidrug resistance cascade. PMID:25294881

  16. Preliminary Crystallographic Studies of the Regulatory Domain of Response Regulator YycF from an Essential Two-Component Signal Transduction System

    SciTech Connect

    Zhao, H.; Heroux, A; Sequeira, R; Tang, L

    2009-01-01

    YycGF is a crucial signal transduction system for the regulation of cell-wall metabolism in low-G+C Gram-positive bacteria, which include many important human pathogens. The response regulator YycF receives signals from its cognate histidine kinase YycG through a phosphotransfer reaction and elicits responses through regulation of gene expression. The N-terminal regulatory domain of YycF from Bacillus subtilis was overproduced and purified. The protein was crystallized and X-ray data were collected to 1.95 A resolution with a completeness of 97.7% and an overall Rmerge of 7.7%. The crystals belonged to space group P3121, with unit-cell parameters a = b = 59.50, c = 79.06 A.

  17. The IRF5–TNPO3 association with systemic lupus erythematosus has two components that other autoimmune disorders variably share

    PubMed Central

    Kottyan, Leah C.; Zoller, Erin E.; Bene, Jessica; Lu, Xiaoming; Kelly, Jennifer A.; Rupert, Andrew M.; Lessard, Christopher J.; Vaughn, Samuel E.; Marion, Miranda; Weirauch, Matthew T.; Namjou, Bahram; Adler, Adam; Rasmussen, Astrid; Glenn, Stuart; Montgomery, Courtney G.; Hirschfield, Gideon M.; Xie, Gang; Coltescu, Catalina; Amos, Chris; Li, He; Ice, John A.; Nath, Swapan K.; Mariette, Xavier; Bowman, Simon; Rischmueller, Maureen; Lester, Sue; Brun, Johan G.; Gøransson, Lasse G.; Harboe, Erna; Omdal, Roald; Cunninghame-Graham, Deborah S.; Vyse, Tim; Miceli-Richard, Corinne; Brennan, Michael T.; Lessard, James A.; Wahren-Herlenius, Marie; Kvarnström, Marika; Illei, Gabor G.; Witte, Torsten; Jonsson, Roland; Eriksson, Per; Nordmark, Gunnel; Ng, Wan-Fai; Anaya, Juan-Manuel; Rhodus, Nelson L.; Segal, Barbara M.; Merrill, Joan T.; James, Judith A.; Guthridge, Joel M.; Hal Scofield, R.; Alarcon-Riquelme, Marta; Bae, Sang-Cheol; Boackle, Susan A.; Criswell, Lindsey A.; Gilkeson, Gary; Kamen, Diane L.; Jacob, Chaim O.; Kimberly, Robert; Brown, Elizabeth; Edberg, Jeffrey; Alarcón, Graciela S.; Reveille, John D.; Vilá, Luis M.; Petri, Michelle; Ramsey-Goldman, Rosalind; Freedman, Barry I.; Niewold, Timothy; Stevens, Anne M.; Tsao, Betty P.; Ying, Jun; Mayes, Maureen D.; Gorlova, Olga Y.; Wakeland, Ward; Radstake, Timothy; Martin, Ezequiel; Martin, Javier; Siminovitch, Katherine; Moser Sivils, Kathy L.; Gaffney, Patrick M.; Langefeld, Carl D.; Harley, John B.; Kaufman, Kenneth M.

    2015-01-01

    Exploiting genotyping, DNA sequencing, imputation and trans-ancestral mapping, we used Bayesian and frequentist approaches to model the IRF5–TNPO3 locus association, now implicated in two immunotherapies and seven autoimmune diseases. Specifically, in systemic lupus erythematosus (SLE), we resolved separate associations in the IRF5 promoter (all ancestries) and with an extended European haplotype. We captured 3230 IRF5–TNPO3 high-quality, common variants across 5 ethnicities in 8395 SLE cases and 7367 controls. The genetic effect from the IRF5 promoter can be explained by any one of four variants in 5.7 kb (P-valuemeta = 6 × 10−49; OR = 1.38–1.97). The second genetic effect spanned an 85.5-kb, 24-variant haplotype that included the genes IRF5 and TNPO3 (P-valuesEU = 10−27–10−32, OR = 1.7–1.81). Many variants at the IRF5 locus with previously assigned biological function are not members of either final credible set of potential causal variants identified herein. In addition to the known biologically functional variants, we demonstrated that the risk allele of rs4728142, a variant in the promoter among the lowest frequentist probability and highest Bayesian posterior probability, was correlated with IRF5 expression and differentially binds the transcription factor ZBTB3. Our analytical strategy provides a novel framework for future studies aimed at dissecting etiological genetic effects. Finally, both SLE elements of the statistical model appear to operate in Sjögren's syndrome and systemic sclerosis whereas only the IRF5–TNPO3 gene-spanning haplotype is associated with primary biliary cirrhosis, demonstrating the nuance of similarity and difference in autoimmune disease risk mechanisms at IRF5–TNPO3. PMID:25205108

  18. Visualization of NO3⁻/NO2⁻ Dynamics in Living Cells by Fluorescence Resonance Energy Transfer (FRET) Imaging Employing a Rhizobial Two-component Regulatory System.

    PubMed

    Hidaka, Masafumi; Gotoh, Aina; Shimizu, Taiki; Minamisawa, Kiwamu; Imamura, Hiromi; Uchida, Takafumi

    2016-01-29

    Nitrate (NO3(-)) and nitrite (NO2(-)) are the physiological sources of nitric oxide (NO), a key biological messenger molecule. NO3(-)/NO2(-) exerts a beneficial impact on NO homeostasis and its related cardiovascular functions. To visualize the physiological dynamics of NO3(-)/NO2(-) for assessing the precise roles of these anions, we developed a genetically encoded intermolecular fluorescence resonance energy transfer (FRET)-based indicator, named sNOOOpy (sensor for NO3(-)/NO2(-) in physiology), by employing NO3(-)/NO2(-)-induced dissociation of NasST involved in the denitrification system of rhizobia. The in vitro use of sNOOOpy shows high specificity for NO3(-) and NO2(-), and its FRET signal is changed in response to NO3(-)/NO2(-) in the micromolar range. Furthermore, both an increase and decrease in cellular NO3(-) concentration can be detected. sNOOOpy is very simple and potentially applicable to a wide variety of living cells and is expected to provide insights into NO3(-)/NO2(-) dynamics in various organisms, including plants and animals. PMID:26631727

  19. Resonance energy transfer in a novel two-component system: two-photon fluorophore and a photo-chromic acceptor molecule

    NASA Astrophysics Data System (ADS)

    Gvishi, Raz; Kotler, Zvi; Berkovic, Garry; Krief, Pnina; Sigalov, Mark; Shapiro, Lev; Huppert, Dan; Khodorkovsky, Vladimir; Lokshin, V.; Samat, A.

    2005-04-01

    To date, a full-scale solar sail has never flown in space. Furthermore, solar sail technology development represents a field that only recently has enjoyed significant support. The goal of this work is to contribute to the development of a low-mass ODS for solar sails that would include research and development in the areas of photogrammetry and thermography. The focus of this work was on the development of the thermography system. A measurement protocol was designed for obtaining accurate temperature measurements using thermal imaging when heat was applied to the membrane surface. Two main limitations were considered during the experimental process. The first is that conventional infrared detector arrays must be kept cool. To minimize the effect that an imager's operating temperature would have on the ODS, a miniature, un-cooled microbolometer was used to acquire temperature measurements from the membrane surface. A second limitation is that a detector array cannot distinguish between emitted and reflected photons, thus presenting a significant problem if one cannot predict the reflected component or if the reflected component is significantly greater than the emitted. To address this limitation, spectral properties of the membrane, including reflectance and transmission, were analyzed using a Hemispherical Directional Reflectometer (HDR) to predict the effects that optical properties would have on sail membrane temperatures. A thermal modeling strategy was also developed. The results of this investigation are presented.

  20. Epsilon-Toxin Production by Clostridium perfringens Type D Strain CN3718 Is Dependent upon the agr Operon but Not the VirS/VirR Two-Component Regulatory System

    PubMed Central

    Chen, Jianming; Rood, Julian I.; McClane, Bruce A.

    2011-01-01

    ABSTRACT Clostridium perfringens type B and D strains cause enterotoxemias and enteritis in livestock after proliferating in the intestines and producing epsilon-toxin (ETX), alpha-toxin (CPA), and, usually, perfringolysin O (PFO). Although ETX is one of the most potent bacterial toxins, the regulation of ETX production by type B or D strains remains poorly understood. The present work determined that the type D strain CN3718 upregulates production of ETX upon close contact with enterocyte-like Caco-2 cells. This host cell-induced upregulation of ETX expression was mediated at the transcriptional level. Using an isogenic agrB null mutant and complemented strain, the agr operon was shown to be required when CN3718 produces ETX in broth culture or, via a secreted signal consistent with a quorum-sensing (QS) effect, upregulates ETX production upon contact with host cells. These findings provide the first insights into the regulation of ETX production, as well as additional evidence that the Agr-like QS system functions as a global regulator of C. perfringens toxin production. Since it was proposed previously that the Agr-like QS system regulates C. perfringens gene expression via the VirS/VirR two-component regulatory system, an isogenic virR null mutant of CN3718 was constructed to evaluate the importance of VirS/VirR for CN3718 toxin production. This mutation affected production of CPA and PFO, but not ETX, by CN3718. These results provide the first indication that C. perfringens toxin expression regulation by the Agr-like quorum-sensing system may not always act via the VirS/VirR two-component system. PMID:22167225

  1. A Two-Component Regulatory System in Transcriptional Control of Photosystem Stoichiometry: Redox-Dependent and Sodium Ion-Dependent Phosphoryl Transfer from Cyanobacterial Histidine Kinase Hik2 to Response Regulators Rre1 and RppA

    PubMed Central

    Ibrahim, Iskander M.; Puthiyaveetil, Sujith; Allen, John F.

    2016-01-01

    Two-component systems (TCSs) are ubiquitous signaling units found in prokaryotes. A TCS consists of a sensor histidine kinase and a response regulator protein as signal transducers. These regulatory systems mediate acclimation to various environmental changes by coupling environmental cues to gene expression. Hik2 is a sensor histidine kinase and its gene is found in all cyanobacteria. Hik2 is the homolog of Chloroplast Sensor Kinase (CSK), a protein involved in redox regulation of chloroplast gene expression during changes in light quality in plants and algae. Here we describe biochemical characterization of the signaling mechanism of Hik2 and its phosphotransferase activity. Results presented here indicate that Hik2 undergoes autophosphorylation on a conserved histidine residue, and becomes rapidly dephosphorylated by the action of response regulators Rre1 and RppA. We also show that the autophosphorylation of Hik2 is specifically inhibited by sodium ions. PMID:26904089

  2. A lesson in efficient killing from two-component lantibiotics.

    PubMed

    Breukink, Eefjan

    2006-07-01

    The combined activity of the constituents of two-component antibiotic systems is always significantly higher than the sum of the activities of the individual pieces. Understanding the principles behind this phenomenon might provide new ways to design new antibiotics. In this issue of Molecular Microbiology, Wiedemann and coworkers have made a big step towards understanding the mechanism of action of the two-component lanthionine-containing antibiotic lacticin 3147. It has now become clear that this two-component system specifically targets the bacterial cell wall precursor Lipid II. This makes this essential bacterial lipid one of the most sought-after targets in nature. Surprisingly, in view of its small size (MW 1875 Da), this is now the fifth different way that this key molecule is known to be targeted. PMID:16771845

  3. In Vivo Characterization of the Activation and Interaction of the VanR-VanS Two-Component Regulatory System Controlling Glycopeptide Antibiotic Resistance in Two Related Streptomyces Species

    PubMed Central

    Novotna, Gabriela Balikova; Kwun, Min Jung

    2015-01-01

    The VanR-VanS two-component system is responsible for inducing resistance to glycopeptide antibiotics in various bacteria. We have performed a comparative study of the VanR-VanS systems from two streptomyces strains, Streptomyces coelicolor and Streptomyces toyocaensis, to characterize how the two proteins cooperate to signal the presence of antibiotics and to define the functional nature of each protein in each strain background. The results indicate that the glycopeptide antibiotic inducer specificity is determined solely by the differences between the amino acid sequences of the VanR-VanS two-component systems present in each strain rather than by any inherent differences in general cell properties, including cell wall structure and biosynthesis. VanR of S. coelicolor (VanRsc) functioned with either sensor kinase partner, while VanR of S. toyocaensis (VanRst) functioned only with its cognate partner, S. toyocaensis VanS (VanSst). In contrast to VanRsc, which is known to be capable of phosphorylation by acetylphosphate, VanRst could not be activated in vivo independently of a VanS sensor kinase. A series of amino acid sequence modifications changing residues in the N-terminal receiver (REC) domain of VanRst to the corresponding residues present in VanRsc failed to create a protein capable of being activated by VanS of S. coelicolor (VanSsc), which suggests that interaction of the response regulator with its cognate sensor kinase may require a region more extended than the REC domain. A T69S amino acid substitution in the REC domain of VanRst produced a strain exhibiting weak constitutive resistance, indicating that this particular amino acid may play a key role for VanS-independent phosphorylation in the response regulator protein. PMID:26711760

  4. Two-component Abelian sandpile models.

    PubMed

    Alcaraz, F C; Pyatov, P; Rittenberg, V

    2009-04-01

    In one-component Abelian sandpile models, the toppling probabilities are independent quantities. This is not the case in multicomponent models. The condition of associativity of the underlying Abelian algebras imposes nonlinear relations among the toppling probabilities. These relations are derived for the case of two-component quadratic Abelian algebras. We show that Abelian sandpile models with two conservation laws have only trivial avalanches. PMID:19518280

  5. Exposure of a 23F Serotype Strain of Streptococcus pneumoniae to Cigarette Smoke Condensate Is Associated with Selective Upregulation of Genes Encoding the Two-Component Regulatory System 11 (TCS11)

    PubMed Central

    Herbert, Jenny A.; Mitchell, Timothy J.; Dix-Peek, Thérèse; Dickens, Caroline; Anderson, Ronald; Feldman, Charles

    2014-01-01

    Alterations in whole genome expression profiles following exposure of the pneumococcus (strain 172, serotype 23F) to cigarette smoke condensate (160 μg/mL) for 15 and 60 min have been determined using the TIGR4 DNA microarray chip. Exposure to CSC resulted in the significant (P < 0.014–0.0006) upregulation of the genes encoding the two-component regulatory system 11 (TCS11), consisting of the sensor kinase, hk11, and its cognate response regulator, rr11, in the setting of increased biofilm formation. These effects of cigarette smoke on the pneumococcus may contribute to colonization of the airways by this microbial pathogen. PMID:25013815

  6. Temporal and evolutionary dynamics of two-component signaling pathways.

    PubMed

    Salazar, Michael E; Laub, Michael T

    2015-04-01

    Bacteria sense and respond to numerous environmental signals through two-component signaling pathways. Typically, a given stimulus will activate a sensor histidine kinase to autophosphorylate and then phosphotransfer to a cognate response regulator, which can mount an appropriate response. Although these signaling pathways often appear to be simple switches, they can also orchestrate surprisingly sophisticated and complex responses. These temporal dynamics arise from several key regulatory features, including the bifunctionality of histidine kinases as well as positive and negative feedback loops. Two-component signaling pathways are also dynamic on evolutionary time-scales, expanding dramatically in many species through gene duplication and divergence. Here, we review recent work probing the temporal and evolutionary dynamics of two-component signaling systems. PMID:25589045

  7. Temporal and Evolutionary Dynamics of Two-Component Signaling Pathways

    PubMed Central

    Salazar, Michael E.; Laub, Michael T.

    2015-01-01

    Bacteria sense and respond to numerous environmental signals through two-component signaling pathways. Typically, a given stimulus will activate a sensor histidine kinase to autophosphorylate and then phosphotransfer to a cognate response regulator, which can mount an appropriate response. Although these signaling pathways often appear to be simple switches, they can also orchestrate surprisingly sophisticated and complex responses. These temporal dynamics arise from several key regulatory features, including the bifunctionality of histidine kinases as well as positive and negative feedback loops. Two-component signaling pathways are also dynamic on evolutionary time-scales, expanding dramatically in many species through gene duplication and divergence. Here, we review recent work probing the temporal and evolutionary dynamics of two-component signaling systems. PMID:25589045

  8. Biological Insights from Structures of Two-Component Proteins

    PubMed Central

    Gao, Rong; Stock, Ann M.

    2013-01-01

    Two-component signal transduction based on phosphotransfer from a histidine protein kinase to a response regulator protein is a prevalent strategy for coupling environmental stimuli to adaptive responses in bacteria. In both histidine kinases and response regulators, modular domains with conserved structures and biochemical activities adopt different conformational states in the presence of stimuli or upon phosphorylation, enabling a diverse array of regulatory mechanisms based on inhibitory and/or activating protein-protein interactions imparted by different domain arrangements. This review summarizes some of the recent structural work that has provided insight to the functioning of bacterial histidine kinases and response regulators. Particular emphasis is placed on identifying features that are expected to be conserved among different two-component proteins from those that are expected to differ, with the goal of defining the extent to which knowledge of previously characterized two-component proteins can be applied to newly discovered systems. PMID:19575571

  9. Collective behaviors of two-component swarms.

    PubMed

    You, Sang Koo; Kwon, Dae Hyuk; Park, Yong-ik; Kim, Sun Myong; Chung, Myung-Hoon; Kim, Chul Koo

    2009-12-01

    We present a particle-based simulation study on two-component swarms where there exist two different types of groups in a swarm. Effects of different parameters between the two groups are studied systematically based on Langevin's equation. It is shown that the mass difference can introduce a protective behavior for the lighter members of the swarm in a vortex state. When the self-propelling strength is allowed to differ between two groups, it is observed that the swarm becomes spatially segregated and finally separated into two components at a certain critical value. We also investigate effects of different preferences for shelters on their collective decision making. In particular, it is found that the probability of selecting a shelter from the other varies sigmoidally as a function of the number ratio. The model is shown to describe the dynamics of the shelter choosing process of the cockroach-robot mixed group satisfactorily. It raises the possibility that the present model can be applied to the problems of pest control and fishing using robots and decoys. PMID:19716374

  10. The auxiliary protein complex SaePQ activates the phosphatase activity of sensor kinase SaeS in the SaeRS two-component system of Staphylococcus aureus

    PubMed Central

    Jeong, Do-Won; Cho, Hoonsik; Jones, Marcus B.; Shatzkes, Kenneth; Sun, Fei; Ji, Quanjiang; Liu, Qian; Peterson, Scott N.; He, Chuan; Bae, Taeok

    2012-01-01

    Summary In bacterial two-component regulatory systems (TCSs), dephosphorylation of phosphorylated response regulators is essential for resetting the activated systems to the pre-activation state. However, in the SaeRS TCS, a major virulence TCS of Staphylococcus aureus, the mechanism for dephosphorylation of the response regulator SaeR has not been identified. Here we report that two auxiliary proteins from the sae operon, SaeP and SaeQ, form a protein complex with the sensor kinase SaeS and activate the sensor kinase’s phosphatase activity. Efficient activation of the phosphatase activity required the presence of both SaeP and SaeQ. When SaeP and SaeQ were ectopically expressed, the expression of coagulase, a sae target with low affinity for phosphorylated SaeR, was greatly reduced, while the expression of alpha-hemolysin, a sae target with high affinity for phosphorylated SaeR, was not, demonstrating a differential effect of SaePQ on sae target gene expression. When expression of SaePQ was abolished, most sae target genes were induced at an elevated level. Since the expression of SaeP and SaeQ is induced by the SaeRS TCS, these results suggest that the SaeRS TCS returns to the pre-activation state by a negative feedback mechanism. PMID:22882143

  11. The Legionella pneumophila CpxRA two-component regulatory system: new insights into CpxR's function as a dual regulator and its connection to the effectors regulatory network.

    PubMed

    Feldheim, Yaron S; Zusman, Tal; Speiser, Yariv; Segal, Gil

    2016-03-01

    Legionella pneumophila utilizes the Icm/Dot type-IV secretion system to translocate approximately 300 effector proteins into host cells, and the CpxRA two-component system (TCS) was previously shown to regulate the expression of several of these effectors. In this study, we expanded the pool of L. pneumophila CpxR-regulated genes to 38, including 27 effector-encoding genes. Our study demonstrates for the first time that the CpxR dual regulator has different requirements for activation and repression of target genes. These differences include the positioning of the CpxR regulatory element relative to the promoter element, and the effect of CpxR phosphate donors on the expression of CpxR target genes. In addition, unlike most response regulators, a mutant form of the L. pneumophila CpxR which cannot be phosphorylated was found to self-interact, and to repress gene expression similarly to wild-type CpxR, even though its ability to activate gene expression was reduced. Moreover, the CpxRA TCS was found to activate the expression of LetE which was found to function as a connector protein between the CpxRA TCS and the LetAS-RsmYZ-CsrA regulatory cascade. Our results show that CpxR plays a major role in L. pneumophila pathogenesis gene expression and functions as part of a regulatory network. PMID:26713766

  12. DECELERATING RELATIVISTIC TWO-COMPONENT JETS

    SciTech Connect

    Meliani, Z.; Keppens, R. E-mail: Rony.Keppens@wis.kuleuven.b

    2009-11-10

    Transverse stratification is a common intrinsic feature of astrophysical jets. There is growing evidence that jets in radio galaxies consist of a fast low-density outflow at the jet axis, surrounded by a slower, denser, extended jet. The inner and outer jet components then have a different origin and launching mechanism, making their effective inertia, magnetization, associated energy flux, and angular momentum content different as well. Their interface will develop differential rotation, where disruptions may occur. Here we investigate the stability of rotating, two-component relativistic outflows typical for jets in radio galaxies. For this purpose, we parametrically explore the long-term evolution of a transverse cross section of radially stratified jets numerically, extending our previous study where a single, purely hydrodynamic evolution was considered. We include cases with poloidally magnetized jet components, covering hydro and magnetohydrodynamic (MHD) models. With grid-adaptive relativistic MHD simulations, augmented with approximate linear stability analysis, we revisit the interaction between the two jet components. We study the influence of dynamically important poloidal magnetic fields, with varying contributions of the inner component jet to the total kinetic energy flux of the jet, on their non-linear azimuthal stability. We demonstrate that two-component jets with high kinetic energy flux and inner jet effective inertia which is higher than the outer jet effective inertia are subject to the development of a relativistically enhanced, rotation-induced Rayleigh-Taylor-type instability. This instability plays a major role in decelerating the inner jet and the overall jet decollimation. This novel deceleration scenario can partly explain the radio source dichotomy, relating it directly to the efficiency of the central engine in launching the inner jet component. The FRII/FRI transition could then occur when the relative kinetic energy flux of the

  13. The HrpX/HrpY two-component system activates hrpS expression, the first step in the regulatory cascade controlling the Hrp regulon in Pantoea stewartii subsp. stewartii.

    PubMed

    Merighi, Massimo; Majerczak, Doris R; Stover, Elizabeth H; Coplin, David L

    2003-03-01

    A regulatory cascade activating hrp/hrc type III secretion and effector genes was delineated in Pantoea stewartii subsp. stewartii, a bacterial pathogen of corn. Four hrp regulatory genes were characterized: hrpX and hrpY encode the sensor kinase and response regulator, respectively, of a two-component signal transduction system; hrpS encodes an NtrC-like transcriptional enhancer; and hrpL encodes an alternative sigma factor. Epistasis analysis, expression studies using gene fusions, and genetic reconstruction of each step in Escherichia coli were used to delineate the following pathway: HrpY activates hrpS and also positively autoregulates the hrpXY operon. In turn, HrpS is required for full activation of the sigma54-dependent hrpL promoter. Finally, HrpL controls expression of all known hrp and wts genes. In vitro, hrpS and all downstream hrp genes were regulated by pH and salt concentration. Mutants with in-frame deletions in hrpX were still partially virulent on corn but were unable to sense the chemical or metabolic signals that induce hrp genes in vitro. Site-directed mutagenesis of HrpY indicated that aspartate 57 is the probable phosphorylation site and that it is needed for activity. These findings suggest that both HrpX and an alternate mechanism are involved in the activation of HrpY in planta. PMID:12650455

  14. The two kinases, AbrC1 and AbrC2, of the atypical two-component system AbrC are needed to regulate antibiotic production and differentiation in Streptomyces coelicolor

    PubMed Central

    Rodríguez, Héctor; Rico, Sergio; Yepes, Ana; Franco-Echevarría, Elsa; Antoraz, Sergio; Santamaría, Ramón I.; Díaz, Margarita

    2015-01-01

    Two-component systems (TCSs) are the most important sensing mechanisms in bacteria. In Streptomyces, TCSs-mediated responses to environmental stimuli are involved in the regulation of antibiotic production. This study examines the individual role of two histidine kinases (HKs), AbrC1 and AbrC2, which form part of an atypical TCS in Streptomyces coelicolor. qRT-PCR analysis of the expression of both kinases demonstrated that both are expressed at similar levels in NB and NMMP media. Single deletion of abrC1 elicited a significant increase in antibiotic production, while deletion of abrC2 did not have any clear effect. The origin of this phenotype, probably related to the differential phosphorylation ability of the two kinases, was also explored indirectly, analyzing the toxic phenotypes associated with high levels of phosphorylated RR. The higher the AbrC3 regulator phosphorylation rate, the greater the cell toxicity. For the first time, the present work shows in Streptomyces the combined involvement of two different HKs in the response of a regulator to environmental signals. Regarding the possible applications of this research, the fact that an abrC1 deletion mutant overproduces three of the S. coelicolor antibiotics makes this strain an excellent candidate as a host for the heterologous production of secondary metabolites. PMID:26029189

  15. The two kinases, AbrC1 and AbrC2, of the atypical two-component system AbrC are needed to regulate antibiotic production and differentiation in Streptomyces coelicolor.

    PubMed

    Rodríguez, Héctor; Rico, Sergio; Yepes, Ana; Franco-Echevarría, Elsa; Antoraz, Sergio; Santamaría, Ramón I; Díaz, Margarita

    2015-01-01

    Two-component systems (TCSs) are the most important sensing mechanisms in bacteria. In Streptomyces, TCSs-mediated responses to environmental stimuli are involved in the regulation of antibiotic production. This study examines the individual role of two histidine kinases (HKs), AbrC1 and AbrC2, which form part of an atypical TCS in Streptomyces coelicolor. qRT-PCR analysis of the expression of both kinases demonstrated that both are expressed at similar levels in NB and NMMP media. Single deletion of abrC1 elicited a significant increase in antibiotic production, while deletion of abrC2 did not have any clear effect. The origin of this phenotype, probably related to the differential phosphorylation ability of the two kinases, was also explored indirectly, analyzing the toxic phenotypes associated with high levels of phosphorylated RR. The higher the AbrC3 regulator phosphorylation rate, the greater the cell toxicity. For the first time, the present work shows in Streptomyces the combined involvement of two different HKs in the response of a regulator to environmental signals. Regarding the possible applications of this research, the fact that an abrC1 deletion mutant overproduces three of the S. coelicolor antibiotics makes this strain an excellent candidate as a host for the heterologous production of secondary metabolites. PMID:26029189

  16. The β-propeller gene Rv1057 of Mycobacterium tuberculosis has a complex promoter directly regulated by both the MprAB and TrcRS two-component systems

    PubMed Central

    Pang, Xiuhua; Cao, Guangxiang; Neuenschwander, Pierre F.; Haydel, Shelley E.; Hou, Guihua; Howard, Susan T.

    2011-01-01

    SUMMARY The β-propeller gene Rv1057 of Mycobacterium tuberculosis is activated by envelope stress and was first characterized as a regulatory target of the TrcRS two-component system (TCS). Rv1057 expression is repressed by TrcRS, and the Rv1057 proximal promoter contains a TrcR binding site. In this study, we determined that Rv1057 is also directly regulated by MprAB, a TCS associated with envelope stress. Multiple potential MprA binding sites (MprA boxes) were identified in the 1 kb intergenic region upstream of Rv1057, and four sites were shown to bind MprA. Although MprA boxes were found in the proximal promoter, analyses suggest that MprA and TrcR do not compete for binding in this region. An MprAB-dependent, detergent-inducible transcriptional start point for Rv1057 was identified downstream of the MprA boxes, and a second TrcR binding site and small ORF of the 13E12 family were discovered in the distal promoter. MprAB was required for activation of Rv1057 during growth in macrophages and under detergent stress, and lacZ promoter constructs suggest the entire intergenic region is utilized during MprAB-dependent activation of Rv1057. These findings indicate that Rv1057 has an extensive and complex promoter, and provide evidence for coordinated regulation of stress response genes by TCSs. PMID:22099420

  17. The PorX Response Regulator of the Porphyromonas gingivalis PorXY Two-Component System Does Not Directly Regulate the Type IX Secretion Genes but Binds the PorL Subunit

    PubMed Central

    Vincent, Maxence S.; Durand, Eric; Cascales, Eric

    2016-01-01

    The Type IX secretion system (T9SS) is a versatile multi-protein complex restricted to bacteria of the Bacteriodetes phylum and responsible for the secretion or cell surface exposition of diverse proteins that participate to S-layer formation, gliding motility or pathogenesis. The T9SS is poorly characterized but a number of proteins involved in the assembly of the secretion apparatus in the oral pathogen Porphyromonas gingivalis have been identified based on genome substractive analyses. Among these proteins, PorY, and PorX encode typical two-component system (TCS) sensor and CheY-like response regulator respectively. Although the porX and porY genes do not localize at the same genetic locus, it has been proposed that PorXY form a bona fide TCS. Deletion of porX in P. gingivalis causes a slight decrease of the expression of a number of other T9SS genes, including sov, porT, porP, porK, porL, porM, porN, and porY. Here, we show that PorX and the soluble cytoplasmic domain of PorY interact. Using electrophoretic mobility shift, DNA-protein co-purification and heterologous host expression assays, we demonstrate that PorX does not bind T9SS gene promoters and does not directly regulate expression of the T9SS genes. Finally, we show that PorX interacts with the cytoplasmic domain of PorL, a component of the T9SS membrane core complex and propose that the CheY-like PorX protein might be involved in the dynamics of the T9SS.

  18. Complement-mediated opsonization of invasive group A Streptococcus pyogenes strain AP53 is regulated by the bacterial two-component cluster of virulence responder/sensor (CovRS) system.

    PubMed

    Agrahari, Garima; Liang, Zhong; Mayfield, Jeffrey A; Balsara, Rashna D; Ploplis, Victoria A; Castellino, Francis J

    2013-09-20

    Group A Streptococcus pyogenes (GAS) strain AP53 is a primary isolate from a patient with necrotizing fasciitis. These AP53 cells contain an inactivating mutation in the sensor component of the cluster of virulence (cov) responder (R)/sensor (S) two-component gene regulatory system (covRS), which enhances the virulence of the primary strain, AP53/covR(+)S(-). However, specific mechanisms by which the covRS system regulates the survival of GAS in humans are incomplete. Here, we show a key role for covRS in the regulation of opsonophagocytosis of AP53 by human neutrophils. AP53/covR(+)S(-) cells displayed potent binding of host complement inhibitors of C3 convertase, viz. Factor H (FH) and C4-binding protein (C4BP), which concomitantly led to minimal C3b deposition on AP53 cells, further showing that these plasma protein inhibitors are active on GAS cells. This resulted in weak killing of the bacteria by human neutrophils and a corresponding high death rate of mice after injection of these cells. After targeted allelic alteration of covS(-) to wild-type covS (covS(+)), a dramatic loss of FH and C4BP binding to the AP53/covR(+)S(+) cells was observed. This resulted in elevated C3b deposition on AP53/covR(+)S(+) cells, a high level of opsonophagocytosis by human neutrophils, and a very low death rate of mice infected with AP53/covR(+)S(+). We show that covRS is a critical transcriptional regulator of genes directing AP53 killing by neutrophils and regulates the levels of the receptors for FH and C4BP, which we identify as the products of the fba and enn genes, respectively. PMID:23928307

  19. Complement-mediated Opsonization of Invasive Group A Streptococcus pyogenes Strain AP53 Is Regulated by the Bacterial Two-component Cluster of Virulence Responder/Sensor (CovRS) System*

    PubMed Central

    Agrahari, Garima; Liang, Zhong; Mayfield, Jeffrey A.; Balsara, Rashna D.; Ploplis, Victoria A.; Castellino, Francis J.

    2013-01-01

    Group A Streptococcus pyogenes (GAS) strain AP53 is a primary isolate from a patient with necrotizing fasciitis. These AP53 cells contain an inactivating mutation in the sensor component of the cluster of virulence (cov) responder (R)/sensor (S) two-component gene regulatory system (covRS), which enhances the virulence of the primary strain, AP53/covR+S−. However, specific mechanisms by which the covRS system regulates the survival of GAS in humans are incomplete. Here, we show a key role for covRS in the regulation of opsonophagocytosis of AP53 by human neutrophils. AP53/covR+S− cells displayed potent binding of host complement inhibitors of C3 convertase, viz. Factor H (FH) and C4-binding protein (C4BP), which concomitantly led to minimal C3b deposition on AP53 cells, further showing that these plasma protein inhibitors are active on GAS cells. This resulted in weak killing of the bacteria by human neutrophils and a corresponding high death rate of mice after injection of these cells. After targeted allelic alteration of covS− to wild-type covS (covS+), a dramatic loss of FH and C4BP binding to the AP53/covR+S+ cells was observed. This resulted in elevated C3b deposition on AP53/covR+S+ cells, a high level of opsonophagocytosis by human neutrophils, and a very low death rate of mice infected with AP53/covR+S+. We show that covRS is a critical transcriptional regulator of genes directing AP53 killing by neutrophils and regulates the levels of the receptors for FH and C4BP, which we identify as the products of the fba and enn genes, respectively. PMID:23928307

  20. Regulation of the AbrA1/A2 Two-Component System in Streptomyces coelicolor and the Potential of Its Deletion Strain as a Heterologous Host for Antibiotic Production

    PubMed Central

    Rico, Sergio; Yepes, Ana; Rodríguez, Héctor; Santamaría, Jorge; Antoraz, Sergio; Krause, Eva M.; Díaz, Margarita; Santamaría, Ramón I.

    2014-01-01

    The Two-Component System (TCS) AbrA1/A2 from Streptomyces coelicolor M145 is a negative regulator of antibiotic production and morphological differentiation. In this work we show that it is able to auto-regulate its expression, exerting a positive induction of its own operon promoter, and that its activation is dependent on the presence of iron. The overexpression of the abrA2 response regulator (RR) gene in the mutant ΔabrA1/A2 results in a toxic phenotype. The reason is an excess of phosphorylated AbrA2, as shown by phosphoablative and phosphomimetic AbrA2 mutants. Therefore, non-cognate histidine kinases (HKs) or small phospho-donors may be responsible for AbrA2 phosphorylation in vivo. The results suggest that in the parent strain S. coelicolor M145 the correct amount of phosphorylated AbrA2 is adjusted through the phosphorylation-dephosphorylation activity rate of the HK AbrA1. Furthermore, the ABC transporter system, which is part of the four-gene operon comprising AbrA1/A2, is necessary to de-repress antibiotic production in the TCS null mutant. Finally, in order to test the possible biotechnological applications of the ΔabrA1/A2 strain, we demonstrate that the production of the antitumoral antibiotic oviedomycin is duplicated in this strain as compared with the production obtained in the wild type, showing that this strain is a good host for heterologous antibiotic production. Thus, this genetically modified strain could be interesting for the biotechnology industry. PMID:25303210

  1. Effects of the two-component system comprising GacA and GacS of Erwinia carotovora subsp. carotovora on the production of global regulatory rsmB RNA, extracellular enzymes, and harpinEcc.

    PubMed

    Cui, Y; Chatterjee, A; Chatterjee, A K

    2001-04-01

    Posttranscriptional regulation mediated by the regulator of secondary metabolites (RSM) RsmA-rsmB pair is the most important factor in the expression of genes for extracellular enzymes and HarpinEcc in Erwinia carotovora subsp. carotovora. RsmA is a small RNA-binding protein, which acts by lowering the half-life of a mRNA species. rsmB specifies an untranslated regulatory RNA and neutralizes the RsmA effect. It has been speculated that GacA-GacS, members of a two-component system, may affect gene expression via RsmA. Because expA, a gacA homolog, and expS (or rpfA), a gacS homolog, have been identified in E. carotovora subsp. carotovora, we examined the effects of these gacA and gacS homologs on the expression of rsmA, rsmB, and an assortment of exoprotein genes. The gacA gene of E. carotovora subsp. carotovora strain 71 stimulated transcription of genes for several extracellular enzymes (pel-1, a pectate lyase gene; peh-1, a polygalacturonase gene; and celV, a cellulase gene), hrpNEcc (an E. carotovora subsp. carotovora gene specifying the elicitor of hypersensitive reaction), and rsmB in GacA+ and GacS+ E. carotovora subsp. carotovora strains. Similarly, the E. carotovora subsp. carotovora gacA gene stimulated csrB (rsmB) transcription in Escherichia coli. A GacS- mutant of E. carotovora subsp. carotovora strain AH2 and a GacA- mutant of E. carotovora subsp. carotovora strain Ecc71 compared with their parent strains produced very low levels of rsmB, pel-1, peh-1, celV, and hrpNEcc transcripts but produced similar levels of rsmA RNA and RsmA protein as well as transcripts of hyperproduction of extracellular enzymes (Hex) hexA, kdgR (repressor of genes for uronate and pectate catabolism), rsmC, and rpoS (gene for Sigma-S, an alternate Sigma factor). The levels of rsmB, pel-1, peh-1, celV, and hrpNEcc transcripts as well as production of pectate lyase, polygalacturonase, cellulase, protease, and HarpinEcc proteins were stimulated in GacS- and GacA- mutants by Gac

  2. Kinetic and mechanistic analyses of new classes of inhibitors of two-component signal transduction systems using a coupled assay containing HpkA-DrrA from Thermotoga maritima.

    PubMed

    Foster, J Estelle; Sheng, Qin; McClain, Jonathan R; Bures, Mark; Nicas, Thalia I; Henry, Kenneth; Winkler, Malcolm E; Gilmour, Raymond

    2004-04-01

    Two-component signal transduction systems (TCSs) play fundamental roles in bacterial survival and pathogenesis and have been proposed as targets for the development of novel classes of antibiotics. A new coupled assay was developed and applied to analyse the kinetic mechanisms of three new kinds of inhibitors of TCS function. The assay exploits the biochemical properties of the cognate HpkA-DrrA histidine kinase-response regulator pair from Thermotoga maritima and allows multiple turnovers of HpkA, linear formation of phosphorylated DrrA, and Michaelis-Menten analysis of inhibitors. The assay was validated in several ways, including confirmation of competitive inhibition by adenosine 5'-beta,gamma-imidotriphosphate (AMP-PNP). The coupled assay, autophosphorylation and chemical cross-linking were used to determine the mechanisms by which several compounds inhibit TCS function. A cyanoacetoacetamide showed non-competitive inhibition with respect to ATP concentration in the coupled assay. The cyanoacetoacetamide also inhibited autophosphorylation of histidine kinases from other bacteria, indicating that the coupled assay could detect general inhibitors of histidine kinase function. Inhibition of HpkA autophosphorylation by this compound was probably caused by aggregation of HpkA, consistent with a previous model for other hydrophobic compounds. In contrast, ethodin was a potent inhibitor of the combined assay, did not inhibit HpkA autophosphorylation, but still led to aggregation of HpkA. These data suggest that ethodin bound to the HpkA kinase and inhibited transfer of the phosphoryl group to DrrA. A peptide corresponding to the phosphorylation site of DrrA appeared to inhibit TCS function by a mechanism similar to that of ethodin, except that autophosphorylation was inhibited at high peptide concentrations. The latter mechanism of inhibition of TCS function is unusual and its analysis demonstrates the utility of these approaches to the kinetic analyses of additional

  3. Dispersion equation for ballooning modes in two-component plasma

    NASA Astrophysics Data System (ADS)

    Kozlov, D. A.; Mazur, N. G.; Pilipenko, V. A.; Fedorov, E. N.; Fedorov

    2014-06-01

    The ballooning magnetohydrodynamic (MHD) modes have been often suggested as a possible instability trigger of the substorm onset, and a mechanism of compressional waves in the outer magnetosphere and magnetotail. Commonly, these disturbances are characterized by the local dispersion equation that is widely applied for the description of ultra-low-frequency oscillatory disturbances and instabilities in the nightside magnetosphere. In realistic situations, especially in the inner magnetosphere, the magnetospheric plasma is composed of two components: background `cold' plasma and `hot' particles. The ballooning disturbances in a two-component plasma immersed into a curved magnetic field are described with the system of coupled equations for the Alfvén and slow magnetosonic (SMS) modes. We have reduced the basic system of MHD equations to the dispersion equation for the small-scale in transverse direction disturbances, and applied WKB approximation along a field line. As a result, we have derived a dispersion equation that can be used for geophysical applications. In particular, from this relationship the dispersion, instability threshold, and stop-bands of the Alfvén and SMS modes in two-component plasma have been examined.

  4. Neural networks using two-component Bose-Einstein condensates

    PubMed Central

    Byrnes, Tim; Koyama, Shinsuke; Yan, Kai; Yamamoto, Yoshihisa

    2013-01-01

    The authors previously considered a method of solving optimization problems by using a system of interconnected network of two component Bose-Einstein condensates (Byrnes, Yan, Yamamoto New J. Phys. 13, 113025 (2011)). The use of bosonic particles gives a reduced time proportional to the number of bosons N for solving Ising model Hamiltonians by taking advantage of enhanced bosonic cooling rates. Here we consider the same system in terms of neural networks. We find that up to the accelerated cooling of the bosons the previously proposed system is equivalent to a stochastic continuous Hopfield network. This makes it clear that the BEC network is a physical realization of a simulated annealing algorithm, with an additional speedup due to bosonic enhancement. We discuss the BEC network in terms of neural network tasks such as learning and pattern recognition and find that the latter process may be accelerated by a factor of N. PMID:23989391

  5. Exact two-component relativistic energy band theory and application.

    PubMed

    Zhao, Rundong; Zhang, Yong; Xiao, Yunlong; Liu, Wenjian

    2016-01-28

    An exact two-component (X2C) relativistic density functional theory in terms of atom-centered basis functions is proposed for relativistic calculations of band structures and structural properties of periodic systems containing heavy elements. Due to finite radial extensions of the local basis functions, the periodic calculation is very much the same as a molecular calculation, except only for an Ewald summation for the Coulomb potential of fluctuating periodic monopoles. For comparison, the nonrelativistic and spin-free X2C counterparts are also implemented in parallel. As a first and pilot application, the band gaps, lattice constants, cohesive energies, and bulk moduli of AgX (X = Cl, Br, I) are calculated to compare with other theoretical results. PMID:26827200

  6. Determinants of specificity in two-component signal transduction.

    PubMed

    Podgornaia, Anna I; Laub, Michael T

    2013-04-01

    Maintaining the faithful flow of information through signal transduction pathways is critical to the survival and proliferation of organisms. This problem is particularly challenging as many signaling proteins are part of large, paralogous families that are highly similar at the sequence and structural levels, increasing the risk of unwanted cross-talk. To detect environmental signals and process information, bacteria rely heavily on two-component signaling systems comprised of sensor histidine kinases and their cognate response regulators. Although most species encode dozens of these signaling pathways, there is relatively little cross-talk, indicating that individual pathways are well insulated and highly specific. Here, we review the molecular mechanisms that enforce this specificity. Further, we highlight recent studies that have revealed how these mechanisms evolve to accommodate the introduction of new pathways by gene duplication. PMID:23352354

  7. An Introductory Idea for Teaching Two-Component Phase Diagrams

    ERIC Educational Resources Information Center

    Peckham, Gavin D.; McNaught, Ian J.

    2011-01-01

    The teaching of two-component phase diagrams has attracted little attention in this "Journal," and it is hoped that this article will make a useful contribution. Current physical chemistry textbooks describe two-component phase diagrams adequately, but do so in a piecemeal fashion one section at a time; first solid-liquid equilibria, then…

  8. Topological objects in two-component Bose-Einstein condensates

    SciTech Connect

    Cho, Y. M.; Khim, Hyojoong; Zhang, Pengming

    2005-12-15

    We study the topological objects in two-component Bose-Einstein condensates. We compare two competing theories of two-component Bose-Einstein condensates, the popular Gross-Pitaevskii theory, and the recently proposed gauge theory of two-component Bose-Einstein condensate which has an induced vorticity interaction. We show that two theories produce very similar topological objects, in spite of the obvious differences in dynamics. Furthermore we show that the gauge theory of two-component Bose-Einstein condensates, with the U(1) gauge symmetry, is remarkably similar to the Skyrme theory. Just like the Skyrme theory this theory admits the non-Abelian vortex, the helical vortex, and the vorticity knot. We construct the lightest knot solution in two-component Bose-Einstein condensates numerically, and discuss how the knot can be constructed in the spin-(1/2) condensate of {sup 87}Rb atoms.

  9. Role of functionality in two-component signal transduction: A stochastic study

    NASA Astrophysics Data System (ADS)

    Maity, Alok Kumar; Bandyopadhyay, Arnab; Chaudhury, Pinaki; Banik, Suman K.

    2014-03-01

    We present a stochastic formalism for signal transduction processes in a bacterial two-component system. Using elementary mass action kinetics, the proposed model takes care of signal transduction in terms of a phosphotransfer mechanism between the cognate partners of a two-component system, viz., the sensor kinase and the response regulator. Based on the difference in functionality of the sensor kinase, the noisy phosphotransfer mechanism has been studied for monofunctional and bifunctional two-component systems using the formalism of the linear noise approximation. Steady-state analysis of both models quantifies different physically realizable quantities, e.g., the variance, the Fano factor (variance/mean), and mutual information. The resultant data reveal that both systems reliably transfer information of extracellular environment under low external stimulus and in a high-kinase-and-phosphatase regime. We extend our analysis further by studying the role of the two-component system in downstream gene regulation.

  10. Role of functionality in two-component signal transduction: a stochastic study.

    PubMed

    Maity, Alok Kumar; Bandyopadhyay, Arnab; Chaudhury, Pinaki; Banik, Suman K

    2014-03-01

    We present a stochastic formalism for signal transduction processes in a bacterial two-component system. Using elementary mass action kinetics, the proposed model takes care of signal transduction in terms of a phosphotransfer mechanism between the cognate partners of a two-component system, viz., the sensor kinase and the response regulator. Based on the difference in functionality of the sensor kinase, the noisy phosphotransfer mechanism has been studied for monofunctional and bifunctional two-component systems using the formalism of the linear noise approximation. Steady-state analysis of both models quantifies different physically realizable quantities, e.g., the variance, the Fano factor (variance/mean), and mutual information. The resultant data reveal that both systems reliably transfer information of extracellular environment under low external stimulus and in a high-kinase-and-phosphatase regime. We extend our analysis further by studying the role of the two-component system in downstream gene regulation. PMID:24730880

  11. Cyanobacterial Two-Component Proteins: Structure, Diversity, Distribution, and Evolution†

    PubMed Central

    Ashby, Mark K.; Houmard, Jean

    2006-01-01

    A survey of the already characterized and potential two-component protein sequences that exist in the nine complete and seven partially annotated cyanobacterial genome sequences available (as of May 2005) showed that the cyanobacteria possess a much larger repertoire of such proteins than most other bacteria. By analysis of the domain structure of the 1,171 potential histidine kinases, response regulators, and hybrid kinases, many various arrangements of about thirty different modules could be distinguished. The number of two-component proteins is related in part to genome size but also to the variety of physiological properties and ecophysiologies of the different strains. Groups of orthologues were defined, only a few of which have representatives with known physiological functions. Based on comparisons with the proposed phylogenetic relationships between the strains, the orthology groups show that (i) a few genes, some of them clustered on the genome, have been conserved by all species, suggesting their very ancient origin and an essential role for the corresponding proteins, and (ii) duplications, fusions, gene losses, insertions, and deletions, as well as domain shuffling, occurred during evolution, leading to the extant repertoire. These mechanisms are put in perspective with the different genetic properties that cyanobacteria have to achieve genome plasticity. This review is designed to serve as a basis for orienting further research aimed at defining the most ancient regulatory mechanisms and understanding how evolution worked to select and keep the most appropriate systems for cyanobacteria to develop in the quite different environments that they have successfully colonized. PMID:16760311

  12. Travelling wave solutions for some two-component shallow water models

    NASA Astrophysics Data System (ADS)

    Dutykh, Denys; Ionescu-Kruse, Delia

    2016-07-01

    In the present study we perform a unified analysis of travelling wave solutions to three different two-component systems which appear in shallow water theory. Namely, we analyze the celebrated Green-Naghdi equations, the integrable two-component Camassa-Holm equations and a new two-component system of Green-Naghdi type. In particular, we are interested in solitary and cnoidal-type solutions, as two most important classes of travelling waves that we encounter in applications. We provide a complete phase-plane analysis of all possible travelling wave solutions which may arise in these models. In particular, we show the existence of new type of solutions.

  13. Capacitance Transducers for Concentration Measurements in Two Component Flow.

    NASA Astrophysics Data System (ADS)

    Matoorianpour, Nasser

    Available from UMI in association with The British Library. This thesis is concerned with the design and development of instrumentation for non-intrusive measurements of component volumetric concentrations on industrial two component flow including gas/liquid and gas/solids systems. The design and optimisation of two amplitude modulated capacitance transducers for "steady state" or slowly varying concentration measurements are described. A new type of capacitance transducer is the symmetrical capacitance bridge which consists of capacitive voltage dividers based on the voltage measuring method. The sensing electrodes of the sensor in this system are driven at two opposite voltages to produce a symmetrical capacitance sensitivity across the sensing region. Optimum transducer parameters, the use of the driven guard technique and minimised input capacitance to the electronics provide maximum sensitivity in this capacitance bridge. The base line stability of the symmetrical capacitance bridge is further improved by applying a Commutating Auto Zero technique to the transducer. The capacitance sensitivity across the sensing volumes of three pairs of concave plate electrode systems, each subtending a different angle has been investigated experimentally. One application of this transducer, considered in this research, is the void fraction determination in air/water two component flow. A second type of high stability capacitance bridge, based on the current measuring method, is the "stray immune" transformer ratio amplifier bridge. Its high pass filter configuration, using an LCR network, provides noise immunity against the charged solids in the applications involving pneumatically conveyed solid materials. A non-intrusive mass flow rate determination system, based on the stray immune transformer ratio amplifier bridge for the steady state concentration measurements and a low cost hardware cross correlation flowmeter for component velocity measurements, has been developed

  14. The Two-Component GacS-GacA System Activates lipA Translation by RsmE but Not RsmA in Pseudomonas protegens Pf-5

    PubMed Central

    Zha, Daiming; Xu, Li; Zhang, Houjin

    2014-01-01

    In Pseudomonas spp., the Gac-Rsm signal transduction system is required for the production of lipases. The current model assumes that the system induces lipase gene transcription mediated through the quorum-sensing (QS) system. However, there are no reports of a QS system based upon N-acyl homoserine lactones or the regulation of lipase gene expression in Pseudomonas protegens. In this study, we investigated the regulatory mechanism acting on lipA expression activated by the Gac-Rsm system in P. protegens Pf-5 through deletion and overexpression of gacA, overexpression of rsmA or rsmE, expression of various lacZ fusions, reverse transcription-PCR analysis, and determination of whole-cell lipase activity. The results demonstrated that the GacS-GacA (GacS/A) system activates lipA expression at both the transcriptional and the translational levels but that the translational level is the key regulatory pathway. Further results showed that the activation of lipA translation by the GacS/A system is mediated through RsmE, which inhibits lipA translation by binding to the ACAAGGAUGU sequence overlapping the Shine-Dalgarno (SD) sequence of lipA mRNA to hinder the access of the 30S ribosomal subunit to the SD sequence. Moreover, the GacS/A system promotes lipA transcription through the mediation of RsmA inhibiting lipA transcription via an unknown pathway. Besides the transcriptional repression, RsmA mainly activates lipA translation by negatively regulating rsmE translation. In summary, in P. protegens Pf-5, the Gac-RsmE system mainly and directly activates lipA translation and the Gac-RsmA system indirectly enhances lipA transcription. PMID:25128345

  15. Complexation in two-component chlortetracycline-melanin solutions

    NASA Astrophysics Data System (ADS)

    Lapina, V. A.; Pershukevich, P. P.; Dontsov, A. E.; Bel'Kov, M. V.

    2008-01-01

    The spectra and kinetics of fluorescence of two-component solutions of the chlortetracycline (CHTC)-DOPA-melanin (melanin or ME) system in water have been investigated. The data obtained have been compared to similar data for solutions of CHTC-melanosome from bull eye (MB), which contains natural melanin, in K-phosphate buffer at pH 7.4. The overall results indicate the occurrence of complexation between molecules of CHTC and ME as they are being excited. The studies of complexation in the solution of CHTC-MB in the buffer are complicated by the formation of a CHTC-buffer complex. The effect of optical radiation in the range 330-750 nm on the CHTC-ME complex shows selectivity: the greatest change in the spectrum occurs when the wavelength of the exciting radiation coincides with the long-wavelength band maximum of the fluorescence excitation spectrum of the CHTC-ME complex in aqueous solution. In this range, CHTC and especially ME show high photochemical stability. The nature of the radiation effect on the studied compounds in the hard UV range (λ < 330 nm) differs greatly from that in the range 330-750 nm. It is apparently accompanied by significant photochemical transmutations of all system components. By comparing the characteristics of the CHTC-ME systems with those of the related drug doxycycline (DC-ME), the conclusion has been made that the chlorine atom plays a vital role in formation of the short-wavelength band in the fluorescence spectrum of the CHTC-ME complex.

  16. Second Moment Closure Near the Two-component Limit

    NASA Technical Reports Server (NTRS)

    Rubinstein, Robert; Girimaji, Sharath S.

    2006-01-01

    The purpose of this paper is to explore some wider implications of the two-component limit for both single point turbulence models and spectral closure theories. Although the two-component limit arises most naturally in inhomogeneous problems like wall-bounded turbulence, the analysis will be restricted to homogeneous turbulence. But since homogeneous turbulence is the crucial case for realizability, the conclusions will nevertheless be applicable to modeling. Th essential point of our argument is that whereas the evolution of the stochastic velocity field is Markovian because it is governed by the Navier-Stokes equations, the exact stress evolution equation is not Markovian because it is unclosed. This property of moment evolution has been stressed by Kraichnan (1959). We will show that modeling stress evolution at the two-component limit with a closure that is Markovian in the stresses alone leads to basic inconsistencies in single-point modeling and, perhaps surprisingly, in spectral modes as well.

  17. Transplantation of prokaryotic two-component signaling pathways into mammalian cells

    PubMed Central

    Hansen, Jonathan; Mailand, Erik; Swaminathan, Krishna Kumar; Schreiber, Joerg; Angelici, Bartolomeo; Benenson, Yaakov

    2014-01-01

    Signaling pathway engineering is a promising route toward synthetic biological circuits. Histidine–aspartate phosphorelays are thought to have evolved in prokaryotes where they form the basis for two-component signaling. Tyrosine-serine–threonine phosphorelays, exemplified by MAP kinase cascades, are predominant in eukaryotes. Recently, a prokaryotic two-component pathway was implemented in a plant species to sense environmental trinitrotoluene. We reasoned that “transplantation” of two-component pathways into mammalian host could provide an orthogonal and diverse toolkit for a variety of signal processing tasks. Here we report that two-component pathways could be partially reconstituted in mammalian cell culture and used for programmable control of gene expression. To enable this reconstitution, coding sequences of histidine kinase (HK) and response regulator (RR) components were codon-optimized for human cells, whereas the RRs were fused with a transactivation domain. Responsive promoters were furnished by fusing DNA binding sites in front of a minimal promoter. We found that coexpression of HKs and their cognate RRs in cultured mammalian cells is necessary and sufficient to strongly induce gene expression even in the absence of pathways’ chemical triggers in the medium. Both loss-of-function and constitutive mutants behaved as expected. We further used the two-component signaling pathways to implement two-input logical AND, NOR, and OR gene regulation. Thus, two-component systems can be applied in different capacities in mammalian cells and their components can be used for large-scale synthetic gene circuits. PMID:25331891

  18. Spontaneous mutations in the CsrRS two-component regulatory system of Streptococcus pyogenes result in enhanced virulence in a murine model of skin and soft tissue infection.

    PubMed

    Engleberg, N C; Heath, A; Miller, A; Rivera, C; DiRita, V J

    2001-04-01

    CsrS/CsrR is a 2-component system in Streptococcus pyogenes that negatively regulates hyaluronic capsule and several exotoxins. To detect spontaneous mutations in csrRS, mucoid and large colony variants of M1 strain MGAS166 were isolated from experimental murine skin infections. By use of complementation with a csrRS(+) plasmid, relevant mutations were also detected in 7 of 12 human clinical isolates. The presence of spontaneous mutants in mouse infection was associated with larger, more necrotic lesions. Most spontaneous changes in CsrR resulted from single amino acid substitutions, whereas most csrS mutations were frameshift or nonsense mutations. In 2 instances, IS1548 insertions were found in csrS. Experimental inoculation of mixtures of wild-type (wt) and csrRS(-) bacteria yielded larger, more necrotic lesions than did either strain at twice the inoculum, which suggests that these variants may exhibit pathogenic synergy. Spontaneous emergence of csrRS(-) mutants in vivo enhances the virulence of wt bacteria and increases severity of murine skin infection. PMID:11237829

  19. Identification and functional assay of the interaction motifs in the partner protein OsNAR2.1 of the two-component system for high-affinity nitrate transport.

    PubMed

    Liu, Xiaoqin; Huang, Daimin; Tao, Jinyuan; Miller, Anthony J; Fan, Xiaorong; Xu, Guohua

    2014-10-01

    A partner protein, NAR2, is essential for high-affinity nitrate transport of the NRT2 protein in plants. However, the NAR2 motifs that interact with NRT2s for their plasma membrane (PM) localization and nitrate transporter activity have not been functionally characterized. In this study, OsNAR2.1 mutations with different carbon (C)-terminal deletions and nine different point mutations in the conserved regions of NAR2 homologs in plants were generated to explore the essential motifs involved in the interaction with OsNRT2.3a. Screening using the membrane yeast two-hybrid system and Xenopus oocytes for nitrogen-15 ((15)N) uptake demonstrated that either R100G or D109N point mutations impaired the OsNAR2.1 interaction with OsNRT2.3a. Western blotting and visualization using green fluorescent protein fused to either the N- or C-terminus of OsNAR2.1 indicated that OsNAR2.1 is expressed in both the PM and cytoplasm. The split-yellow fluorescent protein (YFP)/BiFC analyses indicated that OsNRT2.3a was targeted to the PM in the presence of OsNAR2.1, while either R100G or D109N mutation resulted in the loss of OsNRT2.3a-YFP signal in the PM. Based on these results, arginine 100 and aspartic acid 109 of the OsNAR2.1 protein are key amino acids in the interaction with OsNRT2.3a, and their interaction occurs in the PM but not cytoplasm. PMID:25103875

  20. Two-component integrable generalizations of Burgers equations with nondiagonal linearity

    NASA Astrophysics Data System (ADS)

    Talati, Daryoush; Turhan, Refi˙k.

    2016-04-01

    Two-component second- and third-order Burgers type systems with nondiagonal constant matrix of leading order terms are classified for higher symmetries. New integrable systems are obtained. Master symmetries of the obtained symmetry integrable systems, and bi-Poisson structures of those that also possess conservation laws, are given.

  1. Magnetorheological fluids with two-component dispersed phase

    NASA Astrophysics Data System (ADS)

    Korobko, E. V.; Novikova, Z. A.; Zhurauski, M. A.

    2015-04-01

    In the paper the results of investigations of rheological properties of magnetorheological fluids with two-component dispersed phase are presented. Normal and tangential components of the mechanical stress in fluids in the magnetic field are determined. It is showed that using of carbonyl iron and chromium oxide as dispersed phase components allows to achieve essential structural response on magnetic influence

  2. Entanglement Properties in Two-Component Bose-Einstein Condensate

    NASA Astrophysics Data System (ADS)

    Jiang, Di-You

    2016-05-01

    We investigate entanglement inseparability and bipartite entanglement of in two-component Bose-Einstein condensate in the presence of the nonlinear interatomic interaction, interspecies interaction. Entanglement inseparability and bipartite entanglement have the similar properties. More entanglement can be generated by adjusting the nonlinear interatomic interaction and control the time interval of the entanglement by adjusting interspecies interaction.

  3. Non-destructive testing using two-component/two-wave mixing interferometer

    SciTech Connect

    Wartelle, A.; Pouet, B.; Breugnot, S.

    2011-06-23

    A new laser-based ultrasonic (LBU) receiver was recently introduced. The novel architecture is based on two-wave mixing in photorefractive materials and allows simultaneous measurement of in-plane and out-of-plane displacements (two- component). By taking advantage of recent developments in electronic processing and our knowledge on multi-channel interferometer, we achieved a compact optical system using only a single collecting aperture and a single laser probe beam. We will characterize the system performances and present experimental results demonstrating the capability for this compact two-component interferometer.

  4. Synthesis and Characterization of Two Component Alloy Nanoparticles

    NASA Astrophysics Data System (ADS)

    Tabatabaei, Salomeh

    Alloying is an old trick used to produce new materials by synergistically combining at least two components. New developments in nanoscience have enabled new degrees of freedom, such as size, solubility and concentration of the alloying element to be utilized in the design of the physical properties of alloy nanoparticles (ANPs). ANPs as multi-functional materials have applications in catalysis, biomedical technologies and electronics. Phase diagrams of ANPs are very little known and may not represent that of bulk picture, furthermore, ANPs with different crystallite orientation and compositions could remain far from equilibrium. Here, we studied the synthesis and stability of Au-Sn and Ag-Ni ANPs with chemical reduction method at room temperature. Due to the large difference in the redox potentials of Au and Sn, co-reduction is not a reproducible method. However, two step successive reductions was found to be more reliable to generate Au-Sn ANPs which consists of forming clusters in the first step (either without capping agent or with weakly coordinated surfactant molecules) and then undergoing a second reduction step in the presence of another metal salt. Our observation also showed that capping agents (Cetrimonium bromide or (CTAB)) and Polyacrylic acid (PAA)) play a key role in the alloying process and shorter length capping agent (PAA) may facilitate the diffusion of individual components and thus enabling better alloying. Different molar ratios of Sn and Au precursors were used to study the effect of alloying elements on the melting point and the crystalline structures and melting points were determined by various microscopy and spectroscopy techniques and differential scanning calorimetry (DSC). A significant depression (up to150°C) in the melting transition was observed for the Au-Sn ANPs compared to the bulk eutectic point (Tm 280°C) due to the size and shape effect. Au-Sn ANPs offer a unique set of advantages as lead-free solder material which can

  5. On the possibility of diffusionally driven oscillations in two component gas bubbles in fluids

    NASA Technical Reports Server (NTRS)

    Weinberg, Michael C.

    1986-01-01

    The problem of an isolated, stationary, two-component gas bubble in a fluid is analyzed. The appropriate governing equations, and an approximate version of these equations, for this model system are reviewed. The qualitative differences in bubble dissolution behavior between single- and two-component gas bubbles are elucidated. In particular, it is demonstrated that in the latter case the gas bubble radius may exhibit extrema as a function of time for certain values of the controlling parameters. The conditions under which these extrema may occur, and the maximum number of extrema which are permitted are elucidated.

  6. A two-component rain model for the prediction of attenuation statistics

    NASA Technical Reports Server (NTRS)

    Crane, R. K.

    1982-01-01

    A two-component rain model has been developed for calculating attenuation statistics. In contrast to most other attenuation prediction models, the two-component model calculates the occurrence probability for volume cells or debris attenuation events. The model performed significantly better than the International Radio Consultative Committee model when used for predictions on earth-satellite paths. It is expected that the model will have applications in modeling the joint statistics required for space diversity system design, the statistics of interference due to rain scatter at attenuating frequencies, and the duration statistics for attenuation events.

  7. Block algebra in two-component BKP and D type Drinfeld-Sokolov hierarchies

    SciTech Connect

    Li, Chuanzhong He, Jingsong

    2013-11-15

    We construct generalized additional symmetries of a two-component BKP hierarchy defined by two pseudo-differential Lax operators. These additional symmetry flows form a Block type algebra with some modified (or additional) terms because of a B type reduction condition of this integrable hierarchy. Further we show that the D type Drinfeld-Sokolov hierarchy, which is a reduction of the two-component BKP hierarchy, possess a complete Block type additional symmetry algebra. That D type Drinfeld-Sokolov hierarchy has a similar algebraic structure as the bigraded Toda hierarchy which is a differential-discrete integrable system.

  8. Machine for applying a two component resin to a roadway surface

    DOEpatents

    Huszagh, D.W.

    1984-01-01

    A portable machine for spraying two component resins onto a roadway, the machine having a pneumatic control system, including means for purging the machine of mixed resin with air and then removing remaining resin with solvent. Interlocks prevent contamination of solvent and resin, and mixed resin can be purged in the event of a power failure.

  9. Machine for applying a two component resin to a roadway surface

    DOEpatents

    Huszagh, Donald W.

    1985-01-01

    A portable machine for spraying two component resins onto a roadway, the machine having a pneumatic control system, including apparatus for purging the machine of mixed resin with air and then removing remaining resin with solvent. Interlocks prevent contamination of solvent and resin, and mixed resin can be purged in the event of a power failure.

  10. Electric micro fields in simulated two component plasmas

    SciTech Connect

    Calisti, A.; Talin, B.; Ferri, S.; Mosse, C.; Lisitsa, V.; Bureyeva, L.; Gigosos, M. A.; Gonzalez, M. A.; Rio Gaztelurrutia, T. del

    2008-10-22

    The statistical properties of local electric fields in an classical plasma are investigated by molecular dynamics (MD) simulation. Two-component plasma simulations of neutral hydrogen, protons and electrons for intermediate plasma coupling conditions, typically N{sub e}{approx_equal}10{sup 18}cm{sup -3}, T{sub e}{approx_equal}1eV, have been carried out. These simulations appear as a possible and very useful way to generate relevant microfield sample-sets appropriate for ion emitter lineshape simulations for plasma spectroscopy and to provide guidance for line shape modeling.

  11. Interaction potentials and thermodynamic properties of two component semiclassical plasma

    SciTech Connect

    Ramazanov, T. S.; Moldabekov, Zh. A.; Ismagambetova, T. N.; Gabdullin, M. T.

    2014-01-15

    In this paper, the effective interaction potential in two component semiclassical plasma, taking into account the long-range screening and the quantum-mechanical diffraction effects at short distances, is obtained on the basis of dielectric response function method. The structural properties of the semiclassical plasma are considered. The thermodynamic characteristics (the internal energy and the equation of state) are calculated using two methods: the method of effective potentials and the method of micropotentials with screening effect taken into account by the Ornstein-Zernike equation in the HNC approximation.

  12. Momentum flux in two phase two component low quality flow.

    NASA Technical Reports Server (NTRS)

    Baumeister, K. J.; Graham, R. W.; Henry, R. E.

    1972-01-01

    Values of a one-dimensional momentum flux at a test section discharge station of a two-phase two-component low quality flow computed by two methods, one based on a one-dimensional homogeneous model and the other on a variable slip model, are compared to experimental values for a range of two-phase flow conditions. The comparison seems to indicate the superior accuracy in momentum flux predictions to be on the side of the one-dimensional homogeneous model.

  13. Voids within the two-component dust model

    NASA Astrophysics Data System (ADS)

    Haager, Gernot

    1998-11-01

    A new family within the spherically symmetric two-component dust metrics (Haager G 1997 Class. Quantum Grav. 14 2219) with an additional homothetic vector is investigated in detail. These metrics are regular except for a big bang singularity and can be given by an asymptotic expansion of the metric coefficients for large times after the big bang. Using this family, voids can be described whose edge is not comoving in comparison with its surroundings. A concrete example is given where the edge of the void is contracting, while the dust background is expanding.

  14. Measurement of two-component flow using ultrasonic flowmeters

    NASA Astrophysics Data System (ADS)

    Whitehouse, J. C.; Eghbali, D. A.; Flitton, V. E.; Anderson, D. G.

    Calibration of transit-time and Doppler ultrasonic flowmeters under two-component flow conditions has been conducted on 400 mm (16-in.) pipe. Testing covered total flows of 0.19 to 1.89 m(exp 3)/s (3000 to 30,000 gpm) and void fractions up to 40 percent. Both flowmeter types accurately measured total volumetric flow over a portion of their ranges. Pipe average void fraction, based on a three-beam gamma densitometer, was used to determine water component flow under stratified flow conditions, with similar results.

  15. No electrostatic supersolitons in two-component plasmas

    SciTech Connect

    Verheest, Frank; Lakhina, Gurbax S.; Hellberg, Manfred A.

    2014-06-15

    The concept of acoustic supersolitons was introduced for a very specific plasma with five constituents, and discussed only for a single set of plasma parameters. Supersolitons are characterized by having subsidiary extrema on the sides of a typical bipolar electric field signature, or by association with a root beyond double layers in the fully nonlinear Sagdeev pseudopotential description. It was subsequently found that supersolitons could exist in several plasma models having three constituent species, rather than four or five. In the present paper, it is proved that standard two-component plasma models cannot generate supersolitons, by recalling and extending results already in the literature, and by establishing the necessary properties of a more recent model.

  16. Bounds to the conductivity of some two-component composites

    NASA Astrophysics Data System (ADS)

    Helsing, Johan

    1993-02-01

    Calculation of third-order bounds to the conductivity of isotropic two-component composites is discussed. Coincidence of the Beran bounds and bounds derived using trial fields based on the solution of a single-body electrostatic boundary-value problem is demonstrated for a random distribution of impenetrable ellipsoids. This extends a proof of Beasley and Torquato [J. Appl. Phys. 60, 3576 (1986)]. A structural parameter related to third-order bounds is calculated for a face-centered cubic array of cubes in a matrix. For an array of rectangular blocks an upper bound in one direction is derived. This bound, and its two-dimensional analogs, become very sharp in the limit of strong inhomogeneity. Improved third- and fourth-order bounds for the three-dimensional checkerboard are presented.

  17. Deconvolved spectra of Two Component Advective Flow including jet

    NASA Astrophysics Data System (ADS)

    Mondal, Santanu; Debnath, Dipak; Chakrabarti, Sandip Kumar

    2016-07-01

    Outflows and winds are produced when the accretion flows have positive specific energy. Two Component Advective Flow (TCAF) model suggests that the centrifugal pressure supported region of the flow outside the black hole horizon, acts as the base of this outflow. We study the spectral properties of the TCAF which includes a jet component. We consider the jet as a conical in shape which also up-scatters the soft photons from the Keplerian disc. We see that due to the presence of jet component, spectrum become harder as the jet itself behaves like an another Compton cloud above the inner hot corona. We also see how the jet spectra depends on the flow rates. This gives the direct link in timing properties of the X-rays in CENBOL component and the radiation emitted in the jet component.

  18. Toxicological study of ''Aralhex Brush'' and its two components

    SciTech Connect

    London, J.E.; Smith, D.M.

    1985-09-01

    The acute oral LD/sub 50/ values for the adhesive ''Aralhex Brush'' for mice and rats are greater than 5g/kg. According to classified guidelines, the mixture would be considered only slightly toxic or practically nontoxic in both species. Skin application studies in the rabbit with the adhesive demonstrated that it was cutaneously mildly irritating; however, based on the primary irritation index, the adhesive's two precursor components were nonirritating. The adhesive and components I were mildly irritating in the rabbit eye application studies and component II was non-irritating. The sensitization study in the guinea pig did not show ''Aralhex Brush'' or its two components to be sensitizers. 5 refs., 3 tabs.

  19. Two-component wind fields from single scanning aerosol lidar

    NASA Astrophysics Data System (ADS)

    Mayor, Shane D.; Derian, Pierre; Mauzey, Christopher F.; Hamada, Masaki

    2015-09-01

    An overview of recent research results on the performance of two motion estimation algorithms used to deduce two-component horizontal wind fields from ground-based scanning elastic backscatter lidar is presented. One motion estimation algorithm is a traditional cross-correlation method optimized for atmospheric lidar data. The second algorithm is a recently-developed wavelet-based optical flow. An intercomparison of experimental results with measurements from an independent Doppler lidar over an agricultural area in Chico, California, during daytime convective conditions in 2013-14 are presented. Finally, early results from application of the algorithms to data collected over the ocean from a compact and portable aerosol lidar that was deployed on the northern California coast in March of 2015 are presented.

  20. Dynamics of two-component membranes surrounded by viscoelastic media.

    PubMed

    Komura, Shigeyuki; Yasuda, Kento; Okamoto, Ryuichi

    2015-11-01

    We discuss the dynamics of two-component fluid membranes which are surrounded by viscoelastic media. We assume that membrane-embedded proteins can diffuse laterally and induce a local membrane curvature. The mean squared displacement of a tagged membrane segment is obtained as a generalized Einstein relation. When the elasticity of the surrounding media obeys a power-law behavior in frequency, an anomalous diffusion of the membrane segment is predicted. We also consider the situation where the proteins generate active non-equilibrium forces. The generalized Einstein relation is further modified by an effective temperature that depends on the force dipole energy. The obtained generalized Einstein relations are useful for membrane microrheology experiments. PMID:26448393

  1. Nonlocal Transport Model for Two-Component Plasmas

    NASA Astrophysics Data System (ADS)

    Zheng, Zhen

    My PhD thesis concerns nonlocal effects on the transport processes in two-component (electron and ion) plasmas. My objective is to construct a self-consistent nonlocal transport model that is applicable in fully-ionized homogeneous Maxwellian plasmas with small-amplitude perturbations for arbitrary particle collisionalities. The fundamental method starts with a rigorous solution of the full set of linearized Fokker-Planck kinetic equations with the Landau collision operators for two-component plasmas. Then a procedure is implemented for derivation of the linear fluid equations which are closed by the transport relations. Thereby a complete list of transport coefficients for each component is computed in the broad range of temporal and spatial scales. Some new transport coefficients are found from the nonlocal hydrodynamic formulation. Ion collisions are self-consistently included in all the calculations. The electric susceptibilities and dispersion relation can thus be derived from this linear nonlocal hydrodynamics for both isothermal and non-isothermal cases. With the aid of these formulations, some important plasma quantities are successfully calculated and some practical fitting formulae are proposed, i.e., the mode frequencies and damping rates of ion acoustic wave (IAW) and entropy wave (ENW). In addition, this linear nonlocal hydrodynamics has been applied to a derivation of the dynamic form factor S(k,w) that serves to describe and explain correctly the features of the frequency spectra observed in Thomson scattering experiments. The most significant accomplishment in my research work is a thorough investigation and a deep analysis of nonlocal ion effects on longitudinal low-frequency plasma fluctuations.

  2. Vortices of a rotating two-component dipolar Bose-Einstein condensate in an optical lattice

    NASA Astrophysics Data System (ADS)

    Wang, Lin-Xue; Dong, Biao; Chen, Guang-Ping; Han, Wei; Zhang, Shou-Gang; Shi, Yu-Ren; Zhang, Xiao-Fei

    2016-01-01

    We consider a two-component Bose-Einstein condensate, which consists of both dipolar and scalar bosonic atoms, in a confinement that is composed of a harmonic oscillator and an underlying optical lattice set rotation. When the dipoles are polarized along the symmetry axis of the harmonic potential, the ground-state density distributions of such a system are investigated as a function of the relative strength between the dipolar and contact interactions, and of the rotation frequency. Our results show that the number of vortices and its related vortex structures of such a system depend strongly on such system parameters. The special two-component system considered here opens up alternate ways for exploring the rich physics of dipolar quantum gases.

  3. Two-component coupled KdV equations and its connection with the generalized Harry Dym equations

    SciTech Connect

    Popowicz, Ziemowit

    2014-01-15

    It is shown that three different Lax operators in the Dym hierarchy produce three generalized coupled Harry Dym equations. These equations transform, via the reciprocal link, to the coupled two-component Korteweg de Vries (KdV) system. The first equation gives us known integrable two-component KdV system, while the second reduces to the known symmetrical two-component KdV equation. The last one reduces to the Drienfeld-Sokolov equation. This approach gives us new Lax representation for these equations.

  4. Locating-chromatic number for a graph of two components

    NASA Astrophysics Data System (ADS)

    Welyyanti, Des; Simanjuntak, Rinovia; Uttunggadewa, Saladin; Baskoro, Edy Tri

    2016-02-01

    The study of locating-chromatic number of a graph initiated by Chartrand et al. [5] is only limited for connected graphs. In 2014, Welyyanti et al. extended this notion so that the locating-chromatic number can also be applied to disconnected graphs. Let c be a k-coloring of a disconnected graph H(V, E) and ∏ = {C1,C2, …, Ck} be the partition of V (H) induced by c, where Ci is the set of all vertices receiving color i. The color code c∏(v) of a vertex v ∈ H is the ordered k-tuple (d(v,C1), d(v,C2), …, d(v,Ck)), where d(v,Ci) = min{d(v, x)|x ∈ Ci} and d(v,Ci) < ∞ for all i ∈ [1, k]. If all vertices of H have distinct color codes, then c is called a locating-coloring of H. The locating-chromatic number of H, denoted by χ'L(H ) , is the smallest k such that H admits a locating-coloring with k colors, otherwise we say that χ'L(H )=∞ . In this paper, we determine locating-chromatic number of a graph with two components where each component has the locating-chromatic number 3.

  5. Two-Component Models of Dwarf Galaxy Tidal Disruption

    NASA Astrophysics Data System (ADS)

    Bauer, Jacob; Newberg, Heidi Jo; Judd, Roland; Widrow, Larry; Shelton, Siddhartha; Thompson, Jeffery; Weiss, Jake

    2015-01-01

    Using MilkyWay@Home, a distributed computing platform running BOINC (Berkley Open Infrastructure for Network Computing), we employ 0.5 PFLOPs of computational power to recover the parameters that define a two-component dSph (dark matter and baryons) that has been tidally disrupted in the Milky Way galaxy. Our model consists of nested spherical profiles, each contributing independent scale parameters to the optimization problem, and exploits the properties of the linear Boltzmann equation and statistical equilibrium properties of dSph distributions. The n-body code is based on NEMO Stellar Toolbox and is shown to agree with this software package in the one-component limit. In addition, we employ a new 2D Earth Mover Distance (EMD) algorithm to calculate the similarity between the results of the simulations and the actual distribution of stars in tidal streams. The model has been distributed over approximately 30,000 computers each using a different parameter set; asynchronous optimization algorithms are used to find an optimal set of parameters to generate the Orphan Stream. Our method is calibrated and tested on mock data, and the stability of our model is explored. This work is funded by NSF grant AST 10-09670 and crowd funding from the MilkyWay@home volunteers.

  6. Implementation of two-component advective flow solution in XSPEC

    NASA Astrophysics Data System (ADS)

    Debnath, Dipak; Chakrabarti, Sandip K.; Mondal, Santanu

    2014-05-01

    Spectral and temporal properties of black hole candidates can be explained reasonably well using Chakrabarti-Titarchuk solution of two-component advective flow (TCAF). This model requires two accretion rates, namely the Keplerian disc accretion rate and the halo accretion rate, the latter being composed of a sub-Keplerian, low-angular-momentum flow which may or may not develop a shock. In this solution, the relevant parameter is the relative importance of the halo (which creates the Compton cloud region) rate with respect to the Keplerian disc rate (soft photon source). Though this model has been used earlier to manually fit data of several black hole candidates quite satisfactorily, for the first time, we made it user friendly by implementing it into XSPEC software of Goddard Space Flight Center (GSFC)/NASA. This enables any user to extract physical parameters of the accretion flows, such as two accretion rates, the shock location, the shock strength, etc., for any black hole candidate. We provide some examples of fitting a few cases using this model. Most importantly, unlike any other model, we show that TCAF is capable of predicting timing properties from the spectral fits, since in TCAF, a shock is responsible for deciding spectral slopes as well as quasi-periodic oscillation frequencies. L86

  7. EMW transformation in suddenly created two-component magnetized plasma

    SciTech Connect

    Dimitrijevic, M.M.; Stanic, B.V.

    1995-06-01

    Suddenly created plasmas appear practically in all pulse gas discharges or laser created plasmas as well as following either a lightning or nuclear explosion. The transformation of time-harmonic plane electromagnetic wave (EMW) in a suddenly created cold and lossless magnetoplasma was considered. Static magnetic field was arbitrary oriented. The plasma was considered to be a two component (electron and ion mixture) when longitudinal and transverse propagation were considered. It was shown that for an arbitrary orientation of the static magnetic field in electron plasma, the original linearly polarized EMW splits into eight wave modes with different orientations and energies and on nonpropagating wave mode. Some of the wave modes were strongly influenced by strength or by orientation of the external static magnetic field. When ions are included in analysis it was shown that the energy of low-frequency transverse wave modes exceeds that of the longitudinal modes and also that nonpropagating magnetic field mode disappears, which differs from results where only electron plasma was considered. The energies of the wave modes formed in the pure electron plasma only slightly differ from that when ions are included into account. The dispersion relation and amplitude distribution of the different wave modes were presented by the use of suitable diagrams.

  8. Two component laser velocimeter measurements of turbulence parameters downstream of an axisymmetric sudden expansion

    NASA Technical Reports Server (NTRS)

    Gould, Richard D.; Stevenson, Warren H.; Thompson, H. Doyle

    1986-01-01

    Simultaneous two-component laser velocimeter measurements were made in an axisymmetric sudden expansion flowfield. A specially designed correction lens was employed to correct optical aberrations introduced by the circular tube. This lens system allowed the accurate simultaneous measurement of axial and radial velocities in the test section. The experimental measurements were compared to predictions generated by a code which employed the k-epsilon turbulence model. Possible sources of differences observed between model predictions and the measurements are discussed.

  9. Capillary instability in a two-component Bose-Einstein condensate

    SciTech Connect

    Sasaki, Kazuki; Suzuki, Naoya; Saito, Hiroki

    2011-05-15

    Capillary instability and the resulting dynamics in an immiscible two-component Bose-Einstein condensate are investigated using the mean-field and Bogoliubov analyses. A long, cylindrical condensate surrounded by the other component is dynamically unstable against breakup into droplets due to the interfacial tension arising from the quantum pressure and interactions. A heteronuclear system confined in a cigar-shaped trap is proposed for realizing this phenomenon experimentally.

  10. Ferrofluidity in a Two-Component Dipolar Bose-Einstein Condensate

    SciTech Connect

    Saito, Hiroki; Kawaguchi, Yuki; Ueda, Masahito

    2009-06-12

    It is shown that the interface in a two-component Bose-Einstein condensate (BEC) with a dipole-dipole interaction spontaneously develops patterns similar to those formed in a ferrofluid. Hexagonal, labyrinthine, solitonlike structures, and hysteretic behavior are numerically demonstrated. Superflow is found to circulate around the hexagonal pattern at rest, offering evidence of supersolidity. The system sustains persistent current with a vortex line pinned by the hexagonal pattern. These phenomena may be realized using a {sup 52}Cr BEC.

  11. Monte Carlo simulation of two-component aerosol processes

    NASA Astrophysics Data System (ADS)

    Huertas, Jose Ignacio

    Aerosol processes have been extensively used for production of nanophase materials. However when temperatures and number densities are high, particle agglomeration is a serious drawback for these techniques. This problem can be addressed by encapsulating the particles with a second material before they agglomerate. These particles will agglomerate but the primary particles within them will not. When the encapsulation is later removed, the resulting powder will contain only weakly agglomerated particles. To demonstrate the applicability of the particle encapsulation method for the production of high purity unagglomerated nanosize materials, tungsten (W) and tungsten titanium alloy (W-Ti) particles were synthesized in a sodium/halide flame. The particles were characterized by XRD, SEM, TEM and EDAX. The particles appeared unagglomerated, cubic and hexagonal in shape, and had a size of 30-50 nm. No contamination was detected even after extended exposure to atmospheric conditions. The nanosized W and W-Ti particles were consolidated into pellets of 6 mm diameter and 6-8 mm long. Hardness measurements indicate values 4 times that of conventional tungsten. 100% densification was achieved by hipping the samples. To study the particle encapsulation method, a code to simulate particle formation in two component aerosols was developed. The simulation was carried out using a Monte Carlo technique. This approach allowed for the treatment of both probabilistic and deterministic events. Thus, the coagulation term of the general dynamic equation (GDE) was Monte Carlo simulated, and the condensation term was solved analytically and incorporated into the model. The model includes condensation, coagulation, sources, and sinks for two-component aerosol processes. The Kelvin effect has been included in the model as well. The code is general and does not suffer from problems associated with mass conservation, high rates of condensation and approximations on particle composition. It has

  12. A Simplified Two-Component Model of Blood Pressure Fluctuation

    PubMed Central

    Brychta, Robert J.; Shiavi, Richard; Robertson, David; Biaggioni, Italo; Diedrich, André

    2007-01-01

    We propose a simple moving-average (MA) model that uses the low-frequency (LF) component of the peroneal muscle sympathetic nerve spike rate (LFspike rate) and the high-frequency (HF) component of respiration (HFResp) to describe the LF neurovascular fluctuations and the HF mechanical oscillations in systolic blood pressure (SBP), respectively. This method was validated by data from eight healthy subjects (23–47 yr old, 6 male, 2 female) during a graded tilt (15° increments every 5 min to a 60° angle). The LF component of SBP (LFSBP) had a strong baroreflex-mediated feedback correlation with LFspike rate (r = −0.69 ± 0.05) and also a strong feedforward relation to LFspike rate [r = 0.58 ± 0.03 with LFSBP delay (τ) = 5.625 ± 0.15 s]. The HF components of spike rate (HFspike rate) and SBP (HFSBP) were not significantly correlated. Conversely, HFResp and HFSBP were highly correlated (r = −0.79 ± 0.04), whereas LFResp and LFSBP were significantly less correlated (r = 0.45 ± 0.08). The mean correlation coefficients between the measured and model-predicted LFSBP (r = 0.74 ± 0.03) in the supine position did not change significantly during tilt. The mean correlation between the measured and model-predicted HFSBP was 0.89 ± 0.02 in the supine position. R2 values for the regression analysis of the model-predicted and measured LF and HF powers indicate that 78 and 91% of the variability in power can be explained by the linear relation of LFspike rate to LFSBP and HFResp to HFSBP. We report a simple two-component model using neural sympathetic and mechanical respiratory inputs that can explain the majority of blood pressure fluctuation at rest and during orthostatic stress in healthy subjects. PMID:17012354

  13. Fabrication of a microfluidic channel with differently modified surfaces with a two component approach

    NASA Astrophysics Data System (ADS)

    Bogunovic, L.; Vosskötter, C.; Anselmetti, D.

    2014-07-01

    We report on a two-component fabrication technique for microfluidic channels, allowing for different chemical or physical surface modifications of channel walls within one single channel. The two components are made of polydimethylsiloxane and prepared via soft lithography independently. After appropriate pre-treatment with the desired functions, the two parts are bonded together using oxygen plasma and a Fineplacer® lambda system. As a proof of concept, we present the combination of electroosmosis and opposing hydrodynamic flow in a microfluidic channel leading to different velocity presigns of the resulting flow on opposite channel walls, due to different surface modifications. These results indicate an intact Pluronic® F108 surface coating after assembly.

  14. Substrate temperature controls molecular orientation in two-component vapor-deposited glasses.

    PubMed

    Jiang, J; Walters, D M; Zhou, D; Ediger, M D

    2016-04-01

    Vapor-deposited glasses can be anisotropic and molecular orientation is important for organic electronics applications. In organic light emitting diodes (OLEDs), for example, the orientation of dye molecules in two-component emitting layers significantly influences emission efficiency. Here we investigate how substrate temperature during vapor deposition influences the orientation of dye molecules in a model two-component system. We determine the average orientation of a linear blue light emitter 1,4-di-[4-(N,N-diphenyl)amino]styryl-benzene (DSA-Ph) in mixtures with aluminum-tris(8-hydroxyquinoline) (Alq3) by spectroscopic ellipsometry and IR dichroism. We find that molecular orientation is controlled by the ratio of the substrate temperature during deposition and the glass transition temperature of the mixture. These findings extend recent results for single component vapor-deposited glasses and suggest that, during vapor deposition, surface mobility allows partial equilibration towards orientations preferred at the free surface of the equilibrium liquid. PMID:26922903

  15. Variational method applied to two-component Ginzburg-Landau theory

    NASA Astrophysics Data System (ADS)

    Romaguera, Antonio R. de C.; Silva, K. J. S.

    2013-09-01

    In this paper, we apply a variational method to two-component superconductors, as in the MgB2 materials, using the two-component Ginzburg-Landau (GL) theory. We expand the order parameter in a series of eigenfunctions containing one or two terms in each component. We also assume azimuthal symmetry to the set of eigenfunctions used in the mathematical procedure. The extension of the GL theory to two components leads to the quantization of the magnetic flux in fractions of ϕ0. We consider two kinds of component interaction potentials: Γ1|ΨI|2|ΨII|2 and Γ _2(Ψ _I^*Ψ _{II}+Ψ _IΨ _{II}^*). The simplicity of the method allows one to implement it in a broad range of physical systems, such as hybrid magnetic-superconducting mesoscopic systems, texturized thin films, metallic hydrogen superfluid, and mesoscopic superconductors near inhomogeneous magnetic fields, simply by replacing the vector potential by its corresponding expression. As an example, we apply our results to a disk of radius R and thickness t.

  16. Two-Component Winds from Luminous Late-Type Stars

    NASA Astrophysics Data System (ADS)

    Airapetian, V. S.; Offman, L.; Robinson, R.; Carpenter, K.; Davila, J.

    1998-01-01

    We present the results of a magnetohydrodynamic (MHD) simulation of winds from luminous late-type stars using a 2.5D, non-linear MHD computer code. In this simulation we assume that the wind is generated within a hydrostatic atmosphere with an initial isothermal pressure scale height of 0.072 Rstar and a radial magnetic field. We also assume a transverse density gradient which we we refer to as a ``chromospheric hole''. Tortional Alfven waves are generated at the stellar surface by a forcing function having a single frequency, which is comparable to the turn-over frequency of convective cells in giant stars. To ensure that we are accurately assessing the terminal velocity of the wind, we carried out the calculations to a height of 20 stellar radii and a time period of more than 180 Alfven transit times, which ensures that a steady state has been reached. In the higher density (low Alfven velocity) regions outside of the ``chromospheric hole'' the Alfven waves are freely propagating. Ponderomotive forces associated with these waves drive radial, compressive motions and contribute to stellar wind acceleration. The compressive motions then excite slow magnetosonic waves which non-linearly steepen into solitary waves that propagate on top of a background flow similar to the case of solar coronal holes. This produces a fast (40-80 km/s) and relatively dense component of the wind. In the lower density ``chromospheric hole'' region the Alfven waves are strongly reflected and produce an outflow with both radial and azimuthal velocities which are ~ 10% of the local Alfven speed. This component of the wind is slow ( ~ 10-30 km/s) and less dense than the wind initiated outside of the hole. Depending on the magnetic topology in the atmosphere of a luminous late - type star, we may therefore expect either one (fast) or two components to the wind. Our results are consistent with recent observations of two discrete components to the wind in the K5 III hybrid star gamma Dra. These

  17. Positional isomers of cyanostilbene: two-component molecular assembly and multiple-stimuli responsive luminescence

    NASA Astrophysics Data System (ADS)

    Fan, Guoling; Yan, Dongpeng

    2014-05-01

    An understanding of the aggregates and properties of positional isomers can not only uncover how a slight difference in molecular structure alter crystal packing and bulk solid-state properties, but also plays an important role in developing new types of molecule-based functional materials. Herein, we report a study of the molecular packing and static/dynamic luminescence properties of three cyanostilbene (CS)-based isomers (CS1, CS2, CS3) within their single- and two-component molecular solids. Changing the positions of the cyano substitutents in the CS isomers has a marked influence on their packing modes and luminescent properties. Moreover, two-component CS-based materials have been constructed, which exhibit tunable conformations and packing fashions, as well as fluorescence properties, which differ from the pristine CS solids. The CS-based two-component molecular materials show solvent-responsive luminescence due to the dynamic disassembly of the samples. Moreover, it was found that the system based on CS2 and octafluoronaphthalene shows reversible photochromic fluorescence upon alternating light illumination and grinding. Such co-assembly procedures provide a facile way to fabricate patterned luminescent film materials. Therefore, this work not only affords new insight into the relationship between isomers and luminescence from molecular and supramolecular perspectives, but provides an effective strategy to develop multiple-stimuli-responsive luminescent materials.

  18. Molecular Orientation in Two Component Vapor-Deposited Glasses: Effect of Substrate Temperature and Molecular Shape

    NASA Astrophysics Data System (ADS)

    Powell, Charles; Jiang, Jing; Walters, Diane; Ediger, Mark

    Vapor-deposited glasses are widely investigated for use in organic electronics including the emitting layers of OLED devices. These materials, while macroscopically homogenous, have anisotropic packing and molecular orientation. By controlling this orientation, outcoupling efficiency can be increased by aligning the transition dipole moment of the light-emitting molecules parallel to the substrate. Light-emitting molecules are typically dispersed in a host matrix, as such, it is imperative to understand molecular orientation in two-component systems. In this study we examine two-component vapor-deposited films and the orientations of the constituent molecules using spectroscopic ellipsometry, UV-vis and IR spectroscopy. The role of temperature, composition and molecular shape as it effects molecular orientation is examined for mixtures of DSA-Ph in Alq3 and in TPD. Deposition temperature relative to the glass transition temperature of the two-component mixture is the primary controlling factor for molecular orientation. In mixtures of DSA-Ph in Alq3, the linear DSA-Ph has a horizontal orientation at low temperatures and slight vertical orientation maximized at 0.96Tg,mixture, analogous to one-component films.

  19. Bacitracin and nisin resistance in Staphylococcus aureus: a novel pathway involving the BraS/BraR two-component system (SA2417/SA2418) and both the BraD/BraE and VraD/VraE ABC transporters.

    PubMed

    Hiron, Aurélia; Falord, Mélanie; Valle, Jaione; Débarbouillé, Michel; Msadek, Tarek

    2011-08-01

    Two-component systems (TCSs) are key regulatory pathways allowing bacteria to adapt their genetic expression to environmental changes. Bacitracin, a cyclic dodecylpeptide antibiotic, binds to undecaprenyl pyrophosphate, the lipid carrier for cell wall precursors, effectively inhibiting peptidoglycan biosynthesis. We have identified a novel and previously uncharacterized TCS in the major human pathogen Staphylococcus aureus that we show to be essential for bacitracin and nisin resistance: the BraS/BraR system (Bacitracin resistance associated; SA2417/SA2418). The braRS genes are located immediately upstream from genes encoding an ABC transporter, accordingly designated BraDE. We have shown that the BraSR/BraDE module is a key bacitracin and nisin resistance determinant in S. aureus. In the presence of low antibiotic concentrations, BraSR activate transcription of two operons encoding ABC transporters: braDE and vraDE. We identified a highly conserved imperfect palindromic sequence upstream from the braDE and vraDE promoter sequences, essential for their transcriptional activation by BraSR, suggesting it is the likely BraR binding site. We demonstrated that the two ABC transporters play distinct and original roles in antibiotic resistance: BraDE is involved in bacitracin sensing and signalling through BraSR, whereas VraDE acts specifically as a detoxification module and is sufficient to confer bacitracin and nisin resistance when produced on its own. We show that these processes require functional BraD and VraD nucleotide-binding domain proteins, and that the large extracellular loop of VraE confers its specificity in bacitracin resistance. This is the first example of a TCS associated with two ABC transporters playing separate roles in signal transduction and antibiotic resistance. PMID:21696458

  20. High-temperature superfluidity of the two-component Bose gas in a transition metal dichalcogenide bilayer

    NASA Astrophysics Data System (ADS)

    Berman, Oleg L.; Kezerashvili, Roman Ya.

    2016-06-01

    The high-temperature superfluidity of two-dimensional dipolar excitons in two parallel transition metal dichalcogenide (TMDC) layers is predicted. We study Bose-Einstein condensation in the two-component system of dipolar A and B excitons. The effective mass, energy spectrum of the collective excitations, the sound velocity, and critical temperature are obtained for different TMDC materials. It is shown that in the Bogoliubov approximation, the sound velocity in the two-component dilute exciton Bose gas is always larger than in any one-component exciton system. The difference between the sound velocities for two-component and one-component dilute gases is caused by the fact that the sound velocity for a two-component system depends on the reduced mass of A and B excitons, which is always smaller than the individual mass of A or B exciton. Due to this fact, the critical temperature Tc for superfluidity for the two-component exciton system in a TMDC bilayer is about one order of magnitude higher than Tc in any one-component exciton system. We propose to observe the superfluidity of two-dimensional dipolar excitons in two parallel TMDC layers, which causes two opposite superconducting currents in each TMDC layer.

  1. Two-component Bose-Hubbard model with higher-angular-momentum states

    NASA Astrophysics Data System (ADS)

    Pietraszewicz, Joanna; Sowiński, Tomasz; Brewczyk, Mirosław; Zakrzewski, Jakub; Lewenstein, Maciej; Gajda, Mariusz

    2012-05-01

    Bose-Hubbard Hamiltonian of cold two-component Bose gas of spinor chromium atoms is studied. Dipolar interactions of magnetic moments while tuned resonantly by an ultralow magnetic field can lead to a transfer of atoms from the ground to excited Wannier states with a nonvanishing angular orbital momentum. Hence we propose the way of creating Px+iPy orbital superfluid. The spin introduces an additional degree of control and leads to a variety of different stable phases of the system. The Mott insulator of atoms in a superposition of the ground and vortex Wannier states as well as a superposition of the Mott insulator with orbital superfluid are predicted.

  2. Itinerant ferromagnetism in one-dimensional two-component Fermi gases

    NASA Astrophysics Data System (ADS)

    Jiang, Yuzhu; Kurlov, D. Â. V.; Guan, Xi-Wen; Schreck, F.; Shlyapnikov, G. Â. V.

    2016-07-01

    We study a one-dimensional (1D) two-component atomic Fermi gas with an infinite intercomponent contact repulsion. It is found that adding an attractive nearly resonant odd-wave interaction breaking the rotational symmetry one can make the ground state ferromagnetic. A promising system for the observation of this itinerant ferromagnetic state is a 1D gas of

  3. Structure of two-component lipid membranes on solid support: An x-ray reflectivity study

    SciTech Connect

    Novakova, Eva; Giewekemeyer, Klaus; Salditt, Tim

    2006-11-15

    We report an x-ray reflectivity study of phospholipid membranes deposited on silicon by vesicle fusion. The samples investigated were composed of single phospholipid bilayers as well as two-component lipid bilayer systems with varied charge density. We show that the resolution obtained in the density profile across the bilayer is high enough to distinguish two head-group maxima in the profile if the sample is in the phase coexistence regime. The water layer between the bilayer and silicon is found to depend on the lipid surface charge density.

  4. Topological phases of two-component bosons in species-dependent artificial gauge potentials

    NASA Astrophysics Data System (ADS)

    Wu, Ying-Hai; Shi, Tao

    2016-08-01

    We study bosonic atoms with two internal states in artificial gauge potentials whose strengths are different for the two components. A series of topological phases for such systems is proposed using the composite fermion theory and the parton construction. It is found in exact diagonalization that some of the proposed states may be realized for simple contact interaction between bosons. The ground states and low-energy excitations of these states are modeled using trial wave functions. The effective field theories for these states are also constructed and reveal some interesting properties.

  5. Equilibrium thermodynamic properties of interacting two-component bosons in one dimension

    SciTech Connect

    Klauser, Antoine; Caux, Jean-Sebastien

    2011-09-15

    The interplay of quantum statistics, interactions, and temperature is studied within the framework of the bosonic two-component theory with repulsive delta-function interaction in one dimension. We numerically solve the thermodynamic Bethe ansatz and obtain the equation of state as a function of temperature and of the interaction strength, the relative chemical potential, and either the total chemical potential or a fixed number of particles, allowing quantification of the full crossover behavior of the system between its low-temperature ferromagnetic and high-temperature unpolarized regime, and from the low coupling decoherent regime to the fermionization regime at high interaction.

  6. Improved Convergence for Two-Component Activity Expansions

    SciTech Connect

    DeWitt, H E; Rogers, F J; Sonnad, V

    2007-03-06

    It is well known that an activity expansion of the grand canonical partition function works well for attractive interactions, but works poorly for repulsive interactions, such as occur between atoms and molecules. The virial expansion of the canonical partition function shows just the opposite behavior. This poses a problem for applications that involve both types of interactions, such as occur in the outer layers of low-mass stars. We show that it is possible to obtain expansions for repulsive systems that convert the poorly performing Mayer activity expansion into a series of rational polynomials that converge uniformly to the virial expansion. In the current work we limit our discussion to the second virial approximation. In contrast to the Mayer activity expansion the activity expansion presented herein converges for both attractive and repulsive systems.

  7. Momentum flux in two phase two component low quality flow

    NASA Technical Reports Server (NTRS)

    Baumeister, K. J.; Graham, R. W.; Henry, R. E.

    1972-01-01

    In two phase flow systems line losses comprise frictional and momentum pressure drops. For design purposes, it would be desirable to estimate the line losses employing a one-dimensional calculation. Two methods for computing one-dimensional momentum flux at a test section discharge station are compared to the experimental value for a range of two-phase flow conditions. The one-dimensional homogeneous model appears to be more accurate generally in predicting the momentum than the variable slip model.

  8. Direct Atomic-Orbital-Based Relativistic Two-Component Linear Response Method for Calculating Excited-State Fine Structures.

    PubMed

    Egidi, Franco; Goings, Joshua J; Frisch, Michael J; Li, Xiaosong

    2016-08-01

    In this work, we present a linear-response formalism of the complex two-component Hartree-Fock Hamiltonian that includes relativistic effects within the Douglas-Kroll-Hess and the Exact-Two-Component frameworks. The method includes both scalar and spin relativistic effects in the variational description of electronic ground and excited states, although it neglects the picture-change and explicit spin-orbit contributions arising from the two-electron interaction. An efficient direct formalism of solving the complex two-component response function is also presented in this work. The presence of spin-orbit couplings in the Hamiltonian and the two-component nature of the wave function and Fock operator allows the computation of excited-state zero-field splittings of systems for which relativistic effects are dominated by the one-electron term. Calculated results are compared to experimental reference values to assess the quality of the underlying approximations. The results show that the relativistic two-component linear response methods are able to capture the excited-state zero-field splittings with good agreement with experiments for the systems considered here, with all approximations exhibiting a similar performance. However, the error increases for heavy elements and for states of high orbital angular momentum, suggesting the importance of the two-electron relativistic effect in such situations. PMID:27387787

  9. Mapping the Two-component Regulatory Networks in Desulfovibrio vulgaris

    SciTech Connect

    Rajeev, Lara; Luning, Eric; Dehal, Paramvir; Joachimiak, Marcin; Mukhopadhyay, Aindrila

    2010-05-17

    D. vulgaris Hildenborough has 72 response regulators. The Desulfovibrio are sulfate reducing bacteria that are important in the sulfur and carbon cycles in anoxic habitats. Its large number of two componenent systems are probably critical to its ability to sense and respond to its environment. Our goal is to map these RRs to the genes they regulate using a DNA-affinity-purification-chip (DAP-chip) protocol. First target determined usuing EMSA. A positive target was determined for as many RRs as possible using EMSA. Targets were selected based on gene proximity, regulon predictions and/or predicted sigma54 dependent promoters. qPCR was used to ensure that the target was enriched from sheared genomic DNA before proceeding to the DAP-chip.

  10. Instabilities in relativistic two-component (super)fluids

    NASA Astrophysics Data System (ADS)

    Haber, Alexander; Schmitt, Andreas; Stetina, Stephan

    2016-01-01

    We study two-fluid systems with nonzero fluid velocities and compute their sound modes, which indicate various instabilities. For the case of two zero-temperature superfluids we employ a microscopic field-theoretical model of two coupled bosonic fields, including an entrainment coupling and a nonentrainment coupling. We analyze the onset of the various instabilities systematically and point out that the dynamical two-stream instability can occur only beyond Landau's critical velocity, i.e., in an already energetically unstable regime. A qualitative difference is found for the case of two normal fluids, where certain transverse modes suffer a two-stream instability in an energetically stable regime if there is entrainment between the fluids. Since we work in a fully relativistic setup, our results are very general and are of potential relevance for (super)fluids in neutron stars and, in the nonrelativistic limit of our results, in the laboratory.

  11. Binding between two-component bosons in one dimension

    NASA Astrophysics Data System (ADS)

    Tempfli, Emmerich; Zöllner, Sascha; Schmelcher, Peter

    2009-07-01

    We investigate the ground state of one-dimensional few-atom Bose-Bose mixtures under harmonic confinement throughout the crossover from weak to strong inter-species attraction. The calculations are based on the numerically exact multi-configurational time-dependent Hartree method. For repulsive components, we detail the condition for the formation of a molecular Tonks-Girardeau gas in the regime of intermediate inter-species interactions, and the formation of a molecular condensate for stronger coupling. Beyond a critical inter-species attraction, the system collapses to an overall bound state. Different pathways emerge for unequal particle numbers and intra-species interactions. In particular, for mixtures with one attractive component, this species can be viewed as an effective potential dimple in the trap center for the other, repulsive component.

  12. Two-component dual-scatter laser Doppler velocimeter with frequency burst signal readout.

    PubMed

    Brayton, D B; Kalb, H T; Crosswy, F L

    1973-06-01

    A dual-scatter laser Doppler velocimeter (LDV) system designed for measuring wind tunnel flow velocity is described. The system simultaneously measures two orthogonal velocity components of a flowing fluid at a common point in the flow. Essential single-velocity component dual-scatter concepts are presented to simplify the description of the more sophisticated two-component system. To implement the two-component system three laser beams with a 0 degrees , 45 degrees , and 90 degrees polarization plane relationship are focused to a common point in the flow by the system-transmitting optics. The beams interfere to form two perpendicular sets of interference fringe planes that are orthogonally polarized. The system-receiving optics collect and separate the orthogonally polarized components of laser radiation scattered from micron-size particles moving with the flowing fluid through the ringes. The system requires no artificial seeding, since intrinsic test section aerosols are utilized for radiation scattering. The passage of each scatter particle through the interference fringes simultaneously produces two frequency-burst-type photodetected signals, the frequencies of which are directly proportional to two perpendicular components of particle velocity. The system photodetection, signal-conditioning, and data acquisition instrumentation is specifically designed to process the frequency burst information in the time domain as opposed to spectrum analysis or frequency domain processing. The system was initially evaluated in an AEDC wind tunnel operating over a Mach number range from 0.6 to 1.5. The LDV and calculated wind tunnel mean velocity data agreed to within 1.25%; flow direction deviations of a few milliradians were resolved. PMID:20125494

  13. Arabidopsis ethylene-response gene ETR1: Similiarity of product to two-component regulators

    SciTech Connect

    Chang, C.; Kwok, S.F.; Bleecker, A.B.; Meyerowitz, E.M. )

    1993-10-22

    Ethylene behaves as a hormone in plants, regulating such aspects of growth and development as fruit ripening, flower senescence, and abscission. Ethylene insensitivity is conferred by dominant mutations in the ETR1 gene early in the ethylene signal transduction pathway of Arabidopsis thaliana. The ETR1 gene was cloned by the method of chromosome walking. Each of the four known etr1 mutant alleles contains a missense mutation near the amino terminus of the predicted protein. Although the sequence of the amino-terminal half of the deduced ETR1 protein appears to be novel, the carboxyl-terminal half is similar in sequence to both components of the prokaryotic family of signal transducers known as the two-component systems. Thus, an early step in ethylene signal transduction in plants may involve transfer of phosphate as in prokaryotic two-component systems. The dominant etr1-1 mutant gene conferred ethylene insensitivity to wild-type Arabidopsis plants when introduced by transformation.

  14. Symmetry breaking of solitons in two-component Gross-Pitaevskii equations

    SciTech Connect

    Sakaguchi, Hidetsugu; Malomed, Boris A.

    2011-03-15

    We revisit the problem of the spontaneous symmetry breaking (SSB) of solitons in two-component linearly coupled nonlinear systems, adding the nonlinear interaction between the components. With this feature, the system may be realized in new physical settings, in terms of optics and the Bose-Einstein condensate (BEC). SSB bifurcation points are found analytically, for both symmetric and antisymmetric solitons (the symmetry between the two components is meant here). Asymmetric solitons, generated by the bifurcations, are described by means of the variational approximation (VA) and numerical methods, demonstrating good accuracy of the variational results. In the space of the self-phase-modulation (SPM) parameter and soliton's norm, a border separating stable symmetric and asymmetric solitons is identified. The nonlinear coupling may change the character of the SSB bifurcation, from subcritical to supercritical. Collisions between moving asymmetric and symmetric solitons are investigated too. Antisymmetric solitons are destabilized by a supercritical bifurcation, which gives rise to self-confined modes featuring Josephson oscillations, instead of stationary states with broken antisymmetry. An additional instability against delocalized perturbations is also found for the antisymmetric solitons.

  15. The ground states and spin textures of rotating two-component Bose-Einstein condensates in an annular trap

    NASA Astrophysics Data System (ADS)

    Jin, Jingjing; Zhang, Suying; Han, Wei; Wei, Zhifeng

    2013-04-01

    We investigate the ground states and spin textures of rotating two-component Bose-Einstein condensates (BECs) confined in an annular potential. For the two-component miscible BECs, we analytically give the critical angular velocity of each component with the Thomas-Fermi approximation (TFA), at which the density profile changes from a disc shape into an annulus shape, forming a giant vortex. We present a phase diagram showing three kinds of density profiles of the ground states that are two disc shaped, one disc and another annulus shaped, and two annulus shaped. For the two-component immiscible BECs with particle number grave imbalance, we also discuss their ground states using the TFA, and three kinds of symmetrical structures of the density profiles are classified analytically. The spin textures of the two-component immiscible BECs have been studied and we find three kinds of symmetrical structures of the spin textures in the annular trap. One of these textures is an annular skyrmion which has been observed in harmonic potentials. Both of the other spin textures contain a new structure composed of concentric double-annulus skyrmion whose topological charge is the sum of the ones of two annular skyrmions, and the topological charge of each annular skyrmion is equal to the absolute value of the difference between the quantum numbers of circulation of two components inside this annular skyrmion. We also prove that these new textures are robust by investigating the dynamical behaviours of the system under external disturbances.

  16. Two-component Bose gases with one-body and two-body couplings

    NASA Astrophysics Data System (ADS)

    Lellouch, Samuel; Dao, Tung-Lam; Koffel, Thomas; Sanchez-Palencia, Laurent

    2013-12-01

    We study the competition between one-body and two-body couplings in weakly interacting two-component Bose gases, in particular as regards field correlations. We derive the mean-field theory for both ground-state and low-energy pair excitations in the general case where both one-body and two-body couplings are position dependent and the fluid is subjected to a state-dependent trapping potential. General formulas for phase and density correlations are also derived. Focusing on the case of homogeneous systems, we discuss the pair-excitation spectrum and the corresponding excitation modes, and use them to calculate correlation functions, including both quantum and thermal fluctuation terms. We show that the relative phase of the two components is imposed by that of the one-body coupling, while its fluctuations are determined by the modulus of the one-body coupling and by the two-body coupling. One-body coupling and repulsive two-body coupling cooperate to suppress relative-phase fluctuations, while attractive two-body coupling tends to enhance them. Further applications of the formalism presented here and extensions of our work are also discussed.

  17. Small two-component Fermi gases in a cubic box with periodic boundary conditions

    NASA Astrophysics Data System (ADS)

    Yin, X. Y.; Blume, D.

    2013-06-01

    The properties of two-component Fermi gases become universal if the interspecies s-wave scattering length as and the average interparticle spacing are much larger than the range of the underlying two-body potential. Using an explicitly correlated Gaussian basis set expansion approach, we determine the eigenenergies of two-component Fermi gases in a cubic box with periodic boundary conditions as functions of the interspecies s-wave scattering length and the effective range of the two-body potential. The universal properties of systems consisting of up to four particles are determined by extrapolating the finite-range energies to the zero-range limit. We determine the eigenenergies of states with vanishing and finite momenta. In the weakly attractive BCS regime, we analyze the energy spectra and degeneracies using first-order degenerate perturbation theory. Excellent agreement between the perturbative energy shifts and the numerically determined energies is obtained. For the infinitely large scattering length case, we compare our results—where available—with those presented in the literature.

  18. A light responsive two-component supramolecular hydrogel: a sensitive platform for the fabrication of humidity sensors.

    PubMed

    Samai, Suman; Sapsanis, Christos; Patil, Sachin P; Ezzeddine, Alaa; Moosa, Basem A; Omran, Hesham; Emwas, Abdul-Hamid; Salama, Khaled N; Khashab, Niveen M

    2016-03-01

    The supramolecular assembly of anionic azobenzene dicarboxylate and cationic cetyltrimethylammonium bromide (CTAB) formed a stimuli responsive hydrogel with a critical gelation concentration (CGC) of 0.33 wt%. This self-sustainable two-component system was able to repair damage upon light irradiation. Moreover, it was successfully employed in the fabrication of highly sensitive humidity sensors for the first time. PMID:26908051

  19. Two-component hybrid time-dependent density functional theory within the Tamm-Dancoff approximation.

    PubMed

    Kühn, Michael; Weigend, Florian

    2015-01-21

    We report the implementation of a two-component variant of time-dependent density functional theory (TDDFT) for hybrid functionals that accounts for spin-orbit effects within the Tamm-Dancoff approximation (TDA) for closed-shell systems. The influence of the admixture of Hartree-Fock exchange on excitation energies is investigated for several atoms and diatomic molecules by comparison to numbers for pure density functionals obtained previously [M. Kühn and F. Weigend, J. Chem. Theory Comput. 9, 5341 (2013)]. It is further related to changes upon switching to the local density approximation or using the full TDDFT formalism instead of TDA. Efficiency is demonstrated for a comparably large system, Ir(ppy)3 (61 atoms, 1501 basis functions, lowest 10 excited states), which is a prototype molecule for organic light-emitting diodes, due to its "spin-forbidden" triplet-singlet transition. PMID:25612698

  20. Universal properties of a trapped two-component fermi gas at unitarity.

    PubMed

    Blume, D; von Stecher, J; Greene, Chris H

    2007-12-01

    We treat the trapped two-component Fermi system, in which unlike fermions interact through a two-body short-range potential having no bound state but an infinite scattering length. By accurately solving the Schrödinger equation for up to N=6 fermions, we show that no many-body bound states exist other than those bound by the trapping potential, and we demonstrate unique universal properties of the system: Certain excitation frequencies are separated by 2variant Planck's over 2piomega, the wave functions agree with analytical predictions and a virial theorem is fulfilled. Further calculations up to N=30 determine the excitation gap, an experimentally accessible universal quantity, and it agrees with recent predictions based on a density functional approach. PMID:18233361

  1. Two-component hybrid time-dependent density functional theory within the Tamm-Dancoff approximation

    SciTech Connect

    Kühn, Michael; Weigend, Florian

    2015-01-21

    We report the implementation of a two-component variant of time-dependent density functional theory (TDDFT) for hybrid functionals that accounts for spin-orbit effects within the Tamm-Dancoff approximation (TDA) for closed-shell systems. The influence of the admixture of Hartree-Fock exchange on excitation energies is investigated for several atoms and diatomic molecules by comparison to numbers for pure density functionals obtained previously [M. Kühn and F. Weigend, J. Chem. Theory Comput. 9, 5341 (2013)]. It is further related to changes upon switching to the local density approximation or using the full TDDFT formalism instead of TDA. Efficiency is demonstrated for a comparably large system, Ir(ppy){sub 3} (61 atoms, 1501 basis functions, lowest 10 excited states), which is a prototype molecule for organic light-emitting diodes, due to its “spin-forbidden” triplet-singlet transition.

  2. Two-component hybrid time-dependent density functional theory within the Tamm-Dancoff approximation

    NASA Astrophysics Data System (ADS)

    Kühn, Michael; Weigend, Florian

    2015-01-01

    We report the implementation of a two-component variant of time-dependent density functional theory (TDDFT) for hybrid functionals that accounts for spin-orbit effects within the Tamm-Dancoff approximation (TDA) for closed-shell systems. The influence of the admixture of Hartree-Fock exchange on excitation energies is investigated for several atoms and diatomic molecules by comparison to numbers for pure density functionals obtained previously [M. Kühn and F. Weigend, J. Chem. Theory Comput. 9, 5341 (2013)]. It is further related to changes upon switching to the local density approximation or using the full TDDFT formalism instead of TDA. Efficiency is demonstrated for a comparably large system, Ir(ppy)3 (61 atoms, 1501 basis functions, lowest 10 excited states), which is a prototype molecule for organic light-emitting diodes, due to its "spin-forbidden" triplet-singlet transition.

  3. Cross-talk and specificity in two-component signal transduction pathways.

    PubMed

    Agrawal, Ruchi; Sahoo, Bikash Kumar; Saini, Deepak Kumar

    2016-05-01

    Two-component signaling systems (TCSs) are composed of two proteins, sensor kinases and response regulators, which can cross-talk and integrate information between them by virtue of high-sequence conservation and modular nature, to generate concerted and diversified responses. However, TCSs have been shown to be insulated, to facilitate linear signal transmission and response generation. Here, we discuss various mechanisms that confer specificity or cross-talk among TCSs. The presented models are supported with evidence that indicate the physiological significance of the observed TCS signaling architecture. Overall, we propose that the signaling topology of any TCSs cannot be predicted using obvious sequence or structural rules, as TCS signaling is regulated by multiple factors, including spatial and temporal distribution of the participating proteins. PMID:27159035

  4. Inverse Comptonization in a Two Component Advective Flow: Results of a Monte Carlo simulation

    SciTech Connect

    Ghosh, Himadri; Chakrabarti, S. K.; Laurent, Philippe

    2008-10-08

    We compute the resultant spectrum due to multiple scattering of soft photons emitted from a Keplerian disk by thermal electrons inside a torus axisymmetrically placed around a black hole. In a two component advective flow model, the post-shock region is similar to a thick accretion disk and the pre-shock sub-keplerian flow is highly optically thin. As a preliminary run of the Monte Carlo simulation of the system, we assume the CENBOL to be a small (2-14r{sub g}) thick accretion disk without a cusp to allow bulk motion of the flow. Bulk Motion Comptonization (BMC) has also been added. We show that the spectral behaviour is very similar to what is predicted in Chakrabarti and Titarchuk (1995)

  5. Relevance of the two-component sensor protein CiaH to acid and oxidative stress responses in Streptococcus pyogenes

    PubMed Central

    2014-01-01

    Background The production of virulence proteins depends on environmental factors, and two-component regulatory systems are involved in sensing these factors. We previously established knockout strains in all suspected two-component regulatory sensor proteins of the emm1 clinical strain of S. pyogenes and examined their relevance to acid stimuli in a natural atmosphere. In the present study, their relevance to acid stimuli was re-examined in an atmosphere containing 5% CO2. Results The spy1236 (which is identical to ciaHpy) sensor knockout strain showed significant growth reduction compared with the parental strain in broth at pH 6.0, suggesting that the Spy1236 (CiaHpy) two-component sensor protein is involved in acid response of S. pyogenes. CiaH is also conserved in Streptococcus pneumoniae, and it has been reported that deletion of the gene for its cognate response regulator (ciaRpn) made the pneumococcal strains more sensitive to oxidative stress. In this report, we show that the spy1236 knockout mutant of S. pyogenes is more sensitive to oxidative stress than the parental strain. Conclusions These results suggest that the two-component sensor protein CiaH is involved in stress responses in S. pyogenes. PMID:24673808

  6. Comparison of Dynamical Behaviors Between Monofunctional and Bifunctional Two-Component Signaling Modules

    NASA Astrophysics Data System (ADS)

    Yang, Xiyan; Wu, Yahao; Yuan, Zhanjiang

    2015-06-01

    Two-component signaling modules exist extensively in bacteria and microbes. These modules can be, based on their distinct network structures, divided into two types: the monofunctional system (denoted by MFS) where the sensor kinase (SK) modulates only phosphorylation of the response regulator (RR), and the bifunctional system (denoted by BFS) where the SK catalyzes both phosphorylation and dephosphorylation of the RR. Here, we analyze dynamical behaviors of these two systems based on stability theory, focusing on differences between them. The analysis of the deterministic behavior indicates that there is no difference between the two modules, that is, each system has the unique stable steady state. However, there are significant differences in stochastic behavior between them. Specifically, if the mean phosphorylated SK level is kept the same for the two modules, then the variance and the Fano factor for the phosphorylated RR in the BFS are always no less than those in the MFS, indicating that bifunctionality always enhances fluctuations. The correlation between the phosphorylated SK and the phosphorylated RR in the BFS is always positive mainly due to competition between system components, but this correlation in the MFS may be positive, almost zero, or negative, depending on the ratio between two rate constants. Our overall analysis indicates that differences between dynamical behaviors of monofunctional and bifunctional signaling modules are mainly in the stochastic rather than deterministic aspect.

  7. Phase separation and dynamics of two-component Bose-Einstein condensates

    NASA Astrophysics Data System (ADS)

    Lee, Kean Loon; Jørgensen, Nils B.; Liu, I.-Kang; Wacker, Lars; Arlt, Jan J.; Proukakis, Nick P.

    2016-07-01

    The miscibility of two interacting quantum systems is an important testing ground for the understanding of complex quantum systems. Two-component Bose-Einstein condensates enable the investigation of this scenario in a particularly well controlled setting. In a homogeneous system, the transition between mixed and separated phases is fully characterized by a miscibility parameter based on the ratio of intra- to interspecies interaction strengths. Here we show, however, that this parameter is no longer the optimal one for trapped gases, for which the location of the phase boundary depends critically on atom numbers. We demonstrate how monitoring of damping rates and frequencies of dipole oscillations enables the experimental mapping of the phase diagram by numerical implementation of a fully self-consistent finite-temperature kinetic theory for binary condensates. The change in damping rate is explained in terms of surface oscillation in the immiscible regime, and counterflow instability in the miscible regime, with collisions becoming only important in the long time evolution.

  8. Bioorthogonal two-component drug delivery in HER2(+) breast cancer mouse models

    PubMed Central

    Hapuarachchige, Sudath; Kato, Yoshinori; Artemov, Dmitri

    2016-01-01

    The HER2 receptor is overexpressed in approximately 20% of breast cancers and is associated with tumorigenesis, metastasis, and a poor prognosis. Trastuzumab is a first-line targeted drug used against HER2(+) breast cancers; however, at least 50% of HER2(+) tumors develop resistance to trastuzumab. To treat these patients, trastuzumab-based antibody-drug conjugates (ACDs) have been developed and are currently used in the clinic. Despite their high efficacy, the long circulation half-life and non-specific binding of cytotoxic ADCs can result in systemic toxicity. In addition, standard ADCs do not provide an image-guided mode of administration. Here, we have developed a two-component, two-step, pre-targeting drug delivery system integrated with image guidance to circumvent these issues. In this strategy, HER2 receptors are pre-labeled with a functionalized trastuzumab antibody followed by the delivery of drug-loaded nanocarriers. Both components are cross-linked by multiple bioorthogonal click reactions in situ on the surface of the target cell and internalized as nanoclusters. We have explored the efficacy of this delivery strategy in HER2(+) human breast cancer models. Our therapeutic study confirms the high therapeutic efficacy of the new delivery system, with no significant toxicity. PMID:27068794

  9. Bioorthogonal two-component drug delivery in HER2(+) breast cancer mouse models

    NASA Astrophysics Data System (ADS)

    Hapuarachchige, Sudath; Kato, Yoshinori; Artemov, Dmitri

    2016-04-01

    The HER2 receptor is overexpressed in approximately 20% of breast cancers and is associated with tumorigenesis, metastasis, and a poor prognosis. Trastuzumab is a first-line targeted drug used against HER2(+) breast cancers; however, at least 50% of HER2(+) tumors develop resistance to trastuzumab. To treat these patients, trastuzumab-based antibody-drug conjugates (ACDs) have been developed and are currently used in the clinic. Despite their high efficacy, the long circulation half-life and non-specific binding of cytotoxic ADCs can result in systemic toxicity. In addition, standard ADCs do not provide an image-guided mode of administration. Here, we have developed a two-component, two-step, pre-targeting drug delivery system integrated with image guidance to circumvent these issues. In this strategy, HER2 receptors are pre-labeled with a functionalized trastuzumab antibody followed by the delivery of drug-loaded nanocarriers. Both components are cross-linked by multiple bioorthogonal click reactions in situ on the surface of the target cell and internalized as nanoclusters. We have explored the efficacy of this delivery strategy in HER2(+) human breast cancer models. Our therapeutic study confirms the high therapeutic efficacy of the new delivery system, with no significant toxicity.

  10. Phase topology and percolation in two-component lipid bilayers: a monte Carlo approach.

    PubMed Central

    Coelho, F P; Vaz, W L; Melo, E

    1997-01-01

    Monte Carlo simulations of fluorescence recovery after photobleaching (FRAP) experiments on two-component lipid bilayers systems in the solid-fluid phase coexistence region were carried out to study the geometry and size of fluid domains in these bilayers. The gel phase was simulated by superposable elliptical domains, which were either of predetermined dimensions, increasing in number with increasing gel phase fraction, or of predetermined number, increasing in dimensions with increasing gel phase fraction. The simulations were done from two perspectives: 1) a time-independent analysis of fractional fluorescence recovery as a function of fractional fluid phase in the system; and 2) a time-dependent analysis of fractional fluorescence recovery as a function of time at a given fraction of fluid phase in the system. The time-dependent simulations result in recovery curves that are directly comparable to experimental FRAP curves and provide topological and geometrical models for the coexisting phases that are consistent with the experimental result. Images FIGURE 5 PMID:9083656

  11. Direct molecular dynamics simulation of liquid-solid phase equilibria for two-component plasmas.

    PubMed

    Schneider, A S; Hughto, J; Horowitz, C J; Berry, D K

    2012-06-01

    We determine the liquid-solid phase diagram for carbon-oxygen and oxygen-selenium plasma mixtures using two-phase molecular dynamics simulations. We identify liquid, solid, and interface regions using a bond angle metric. To study finite-size effects, we perform 27,648- and 55,296-ion simulations. To help monitor nonequilibrium effects, we calculate diffusion constants D(i). For the carbon-oxygen system we find that D(O) for oxygen ions in the solid is much smaller than D(C) for carbon ions and that both diffusion constants are 80 or more times smaller than diffusion constants in the liquid phase. There is excellent agreement between our carbon-oxygen phase diagram and that predicted by Medin and Cumming. This suggests that errors from finite-size and nonequilibrium effects are small and that the carbon-oxygen phase diagram is now accurately known. The oxygen-selenium system is a simple two-component model for more complex rapid proton capture nucleosynthesis ash compositions for an accreting neutron star. Diffusion of oxygen, in a predominantly selenium crystal, is remarkably fast, comparable to diffusion in the liquid phase. We find a somewhat lower melting temperature for the oxygen-selenium system than that predicted by Medin and Cumming. This is probably because of electron screening effects. PMID:23005226

  12. Phase Separation and Dynamics of Trapped Two-component Bose-Einstein condensates

    NASA Astrophysics Data System (ADS)

    Proukakis, Np; Lee, Kl; Edmonds, M.; Liu, I.-K.; Jorgensen, Nb; Wacker, L.; Arlt, Jj

    2016-05-01

    Two-component Bose-Einstein condensates (BECs) are an attractive system to study the non-equilibrium dynamics of interacting quantum gases. We recently formulated a self-consistent kinetic model to study such systems at finite-temperature, where both components are partially-condensed. The BECs and the thermal atoms are coupled together through both the mean-field interactions and all possible collisional processes. We demonstrate the potential dominance of an energy-conserving exchange collision involving a BEC atom and a thermal atom from different components, and discuss the control of the hydrodynamicity through variations of temperature, trap frequencies and trap geometries. Numerically analysing the miscibility-immiscibility phase diagram for the trapped 87Rb-39K experimental system, we demonstrate deviations from the simple (homogeneous) interaction strength criterion (g122 /g11g22 = 1), with the transition boundary depending on the BEC atom numbers. We propose the experimental mapping of this boundary by monitoring the damping rate of the dipole oscillations, supported by detailed numerical simulations at zero and finite temperatures. Acknowledge: EPSRC (Grant No. EP/K03250X/1).

  13. Direct molecular dynamics simulation of liquid-solid phase equilibria for two-component plasmas

    NASA Astrophysics Data System (ADS)

    Schneider, A. S.; Hughto, J.; Horowitz, C. J.; Berry, D. K.

    2012-06-01

    We determine the liquid-solid phase diagram for carbon-oxygen and oxygen-selenium plasma mixtures using two-phase molecular dynamics simulations. We identify liquid, solid, and interface regions using a bond angle metric. To study finite-size effects, we perform 27 648- and 55 296-ion simulations. To help monitor nonequilibrium effects, we calculate diffusion constants Di. For the carbon-oxygen system we find that DO for oxygen ions in the solid is much smaller than DC for carbon ions and that both diffusion constants are 80 or more times smaller than diffusion constants in the liquid phase. There is excellent agreement between our carbon-oxygen phase diagram and that predicted by Medin and Cumming. This suggests that errors from finite-size and nonequilibrium effects are small and that the carbon-oxygen phase diagram is now accurately known. The oxygen-selenium system is a simple two-component model for more complex rapid proton capture nucleosynthesis ash compositions for an accreting neutron star. Diffusion of oxygen, in a predominantly selenium crystal, is remarkably fast, comparable to diffusion in the liquid phase. We find a somewhat lower melting temperature for the oxygen-selenium system than that predicted by Medin and Cumming. This is probably because of electron screening effects.

  14. Rayleigh-Taylor instability and mushroom-pattern formation in a two-component Bose-Einstein condensate

    SciTech Connect

    Sasaki, Kazuki; Suzuki, Naoya; Saito, Hiroki; Akamatsu, Daisuke

    2009-12-15

    The Rayleigh-Taylor instability at the interface in an immiscible two-component Bose-Einstein condensate is investigated using the mean field and Bogoliubov theories. Rayleigh-Taylor fingers are found to grow from the interface and mushroom patterns are formed. Quantized vortex rings and vortex lines are then generated around the mushrooms. The Rayleigh-Taylor instability and mushroom-pattern formation can be observed in a trapped system.

  15. Scale and Contour: Two Components of a Theory of Memory for Melodies.

    ERIC Educational Resources Information Center

    Dowling, W. Jay

    1978-01-01

    The author concentrates on two components of memory which contribute to the reproduction and recognition of melodies, namely, melodic contour and musical scale. A new experiment is reported that shows the interdependence of both components. (Author/RK)

  16. The rapid control of interactions in a two-component Fermi gas

    NASA Astrophysics Data System (ADS)

    Stites, Ronald William Donald

    In this dissertation, we describe a variety of experiments having application to ultra-cold atomic gases. While the majority of the experimental results focus on the development of a novel laser source for cooling and manipulating a gas of fermionic 6Li atoms, we also report on a preliminary investigation of rapidly controlling interactions in a two-component Fermi gas. One of the primary tools for our ultra-cold atomic physics experiments is 671 nm laser light nearly resonant with the D1 and D2 spectroscopic lines of ultracold fermionic 6Li atoms. Traditionally, this light is generated using dye lasers or tapered amplifier systems. Here we describe a diode pumped solid state ring laser system utilizing a Nd:YVO 4 gain crystal. Nd:YVO4 has a 4F 3/2 → 4I13/2 emission line at 1342 nm. This wavelength is double the 671 nm needed for our experiments. As a part of this investigation, we also measured the Verdet constant of undoped Y3Al5O12 in the near infrared for constructing a Faraday rotator used to drive unidirectional operation of our ring laser. As an alternative method to achieve unidirectional, single-frequency operation of the laser, we developed a novel scheme of "self-injection locking" where a small portion of the output beam is coupled back into the cavity to break the symmetry. This technique is useful for high-power, single-frequency operation of a ring laser because lossy elements needed for frequency selection and unidirectional operation of the laser can be removed from the internal cavity. In addition to our laser experiments, we also drive Raman transitions between different magnetic hyperfine states within 6Li atoms. For atoms in the two lowest hyperfine states, there exists a broad Feshbach resonance at 834.1 Gauss whereby the s-wave scattering length diverges, resulting in strong interactions between the two species. By using two phase locked lasers to drive a transition from a strongly interacting state to a weakly interacting state, we can

  17. A two-component rain model for the prediction of site diversity performance

    NASA Astrophysics Data System (ADS)

    Crane, Robert K.; Shieh, Horng-Chung

    1989-09-01

    A two-component rain attenuation model is presented for the prediction of single- and joint-(diversity) path rain attenuation statistics and for the prediction of the relative measures of diversity performance, diversity gain, and diversity improvement factor (or advantage). The model is based entirely on the use of geophysical parameters for the prediction of the effects of rain. It contains no free parameters to adjust to fit the available attenuation observations. The model is general and will handle both balanced and unbalanced diversity system design for terrestrial and satellite communication systems. Model performance was evaluated by comparison with published single-path and site diversity observations. The model performs well when tested against the International Radio Consultative Committee (CCIR) site diversity data base, providing predictions of the single-path attenuation values exceeded for specified percentages of a year with a root-mean-square difference (RMSD) from the observed values of 49% and providing predictions of the minimum attenuation value simultaneously exceeded on two links for specified percentages of a year with a RMSD of 59%.

  18. Surfactant effect on cloud condensation nuclei for two-component internally mixed aerosols

    NASA Astrophysics Data System (ADS)

    Petters, Sarah Suda; Petters, Markus Dirk

    2016-02-01

    This work presents experimental data on the cloud condensation nuclei (CCN) activity of two-component mixtures containing surfactants. Nine binary systems were tested combining strong ionic (sodium dodecyl sulfate) and nonionic surfactants (Zonyl FS-300 and Triton X-100) with nonsurfactant compounds (glucose, ammonium sulfate, or sodium chloride). Control tests were performed for systems combining organic (glucose) and inorganic compounds (ammonium sulfate or sodium chloride). Results show that CCN activity deviates strongly relative to predictions made from measurements of bulk surface tension. Köhler theory accounting for surface tension reduction and surface partitioning underpredicts the CCN activity of particles containing Zonyl FS-300 and Triton X-100. Partitioning theory better describes data for Zonyl FS-300 and Triton X-100 when limiting surface adsorption to 1.5 monolayers of the growing drop. Deviations from predictions were observed. Likely explanations include solute-solute interactions and nonspherical particle shape. The findings presented here examine in detail the perturbation of CCN activity by surfactants and may offer insight into both the success and limitations of physical models describing CCN activity of surface active molecules.

  19. Non-equilibrium dynamics around integrability in a one-dimensional two-component Bose gas

    NASA Astrophysics Data System (ADS)

    van Druten, Nicolaas; Wicke, Philipp; Whitlock, Shannon

    2011-05-01

    We investigate a one-dimensional two-component Bose gas near the point of state-independent interactions. At this specific point the system is integrable, in the sense that exact (thermodynamic) Bethe Ansatz solutions can be applied locally. In the experiments, we employ an atom chip and the magnetically trappable clock states in 87Rb. State-dependent potentials are generated by using the polarization dependence of radio-frequency dressing. We show that this allows us to continuously and dynamically tune both the local interactions and the global trapping potential. The experimentally accessible range in interactions includes the region around the integrability point. We study the spin motion that follows upon a sudden change in the system, a quantum quench. When starting from a low-temperature, quantum-degenerate gas in the weakly interacting regime, good agreement with a Gross-Pitaevskii description is found. The experiment allows exploring regimes that go beyond such a description and opens up a novel route to the study of the relation between non-equilibrium dynamics, thermalization and the making and breaking of integrability in quantum many-body physics. Supported by FOM, NWO and EU

  20. Molecular Mechanism of the Two-Component Suicidal Weapon of Neocapritermes taracua Old Workers.

    PubMed

    Bourguignon, Thomas; Šobotník, Jan; Brabcová, Jana; Sillam-Dussès, David; Buček, Aleš; Krasulová, Jana; Vytisková, Blahoslava; Demianová, Zuzana; Mareš, Michael; Roisin, Yves; Vogel, Heiko

    2016-03-01

    In termites, as in many social insects, some individuals specialize in colony defense, developing diverse weaponry. As workers of the termite Neocapritermes taracua (Termitidae: Termitinae) age, their efficiency to perform general tasks decreases, while they accumulate defensive secretions and increase their readiness to fight. This defensive mechanism involves self-sacrifice through body rupture during which an enzyme, stored as blue crystals in dorsal pouches, converts precursors produced by the labial glands into highly toxic compounds. Here, we identify both components of this activated defense system and describe the molecular basis responsible for the toxicity of N. taracua worker autothysis. The blue crystals are formed almost exclusively by a specific protein named BP76. By matching N. taracua transcriptome databases with amino acid sequences, we identified BP76 to be a laccase. Following autothysis, the series of hydroquinone precursors produced by labial glands get mixed with BP76, resulting in the conversion of relatively harmless hydroquinones into toxic benzoquinone analogues. Neocapritermes taracua workers therefore rely on a two-component activated defense system, consisting of two separately stored secretions that can react only after suicidal body rupture, which produces a sticky and toxic cocktail harmful to opponents. PMID:26609080

  1. Energy spectra of small two-component Fermi gases in a cubic box with periodic boundary conditions

    NASA Astrophysics Data System (ADS)

    Yin, X. Y.; Blume, D.

    2013-05-01

    The properties of two-component Fermi gases become universal if the interspecies s-wave scattering length and the average interparticle spacing are much larger than the range of the underlying two-body potential. Using an explicitly correlated Gaussian basis set expansion approach, we determine the eigenenergies of two-component Fermi gases in a cubic box with periodic boundary conditions as functions of the interspecies s-wave scattering length and the effective range of the two-body potential. The universal properties of systems consisting of up to five particles are determined by extrapolating the finite-range energies to the zero-range limit. We determine the eigenenergies of states with vanishing and finite momentum. For the infinitely large scattering length case, we compare our results with those presented in the literature. Support by the ARO is gratefully acknowledged.

  2. Two-component Dirac-like Hamiltonian for generating quantum walk on one-, two- and three-dimensional lattices

    PubMed Central

    Chandrashekar, C. M.

    2013-01-01

    From the unitary operator used for implementing two-state discrete-time quantum walk on one-, two- and three- dimensional lattice we obtain a two-component Dirac-like Hamiltonian. In particular, using different pairs of Pauli basis as position translation states we obtain three different form of Hamiltonians for evolution on one-dimensional lattice. We extend this to two- and three-dimensional lattices using different Pauli basis states as position translation states for each dimension and show that the external coin operation, which is necessary for one-dimensional walk is not a necessary requirement for a walk on higher dimensions but can serve as an additional resource to control the dynamics. The two-component Hamiltonian we present here for quantum walk on different lattices can serve as a general framework to simulate, control, and study the dynamics of quantum systems governed by Dirac-like Hamiltonian. PMID:24088731

  3. Stenotrophomonas maltophilia PhoP, a Two-Component Response Regulator, Involved in Antimicrobial Susceptibilities.

    PubMed

    Liu, Ming-Che; Tsai, Yi-Lin; Huang, Yi-Wei; Chen, Hsing-Yu; Hsueh, Po-Ren; Lai, Szu-Yu; Chen, Li-Chia; Chou, Yi-Hwa; Lin, Wen-Yuan; Liaw, Shwu-Jen

    2016-01-01

    Stenotrophomonas maltophilia, a gram-negative bacterium, has increasingly emerged as an important nosocomial pathogen. It is well-known for resistance to a variety of antimicrobial agents including cationic antimicrobial polypeptides (CAPs). Resistance to polymyxin B, a kind of CAPs, is known to be controlled by the two-component system PhoPQ. To unravel the role of PhoPQ in polymyxin B resistance of S. maltophilia, a phoP mutant was constructed. We found MICs of polymyxin B, chloramphenicol, ampicillin, gentamicin, kanamycin, streptomycin and spectinomycin decreased 2-64 fold in the phoP mutant. Complementation of the phoP mutant by the wild-type phoP gene restored all of the MICs to the wild type levels. Expression of PhoP was shown to be autoregulated and responsive to Mg2+ levels. The polymyxin B and gentamicin killing tests indicated that pretreatment of low Mg2+ can protect the wild-type S. maltophilia from killing but not phoP mutant. Interestingly, we found phoP mutant had a decrease in expression of SmeZ, an efflux transporter protein for aminoglycosides in S. maltophilia. Moreover, phoP mutant showed increased permeability in the cell membrane relative to the wild-type. In summary, we demonstrated the two-component regulator PhoP of S. maltophilia is involved in antimicrobial susceptibilities and low Mg2+ serves as a signal for triggering the pathway. Both the alteration in membrane permeability and downregulation of SmeZ efflux transporter in the phoP mutant contributed to the increased drug susceptibilities of S. maltophilia, in particular for aminoglycosides. This is the first report to describe the role of the Mg2+-sensing PhoP signaling pathway of S. maltophilia in regulation of the SmeZ efflux transporter and in antimicrobial susceptibilities. This study suggests PhoPQ TCS may serve as a target for development of antimicrobial agents against multidrug-resistant S. maltophilia. PMID:27159404

  4. Stenotrophomonas maltophilia PhoP, a Two-Component Response Regulator, Involved in Antimicrobial Susceptibilities

    PubMed Central

    Huang, Yi-Wei; Chen, Hsing-Yu; Hsueh, Po-Ren; Lai, Szu-Yu; Chen, Li-Chia; Chou, Yi-Hwa; Lin, Wen-Yuan; Liaw, Shwu-Jen

    2016-01-01

    Stenotrophomonas maltophilia, a gram-negative bacterium, has increasingly emerged as an important nosocomial pathogen. It is well-known for resistance to a variety of antimicrobial agents including cationic antimicrobial polypeptides (CAPs). Resistance to polymyxin B, a kind of CAPs, is known to be controlled by the two-component system PhoPQ. To unravel the role of PhoPQ in polymyxin B resistance of S. maltophilia, a phoP mutant was constructed. We found MICs of polymyxin B, chloramphenicol, ampicillin, gentamicin, kanamycin, streptomycin and spectinomycin decreased 2–64 fold in the phoP mutant. Complementation of the phoP mutant by the wild-type phoP gene restored all of the MICs to the wild type levels. Expression of PhoP was shown to be autoregulated and responsive to Mg2+ levels. The polymyxin B and gentamicin killing tests indicated that pretreatment of low Mg2+ can protect the wild-type S. maltophilia from killing but not phoP mutant. Interestingly, we found phoP mutant had a decrease in expression of SmeZ, an efflux transporter protein for aminoglycosides in S. maltophilia. Moreover, phoP mutant showed increased permeability in the cell membrane relative to the wild-type. In summary, we demonstrated the two-component regulator PhoP of S. maltophilia is involved in antimicrobial susceptibilities and low Mg2+ serves as a signal for triggering the pathway. Both the alteration in membrane permeability and downregulation of SmeZ efflux transporter in the phoP mutant contributed to the increased drug susceptibilities of S. maltophilia, in particular for aminoglycosides. This is the first report to describe the role of the Mg2+-sensing PhoP signaling pathway of S. maltophilia in regulation of the SmeZ efflux transporter and in antimicrobial susceptibilities. This study suggests PhoPQ TCS may serve as a target for development of antimicrobial agents against multidrug-resistant S. maltophilia. PMID:27159404

  5. Regulation of cytotoxin expression by converging eukaryotic-type and two-component signalling mechanisms in Streptococcus agalactiae.

    PubMed

    Rajagopal, Lakshmi; Vo, Anthony; Silvestroni, Aurelio; Rubens, Craig E

    2006-11-01

    Signal transducing mechanisms are essential for regulation of gene expression in both prokaryotic and eukaryotic organisms. Regulation of gene expression in eukaryotes is accomplished by serine/threonine and tyrosine kinases and cognate phosphatases. In contrast, gene expression in prokaryotes is controlled by two-component systems that comprise a sensor histidine kinase and a cognate DNA binding response regulator. Pathogenic bacteria utilize two-component systems to regulate expression of their virulence factors and for adaptive responses to the external environment. We have previously shown that the human pathogen Streptococcus agalactiae (Group B Streptococci, GBS) encodes a single eukaryotic-type serine/threonine kinase Stk1, which is important for virulence of the organism. In this study, we aimed to understand how Stk1 contributes to virulence of GBS. Our results indicate that Stk1 expression is important for resistance of GBS to human blood, neutrophils and oxidative stress. Consistent with these observations, Stk1 positively regulates transcription of a cytotoxin, beta-haemolysin/cytolysin (beta-H/C) that is critical for survival of GBS in the bloodstream and for resistance to oxidative stress. Interestingly, positive regulation of beta-H/C by Stk1 requires the two-component regulator CovR. Further, we show that Stk1 can negatively regulate transcription of CAMP factor in a CovR-dependent manner. As Stk1 phosphorylates CovR in vitro, these data suggest that serine/threonine phosphorylation impacts CovR-mediated regulation of GBS gene expression. In summary, our studies provide novel information that a eukaryotic-type serine/threonine kinase regulates two-component-mediated expression of GBS cytotoxins. PMID:17005013

  6. Vapour-mediated sensing and motility in two-component droplets

    NASA Astrophysics Data System (ADS)

    Cira, N. J.; Benusiglio, A.; Prakash, M.

    2015-03-01

    Controlling the wetting behaviour of liquids on surfaces is important for a variety of industrial applications such as water-repellent coatings and lubrication. Liquid behaviour on a surface can range from complete spreading, as in the `tears of wine' effect, to minimal wetting as observed on a superhydrophobic lotus leaf. Controlling droplet movement is important in microfluidic liquid handling, on self-cleaning surfaces and in heat transfer. Droplet motion can be achieved by gradients of surface energy. However, existing techniques require either a large gradient or a carefully prepared surface to overcome the effects of contact line pinning, which usually limit droplet motion. Here we show that two-component droplets of well-chosen miscible liquids such as propylene glycol and water deposited on clean glass are not subject to pinning and cause the motion of neighbouring droplets over a distance. Unlike the canonical predictions for these liquids on a high-energy surface, these droplets do not spread completely but exhibit an apparent contact angle. We demonstrate experimentally and analytically that these droplets are stabilized by evaporation-induced surface tension gradients and that they move in response to the vapour emitted by neighbouring droplets. Our fundamental understanding of this robust system enabled us to construct a wide variety of autonomous fluidic machines out of everyday materials.

  7. Nitrogen Oxyanion-dependent Dissociation of a Two-component Complex That Regulates Bacterial Nitrate Assimilation*

    PubMed Central

    Luque-Almagro, Victor M.; Lyall, Verity J.; Ferguson, Stuart J.; Roldán, M. Dolores; Richardson, David J.; Gates, Andrew J.

    2013-01-01

    Nitrogen is an essential nutrient for growth and is readily available to microbes in many environments in the form of ammonium and nitrate. Both ions are of environmental significance due to sustained use of inorganic fertilizers on agricultural soils. Diverse species of bacteria that have an assimilatory nitrate/nitrite reductase system (NAS) can use nitrate or nitrite as the sole nitrogen source for growth when ammonium is limited. In Paracoccus denitrificans, the pathway-specific two-component regulator for NAS expression is encoded by the nasT and nasS genes. Here, we show that the putative RNA-binding protein NasT is a positive regulator essential for expression of the nas gene cluster (i.e. nasABGHC). By contrast, a nitrogen oxyanion-binding sensor (NasS) is required for nitrate/nitrite-responsive control of nas gene expression. The NasS and NasT proteins co-purify as a stable heterotetrameric regulatory complex, NasS-NasT. This protein-protein interaction is sensitive to nitrate and nitrite, which cause dissociation of the NasS-NasT complex into monomeric NasS and an oligomeric form of NasT. NasT has been shown to bind the leader RNA for nasA. Thus, upon liberation from the complex, the positive regulator NasT is free to up-regulate nas gene expression. PMID:24005668

  8. The decoupling of the glass transitions in the two-component p-spin spherical model

    NASA Astrophysics Data System (ADS)

    Ikeda, Harukuni; Ikeda, Atsushi

    2016-07-01

    Binary mixtures of large and small particles with a disparate size ratio exhibit a rich phenomenology at their glass transition points. In order to gain insights on such systems, we introduce and study a two-component version of the p-spin spherical spin glass model. We employ the replica method to calculate the free energy and the phase diagram. We show that when the strengths of the interactions of each component are not widely separated, the model has only one glass phase characterized by the conventional one-step replica symmetry breaking. However when the strengths of the interactions are well separated, the model has three glass phases depending on the temperature and component ratio. One is the ‘single’ glass phase in which only the spins of one component are frozen while the spins of the other component remain mobile. This phase is characterized by the one-step replica symmetry breaking. The second is the ‘double’ glass phase obtained by cooling the single glass phase further, in which the spins of the remaining mobile component are also frozen. This phase is characterized by the two-step replica symmetry breaking. The third is also the ‘double’ glass phase, which, however, is formed by the simultaneous freezing of the spins of both components at the same temperatures and is characterized by the one-step replica symmetry breaking. We discuss the implications of these results for the glass transitions of binary mixtures.

  9. Stationary States and Modulational Instability of Coupled Two-Component Bose-Einstein Condensates in a Ring Trap

    NASA Astrophysics Data System (ADS)

    Deng, Hai-Ming; Zhong, Hong-Hua; Huang, Jia-Hao; Dai, Hui; Yao, Min; Huang, Xiao-Yi

    2015-08-01

    We investigate modulational instability (MI) of a coupled two-component Bose-Einstein condensates in a rotating ring trap. The excitation spectrum and the MI condition of the system are presented analytically. We find that the coupling between the two components strongly modifies the MI condition, and the MI condition is phase-dependent. Furthermore, we discuss the effect of MI on both density excitation and spin excitation. If the inter- and intra-component interaction strengths are all equal, the MI causes density excitation but not spin excitation, and if the inter- and intra-component interaction strengths are different, the MI causes both density excitation and spin excitation. Our results provide a promising approach for controlling the stability and excitation of a rotating two-component Bose-Einstein condensates by modulating its coupling strength and interaction strength. Supported by the National Natural Science Foundation of China under Grant No. 11465008, the Hunan Provincial Natural Science Foundation under Grant No. 2015JJ2114, the Scientific Research Fund of Hunan Provincial Education Department under Grant Nos. 14A118, 13C881, Science and Technology Innovative Research Team in Higher Educational Instituions of Hunan Province, and Science Research Foundation of Xiangnan University under Grant No. 2012-126(41)

  10. Tutorial on Quantification of Differences between Single- and Two-Component Two-Phase Flow and Heat Transfer

    NASA Astrophysics Data System (ADS)

    Delil, A. A. M.

    2003-01-01

    Single-component two-phase systems are envisaged for aerospace thermal control applications: Mechanically Pumped Loops, Vapour Pressure Driven Loops, Capillary Pumped Loops and Loop Heat Pipes. Thermal control applications are foreseen in different gravity environments: Micro-g, reduced-g for Mars or Moon bases, 1-g during terrestrial testing, and hyper-g in rotating spacecraft, during combat aircraft manoeuvres and in systems for outer planets. In the evaporator, adiabatic line and condenser sections of such single-component two-phase systems, the fluid is a mixture of the working liquid (for example ammonia, carbon dioxide, ethanol, or other refrigerants, etc.) and its saturated vapour. Results of two-phase two-component flow and heat transfer research (pertaining to liquid-gas mixtures, e.g. water/air, or argon or helium) are often applied to support research on flow and heat transfer in two-phase single-component systems. The first part of the tutorial updates the contents of two earlier tutorials, discussing various aerospace-related two-phase flow and heat transfer research. It deals with the different pressure gradient constituents of the total pressure gradient, with flow regime mapping (including evaporating and condensing flow trajectories in the flow pattern maps), with adiabatic flow and flashing, and with thermal-gravitational scaling issues. The remaining part of the tutorial qualitatively and quantitatively determines the differences between single- and two-component systems: Two systems that physically look similar and close, but in essence are fully different. It was already elucidated earlier that, though there is a certain degree of commonality, the differences will be anything but negligible, in many cases. These differences (quantified by some examples) illustrates how careful one shall be in interpreting data resulting from two-phase two-component simulations or experiments, for the development of single-component two-phase thermal control

  11. Two components in charged particle production in heavy-ion collisions

    NASA Astrophysics Data System (ADS)

    Bylinkin, A. A.; Chernyavskaya, N. S.; Rostovtsev, A. A.

    2016-02-01

    Transverse momentum spectra of charged particle production in heavy-ion collisions are considered in terms of a recently introduced Two Component parameterization combining exponential ("soft") and power-law ("hard") functional forms. The charged hadron densities calculated separately for them are plotted versus number of participating nucleons, Npart. The obtained dependences are discussed and the possible link between the two component parameterization introduced by the authors and the two component model historically used for the case of heavy-ion collisions is established. Next, the variations of the parameters of the introduced approach with the center of mass energy and centrality are studied using the available data from RHIC and LHC experiments. The spectra shapes are found to show universal dependences on Npart for all investigated collision energies.

  12. Nonlinear low frequency electrostatic structures in a magnetized two-component auroral plasma

    NASA Astrophysics Data System (ADS)

    Rufai, O. R.; Bharuthram, R.; Singh, S. V.; Lakhina, G. S.

    2016-03-01

    Finite amplitude nonlinear ion-acoustic solitons, double layers, and supersolitons in a magnetized two-component plasma composed of adiabatic warm ions fluid and energetic nonthermal electrons are studied by employing the Sagdeev pseudopotential technique and assuming the charge neutrality condition at equilibrium. The model generates supersoliton structures at supersonic Mach numbers regime in addition to solitons and double layers, whereas in the unmagnetized two-component plasma case only, soliton and double layer solutions can be obtained. Further investigation revealed that wave obliqueness plays a critical role for the evolution of supersoliton structures in magnetized two-component plasmas. In addition, the effect of ion temperature and nonthermal energetic electron tends to decrease the speed of oscillation of the nonlinear electrostatic structures. The present theoretical results are compared with Viking satellite observations.

  13. Modeling Thermal Dust Emission with Two Components: Application to the Planck High Frequency Instrument Maps

    NASA Astrophysics Data System (ADS)

    Meisner, Aaron M.; Finkbeiner, Douglas P.

    2015-01-01

    We apply the Finkbeiner et al. two-component thermal dust emission model to the Planck High Frequency Instrument maps. This parameterization of the far-infrared dust spectrum as the sum of two modified blackbodies (MBBs) serves as an important alternative to the commonly adopted single-MBB dust emission model. Analyzing the joint Planck/DIRBE dust spectrum, we show that two-component models provide a better fit to the 100-3000 GHz emission than do single-MBB models, though by a lesser margin than found by Finkbeiner et al. based on FIRAS and DIRBE. We also derive full-sky 6.'1 resolution maps of dust optical depth and temperature by fitting the two-component model to Planck 217-857 GHz along with DIRBE/IRAS 100 μm data. Because our two-component model matches the dust spectrum near its peak, accounts for the spectrum's flattening at millimeter wavelengths, and specifies dust temperature at 6.'1 FWHM, our model provides reliable, high-resolution thermal dust emission foreground predictions from 100 to 3000 GHz. We find that, in diffuse sky regions, our two-component 100-217 GHz predictions are on average accurate to within 2.2%, while extrapolating the Planck Collaboration et al. single-MBB model systematically underpredicts emission by 18.8% at 100 GHz, 12.6% at 143 GHz, and 7.9% at 217 GHz. We calibrate our two-component optical depth to reddening, and compare with reddening estimates based on stellar spectra. We find the dominant systematic problems in our temperature/reddening maps to be zodiacal light on large angular scales and the cosmic infrared background anisotropy on small angular scales.

  14. MODELING THERMAL DUST EMISSION WITH TWO COMPONENTS: APPLICATION TO THE PLANCK HIGH FREQUENCY INSTRUMENT MAPS

    SciTech Connect

    Meisner, Aaron M.; Finkbeiner, Douglas P. E-mail: dfinkbeiner@cfa.harvard.edu

    2015-01-10

    We apply the Finkbeiner et al. two-component thermal dust emission model to the Planck High Frequency Instrument maps. This parameterization of the far-infrared dust spectrum as the sum of two modified blackbodies (MBBs) serves as an important alternative to the commonly adopted single-MBB dust emission model. Analyzing the joint Planck/DIRBE dust spectrum, we show that two-component models provide a better fit to the 100-3000 GHz emission than do single-MBB models, though by a lesser margin than found by Finkbeiner et al. based on FIRAS and DIRBE. We also derive full-sky 6.'1 resolution maps of dust optical depth and temperature by fitting the two-component model to Planck 217-857 GHz along with DIRBE/IRAS 100 μm data. Because our two-component model matches the dust spectrum near its peak, accounts for the spectrum's flattening at millimeter wavelengths, and specifies dust temperature at 6.'1 FWHM, our model provides reliable, high-resolution thermal dust emission foreground predictions from 100 to 3000 GHz. We find that, in diffuse sky regions, our two-component 100-217 GHz predictions are on average accurate to within 2.2%, while extrapolating the Planck Collaboration et al. single-MBB model systematically underpredicts emission by 18.8% at 100 GHz, 12.6% at 143 GHz, and 7.9% at 217 GHz. We calibrate our two-component optical depth to reddening, and compare with reddening estimates based on stellar spectra. We find the dominant systematic problems in our temperature/reddening maps to be zodiacal light on large angular scales and the cosmic infrared background anisotropy on small angular scales.

  15. The formation of bulges, discs and two-component galaxies in the CANDELS Survey at z < 3

    NASA Astrophysics Data System (ADS)

    Margalef-Bentabol, Berta; Conselice, Christopher J.; Mortlock, Alice; Hartley, Will; Duncan, Kenneth; Ferguson, Harry C.; Dekel, Avishai; Primack, Joel R.

    2016-09-01

    We examine a sample of 1495 galaxies in the CANDELS fields to determine the evolution of two-component galaxies, including bulges and discs, within massive galaxies at the epoch 1 < z < 3 when the Hubble sequence forms. We fit all of our galaxies' light profiles with a single Sérsic fit, as well as with a combination of exponential and Sérsic profiles. The latter is done in order to describe a galaxy with an inner and an outer component, or bulge and disc component. We develop and use three classification methods (visual, F-test and the residual flux fraction) to separate our sample into one-component galaxies (disc/spheroids-like galaxies) and two-component galaxies (galaxies formed by an `inner part' or bulge and an `outer part' or disc). We then compare the results from using these three different ways to classify our galaxies. We find that the fraction of galaxies selected as two-component galaxies increases on average 50 per cent from the lowest mass bin to the most massive galaxies, and decreases with redshift by a factor of 4 from z = 1 to 3. We find that single Sérsic `disc-like' galaxies have the highest relative number densities at all redshifts, and that two-component galaxies have the greatest increase and become at par with Sérsic discs by z = 1. We also find that the systems we classify as two-component galaxies have an increase in the sizes of their outer components, or `discs', by about a factor of 3 from z = 3 to 1.5, while the inner components or `bulges' stay roughly the same size. This suggests that these systems are growing from the inside out, whilst the bulges or protobulges are in place early in the history of these galaxies. This is also seen to a lesser degree in the growth of single `disc-like' galaxies versus `spheroid-like' galaxies over the same epoch.

  16. Physical and petrologic evidence for a two component mantle MORB source

    NASA Astrophysics Data System (ADS)

    Dick, H.; Standish, J.; Snow, J.; Michael, P.; Salters, V.

    2003-04-01

    Study of ultra-slow spreading sections of the Southwest Indian and Gakkel Ridges support a two-component (veined?) mantle source for MORB. At both the Southwest Indian and Gakkel Ridges, mantle upwelling slows continuously over long sections of the ridge system due to changing ridge geometry and position with respect to the pole of rotation. For a simple peridotitic mantle this predicts steadily decreasing crustal production due to conductive heat loss depressing the top of the mantle-melting column. Instead, at 16 degrees E on the Southwest Indian Ridge and at 3 degrees E on the Gakkel, seafloor spreading abruptly goes from magmatic to amagmatic, with peridotite instead of basalt emplaced to the sea floor for long distances. As the mantle upwelling rate continues to decrease, however, volcanism reappears on both ridges at point source volcanoes and at large long-lived cross-axis volcanic highs, with intervening amagmatic segments. Such low levels of crustal production show that mantle melting is limited, and that abyssal peridotites there must have compositions close to unmelted mantle. However, significant areas of the amagmatic sections of the SW Indian and Gakkel Ridges appear to be floored dominantly by harzburgite, while other regions predominantly expose lherzolite. This poses a problem for modeling the MORB source as simply peridotite; as harzburgite is too depleted too generate MORB. The limited melt production during ultra-slow spreading also makes it difficult to produce the harzburgite during the axial mantle-melting event from lherzolite. In this case there is likely another mantle component contributing to MORB generation. Basalts over the transition from slow to ultra-slow spreading show a regular compositional gradient over 1000 km. Helium isotopes range from only 7.3 RA to 6.3 RA across this region, suggesting that while there is a chemical gradient in the mantle, there is not an abrupt change in the mantle source at the 16 degree E discontinuity

  17. Incipient flow properties of two-component fine powder mixtures: Changing the flowability of smaller particles

    NASA Astrophysics Data System (ADS)

    Kojima, Takehiro; Elliott, James A.

    2013-06-01

    Understanding the flow properties of two-component fine powder systems with micrometre-sized constituents is important for the quality control of electrophotographic printing applications such as photocopiers. In previous work, we studied the incipient flow properties of model powder mixtures of large (d50 ˜ 70 μm) and small (d50 ˜ 6-8 μm) particles under a consolidation stress of 2 kPa, and reported that they were strongly related to the properties of the small particles where the volume ratio of small powder (xs) exceeds ˜0.1 [1]. In this follow-up study, we examine the effect of changing the flowability of the smaller components on the structure and flow properties of the binary mixtures. For the smaller particles, we used poly(styrene-co-divinylbenzene) (PS-DVB) microspheres (d50 = 7.84 μm). The particle surfaces were modified by adding silica nanoparticles in order to prepare PS-DVB powders with a range of flowabilities. These were then mixed with glass ballotini (d50 = 71.9 μm), and the flow properties of these mixtures were evaluated using the shear testing technique. The cohesion of the mixtures showed essentially the same trend as reported in [1] in terms of their dependence on xs and was related to the number of contacts between the PS-DVB particles. Also, it was strongly dependent on the cohesion of the PS-DVB powders despite a very small xs (xs < 0.01). As for the internal angle of friction, although its value for each PS-DVB powder was similar, it also showed a correlation with the number of contacts between PS-DVB particles.

  18. Transcriptional and proteomic analyses of two-component response regulators in multidrug-resistant Mycobacterium tuberculosis.

    PubMed

    Zhou, Lei; Yang, Liu; Zeng, Xianfei; Danzheng, Jiacuo; Zheng, Qing; Liu, Jiayun; Liu, Feng; Xin, Yijuan; Cheng, Xiaodong; Su, Mingquan; Ma, Yueyun; Hao, Xiaoke

    2015-07-01

    Two-component systems (TCSs) have been reported to exhibit a sensing and responding role under drug stress that induces drug resistance in several bacterial species. However, the relationship between TCSs and multidrug resistance in Mycobacterium tuberculosis has not been comprehensively analysed to date. In this study, 90 M. tuberculosis clinical isolates were analysed using 15-loci mycobacterial interspersed repetitive unit (MIRU)-variable number tandem repeat (VNTR) typing and repetitive extragenic palindromic (rep)-PCR-based DNA fingerprinting. The results showed that all of the isolates were of the Beijing lineage, and strains with a drug-susceptible phenotype had not diverged into similar genotype clusters. Expression analysis of 13 response regulators of TCSs using real-time PCR and tandem mass spectrometry (MS/MS) proteomic analysis demonstrated that four response regulator genes (devR, mtrA, regX3 and Rv3143) were significantly upregulated in multidrug-resistant (MDR) strains compared with the laboratory strain H37Rv as well as drug-susceptible and isoniazid-monoresistant strains (P<0.05). DNA sequencing revealed that the promoter regions of devR, mtrA, regX3 and Rv3143 did not contain any mutations. Moreover, expression of the four genes could be induced by most of the four first-line antitubercular agents. In addition, either deletion or overexpression of devR in Mycobacterium bovis BCG did not alter its sensitivity to the four antitubercular drugs. This suggests that upregulation of devR, which is common in MDR-TB strains, might be induced by drug stress and hypoxic adaptation following the acquisition of multidrug resistance. PMID:25937537

  19. Structural studies of the activation of the two component receiver domain NTRC by multidimensional heteronuclear NMR

    SciTech Connect

    Nohaile, M J

    1996-05-01

    Multidimensional heteronuclear NMR spectroscopy was used to investigate the N-terminal domain of the transcriptional enhancer NTRC (NiTrogen Regulatory protein C). This domain belongs to the family of receiver domains of two-component regulatory systems involved in signal transduction. Phosphorylation of NTRC at D54 leads to an activated form of the molecule which stimulates transcription of genes involved in nitrogen regulation. Three and four dimensional NMR techniques were used to determine an intermediate resolution structure of the unphosphorylated, inactive form of the N-terminal domain of NTRC. The structure is comprised of five {alpha}-helices and a five-stranded {beta}-sheet in a ({beta}/{alpha}){sub 5} topology. Analysis of the backbone dynamics of NTRC indicate that helix 4 and strand 5 are significantly more flexible than the rest of the secondary structure of the protein and that the loops making up the active site are flexible. The short lifetime of phospho-NTRC hampers the study of this form. However, conditions for determining the resonance assignments and, possibly, the three dimensional structure of phosphorylated NTRC have been obtained. Tentative assignments of the phosphorylated form indicate that the majority of the changes that NTRC experiences upon phosphorylation occur in helix 3, strand 4, helix 4, strand 5, and the loop between strand 5 and helix 5 (the 3445 face of NTRC) as well as near the site of phosphorylation. In order to examine a stable, activated form of the protein, constitutively active mutants of NTRC were investigated.

  20. Temporal Variability from the Two-Component Advective Flow Solution and Its Observational Evidence

    NASA Astrophysics Data System (ADS)

    Dutta, Broja G.; Chakrabarti, Sandip K.

    2016-09-01

    In the propagating oscillatory shock model, the oscillation of the post-shock region, i.e., the Compton cloud, causes the observed low-frequency quasi-periodic oscillations (QPOs). The evolution of QPO frequency is explained by the systematic variation of the Compton cloud size, i.e., the steady radial movement of the shock front, which is triggered by the cooling of the post-shock region. Thus, analysis of the energy-dependent temporal properties in different variability timescales can diagnose the dynamics and geometry of accretion flows around black holes. We study these properties for the high-inclination black hole source XTE J1550-564 during its 1998 outburst and the low-inclination black hole source GX 339-4 during its 2006–07 outburst using RXTE/PCA data, and we find that they can satisfactorily explain the time lags associated with the QPOs from these systems. We find a smooth decrease of the time lag as a function of time in the rising phase of both sources. In the declining phase, the time lag increases with time. We find a systematic evolution of QPO frequency and hard lags in these outbursts. In XTE J1550-564, the lag changes from hard to soft (i.e., from a positive to a negative value) at a crossing frequency (ν c) of ∼3.4 Hz. We present possible mechanisms to explain the lag behavior of high and low-inclination sources within the framework of a single two-component advective flow model.

  1. Computer simulation study of waterborne two-component polyurethane film formation

    NASA Astrophysics Data System (ADS)

    Yang, Shihai

    2007-12-01

    In this thesis, a coarse-grained computer simulation model is presented to study the film growth and macroscopic morphological feature (film thickness, surface roughness and longitudinal constituent density profile) in a multi-component polymer system. The mixture consists of reactive hydrophobic (H) and polar groups (P) in a reactive aqueous solvent ( A) which is also allowed to evaporate. Characteristics of each component such as hydrophobic and polar interactions, molecular weights, and specific functionality for the covalent bonding are used to describe the waterborne two-component polyurethane (WB 2K-PUR) film growth as an example. Systematic approach is employed to study the film growth step by step starting from the mixture of its basic ingradients. Attempts are made to capture such realistic features as perceived reaction kinetics and polymerization mechanism in the model. Constituents move stochastically via the Metropolis algorithm to explore thermo-dynamic equilibration while the kinetic reactions are incorporated through flexible covalent bonding (Bond Fluctuation Model) which may arrest the growth before reaching equilibrium. Film thickness grows and its interface evolves and equilibrates as the simulation continues. Power-law dependence is found for the initial growth of film thickness (h) and surface roughness (W) with time (t), i.e., h ∝ tgamma, W ∝ tbeta, with all simulations. In addition to the study of film evolution and surface morphlogy, constituent density profiles along the longitudinal direction are also investigated to develop a deep understanding of film infra-structure as well as to track the post-reaction product distribution. Effects of parameters such as temperature, relative humidity (initial water concentration), stoichiometry (NCO:OH ratio) and reaction rate are examined specifically in these simulations. Qualitative agreements with laboratory observations are found with our simulation results.

  2. Intracavity Rayleigh/Mie Scattering for Multipoint, Two-Component Velocity Measurement

    NASA Technical Reports Server (NTRS)

    Bivolaru, Daniel; Danehy, Paul M.; Lee, Joseph W.

    2006-01-01

    A simultaneous multi-point two-component Doppler velocimeter is described. The system uses two optical cavities: a Fabry-Perot etalon and an optical cavity for collecting and re-circulating the Rayleigh/Mie scattered light that is collected from the measurement volume in two parallel, but opposite directions. Single-pulse measurements of two orthogonal components of the velocity vector in a supersonic free jet were performed to demonstrate the technique. The re-circulation of the light rejected by the interferometer input mirror also increased the signal intensity by a factor of 3.5. 2005 Optical Society of America Interferometric Rayleigh scattering has previously been used for single-point velocity measurements in unseeded gas flow. However, this past work has generally been limited to probing with continuous-wave lasers resulting in time-averaged measurements of velocity. Multiple velocity components have been measured simultaneously by separate instruments.1,2 It has also been demonstrated that two orthogonal velocity components can be measured simultaneously at one point using one interferometer by reflecting back the probing laser beam, although this approach results in directional ambiguity of the flow velocity vector.3 This measurement ambiguity was removed by prior knowledge of the approximate magnitude and sign of the velocity components. Furthermore, it was shown that multiple points could be measured simultaneously with a Rayleigh scattering interferometric approach, but only one component of velocity was measured.4 Another method of performing multiple component velocity measurements with Rayleigh scattering uses a pair of cameras to image the flow, one of which views the flow through an iodine gas filter. This iodine-filter technique has the advantage of allowing high-resolution velocity imaging, but it generally has a lower dynamic range.

  3. Low temperatures shear viscosity of a two-component dipolar Fermi gas with unequal population

    NASA Astrophysics Data System (ADS)

    Darsheshdar, E.; Yavari, H.; Zangeneh, Z.

    2016-07-01

    By using the Green's functions method and linear response theory we calculate the shear viscosity of a two-component dipolar Fermi gas with population imbalance (spin polarized) in the low temperatures limit. In the strong-coupling Bose-Einstein condensation (BEC) region where a Feshbach resonance gives rise to tightly bound dimer molecules, a spin-polarized Fermi superfluid reduces to a simple Bose-Fermi mixture of Bose-condensed dimers and the leftover unpaired fermions (atoms). The interactions between dimer-atom, dimer-dimer, and atom-atom take into account to the viscous relaxation time (τη) . By evaluating the self-energies in the ladder approximation we determine the relaxation times due to dimer-atom (τDA) , dimer-dimer (τcDD ,τdDD) , and atom-atom (τAA) interactions. We will show that relaxation rates due to these interactions τDA-1 ,τcDD-1, τdDD-1, and τAA-1 have T2, T4, e - E /kB T (E is the spectrum of the dimer atoms), and T 3 / 2 behavior respectively in the low temperature limit (T → 0) and consequently, the atom-atom interaction plays the dominant role in the shear viscosity in this rang of temperatures. For small polarization (τDA ,τAA ≫τcDD ,τdDD), the low temperatures shear viscosity is determined by contact interaction between dimers and the shear viscosity varies as T-5 which has the same behavior as the viscosity of other superfluid systems such as superfluid neutron stars, and liquid helium.

  4. Lipase Expression in Pseudomonas alcaligenes Is Under the Control of a Two-Component Regulatory System▿

    PubMed Central

    Krzeslak, Joanna; Gerritse, Gijs; van Merkerk, Ronald; Cool, Robbert H.; Quax, Wim J.

    2008-01-01

    Preliminary observations in a large-scale fermentation process suggested that the lipase expression of Pseudomonas alcaligenes can be switched on by the addition of certain medium components, such as soybean oil. In an attempt to elucidate the mechanism of induction of lipase expression, we have set up a search method for genes controlling lipase expression by use of a cosmid library containing fragments of P. alcaligenes genomic DNA. A screen for lipase hyperproduction resulted in the selection of multiple transformants, of which the best-producing strains comprised cosmids that shared an overlapping genomic fragment. Within this fragment, two previously unidentified genes were found and named lipQ and lipR. Their encoded proteins belong to the NtrBC family of regulators that regulate gene expression via binding to a specific upstream activator sequence (UAS). Such an NtrC-like UAS was identified in a previous study in the P. alcaligenes lipase promoter, strongly suggesting that LipR acts as a positive regulator of lipase expression. The regulating role could be confirmed by down-regulated lipase expression in a strain with an inactivated lipR gene and a threefold increase in lipase yield in a large-scale fermentation when expressing the lipQR operon from the multicopy plasmid pLAFR3. Finally, cell extracts of a LipR-overexpressing strain caused a retardation of the lipase promoter fragment in a band shift assay. Our results indicate that lipase expression in Pseudomonas alcaligenes is under the control of the LipQR two-component system. PMID:18192420

  5. Concentration Fluctuation in a Two-Component Fluid Membrane Surrounded with Three-Dimensional Fluids

    NASA Astrophysics Data System (ADS)

    Inaura, Keiichiro; Fujitani, Youhei

    2008-11-01

    We calculate the relaxation rate of the critical concentration fluctuation in a two-component fluid membrane by considering hydrodynamics of the surrounding fluids. Results are compared with the previous results obtained by Seki, Komura, and Imai (2007), who treated the momentum flux from the membrane to its environments using the friction coefficient.

  6. Two component model for X-ray emission of radio selected QSO's

    NASA Technical Reports Server (NTRS)

    Isobe, T.; Feigelson, E. D.; Singh, K. P.; Kembhavi, A.

    1986-01-01

    Using a large database of radio, optical, and x ray luminosities of AGNs with survival analysis, it was found that the x ray emission of the radio selected quasars has two components. One is related to the optical luminosity and the other is related to the radio luminosity.

  7. On bi-Hamiltonian structure of two-component Novikov equation

    NASA Astrophysics Data System (ADS)

    Li, Nianhua; Liu, Q. P.

    2013-01-01

    In this Letter, we present a bi-Hamiltonian structure for the two-component Novikov equation. We also show that proper reduction of this bi-Hamiltonian structure leads to the Hamiltonian operators found by Hone and Wang for the Novikov equation.

  8. Cascade stability of the debris catalog under a two-component flux model

    SciTech Connect

    Canavan, G.H.

    1997-01-01

    Stability is analyzed with a two component model. The critical densities derived are in agreement with other estimates in the appropriate limits. The current catalog is stable for nominal decay parameters, although further growth or cascade coefficients higher than nominal could be causes for concern. Sources reduce stability, which is more of a problem at high altitudes than low.

  9. Excitations of the quantum phases of a two-component Bose gas in an optical lattice

    NASA Astrophysics Data System (ADS)

    Luxat, David L.

    2004-03-01

    We consider the dynamics of a two-component Bose gas in an optical lattice at T=0. As shown recently, the phase diagram has several quantum phase transitions, which arise because of intra-component correlations. We focus on the two-component Mott insulating (2MI) and the xy-ferromagnetic or super-counter-fluid (SCF) phases. Starting from the two-component Bose-Hubbard model, an effective Hamiltonian is used to study the excitations and collective modes of these two quantum phases. The two-particle excitations associated with the intra-component or spin dynamics are markedly different in these two phases, exhibiting a Goldstone mode in the SCF phase. These collective modes are the poles of the intra-component two-particle correlation function or transverse spin susceptibility. We show how this intra-component two-particle correlation function, and thus the two-particle excitation spectrum, may be measured using a two-photon Raman probe that couples the two components. We also show how a Raman probe may be used to study the single-particle excitations when it couples one of the components to another hyperfine state. This could provide a direct measure of the Mott insulating gap.

  10. Quantum particle-number fluctuations in a two-component Bose gas in a double-well potential

    SciTech Connect

    Zin, Pawel; Oles, Bartlomiej; Sacha, Krzysztof

    2011-09-15

    A two-component Bose gas in a double-well potential with repulsive interactions may undergo a phase separation transition if the interspecies interactions outweigh the intraspecies ones. We analyze the transition in the strong interaction limit within the two-mode approximation. Numbers of particles in each potential well are equal and constant. However, at the transition point, the ground state of the system reveals huge fluctuations of numbers of particles belonging to the different gas components; that is, the probability for observation of any mixture of particles in each potential well becomes uniform.

  11. The dynamics of a slider-crank mechanism with an initially curved coupler under two-component parametric resonance

    NASA Astrophysics Data System (ADS)

    Wang, Yi-Ming

    2005-02-01

    The objective of this paper is to study the dynamics and dynamic instability of a slider-crank mechanism with an initially curved coupler under parametric resonance. An attention is given to the phenomena arising due to initial curvature, geometric imperfection, of a connecting rod and modal interactions produced by the existence of two-component parametric resonance. The two-component parametric resonance can occur, for example, when the fundamental frequency of the flexible part of a slider-crank mechanism is close to one-half of the excitation frequency and simultaneously the difference between the first and the second natural frequencies is near the frequency of excitation. It is known that for the case of one-component parametric resonance, an initially curved connecting rod enlarges the amplitude of fundamental mode of vibration significantly only if the motion is in the vicinity of the secondary region of instability. In other words, the initial curvature of a coupler plays no effects to the fundamental response of the system if the oscillation is near the primary region of instability. However, result of present study shows that under the condition of two-component parametric resonance, unlike the case of one-component parametric resonance, an initially curved linkage can result significant effects to the vibration of the system even if the motion is close to the primary region of instability. In addition, the result also indicates that the growth of small amplitude vibration into large motion regime occurs if vibrations arise near the boundary of stable region.

  12. The role of the Kubo number in two-component turbulence

    SciTech Connect

    Qin, G.; Shalchi, A.

    2013-09-15

    We explore the random walk of magnetic field lines in two-component turbulence by using computer simulations. It is often assumed that the two-component model provides a good approximation for solar wind turbulence. We explore the dependence of the field line diffusion coefficient on the Kubo number which is a fundamental and characteristic quantity in the theory of turbulence. We show that there are two transport regimes. One is the well-known quasilinear regime in which the diffusion coefficient is proportional to the Kubo number squared, and the second one is a nonlinear regime in which the diffusion coefficient is directly proportional to the Kubo number. The so-called percolative transport regime which is often discussed in the literature cannot be found. The numerical results obtained in the present paper confirm analytical theories for random walking field lines developed in the past.

  13. Countersuperflow instability in miscible two-component Bose-Einstein condensates

    SciTech Connect

    Ishino, Shungo; Tsubota, Makoto; Takeuchi, Hiromitsu

    2011-06-15

    We study theoretically the instability of countersuperflow, i.e., two counterpropagating miscible superflows, in uniform two-component Bose-Einstein condensates. Countersuperflow instability causes mutual friction between the superfluids, causing a momentum exchange between the two condensates, when the relative velocity of the counterflow exceeds a critical value. The momentum exchange leads to nucleation of vortex rings from characteristic density patterns due to the nonlinear development of the instability. Expansion of the vortex rings drastically accelerates the momentum exchange, leading to a highly nonlinear regime caused by intervortex interaction and vortex reconnection between the rings. For a sufficiently large interaction between the two components, rapid expansion of the vortex rings causes isotropic turbulence and the global relative motion of the two condensates relaxes. The maximum vortex line density in the turbulence is proportional to the square of the relative velocity.

  14. Two-component Fermi-liquid theory - Equilibrium properties of liquid metallic hydrogen

    NASA Technical Reports Server (NTRS)

    Oliva, J.; Ashcroft, N. W.

    1981-01-01

    It is reported that the transition of condensed hydrogen from an insulating molecular crystal phase to a metallic liquid phase, at zero temperature and high pressure, appears possible. Liquid metallic hydrogen (LMH), comprising interpenetrating proton and electron fluids, would constitute a two-component Fermi liquid with both a very high component-mass ratio and long-range, species-dependent bare interactions. The low-temperature equilibrium properties of LMH are examined by means of a generalization to the case of two components of the phenomenological Landau Fermi-liquid theory, and the low-temperature specific heat, compressibility, thermal expansion coefficient and spin susceptibility are given. It is found that the specific heat and the thermal expansion coefficient are vastly greater in the liquid than in the corresponding solid, due to the presence of proton quasiparticle excitations in the liquid.

  15. On the spin separation of algebraic two-component relativistic Hamiltonians

    NASA Astrophysics Data System (ADS)

    Li, Zhendong; Xiao, Yunlong; Liu, Wenjian

    2012-10-01

    The separation of the spin-free and spin-dependent terms of a given relativistic Hamiltonian is usually facilitated by the Dirac identity. However, this is no longer possible for the recently developed exact two-component relativistic Hamiltonians derived from the matrix representation of the Dirac equation in a kinetically balanced basis. This stems from the fact that the decoupling matrix does not have an explicit form. To resolve this formal difficulty, we first define the spin-dependent term as the difference between a two-component Hamiltonian corresponding to the full Dirac equation and its one-component counterpart corresponding to the spin-free Dirac equation. The series expansion of the spin-dependent term is then developed in two different ways. One is in the spirit of the Douglas-Kroll-Hess (DKH) transformation and the other is based on the perturbative expansion of a two-component Hamiltonian of fixed structure, either the two-step Barysz-Sadlej-Snijders (BSS) or the one-step exact two-component (X2C) form. The algorithms for constructing arbitrary order terms are proposed for both schemes and their convergence patterns are assessed numerically. Truncating the expansions to finite orders leads naturally to a sequence of novel spin-dependent Hamiltonians. In particular, the order-by-order distinctions among the DKH, BSS, and X2C approaches can nicely be revealed. The well-known Pauli, zeroth-order regular approximation, and DKH1 spin-dependent Hamiltonians can also be recovered naturally by appropriately approximating the decoupling and renormalization matrices. On the practical side, the sf-X2C+so-DKH3 Hamiltonian, together with appropriately constructed generally contracted basis sets, is most promising for accounting for relativistic effects in two steps, first spin-free and then spin-dependent, with the latter applied either perturbatively or variationally.

  16. Kinetics and mechanism of the oxidation process of two-component Fe-Al alloys

    NASA Technical Reports Server (NTRS)

    Przewlocka, H.; Siedlecka, J.

    1982-01-01

    The oxidation process of two-component Fe-Al alloys containing up to 7.2% Al and from 18 to 30% Al was studied. Kinetic measurements were conducted using the isothermal gravimetric method in the range of 1073-1223 K and 1073-1373 K for 50 hours. The methods used in studies of the mechanism of oxidation included: X-ray microanalysis, X-ray structural analysis, metallographic analysis and marker tests.

  17. On the spin separation of algebraic two-component relativistic Hamiltonians.

    PubMed

    Li, Zhendong; Xiao, Yunlong; Liu, Wenjian

    2012-10-21

    The separation of the spin-free and spin-dependent terms of a given relativistic Hamiltonian is usually facilitated by the Dirac identity. However, this is no longer possible for the recently developed exact two-component relativistic Hamiltonians derived from the matrix representation of the Dirac equation in a kinetically balanced basis. This stems from the fact that the decoupling matrix does not have an explicit form. To resolve this formal difficulty, we first define the spin-dependent term as the difference between a two-component Hamiltonian corresponding to the full Dirac equation and its one-component counterpart corresponding to the spin-free Dirac equation. The series expansion of the spin-dependent term is then developed in two different ways. One is in the spirit of the Douglas-Kroll-Hess (DKH) transformation and the other is based on the perturbative expansion of a two-component Hamiltonian of fixed structure, either the two-step Barysz-Sadlej-Snijders (BSS) or the one-step exact two-component (X2C) form. The algorithms for constructing arbitrary order terms are proposed for both schemes and their convergence patterns are assessed numerically. Truncating the expansions to finite orders leads naturally to a sequence of novel spin-dependent Hamiltonians. In particular, the order-by-order distinctions among the DKH, BSS, and X2C approaches can nicely be revealed. The well-known Pauli, zeroth-order regular approximation, and DKH1 spin-dependent Hamiltonians can also be recovered naturally by appropriately approximating the decoupling and renormalization matrices. On the practical side, the sf-X2C+so-DKH3 Hamiltonian, together with appropriately constructed generally contracted basis sets, is most promising for accounting for relativistic effects in two steps, first spin-free and then spin-dependent, with the latter applied either perturbatively or variationally. PMID:23083155

  18. Analytic second derivatives for the spin-free exact two-component theory.

    PubMed

    Cheng, Lan; Gauss, Jürgen

    2011-12-28

    The formulation and implementation of the spin-free (SF) exact two-component (X2c) theory at the one-electron level (SFX2c-1e) is extended in the present work to the analytic evaluation of second derivatives of the energy. In the X2c-1e scheme, the four-component one-electron Dirac Hamiltonian is block diagonalized in its matrix representation and the resulting "electrons-only" two-component Hamiltonian is then used together with untransformed two-electron interactions. The derivatives of the two-component Hamiltonian can thus be obtained by means of simple manipulations of the parent four-component Hamiltonian integrals and derivative integrals. The SF version of X2c-1e can furthermore exploit available nonrelativistic quantum-chemical codes in a straightforward manner. As a first application of analytic SFX2c-1e second derivatives, we report a systematic study of the equilibrium geometry and vibrational frequencies for the bent ground state of the copper hydroxide (CuOH) molecule. Scalar-relativistic, electron-correlation, and basis-set effects on these properties are carefully assessed. PMID:22225141

  19. Two-component flux explanation for the high energy neutrino events at IceCube

    NASA Astrophysics Data System (ADS)

    Chen, Chien-Yi; Dev, P. S. Bhupal; Soni, Amarjit

    2015-10-01

    Understanding the spectral and flavor composition of the astrophysical neutrino flux responsible for the recently observed ultrahigh-energy events at IceCube is of great importance for both astrophysics and particle physics. We perform a statistical likelihood analysis to the three-year IceCube data and derive the allowed range of the spectral index and flux normalization for various well-motivated physical flavor compositions at the source. While most of the existing analyses so far assume the flavor composition of the neutrinos at an astrophysical source to be (1:2:0), it seems rather unnatural to assume only one type of source, once we recognize the possibility of at least two physical sources. Bearing this in mind, we entertain the possibility of a two-component source for the analysis of IceCube data. It appears that our two-component hypothesis explains some key features of the data better than a single-component scenario; i.e. it addresses the apparent energy gap between 400 TeV and about 1 PeV and easily accommodates the observed track-to-shower ratio. Given the extreme importance of the flavor composition for the correct interpretation of the underlying astrophysical processes as well as for the ramification for particle physics, this two-component flux should be tested as more data is accumulated.

  20. Vortices in a rotating two-component Bose–Einstein condensate with tunable interactions and harmonic potential

    SciTech Connect

    Zhang, Xiao-Fei; Du, Zhi-Jing; Tan, Ren-Bing; Dong, Rui-Fang; Chang, Hong; Zhang, Shou-Gang

    2014-07-15

    We consider a pair of coupled nonlinear Schrödinger equations modeling a rotating two-component Bose–Einstein condensate with tunable interactions and harmonic potential, with emphasis on the structure of vortex states by varying the strength of inter-component interaction, rotational frequency, and the aspect ratio of the harmonic potential. Our results show that the inter-component interaction greatly enhances the effect of rotation. For the case of isotropic harmonic potential and small inter-component interaction, the initial vortex structure remains unchanged. As the ratio of inter- to intra-component interactions increases, each component undergoes a transition from a vortex lattice (vortex line) in an isotropic (anisotropic) harmonic potential to an alternatively arranged stripe pattern, and eventually to the interwoven “serpentine” vortex sheets. Moreover, in the case of anisotropic harmonic potential the system can develop to a rotating droplet structure. -- Highlights: •Different vortex structures are obtained within the full parameter space. •Effects of system parameters on the ground state structure are discussed. •Phase transition between different vortex structures is also examined. •Present one possible way to obtain the rotating droplet structure. •Provide many possibilities to manipulate vortex in two-component BEC.

  1. Evaluation of the operational parameters for NBI-driven fusion in low-gain tokamaks with two-component plasma

    NASA Astrophysics Data System (ADS)

    Chirkov, A. Yu.

    2015-09-01

    Low gain (Q ~ 1) fusion plasma systems are of interest for concepts of fusion-fission hybrid reactors. Operational regimes of large modern tokamaks are close to Q  ≈  1. Therefore, they can be considered as prototypes of neutron sources for fusion-fission hybrids. Powerful neutral beam injection (NBI) can support the essential population of fast particles compared with the Maxwellial population. In such two-component plasma, fusion reaction rate is higher than for Maxwellian plasma. Increased reaction rate allows the development of relatively small-size and relatively inexpensive neutron sources. Possible operating regimes of the NBI-heated tokamak neutron source are discussed. In a relatively compact device, the predictions of physics of two-component fusion plasma have some volatility that causes taking into account variations of the operational parameters. Consequent parameter ranges are studied. The feasibility of regimes with Q  ≈  1 is shown for the relatively small and low-power system. The effect of NBI fraction in total heating power is analyzed.

  2. A phase-space fluid simulation of a two-component narrow planetary ring - Particle size segregation, edge formation, and spreading rates

    NASA Technical Reports Server (NTRS)

    Brophy, Thomas G.; Stewart, Glen R.; Esposito, Larry W.

    1990-01-01

    The Krook kinetic equation for identical planetary ring particles is presently generalized for the case of two-component systems, and the equations are numerically solved on the basis of Brophy and Esposito's (1989) phase-space CFD method. Attention is given to the simulation results obtained for a two-component narrow ring, in which the large particles are eight times as massive as the small particles. This ring's unconstrained edge dynamics are resolved by the simulation, and are found to exhibit a sharpening that would not have been expected in single-component rings.

  3. How insects overcome two-component plant chemical defence: plant β-glucosidases as the main target for herbivore adaptation.

    PubMed

    Pentzold, Stefan; Zagrobelny, Mika; Rook, Fred; Bak, Søren

    2014-08-01

    Insect herbivory is often restricted by glucosylated plant chemical defence compounds that are activated by plant β-glucosidases to release toxic aglucones upon plant tissue damage. Such two-component plant defences are widespread in the plant kingdom and examples of these classes of compounds are alkaloid, benzoxazinoid, cyanogenic and iridoid glucosides as well as glucosinolates and salicinoids. Conversely, many insects have evolved a diversity of counteradaptations to overcome this type of constitutive chemical defence. Here we discuss that such counter-adaptations occur at different time points, before and during feeding as well as during digestion, and at several levels such as the insects’ feeding behaviour, physiology and metabolism. Insect adaptations frequently circumvent or counteract the activity of the plant β-glucosidases, bioactivating enzymes that are a key element in the plant’s two-component chemical defence. These adaptations include host plant choice, non-disruptive feeding guilds and various physiological adaptations as well as metabolic enzymatic strategies of the insect’s digestive system. Furthermore, insect adaptations often act in combination, may exist in both generalists and specialists, and can act on different classes of defence compounds. We discuss how generalist and specialist insects appear to differ in their ability to use these different types of adaptations: in generalists, adaptations are often inducible, whereas in specialists they are often constitutive. Future studies are suggested to investigate in detail how insect adaptations act in combination to overcome plant chemical defences and to allow ecologically relevant conclusions. PMID:25165798

  4. Thermal Regulation of Membrane Lipid Fluidity by a Two-Component System in "Bacillus Subtilis"

    ERIC Educational Resources Information Center

    Bredeston, L. M.; Marciano, D.; Albanesi, D.; De Mendoza, D.; Delfino, J. M.

    2011-01-01

    This article describes a simple and robust laboratory exercise on the regulation of membrane unsaturated fatty acid composition in bacteria by a decrease in growth temperature. We take advantage of the well characterized Des pathway of "Bacillus subtilis", composed of a [delta]5-desaturase (encoded by the "des" gene) and the canonical…

  5. Resistance to the Poerovirus Cereal Yellow Dwarf Virus in Wheat: A Two-component system

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The mechanism of resistance to Cereal yellow dwarf virus (CYDV), introgressed into wheat from Thinopyrum intermedium, is unclear as previous data demonstrated that it was not due to a block in virus replication. Through cellular analysis we have examined the movement of CYDV within inoculated and u...

  6. Local-dephasing-induced entanglement sudden death in two-component finite-dimensional systems

    SciTech Connect

    Ann, Kevin; Jaeger, Gregg

    2007-10-15

    Entanglement sudden death (ESD), the complete loss of entanglement in finite time, is demonstrated to occur in a class of bipartite states of qudit pairs of any finite dimension d>2, when prepared in so-called 'isotropic states' and subject to multilocal dephasing noise alone. This extends previous results for qubit pairs [T. Yu and J. H. Eberly, Phys. Rev. Lett. 97, 140403 (2006)] to all qudit pairs with d>2.

  7. Two-component model of strong Langmuir turbulence - Scalings, spectra, and statistics of Langmuir waves

    NASA Technical Reports Server (NTRS)

    Robinson, P. A.; Newman, D. L.

    1990-01-01

    A simple two-component model of strong turbulence that makes clear predictions for the scalings, spectra, and statistics of Langmuir waves is developed. Scalings of quantities such as energy density, power input, dissipation power wave collapse, and number density of collapsing objects are investigated in detail and found to agree well with model predictions. The nucleation model of wave-packet formation is strongly supported by the results. Nucleation proceeds with energy flowing from background to localized states even in the absence of a driver. Modulational instabilities play little or no role in maintaining the turbulent state when significant density nonuniformities are present.

  8. Investigation of the adhesion interface obtained through two-component injection molding

    NASA Astrophysics Data System (ADS)

    Fetecau, Catalin; Stan, Felicia; Dobrea, Daniel

    2011-01-01

    In this paper we study the interface strength obtained through two-component (2C) injection molding of LDPE-HDPE polymers. First, numerical simulation of the over-molding process is carried out using Moldflow technology. Second, butt-joint specimens were produced by over-molding under different process condition, and tested. Two injection sequences were considered, injection of LDPE on HDPE polymer, and HDLE on LDPE, respectively. To investigate the effects of the mold surface roughness on the polymers adhesion at interface, different inserts with different roughness are employed.

  9. Dynamics of bubbles in a two-component Bose-Einstein condensate

    NASA Astrophysics Data System (ADS)

    Sasaki, Kazuki; Suzuki, Naoya; Saito, Hiroki

    2011-03-01

    The dynamics of a phase-separated two-component Bose-Einstein condensate are investigated, in which a bubble of one component moves through the other component. Numerical simulations of the Gross-Pitaevskii equation reveal a variety of dynamics associated with the creation of quantized vortices. In two dimensions, a circular bubble deforms into an ellipse and splits into fragments with vortices, which undergo the Magnus effect. The Bénard-von Kármán vortex street is also generated. In three dimensions, a spherical bubble deforms into toruses with vortex rings. When two rings are formed, they exhibit leapfrogging dynamics.

  10. Dynamics of bubbles in a two-component Bose-Einstein condensate

    SciTech Connect

    Sasaki, Kazuki; Suzuki, Naoya; Saito, Hiroki

    2011-03-15

    The dynamics of a phase-separated two-component Bose-Einstein condensate are investigated, in which a bubble of one component moves through the other component. Numerical simulations of the Gross-Pitaevskii equation reveal a variety of dynamics associated with the creation of quantized vortices. In two dimensions, a circular bubble deforms into an ellipse and splits into fragments with vortices, which undergo the Magnus effect. The Benard-von Karman vortex street is also generated. In three dimensions, a spherical bubble deforms into toruses with vortex rings. When two rings are formed, they exhibit leapfrogging dynamics.

  11. Interaction of half-quantized vortices in two-component Bose-Einstein condensates

    SciTech Connect

    Eto, Minoru; Kasamatsu, Kenichi; Nitta, Muneto; Takeuchi, Hiromitsu; Tsubota, Makoto

    2011-06-15

    We study the asymptotic interaction between two half-quantized vortices in two-component Bose-Einstein condensates. When two vortices in different components are placed at distance 2R, the leading order of the force between them is found to be (lnR/{xi}-1/2)/R{sup 3}, in contrast to 1/R between vortices placed in the same component. We derive it analytically using the Abrikosov ansatz and the profile functions of the vortices, confirmed numerically with the Gross-Pitaevskii model. We also find that the short-range cutoff of the intervortex potential linearly depends on the healing length.

  12. Experimental studies of heat and mass exchange phenomena in the two-component heat pipe

    NASA Astrophysics Data System (ADS)

    Baum, J. M.; Ivanovskii, M. N.; Serbin, V. I.; Iurov, S. S.

    The results of the experimental studies of the two-component heat pipe performance are presented in this paper. The water/ethanol mixture was used as the working fluid. The qualitative mechanism of mass exchange in different sections of the heat pipe is suggested as a model. The value of the power transferred by the heat pipe, as well as the correlation of the evaporator, the condenser, and the transport section lengths practically do not influence the extent of separation of the components in the heat pipe.

  13. Effect of scattering lengths on the dynamics of a two-component Bose-Einstein condensate

    SciTech Connect

    Csire, Gabor; Apagyi, Barnabas

    2010-12-15

    We examine the effect of the intra- and interspecies scattering lengths on the dynamics of a two-component Bose-Einstein condensate, particularly focusing on the existence and stability of solitonic excitations. For each type of possible soliton pairs, stability ranges are presented in tabulated form. We also compare the numerically established stability of bright-bright, bright-dark, and dark-dark solitons with our analytical prediction and with that of Painleve analysis of the dynamical equation. We demonstrate that tuning the interspecies scattering length away from the predicted value (keeping the intraspecies coupling fixed) breaks the stability of the soliton pairs.

  14. Optimization and control of two-component radially self-accelerating beams

    SciTech Connect

    Vetter, Christian; Eichelkraut, Toni; Ornigotti, Marco; Szameit, Alexander

    2015-11-23

    We report on the properties of radially self-accelerating intensity distributions consisting of two components in the angular frequency domain. We show how this subset of solutions, in literature also known as helicon beams, possesses peculiar characteristics that enable a better control over its properties. In this work, we present a step-by-step optimization procedure to achieve the best possible intensity contrast, a distinct rotation rate and long propagation lengths. All points are discussed on a theoretical basis and are experimentally verified.

  15. Disorder-Induced Order in Two-Component Bose-Einstein Condensates

    SciTech Connect

    Niederberger, A.; Schulte, T.; Wehr, J.; Lewenstein, M.; Sanchez-Palencia, L.; Sacha, K.

    2008-01-25

    We propose and analyze a general mechanism of disorder-induced order in two-component Bose-Einstein condensates, analogous to corresponding effects established for XY spin models. We show that a random Raman coupling induces a relative phase of {pi}/2 between the two BECs and that the effect is robust. We demonstrate it in one, two, and three dimensions at T=0 and present evidence that it persists at small T>0. Applications to phase control in ultracold spinor condensates are discussed.

  16. Self-duality for the two-component asymmetric simple exclusion process

    SciTech Connect

    Belitsky, V.; Schütz, G. M.

    2015-08-15

    We study a two-component asymmetric simple exclusion process (ASEP) that is equivalent to the ASEP with second-class particles. We prove self-duality with respect to a family of duality functions which are shown to arise from the reversible measures of the process and the symmetry of the generator under the quantum algebra U{sub q}[gl{sub 3}]. We construct all invariant measures in explicit form and discuss some of their properties. We also prove a sum rule for the duality functions.

  17. Two-Dimensional Crystal Structure Formed by Two Components of DNA Nanoparticles on a Substrate

    NASA Astrophysics Data System (ADS)

    Katsuno, Hiroyasu; Maegawa, Yuya; Sato, Masahide

    2016-07-01

    We study the two-dimensional crystal structure of two components of DNA nanoparticles on a substrate by Brownian dynamics simulation. We use the Lennard-Jones potential as the interaction potential between particles and assume that the interaction length between different types of particles, σAB, is smaller than that between the same types of particles, σ. Two types of particles form an alloy structure. With decreasing σAB/σ, the crystal structure changes from a triangular lattice, to a square lattice, a honeycomb lattice, a rectangular lattice, and a triangular lattice.

  18. Exact two-component relativistic theory for NMR parameters: General formulation and pilot application

    NASA Astrophysics Data System (ADS)

    Sun, Qiming; Xiao, Yunlong; Liu, Wenjian

    2012-11-01

    The previously proposed exact two-component (X2C) relativistic theory of nuclear magnetic resonance (NMR) parameters [Q. Sun, W. Liu, Y. Xiao, and L. Cheng, J. Chem. Phys. 131, 081101 (2009), 10.1063/1.3216471] is reformulated to accommodate two schemes for kinetic balance, five schemes for magnetic balance, and three schemes for decoupling in a unified manner, at both matrix and operator levels. In addition, three definitions of spin magnetization are considered in the coupled-perturbed Kohn-Sham equation. Apart from its simplicity, the most salient feature of X2C-NMR lies in that its diamagnetic and paramagnetic terms agree individually with the corresponding four-component counterparts for any finite basis. For practical applications, five approximate schemes for the first order coupling matrix X10 and four approximate schemes for the treatment of two-electron integrals are introduced, which render the computations of X2C-NMR very much the same as those of approximate two-component approaches.

  19. Analytical energy gradient for the two-component normalized elimination of the small component method

    NASA Astrophysics Data System (ADS)

    Zou, Wenli; Filatov, Michael; Cremer, Dieter

    2015-06-01

    The analytical gradient for the two-component Normalized Elimination of the Small Component (2c-NESC) method is presented. The 2c-NESC is a Dirac-exact method that employs the exact two-component one-electron Hamiltonian and thus leads to exact Dirac spin-orbit (SO) splittings for one-electron atoms. For many-electron atoms and molecules, the effect of the two-electron SO interaction is modeled by a screened nucleus potential using effective nuclear charges as proposed by Boettger [Phys. Rev. B 62, 7809 (2000)]. The effect of spin-orbit coupling (SOC) on molecular geometries is analyzed utilizing the properties of the frontier orbitals and calculated SO couplings. It is shown that bond lengths can either be lengthened or shortened under the impact of SOC where in the first case the influence of low lying excited states with occupied antibonding orbitals plays a role and in the second case the jj-coupling between occupied antibonding and unoccupied bonding orbitals dominates. In general, the effect of SOC on bond lengths is relatively small (≤5% of the scalar relativistic changes in the bond length). However, large effects are found for van der Waals complexes Hg2 and Cn2, which are due to the admixture of more bonding character to the highest occupied spinors.

  20. Analytical energy gradient for the two-component normalized elimination of the small component method

    SciTech Connect

    Zou, Wenli; Filatov, Michael; Cremer, Dieter

    2015-06-07

    The analytical gradient for the two-component Normalized Elimination of the Small Component (2c-NESC) method is presented. The 2c-NESC is a Dirac-exact method that employs the exact two-component one-electron Hamiltonian and thus leads to exact Dirac spin-orbit (SO) splittings for one-electron atoms. For many-electron atoms and molecules, the effect of the two-electron SO interaction is modeled by a screened nucleus potential using effective nuclear charges as proposed by Boettger [Phys. Rev. B 62, 7809 (2000)]. The effect of spin-orbit coupling (SOC) on molecular geometries is analyzed utilizing the properties of the frontier orbitals and calculated SO couplings. It is shown that bond lengths can either be lengthened or shortened under the impact of SOC where in the first case the influence of low lying excited states with occupied antibonding orbitals plays a role and in the second case the jj-coupling between occupied antibonding and unoccupied bonding orbitals dominates. In general, the effect of SOC on bond lengths is relatively small (≤5% of the scalar relativistic changes in the bond length). However, large effects are found for van der Waals complexes Hg{sub 2} and Cn{sub 2}, which are due to the admixture of more bonding character to the highest occupied spinors.

  1. Analytical energy gradient for the two-component normalized elimination of the small component method.

    PubMed

    Zou, Wenli; Filatov, Michael; Cremer, Dieter

    2015-06-01

    The analytical gradient for the two-component Normalized Elimination of the Small Component (2c-NESC) method is presented. The 2c-NESC is a Dirac-exact method that employs the exact two-component one-electron Hamiltonian and thus leads to exact Dirac spin-orbit (SO) splittings for one-electron atoms. For many-electron atoms and molecules, the effect of the two-electron SO interaction is modeled by a screened nucleus potential using effective nuclear charges as proposed by Boettger [Phys. Rev. B 62, 7809 (2000)]. The effect of spin-orbit coupling (SOC) on molecular geometries is analyzed utilizing the properties of the frontier orbitals and calculated SO couplings. It is shown that bond lengths can either be lengthened or shortened under the impact of SOC where in the first case the influence of low lying excited states with occupied antibonding orbitals plays a role and in the second case the jj-coupling between occupied antibonding and unoccupied bonding orbitals dominates. In general, the effect of SOC on bond lengths is relatively small (≤5% of the scalar relativistic changes in the bond length). However, large effects are found for van der Waals complexes Hg2 and Cn2, which are due to the admixture of more bonding character to the highest occupied spinors. PMID:26049478

  2. Investigation of K-shell radiation from two-component wire arrays

    NASA Astrophysics Data System (ADS)

    Papp, Daniel; Ivanov, Vladimir; Mancini, Roberto; Hakel, Peter; Altemara, Sara; Anderson, Austin

    2012-10-01

    Two-component plasma was studied in star and planar wire-array Z pinches. Arrays consisted of Al wires as the first component in all shots and Ti, Cu, Ni, Mo, and Au wires as the second component. Cascading implosion in star arrays provides the mixing of wire materials in one ray during implosion. The implosion dynamic was not affected by variation of materials in wire arrays that allows observation of features of the two-component plasma. Compared to pure Al plasmas, decreased Al K-shell radiation and increased soft x-ray radiation were observed in Al-Au and Al-W plasma. Mixt plasma with 80-90% of Al ions displayed radiative properties similar to pure W or Au Z-pinch plasma. Al K-shell x-ray spectra simulations with the PrismSpect code showed a fall of the electron temperature from 400 eV in Al plasma to 250-300 eV in the Al-W and Al-Au mix. There was no corresponding cooling effect when the second component was Ti, Cu, and Ni. Spectra of the Z-pinch plasmas were compared with the spectra from laser produced Al-Au plasma experiments carried out at the Leopard laser. Work was supported by the DOE/NNSA under UNR grant DE-FC52-06NA27616.

  3. A theory of scintillation for two-component power law irregularity spectra: Overview and numerical results

    NASA Astrophysics Data System (ADS)

    Carrano, Charles S.; Rino, Charles L.

    2016-06-01

    We extend the power law phase screen theory for ionospheric scintillation to account for the case where the refractive index irregularities follow a two-component inverse power law spectrum. The two-component model includes, as special cases, an unmodified power law and a modified power law with spectral break that may assume the role of an outer scale, intermediate break scale, or inner scale. As such, it provides a framework for investigating the effects of a spectral break on the scintillation statistics. Using this spectral model, we solve the fourth moment equation governing intensity variations following propagation through two-dimensional field-aligned irregularities in the ionosphere. A specific normalization is invoked that exploits self-similar properties of the structure to achieve a universal scaling, such that different combinations of perturbation strength, propagation distance, and frequency produce the same results. The numerical algorithm is validated using new theoretical predictions for the behavior of the scintillation index and intensity correlation length under strong scatter conditions. A series of numerical experiments are conducted to investigate the morphologies of the intensity spectrum, scintillation index, and intensity correlation length as functions of the spectral indices and strength of scatter; retrieve phase screen parameters from intensity scintillation observations; explore the relative contributions to the scintillation due to large- and small-scale ionospheric structures; and quantify the conditions under which a general spectral break will influence the scintillation statistics.

  4. Approximate singly excited states from a two-component Hartree-Fock reference

    SciTech Connect

    Goings, Joshua J.; Ding, Feizhi; Davidson, Ernest R.; Li, Xiaosong

    2015-10-14

    For many molecules, relaxing the spin symmetry constraint on the wave function results in the lowest energy mean-field solution. The two-component Hartree-Fock (2cHF) method relaxes all spin symmetry constraints, and the wave function is no longer an eigenfunction of the total spin, spin projection, or time-reversal symmetry operators. For ground state energies, 2cHF is a superior mean-field method for describing spin-frustrated molecules. For excited states, the utility of 2cHF is uncertain. Here, we implement the 2cHF extensions of two single-reference excited state methods, the two-component configuration interaction singles and time-dependent Hartree-Fock. We compare the results to the analogous methods based off of the unrestricted Hartree-Fock approximation, as well as the full configuration interaction for three small molecules with distinct 2cHF solutions, and discuss the nature of the 2cHF excited state solutions.

  5. Two-component vector solitons in defocusing Kerr-type media with spatially modulated nonlinearity

    SciTech Connect

    Zhong, Wei-Ping; Belić, Milivoj

    2014-12-15

    We present a class of exact solutions to the coupled (2+1)-dimensional nonlinear Schrödinger equation with spatially modulated nonlinearity and a special external potential, which describe the evolution of two-component vector solitons in defocusing Kerr-type media. We find a robust soliton solution, constructed with the help of Whittaker functions. For specific choices of the topological charge, the radial mode number and the modulation depth, the solitons may exist in various forms, such as the half-moon, necklace-ring, and sawtooth vortex-ring patterns. Our results show that the profile of such solitons can be effectively controlled by the topological charge, the radial mode number, and the modulation depth. - Highlights: • Two-component vector soliton clusters in defocusing Kerr-type media are reported. • These soliton clusters are constructed with the help of Whittaker functions. • The half-moon, necklace-ring and vortex-ring patterns are found. • The profile of these solitons can be effectively controlled by three soliton parameters.

  6. An efficient implementation of two-component relativistic exact-decoupling methods for large molecules.

    PubMed

    Peng, Daoling; Middendorf, Nils; Weigend, Florian; Reiher, Markus

    2013-05-14

    We present an efficient algorithm for one- and two-component relativistic exact-decoupling calculations. Spin-orbit coupling is thus taken into account for the evaluation of relativistically transformed (one-electron) Hamiltonian. As the relativistic decoupling transformation has to be evaluated with primitive functions, the construction of the relativistic one-electron Hamiltonian becomes the bottleneck of the whole calculation for large molecules. For the established exact-decoupling protocols, a minimal matrix operation count is established and discussed in detail. Furthermore, we apply our recently developed local DLU scheme [D. Peng and M. Reiher, J. Chem. Phys. 136, 244108 (2012)] to accelerate this step. With our new implementation two-component relativistic density functional calculations can be performed invoking the resolution-of-identity density-fitting approximation and (Abelian as well as non-Abelian) point group symmetry to accelerate both the exact-decoupling and the two-electron part. The capability of our implementation is illustrated at the example of silver clusters with up to 309 atoms, for which the cohesive energy is calculated and extrapolated to the bulk. PMID:23676027

  7. Critical point of gas-liquid type phase transition and phase equilibrium functions in developed two-component plasma model.

    PubMed

    Butlitsky, M A; Zelener, B B; Zelener, B V

    2014-07-14

    A two-component plasma model, which we called a "shelf Coulomb" model has been developed in this work. A Monte Carlo study has been undertaken to calculate equations of state, pair distribution functions, internal energies, and other thermodynamics properties. A canonical NVT ensemble with periodic boundary conditions was used. The motivation behind the model is also discussed in this work. The "shelf Coulomb" model can be compared to classical two-component (electron-proton) model where charges with zero size interact via a classical Coulomb law. With important difference for interaction of opposite charges: electrons and protons interact via the Coulomb law for large distances between particles, while interaction potential is cut off on small distances. The cut off distance is defined by an arbitrary ɛ parameter, which depends on system temperature. All the thermodynamics properties of the model depend on dimensionless parameters ɛ and γ = βe(2)n(1/3) (where β = 1/kBT, n is the particle's density, kB is the Boltzmann constant, and T is the temperature) only. In addition, it has been shown that the virial theorem works in this model. All the calculations were carried over a wide range of dimensionless ɛ and γ parameters in order to find the phase transition region, critical point, spinodal, and binodal lines of a model system. The system is observed to undergo a first order gas-liquid type phase transition with the critical point being in the vicinity of ɛ(crit) ≈ 13(T(*)(crit) ≈ 0.076), γ(crit) ≈ 1.8(v(*)(crit) ≈ 0.17), P(*)(crit) ≈ 0.39, where specific volume v* = 1/γ(3) and reduced temperature T(*) = ɛ(-1). PMID:25028031

  8. Critical point of gas-liquid type phase transition and phase equilibrium functions in developed two-component plasma model

    SciTech Connect

    Butlitsky, M. A.; Zelener, B. V.

    2014-07-14

    A two-component plasma model, which we called a “shelf Coulomb” model has been developed in this work. A Monte Carlo study has been undertaken to calculate equations of state, pair distribution functions, internal energies, and other thermodynamics properties. A canonical NVT ensemble with periodic boundary conditions was used. The motivation behind the model is also discussed in this work. The “shelf Coulomb” model can be compared to classical two-component (electron-proton) model where charges with zero size interact via a classical Coulomb law. With important difference for interaction of opposite charges: electrons and protons interact via the Coulomb law for large distances between particles, while interaction potential is cut off on small distances. The cut off distance is defined by an arbitrary ε parameter, which depends on system temperature. All the thermodynamics properties of the model depend on dimensionless parameters ε and γ = βe{sup 2}n{sup 1/3} (where β = 1/k{sub B}T, n is the particle's density, k{sub B} is the Boltzmann constant, and T is the temperature) only. In addition, it has been shown that the virial theorem works in this model. All the calculations were carried over a wide range of dimensionless ε and γ parameters in order to find the phase transition region, critical point, spinodal, and binodal lines of a model system. The system is observed to undergo a first order gas-liquid type phase transition with the critical point being in the vicinity of ε{sub crit}≈13(T{sub crit}{sup *}≈0.076),γ{sub crit}≈1.8(v{sub crit}{sup *}≈0.17),P{sub crit}{sup *}≈0.39, where specific volume v* = 1/γ{sup 3} and reduced temperature T{sup *} = ε{sup −1}.

  9. Riboswitches. Sequestration of a two-component response regulator by a riboswitch-regulated noncoding RNA.

    PubMed

    Mellin, J R; Koutero, Mikael; Dar, Daniel; Nahori, Marie-Anne; Sorek, Rotem; Cossart, Pascale

    2014-08-22

    Riboswitches are ligand-binding elements contained within the 5' untranslated regions of bacterial transcripts, which generally regulate expression of downstream open reading frames. Here, we show that in Listeria monocytogenes, a riboswitch that binds vitamin B12 controls expression of a noncoding regulatory RNA, Rli55. Rli55, in turn, controls expression of the eut genes, whose products enable ethanolamine utilization and require B12 as a cofactor. Defects in ethanolamine utilization, or in its regulation by Rli55, significantly attenuate Listeria virulence in mice. Rli55 functions by sequestering the two-component response regulator EutV by means of a EutV-binding site contained within the RNA. Thus, Rli55 is a riboswitch-regulated member of the small group of regulatory RNAs that function by sequestering a protein and reveals a distinctive mechanism of signal integration in bacterial gene regulation. PMID:25146292

  10. Ground-state densities of repulsive two-component Fermi gases

    NASA Astrophysics Data System (ADS)

    Trappe, Martin-Isbjörn; Grochowski, Piotr; Brewczyk, Mirosław; Rzążewski, Kazimierz

    2016-02-01

    We investigate separations of trapped balanced two-component atomic Fermi gases with repulsive contact interaction. Candidates for ground-state densities are obtained from the imaginary-time evolution of a nonlinear pseudo-Schrödinger equation in three dimensions, rather than from the cumbersome variational equations of the underlying energy density functional. With the employed hydrodynamical approach, gradient corrections to the Thomas-Fermi approximation are conveniently included and are shown to be vital for reliable density profiles. We provide critical repulsion strengths that mark the onset of phase transitions in a harmonic trap. We present transitions from identical density profiles of the two fermion species towards isotropic and anisotropic separations for various confinements, including harmonic and double-well-type traps. Our proposed method is suited for arbitrary trap geometries and can be straightforwardly extended to study dynamics in the light of ongoing experiments on degenerate Fermi gases.

  11. [Acute cholangitis in interstenosis space accompanied by two-component unit of the main bile duct].

    PubMed

    Yurchenko, V V

    2016-02-01

    Palliative treatment of obstructive jaundice with the help of biliary endoprosthesis due to the possible complication of post-intervention in the form of insolvency stent deformation or dislocation. The study features in the postoperative period of the main bile duct endoprosthesis about their two-component unit, described the syndrome of the closed space of the bile ducts. On the basis of observation of 14 patients with the given anatomical feature of endoscopic, who were underwent stenting, was assessed frequency of the syndrome and possibilities of its prevention. Interstenosis space expansion of the main bile duct can be a reason for local cholangitis. For the prevention of cholangitis, it should be carried out a separate drainage of interstenosis space with the help of endoprosthesis or by proximal supra-stenotic extension of two or more stents. PMID:27263209

  12. Segmented contracted basis sets for one- and two-component Dirac-Fock effective core potentials.

    PubMed

    Weigend, Florian; Baldes, Alexander

    2010-11-01

    Segmented contracted basis sets for 4d, 5d, 5s, and 6s elements of split (double zeta) valence to quadruple zeta valence quality optimized for Dirac-Fock effective core potentials (ECPs) are presented. They were obtained from previous bases optimized for Wood-Boring ECPs by comparably small modifications and reoptimizations. Additionally extensions for two-component self-consistent-field treatments accounting for spin-orbit (SO) coupling were designed and optimized. Reliability for chemical applications was assessed by comparing results to those obtained with a very large (19s16p17d7f6g) reference basis for a set of more than 80 representatively chosen 5s-5d compounds. Moreover, the effect of different types of ECPs and that of the SO-coupling at the basis set limit of density functional theory is documented for the above set of molecules extended by 40 5p-6p compounds. PMID:21054001

  13. Two-component mixture model: Application to palm oil and exchange rate

    NASA Astrophysics Data System (ADS)

    Phoong, Seuk-Yen; Ismail, Mohd Tahir; Hamzah, Firdaus Mohamad

    2014-12-01

    Palm oil is a seed crop which is widely adopt for food and non-food products such as cookie, vegetable oil, cosmetics, household products and others. Palm oil is majority growth in Malaysia and Indonesia. However, the demand for palm oil is getting growth and rapidly running out over the years. This phenomenal cause illegal logging of trees and destroy the natural habitat. Hence, the present paper investigates the relationship between exchange rate and palm oil price in Malaysia by using Maximum Likelihood Estimation via Newton-Raphson algorithm to fit a two components mixture model. Besides, this paper proposes a mixture of normal distribution to accommodate with asymmetry characteristics and platykurtic time series data.

  14. A two-component model for fitting light curves of core-collapse supernovae

    NASA Astrophysics Data System (ADS)

    Nagy, A. P.; Vinkó, J.

    2016-05-01

    We present an improved version of a light curve model that is able to estimate the physical properties of different types of core-collapse supernovae that have double-peaked light curves and do so in a quick and efficient way. The model is based on a two-component configuration consisting of a dense inner region and an extended low-mass envelope. Using this configuration, we estimate the initial parameters of the progenitor by fitting the shape of the quasi-bolometric light curves of 10 SNe, including Type IIP and IIb events, with model light curves. In each case we compare the fitting results with available hydrodynamic calculations and also match the derived expansion velocities with the observed ones. Furthermore, we compare our calculations with hydrodynamic models derived by the SNEC code and examine the uncertainties of the estimated physical parameters caused by the assumption of constant opacity and the inaccurate knowledge of the moment of explosion.

  15. “A two-component pre-seeded dermal-epidermal scaffold”

    PubMed Central

    Monteiro, I.P.; Gabriel, D.; Timko, B.P.; Hashimoto, M.; Karajanagi, S.; Tong, R.; Marques, A.P.; Reis, R.L.; Kohane, D.S.

    2014-01-01

    We have developed a bilayered dermal-epidermal scaffold for application in the treatment of full thickness skin defects. The dermal component gels in situ and adapts to the lesion shape, delivering human dermal fibroblasts in a matrix of fibrin and cross-linked hyaluronic acid modified with a cell adhesion-promoting peptide. Fibroblasts were able to form a tridimensional matrix due to material features such as tailored mechanical properties, presence of protease degradable elements and cell binding ligands. The epidermal component is a robust membrane containing cross-linked hyaluronic acid and poly-L-lysine, on which keratinocytes were able to attach and to form a monolayer. Amine-aldehyde bonding at the interface between the two components allows the formation of a tightly bound composite scaffold. Both parts of the scaffold were designed to provide cell type specific cues to allow for cell proliferation and form a construct that mimics the skin environment. PMID:25192821

  16. Two-component density functional theory calculations of positron lifetimes for small vacancy clusters in silicon

    NASA Astrophysics Data System (ADS)

    Makhov, D. V.; Lewis, Laurent J.

    2005-05-01

    The positron lifetimes for various vacancy clusters in silicon are calculated within the framework of the two-component electron-positron density functional theory. The effect of the trapped positron on the electron density and on the relaxation of the structure is investigated. Our calculations show that, contrary to the usual assumption, the positron-induced forces do not compensate in general for electronic inward forces. Thus, geometry optimization is required in order to determine positron lifetime accurately. For the monovacancy and the divacancy, the results of our calculations are in good agreement with the experimental positron lifetimes, suggesting that this approach gives good estimates of positron lifetimes for larger vacancy clusters, required for their correct identification with positron annihilation spectroscopy. As an application, our calculations show that fourfold trivacancies and symmetric fourfold tetravacancies have positron lifetimes similar to monovacancies and divacancies, respectively, and can thus be confused in the interpretation of positron annihilation experiments.

  17. Correlation inequalities for two-component hypercubic /var phi//sub 4/ models

    SciTech Connect

    Soria, J.L.

    1988-08-01

    A collection of new and already known correlation inequalities is found for a family of two-component hypercubic /var phi//sub 4/ models, using techniques of duplicated variables, rotated correlation inequalities, and random walk representation. Among the interesting new inequalities are: rotated very special Dunlop-Newman inequality greater than or equal to 0, and anti-Lebowitz inequality u/sub 4//sup 1111/ greater than or equal to 0.

  18. Nonlinear stopping power for ions moving in magnetized two-component plasmas

    SciTech Connect

    Hu Zhanghu; Song Yuanhong; Wang Younian; Wang Guiqiu

    2009-11-15

    Energy losses of test particles in magnetized two-component plasmas are investigated by means of particle-in-cell (PIC) simulations, taking into account the dynamic polarization effects of both the plasma ions and electrons. The influences of the magnetic field, the angle between the test particle velocity and magnetic field, and certain plasma parameters on the nonlinear stopping power are studied. Comparisons are made between the PIC simulations and the linearized dielectric theory to show the nonlinear effects on the stopping power. Simulation results show that the dynamic polarization effects of the plasma ions become significant and contribute mainly to the nonlinear stopping power for low particle velocities and strong magnetic field. The nonlinear effects are found to enhance the stopping power in low particle velocity regions.

  19. RADIATION MAGNETOHYDRODYNAMICS SIMULATION OF PROTO-STELLAR COLLAPSE: TWO-COMPONENT MOLECULAR OUTFLOW

    SciTech Connect

    Tomida, Kengo; Tomisaka, Kohji; Ohsuga, Ken; Matsumoto, Tomoaki; Machida, Masahiro N.; Saigo, Kazuya E-mail: tomisaka@th.nao.ac.jp E-mail: masahiro.machida@nao.ac.jp E-mail: matsu@hosei.ac.jp

    2010-05-01

    We perform a three-dimensional nested-grid radiation magnetohydrodynamics (RMHD) simulation with self-gravity to study the early phase of the low-mass star formation process from a rotating molecular cloud core to a first adiabatic core just before the second collapse begins. Radiation transfer is implemented with the flux-limited diffusion approximation, operator-splitting, and implicit time integrator. In the RMHD simulation, the outer region of the first core attains a higher entropy and its size is larger than that in the magnetohydrodynamics simulations with the barotropic approximation. Bipolar molecular outflow consisting of two components is driven by magnetic Lorentz force via different mechanisms, and shock heating by the outflow is observed. Using the RMHD simulation we can predict and interpret the observed properties of star-forming clouds, first cores, and outflows with millimeter/submillimeter radio interferometers, especially the Atacama Large Millimeter/submillimeter Array.

  20. Heat and mass transfer in two-component film evaporation in a vertical tube

    NASA Astrophysics Data System (ADS)

    Baumann, W. W.; Thiele, F.

    An elaborate physical model is developed for the problem of two-component film evaporation. Special attention is drawn to the accurate modeling of the two-phase multicomponent flow. This includes separate description of each phase, turbulent gas flow, and thermophysical properties depending on temperature and species concentrations. Whereas the basic equations for the film flow can be treated analytically those for the gas flow have to be solved numerically by means of an accurate finite difference method. An efficient overall iteration procedure links the solutions in both phases. The evaporation of benzene-methyl alcohol mixtures in vertical tube flows for various thermal flow conditions is investigated. Results are presented in terms of local temperature, heat and mass fluxes, and Stanton numbers for heat and mass transfer. They indicate a strong influence of the mixture composition.

  1. Structure of ion acoustic solitons and shock waves in a two-component plasma.

    NASA Technical Reports Server (NTRS)

    White, R. B.; Fried, B. D.; Coroniti, F. V.

    1972-01-01

    Time-independent solitary waves and shocks are investigated in a two-component plasma using a fluid model and kinetic theory. It is found that very small concentrations of a light ion can drastically alter the structure, changing the potential maximum by an order of magnitude. For a fixed Mach number, a critical density ratio of light to heavy ions is found at which the potential maximum changes discontinuously from a value large enough to reflect the light ions to one which allows them to traverse the shock front and enter the downstream flow. The downstream oscillatory structure normally seen in a shock is completely quenched by dissipation due to light ion reflection at concentrations of 3-8% He in an Ar plasma for typical electron to ion temperature ratios and Mach number values.

  2. Basis-set extensions for two-component spin-orbit treatments of heavy elements.

    PubMed

    Armbruster, Markus K; Klopper, Wim; Weigend, Florian

    2006-11-14

    The accuracy of standard basis sets of quadruple-zeta and lower quality for the use in two-component self-consistent field procedures including spin-orbit coupling is investigated for the elements In-I and Au-At. Spin-orbit coupling leads to energetic and spatial splittings of inner shells, which are not described accurately with standard basis sets optimized for scalar relativistic calculations. This results in large errors in total atomic energies and significant errors in atomization energies of compounds containing these atoms. We show how these errors can be corrected by adding just a few steep sets of basis functions and demonstrate the quality of the resulting extended basis sets. PMID:17066175

  3. Carbon phenolic roll torque measurements using a two component skin friction balance

    NASA Astrophysics Data System (ADS)

    Martellucci, A.; Somers, J.; Driftmyer, R.

    The objective of the current effort was to evaluate the reentry roll torque performance potential of the heatshield of a ballistic vehicle which has undergone exospheric nuclear damage. This damage causes the vehicle's heatshield to be rough on one side (i.e., with a velvet-like finish caused by phenolic removal and raised carbon fibers) and smooth on the other side. Roll torque performance of the heatshield specimens was established through a series of ground tests in ablation test and supersonic wind tunnel facilities. The roll torque performance was measured with a two component skin friction balance developed as part of this program. The balance was required to simultaneously resolve a side (torque) force of a fraction of a gram and which is more than an order of magnitude smaller than the axial force. This paper will describe details of the balance design and highlights of the results of these tests.

  4. Two-component LDV investigation of 3-dimensional shock/turbulent boundary layer interactions

    NASA Technical Reports Server (NTRS)

    Brown, J. D.; Brown, J. L.; Kussoy, M. I.; Horstman, C. C.; Holt, M.

    1987-01-01

    Mean-velocity and turbulence measurements obtained by two-component laser Doppler velocimetry are presented, together with numerical predictions, for the shock-related separation of a turbulent boundary layer at Mach 2.85. The basic geometry, a 30 deg half-angle flare mounted on a long cylinder, is made three-dimensional by tipping the flare at an angle of attack, alpha. The separation length and general upstream influence increase with alpha. A recirculating vortex in the separated zone becomes stronger as three-dimensionality increases. A large-scale unsteadiness of the separation shock wave and surrounding flowfields grows in amplitude with alpha, and appears to strongly influence the amplification of turbulence correlations ahead of detachment. Scaling of the streamwise coordinate by separation length causes two-dimensional and three-dimensional data profiles on the cylinder to collapse for most measured quantities.

  5. Cloning, purification and characterization of two components of phenol hydroxylase from Rhodococcus erythropolis UPV-1.

    PubMed

    Saa, Laura; Jaureguibeitia, Arrate; Largo, Eneko; Llama, María J; Serra, Juan L

    2010-03-01

    Phenol hydroxylase that catalyzes the conversion of phenol to catechol in Rhodococcus erythropolis UPV-1 was identified as a two-component flavin-dependent monooxygenase. The two proteins are encoded by the genes pheA1 and pheA2, located very closely in the genome. The sequenced pheA1 gene was composed of 1,629 bp encoding a protein of 542 amino acids, whereas the pheA2 gene consisted of 570 bp encoding a protein of 189 amino acids. The deduced amino acid sequences of both genes showed high homology with several two-component aromatic hydroxylases. The genes were cloned separately in cells of Escherichia coli M15 as hexahistidine-tagged proteins, and the recombinant proteins His(6)PheA1 and His(6)PheA2 were purified and its catalytic activity characterized. His(6)PheA1 exists as a homotetramer of four identical subunits of 62 kDa that has no phenol hydroxylase activity on its own. His(6)PheA2 is a homodimeric flavin reductase, consisting of two identical subunits of 22 kDa, that uses NAD(P)H in order to reduce flavin adenine dinucleotide (FAD), according to a random sequential kinetic mechanism. The reductase activity was strongly inhibited by thiol-blocking reagents. The hydroxylation of phenol in vitro requires the presence of both His(6)PheA1 and His(6)PheA2 components, in addition to NADH and FAD, but the physical interaction between the proteins is not necessary for the reaction. PMID:19787347

  6. Acetogenesis from dichloromethane by a two-component mixed culture comprising a novel bacterium.

    PubMed

    Magli, A; Rainey, F A; Leisinger, T

    1995-08-01

    A strictly anaerobic two-component culture able to grow exponentially with a doubling time of 20 h on a medium containing dichloromethane as the carbon and energy source was characterized. On a medium without sulfate, we observed (per mol of dichloromethane) a mass balance of 2 mol of chloride, 0.26 mol of acetate, 0.05 mol of formate, and 0.25 mol of carbon in biomass. One component of the culture, strain DMB, was identified by a 16S ribosomal DNA analysis as a Desulfovibrio sp. The other component, the gram-positive organism strain DMC, could not be isolated. It was possible, however, to associate strain DMC on a medium containing dichloromethane in a coculture with Acetobacterium woodii or Methanospirillum hungatei. Coculture of strain DMC with the Archaeon M. hungatei allowed us to specifically amplify by PCR the 16S rRNA gene of strain DMC. A phylogenetic analysis of the 16S ribosomal DNA sequence revealed that this organism groups within the radiation of the Clostridium-Bacillus subphylum and exhibits the highest levels of sequence similarity (89%) with Desulfotomaculum orientis and Desulfitobacterium dehalogenans. Since the novel organism strain DMC was able to grow acetogenically with dichloromethane when it was associated with one of three metabolically different partners and since, in contrast to strain DMB, strain DMC contained carbon monoxide dehydrogenase activity, this bacterium is responsible for both the dehalogenation of dichloromethane and the acetogenesis observed in the original two-component culture. The obligatory dependence of strain DMC on a partner during growth with dichloromethane is thought to stem from the need for a growth factor produced by the associated organism. PMID:16535097

  7. Communication: Two-component ring-coupled-cluster computation of the correlation energy in the random-phase approximation

    SciTech Connect

    Krause, Katharina; Klopper, Wim

    2013-11-21

    Within the framework of density-functional theory, the correlation energy is computed in the random-phase approximation (RPA) using spinors obtained from a two-component relativistic Kohn–Sham calculation accounting for spin–orbit interactions. Ring-coupled-cluster equations are solved to obtain the two-component RPA correlation energy. Results are presented for the hydrides of the halogens Br, I, and At as well as of the coinage metals Cu, Ag, and Au, based on two-component relativistic exact-decoupling Kohn–Sham calculations.

  8. Communication: Two-component ring-coupled-cluster computation of the correlation energy in the random-phase approximation

    NASA Astrophysics Data System (ADS)

    Krause, Katharina; Klopper, Wim

    2013-11-01

    Within the framework of density-functional theory, the correlation energy is computed in the random-phase approximation (RPA) using spinors obtained from a two-component relativistic Kohn-Sham calculation accounting for spin-orbit interactions. Ring-coupled-cluster equations are solved to obtain the two-component RPA correlation energy. Results are presented for the hydrides of the halogens Br, I, and At as well as of the coinage metals Cu, Ag, and Au, based on two-component relativistic exact-decoupling Kohn-Sham calculations.

  9. Escherichia coli Isolate for Studying Colonization of the Mouse Intestine and Its Application to Two-Component Signaling Knockouts

    PubMed Central

    Lasaro, Melissa; Liu, Zhi; Bishar, Rima; Kelly, Kathryn; Chattopadhyay, Sujay; Paul, Sandip; Sokurenko, Evgeni

    2014-01-01

    The biology of Escherichia coli in its primary niche, the animal intestinal tract, is remarkably unexplored. Studies with the streptomycin-treated mouse model have produced important insights into the metabolic requirements for Escherichia coli to colonize mice. However, we still know relatively little about the physiology of this bacterium growing in the complex environment of an intestine that is permissive for the growth of competing flora. We have developed a system for studying colonization using an E. coli strain, MP1, isolated from a mouse. MP1 is genetically tractable and does not require continuous antibiotic treatment for stable colonization. As an application of this system, we separately knocked out each two-component system response regulator in MP1 and performed competitions against the wild-type strain. We found that only three response regulators, ArcA, CpxR, and RcsB, produce strong colonization defects, suggesting that in addition to anaerobiosis, adaptation to cell envelope stress is a critical requirement for E. coli colonization of the mouse intestine. We also show that the response regulator OmpR, which had previously been hypothesized to be important for adaptation between in vivo and ex vivo environments, is not required for MP1 colonization due to the presence of a third major porin. PMID:24563035

  10. Miscibility behavior of two-component monolayers at the air-water interface: perfluorocarboxylic acids and DMPE.

    PubMed

    Yokoyama, Hiroki; Nakahara, Hiromichi; Nakagawa, Takahiro; Shimono, Satoshi; Sueishi, Kunihiko; Shibata, Osamu

    2009-09-01

    Surface pressure (pi)-molecular area (A) and surface potential (DeltaV)-A isotherms have been measured for two-component monolayers of four different perfluorocarboxylic acids [FCn; perfluorododecanoic acid (FC12), perfluorotetradecanoic acid (FC14), perfluorohexadecanoic acid (FC16), and perfluorooctadecanoic acid (FC18)] and dimyristoylphosphatidylethanolamine (DMPE) on 0.15M NaCl (pH 2) at 298.2K. The present study is focused on the miscibility and the interfacial behavior for the binary DMPE/FCn monolayers upon compression. From the isotherms, the miscibility has been elucidated in terms of the additivity rule, the interaction parameter, and the interaction energy. The interaction parameter (or energy) is compared with that for the previous dipalmitoylphosphatidylcholine (DPPC)/FCn systems [Colloids Surf. B 41 (2005) 285-298] to understand the effect of phospholipids' polar headgroup on the binary miscibility. Furthermore, the phase behavior of the DMPE/FCn systems has been morphologically examined using fluorescence microscopy (FM) and atomic force microscopy (AFM). These images reveal the different interaction modes among the four systems; DMPE can be miscible with FC12 and FC14 and immiscible with FC16 and FC18 in the monolayer state. These systematic examinations indicate that the miscibility of perfluorocarboxylic acids and phospholipids depends on combination of hydrocarbon and fluorocarbon chain lengths and on phospholipids' polar headgroups within a monolayer. PMID:19481762

  11. Interactions in two-component liposomes studied by 2D correlation spectroscopy

    NASA Astrophysics Data System (ADS)

    Murawska, Agnieszka; Cieślik-Boczula, Katarzyna; Czarnik-Matusewicz, Bogusława

    2010-06-01

    The effect of dipping amphiphilic ICPANs (1-Alkylaminium, N-[2-[3-[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]-1-oxopropoxy]ethyl]-N,N-dimethyl-, bromide) homologues, characterized by varying alkyl chain length ( n = 8, 10, 12, and 16), into large multilamellar vesicles (MLVs) of dipalmitoylphosphatidylcholine (DPPC) was studied. Attenuated total reflectance infrared (ATR-IR) spectroscopy combined with 31P-NMR enabled observing a cut-off effect for the longest homologue. By employing two-dimensional correlation spectroscopy (2DCOS) for monitoring spectral changes induced by the heating process, detailed information about structural changes was obtained. They confirmed the substantial reorganization in the structure of the interfacial region in the ICPAN-C16/DPPC vesicles compared with the shorter homologues, where mainly the alkyl chains experience significant trans-to-gauche reorganization. Absorbance changes around 1400 cm -1 assigned to the symmetric deformation mode δsym ( +N(CH 3) 3) are a good marker of changes in vesicle shape and are sensitive to the percentage of DPPC molecules directly interacting with the surface of the ATR crystal. This study clearly demonstrates the potential of 2DCOS in investigating interactions in two-component liposomes.

  12. Competing interactions in population-imbalanced two-component Bose-Einstein condensates

    NASA Astrophysics Data System (ADS)

    Galteland, Peder Notto; Sudbø, Asle

    2016-08-01

    We consider a two-component Bose-Einstein condensate with and without synthetic "spin-orbit" interactions in two dimensions. Density and phase fluctuations of the condensate are included, allowing us to study the impact of thermal fluctuations and density-density interactions on the physics originating with spin-orbit interactions. In the absence of spin-orbit interactions, we find that intercomponent density interactions deplete the minority condensate. The thermally driven phase transition is driven by coupled density and phase-fluctuations, but is nevertheless shown to be a phase-transition in the Kosterlitz-Thouless universality class with close to universal amplitude ratios irrespective of whether both the minority- and majority condensates exist in the ground state, or only one condensate exists. In the presence of spin-orbit interactions we observe three separate phases, depending on the strength of the spin-orbit coupling and intercomponent density-density interactions: a phase-modulated phase with uniform amplitudes for small intercomponent interactions, a completely imbalanced, effectively single-component condensate for intermediate spin-orbit coupling strength and sufficiently large intercomponent interactions, and a phase-modulated and amplitude-modulated phase for sufficiently large values of both the spin-orbit coupling and the intercomponent density-density interactions. The phase that is modulated by a single q -vector only is observed to transition into an isotropic liquid through a strong depinning transition with periodic boundary conditions, which weakens with open boundaries.

  13. Freshwater DOM quantity and quality from a two-component model of UV absorbance

    USGS Publications Warehouse

    Carter, Heather T.; Tipping, Edward; Koprivnjak, Jean-Francois; Miller, Matthew P.; Cookson, Brenda; Hamilton-Taylor, John

    2012-01-01

    We present a model that considers UV-absorbing dissolved organic matter (DOM) to consist of two components (A and B), each with a distinct and constant spectrum. Component A absorbs UV light strongly, and is therefore presumed to possess aromatic chromophores and hydrophobic character, whereas B absorbs weakly and can be assumed hydrophilic. We parameterised the model with dissolved organic carbon concentrations [DOC] and corresponding UV spectra for c. 1700 filtered surface water samples from North America and the United Kingdom, by optimising extinction coefficients for A and B, together with a small constant concentration of non-absorbing DOM (0.80 mg DOC L-1). Good unbiased predictions of [DOC] from absorbance data at 270 and 350 nm were obtained (r2 = 0.98), the sum of squared residuals in [DOC] being reduced by 66% compared to a regression model fitted to absorbance at 270 nm alone. The parameterised model can use measured optical absorbance values at any pair of suitable wavelengths to calculate both [DOC] and the relative amounts of A and B in a water sample, i.e. measures of quantity and quality. Blind prediction of [DOC] was satisfactory for 9 of 11 independent data sets (181 of 213 individual samples).

  14. Modified Baryonic Dynamics: two-component cosmological simulations with light sterile neutrinos

    SciTech Connect

    Angus, G.W.; Gentile, G.; Diaferio, A.; Famaey, B.; Heyden, K.J. van der E-mail: diaferio@ph.unito.it E-mail: gianfranco.gentile@ugent.be

    2014-10-01

    In this article we continue to test cosmological models centred on Modified Newtonian Dynamics (MOND) with light sterile neutrinos, which could in principle be a way to solve the fine-tuning problems of the standard model on galaxy scales while preserving successful predictions on larger scales. Due to previous failures of the simple MOND cosmological model, here we test a speculative model where the modified gravitational field is produced only by the baryons and the sterile neutrinos produce a purely Newtonian field (hence Modified Baryonic Dynamics). We use two-component cosmological simulations to separate the baryonic N-body particles from the sterile neutrino ones. The premise is to attenuate the over-production of massive galaxy cluster halos which were prevalent in the original MOND plus light sterile neutrinos scenario. Theoretical issues with such a formulation notwithstanding, the Modified Baryonic Dynamics model fails to produce the correct amplitude for the galaxy cluster mass function for any reasonable value of the primordial power spectrum normalisation.

  15. On the spin separation of algebraic two-component relativistic Hamiltonians: Molecular properties

    NASA Astrophysics Data System (ADS)

    Li, Zhendong; Xiao, Yunlong; Liu, Wenjian

    2014-08-01

    The idea for separating the algebraic exact two-component (X2C) relativistic Hamiltonians into spin-free (sf) and spin-dependent terms [Z. Li, Y. Xiao, and W. Liu, J. Chem. Phys. 137, 154114 (2012)] is extended to both electric and magnetic molecular properties. Taking the spin-free terms (which are correct to infinite order in α ≈ 1/137) as zeroth order, the spin-dependent terms can be treated to any desired order via analytic derivative technique. This is further facilitated by unified Sylvester equations for the response of the decoupling and renormalization matrices to single or multiple perturbations. For practical purposes, explicit expressions of order α2 in spin are also given for electric and magnetic properties, as well as two-electron spin-orbit couplings. At this order, the response of the decoupling and renormalization matrices is not required, such that the expressions are very compact and completely parallel to those based on the Breit-Pauli (BP) Hamiltonian. However, the former employ sf-X2C wave functions, whereas the latter can only use nonrelativistic wave functions. As the sf-X2C terms can readily be interfaced with any nonrelativistic program, the implementation of the O(α ^2) spin-orbit corrections to sf-X2C properties requires only marginal revisions of the routines for evaluating the BP type of corrections.

  16. Radiative cooling of two-component wire-array Z-pinch plasma

    SciTech Connect

    Ivanov, V. V.; Mancini, R. C.; Papp, D.; Hakel, P.; Durmaz, T.; Florido, R.

    2014-08-15

    Wire-array two-component Z-pinch plasmas containing Al and other elements were studied experimentally and the observations interpreted with the help of theoretical modeling. Special attention was given to achieving reproducible implosions. Cascading implosions in star wire arrays mix components during the implosion phase and implosion dynamics were not affected by changes in concentration. A reduction in Al K-shell radiation and an increase in soft x-ray radiation emission were observed in Al-W plasma with 84% concentration of Al ions compared to only-Al plasma. Plasma with 84% of Al ions has radiative properties like those of W Z-pinches. The analysis of Al K-shell x-ray spectra with a collisional-radiative atomic kinetics model shows a drop of the electron temperature from 400 eV in pure Al plasma to below 300 eV in the Al-W mix. Al-Au Z-pinches present radiation features similar to Al-W plasma. This is indicative of a similar plasma cooling effect due to the presence of a high-Z element.

  17. Adhesion-Induced Phase Behavior of Two-Component Membranes and Vesicles

    PubMed Central

    Rouhiparkouhi, Tahereh; Weikl, Thomas R.; Discher, Dennis E.; Lipowsky, Reinhard

    2013-01-01

    The interplay of adhesion and phase separation is studied theoretically for two-component membranes that can phase separate into two fluid phases such as liquid-ordered and liquid-disordered phases. Many adhesion geometries provide two different environments for these membranes and then partition the membranes into two segments that differ in their composition. Examples are provided by adhering vesicles, by hole- or pore-spanning membranes, and by membranes supported by chemically patterned surfaces. Generalizing a lattice model for binary mixtures to these adhesion geometries, we show that the phase behavior of the adhering membranes depends, apart from composition and temperature, on two additional parameters, the area fraction of one membrane segment and the affinity contrast between the two segments. For the generic case of non-vanishing affinity contrast, the adhering membranes undergo two distinct phase transitions and the phase diagrams in the composition/temperature plane have a generic topology that consists of two two-phase coexistence regions separated by an intermediate one-phase region. As a consequence, phase separation and domain formation is predicted to occur separately in each of the two membrane segments but not in both segments simultaneously. Furthermore, adhesion is also predicted to suppress the phase separation process for certain regions of the phase diagrams. These generic features of the adhesion-induced phase behavior are accessible to experiment. PMID:23340655

  18. Gradients for two-component quasirelativistic methods. Application to dihalogenides of element 116.

    PubMed

    van Wüllen, Christoph; Langermann, Norbert

    2007-03-21

    The authors report the implementation of geometry gradients for quasirelativistic two-component Hartree-Fock and density functional methods using either the zero-order regular approximation Hamiltonian or spin-dependent effective core potentials. The computational effort of the resulting program is comparable to that of corresponding nonrelativistic calculations, as it is dominated by the evaluation of derivative two-electron integrals, which is the same for both types of calculations. Besides the implementation of derivatives of matrix elements of the one-particle Hamiltonian with respect to nuclear displacements, the calculation of the derivative exchange-correlation energy for the open shell case involves complicated expressions because of the noncollinear approach chosen to define the spin density. A pilot application to dihalogenides of element 116 shows how spin-orbit coupling strongly affects the chemistry of the superheavy p-block elements. While these molecules are bent at a scalar-relativistic level, spin-orbit coupling is so strong that only the 7p3/2 atomic orbitals of element 116 are involved in bonding, which favors linear molecular geometries for dihalogenides with heavy terminal halogen atoms. PMID:17381195

  19. Two-Component Structure in the Entanglement Spectrum of Highly Excited States.

    PubMed

    Yang, Zhi-Cheng; Chamon, Claudio; Hamma, Alioscia; Mucciolo, Eduardo R

    2015-12-31

    We study the entanglement spectrum of highly excited eigenstates of two known models that exhibit a many-body localization transition, namely the one-dimensional random-field Heisenberg model and the quantum random energy model. Our results indicate that the entanglement spectrum shows a "two-component" structure: a universal part that is associated with random matrix theory, and a nonuniversal part that is model dependent. The nonuniversal part manifests the deviation of the highly excited eigenstate from a true random state even in the thermalized phase where the eigenstate thermalization hypothesis holds. The fraction of the spectrum containing the universal part decreases as one approaches the critical point and vanishes in the localized phase in the thermodynamic limit. We use the universal part fraction to construct an order parameter for measuring the degree of randomness of a generic highly excited state, which is also a promising candidate for studying the many-body localization transition. Two toy models based on Rokhsar-Kivelson type wave functions are constructed and their entanglement spectra are shown to exhibit the same structure. PMID:26765022

  20. Accurate design of megadalton-scale two-component icosahedral protein complexes.

    PubMed

    Bale, Jacob B; Gonen, Shane; Liu, Yuxi; Sheffler, William; Ellis, Daniel; Thomas, Chantz; Cascio, Duilio; Yeates, Todd O; Gonen, Tamir; King, Neil P; Baker, David

    2016-07-22

    Nature provides many examples of self- and co-assembling protein-based molecular machines, including icosahedral protein cages that serve as scaffolds, enzymes, and compartments for essential biochemical reactions and icosahedral virus capsids, which encapsidate and protect viral genomes and mediate entry into host cells. Inspired by these natural materials, we report the computational design and experimental characterization of co-assembling, two-component, 120-subunit icosahedral protein nanostructures with molecular weights (1.8 to 2.8 megadaltons) and dimensions (24 to 40 nanometers in diameter) comparable to those of small viral capsids. Electron microscopy, small-angle x-ray scattering, and x-ray crystallography show that 10 designs spanning three distinct icosahedral architectures form materials closely matching the design models. In vitro assembly of icosahedral complexes from independently purified components occurs rapidly, at rates comparable to those of viral capsids, and enables controlled packaging of molecular cargo through charge complementarity. The ability to design megadalton-scale materials with atomic-level accuracy and controllable assembly opens the door to a new generation of genetically programmable protein-based molecular machines. PMID:27463675

  1. Photonic-band-gap properties for two-component slow light

    SciTech Connect

    Ruseckas, J.; Kudriasov, V.; Juzeliunas, G.; Unanyan, R. G.; Otterbach, J.; Fleischhauer, M.

    2011-06-15

    We consider two-component ''spinor'' slow light in an ensemble of atoms coherently driven by two pairs of counterpropagating control laser fields in a double tripod-type linkage scheme. We derive an equation of motion for the spinor slow light (SSL) representing an effective Dirac equation for a massive particle with the mass determined by the two-photon detuning. By changing the detuning the atomic medium acts as a photonic crystal with a controllable band gap. If the frequency of the incident probe light lies within the band gap, the light experiences reflection from the sample and can tunnel through it. For frequencies outside the band gap, the transmission and reflection probabilities oscillate with the increasing length of the sample. In both cases the reflection takes place into the complementary mode of the probe field. We investigate the influence of the finite excited state lifetime on the transmission and reflection coefficients of the probe light. We discuss possible experimental implementations of the SSL using alkali-metal atoms such as rubidium or sodium.

  2. Probing bilayer-cytoskeletal interactions in erythrocytes using a two-component dissipative particle dynamics model

    NASA Astrophysics Data System (ADS)

    Peng, Zhangli; Li, Xuejin; Pivkin, Igor; Dao, Ming; Karniadakis, George

    2013-11-01

    We develop a two-component dissipative particle dynamics (DPD) model of the red blood cell (RBC) membrane by modeling the lipid bilayer and the cytoskeleton separately. By applying this model to simulate four different experiments on RBCs, including micropipette aspiration, membrane fluctuations, tank-treading motions in shear flow and bilayer tethering in a flow channel, we validated our model and studied the mechanical properties of the bilayer-cytoskeletal interaction in a systematic and controlled manner, such as its elastic stiffness, viscous friction and strength. In the same time, we also resolved several controversies in RBC mechanics, e.g., the dependence of tank-treading frequency on shear rates and the possibility of bilayer-cytoskeletal slip. Furthermore, to investigate RBC dynamics in the microcirculation, we simulated the passages of RBCs through narrow channels of the flow cytometer in vitro and their passages through the splenic inter-endothelial slits in vivo. The effects of RBC geometry and membrane stiffness on the critical pressure gradient of passage were studied, and the simulation results agree well with experimental measurements. This work was supported by National Institutes of Health Grant R01HL094270 and the new Department of Energy Collaboratory on Mathematics for Mesoscopic Modeling of Materials (CM4).

  3. Two-component Structure in the Entanglement Spectrum of Highly Excited States

    NASA Astrophysics Data System (ADS)

    Yang, Zhi-Cheng; Chamon, Claudio; Hamma, Alioscia; Mucciolo, Eduardo

    We study the entanglement spectrum of highly excited eigenstates of two known models which exhibit a many-body localization transition, namely the one-dimensional random-field Heisenberg model and the quantum random energy model. Our results indicate that the entanglement spectrum shows a ``two-component'' structure: a universal part that is associated to Random Matrix Theory, and a non-universal part that is model dependent. The non-universal part manifests the deviation of the highly excited eigenstate from a true random state even in the thermalized phase where the Eigenstate Thermalization Hypothesis holds. The fraction of the spectrum containing the universal part decreases continuously as one approaches the critical point and vanishes in the localized phase in the thermodynamic limit. We use the universal part fraction to construct a new order parameter for the many-body delocalized-to-localized transition. Two toy models based on Rokhsar-Kivelson type wavefunctions are constructed and their entanglement spectra are shown to exhibit the same structure.

  4. Two-component dipolar Bose-Einstein condensate in concentrically coupled annular traps

    PubMed Central

    Zhang, Xiao-Fei; Han, Wei; Wen, Lin; Zhang, Peng; Dong, Rui-Fang; Chang, Hong; Zhang, Shou-Gang

    2015-01-01

    Dipolar Bosonic atoms confined in external potentials open up new avenues for quantum-state manipulation and will contribute to the design and exploration of novel functional materials. Here we investigate the ground-state and rotational properties of a rotating two-component dipolar Bose-Einstein condensate, which consists of both dipolar bosonic atoms with magnetic dipole moments aligned vertically to the condensate and one without dipole moments, confined in concentrically coupled annular traps. For the nonrotational case, it is found that the tunable dipolar interaction can be used to control the location of each component between the inner and outer rings, and to induce the desired ground-state phase. Under finite rotation, it is shown that there exists a critical value of rotational frequency for the nondipolar case, above which vortex state can form at the trap center, and the related vortex structures depend strongly on the rotational frequency. For the dipolar case, it is found that various ground-state phases and the related vortex structures, such as polygonal vortex clusters and vortex necklaces, can be obtained via a proper choice of the dipolar interaction and rotational frequency. Finally, we also study and discuss the formation process of such vortex structures. PMID:25731962

  5. One- and two-component analysis of cyan fluorescent protein: FLIM-FRET microscopy

    NASA Astrophysics Data System (ADS)

    Chen, Ye; King, Michelle; Periasamy, Ammasi

    2005-03-01

    Remarkable advances have been made in studying the dynamic events of protein molecules in living cells and tissues using advanced light microscopy imaging techniques and green fluorescent proteins (GFPs). Identification of the interacting protein partners is critical in understanding its function and place in the biochemical pathway, thereby establishing its role in important disease processes. FLIM-FRET microscopy technique, allow the study of proteins in multiple ways including what proteins are expressed, where they are expressed- and where they move over time. It has been observed that the eCFP-eYFP FRET pair may not be that suitable to localize the association of protein molecules since the eCFP has two-components lifetime. The new Cerulean green fluorescent protein appears to have only one-component lifetime. We describe the extensive investigation of eCFP and Cerulean to study the dimerization of the transcription factor CCAAT/enhancer binding protein alpha in GHFT1-5 living cell nucleus using the time-correlated single photon counting (TCSPC) FLIM-FRET microscopy.

  6. The two-component model of memory development, and its potential implications for educational settings.

    PubMed

    Sander, Myriam C; Werkle-Bergner, Markus; Gerjets, Peter; Shing, Yee Lee; Lindenberger, Ulman

    2012-02-15

    We recently introduced a two-component model of the mechanisms underlying age differences in memory functioning across the lifespan. According to this model, memory performance is based on associative and strategic components. The associative component is relatively mature by middle childhood, whereas the strategic component shows a maturational lag and continues to develop until young adulthood. Focusing on work from our own lab, we review studies from the domains of episodic and working memory informed by this model, and discuss their potential implications for educational settings. The episodic memory studies uncover the latent potential of the associative component in childhood by documenting children's ability to greatly improve their memory performance following mnemonic instruction and training. The studies on working memory also point to an immature strategic component in children whose operation is enhanced under supportive conditions. Educational settings may aim at fostering the interplay between associative and strategic components. We explore possible routes towards this goal by linking our findings to recent trends in research on instructional design. PMID:22682913

  7. Two-Component Coarse-Grained Molecular-Dynamics Model for the Human Erythrocyte Membrane

    PubMed Central

    Li, He; Lykotrafitis, George

    2012-01-01

    We present a two-component coarse-grained molecular-dynamics model for simulating the erythrocyte membrane. The proposed model possesses the key feature of combing the lipid bilayer and the erythrocyte cytoskeleton, thus showing both the fluidic behavior of the lipid bilayer and the elastic properties of the erythrocyte cytoskeleton. In this model, three types of coarse-grained particles are introduced to represent clusters of lipid molecules, actin junctions, and band-3 complexes, respectively. The proposed model facilitates simulations that span large length scales (approximately micrometers) and timescales (approximately milliseconds). By tuning the interaction potential parameters, we were able to control the diffusivity and bending rigidity of the membrane model. We studied the membrane under shearing and found that at a low shear strain rate, the developed shear stress was due mainly to the spectrin network, whereas the viscosity of the lipid bilayer contributed to the resulting shear stress at higher strain rates. In addition, we investigated the effects of a reduced spectrin network connectivity on the shear modulus of the membrane. PMID:22225800

  8. Two-component dipolar Bose-Einstein condensate in concentrically coupled annular traps.

    PubMed

    Zhang, Xiao-Fei; Han, Wei; Wen, Lin; Zhang, Peng; Dong, Rui-Fang; Chang, Hong; Zhang, Shou-Gang

    2015-01-01

    Dipolar Bosonic atoms confined in external potentials open up new avenues for quantum-state manipulation and will contribute to the design and exploration of novel functional materials. Here we investigate the ground-state and rotational properties of a rotating two-component dipolar Bose-Einstein condensate, which consists of both dipolar bosonic atoms with magnetic dipole moments aligned vertically to the condensate and one without dipole moments, confined in concentrically coupled annular traps. For the nonrotational case, it is found that the tunable dipolar interaction can be used to control the location of each component between the inner and outer rings, and to induce the desired ground-state phase. Under finite rotation, it is shown that there exists a critical value of rotational frequency for the nondipolar case, above which vortex state can form at the trap center, and the related vortex structures depend strongly on the rotational frequency. For the dipolar case, it is found that various ground-state phases and the related vortex structures, such as polygonal vortex clusters and vortex necklaces, can be obtained via a proper choice of the dipolar interaction and rotational frequency. Finally, we also study and discuss the formation process of such vortex structures. PMID:25731962

  9. Functionalization of PDMS modified and plasma activated two-component polyurethane coatings by surface attachment of enzymes

    NASA Astrophysics Data System (ADS)

    Kreider, Alexej; Richter, Katharina; Sell, Stephan; Fenske, Mandus; Tornow, Christian; Stenzel, Volkmar; Grunwald, Ingo

    2013-05-01

    This article describes a new strategy for coupling the enzyme horseradish peroxidase to a two-component polyurethane (2C-PUR) coating. A stable polymer conjugate was achieved by combining the enzyme and the 2C-PUR coating which was modified with poly(dimethylsiloxane) (PDMS), located at the surface. An atmospheric pressure plasma jet system was used to convert alkyl groups from the PDMS into polar silanol functionalities. This conversion was proven by X-ray photoelectron spectroscopy and dynamic contact angle measurements. In addition, the stability of the activated 2C-PUR surface containing silanol groups was determined by measuring the contact angle as a function of time. Compared to the non-modified 2C-PUR systems the one with PDMS displayed a higher stability over a time period over 28 h. In a silanization process the coating was treated with (3-aminopropyl) trimethoxysilane and the enzyme was subsequently immobilized to the coating via the cross linker glutaraldehyde to receive new biomimetic catalytic/enzymatic functions. The chemical immobilization (chemisorption) of the enzyme to the surface showed statistically significant higher biological activity as compared to references samples without using a cross linker (physisorption). The presented technique offers the opportunity to design new and smart multifunctional surface coatings which employ biomimetic capabilities.

  10. The Physarum polycephalum Genome Reveals Extensive Use of Prokaryotic Two-Component and Metazoan-Type Tyrosine Kinase Signaling.

    PubMed

    Schaap, Pauline; Barrantes, Israel; Minx, Pat; Sasaki, Narie; Anderson, Roger W; Bénard, Marianne; Biggar, Kyle K; Buchler, Nicolas E; Bundschuh, Ralf; Chen, Xiao; Fronick, Catrina; Fulton, Lucinda; Golderer, Georg; Jahn, Niels; Knoop, Volker; Landweber, Laura F; Maric, Chrystelle; Miller, Dennis; Noegel, Angelika A; Peace, Rob; Pierron, Gérard; Sasaki, Taeko; Schallenberg-Rüdinger, Mareike; Schleicher, Michael; Singh, Reema; Spaller, Thomas; Storey, Kenneth B; Suzuki, Takamasa; Tomlinson, Chad; Tyson, John J; Warren, Wesley C; Werner, Ernst R; Werner-Felmayer, Gabriele; Wilson, Richard K; Winckler, Thomas; Gott, Jonatha M; Glöckner, Gernot; Marwan, Wolfgang

    2016-01-01

    Physarum polycephalum is a well-studied microbial eukaryote with unique experimental attributes relative to other experimental model organisms. It has a sophisticated life cycle with several distinct stages including amoebal, flagellated, and plasmodial cells. It is unusual in switching between open and closed mitosis according to specific life-cycle stages. Here we present the analysis of the genome of this enigmatic and important model organism and compare it with closely related species. The genome is littered with simple and complex repeats and the coding regions are frequently interrupted by introns with a mean size of 100 bases. Complemented with extensive transcriptome data, we define approximately 31,000 gene loci, providing unexpected insights into early eukaryote evolution. We describe extensive use of histidine kinase-based two-component systems and tyrosine kinase signaling, the presence of bacterial and plant type photoreceptors (phytochromes, cryptochrome, and phototropin) and of plant-type pentatricopeptide repeat proteins, as well as metabolic pathways, and a cell cycle control system typically found in more complex eukaryotes. Our analysis characterizes P. polycephalum as a prototypical eukaryote with features attributed to the last common ancestor of Amorphea, that is, the Amoebozoa and Opisthokonts. Specifically, the presence of tyrosine kinases in Acanthamoeba and Physarum as representatives of two distantly related subdivisions of Amoebozoa argues against the later emergence of tyrosine kinase signaling in the opisthokont lineage and also against the acquisition by horizontal gene transfer. PMID:26615215

  11. Sequence and Function of LuxU: a Two-Component Phosphorelay Protein That Regulates Quorum Sensing in Vibrio harveyi

    PubMed Central

    Freeman, Jeremy A.; Bassler, Bonnie L.

    1999-01-01

    Vibrio harveyi regulates the expression of bioluminescence (lux) in response to cell density, a phenomenon known as quorum sensing. In V. harveyi, two independent quorum-sensing systems exist, and each produces, detects, and responds to a specific cell density-dependent autoinducer signal. The autoinducers are recognized by two-component hybrid sensor kinases called LuxN and LuxQ, and sensory information from both systems is transduced by a phosphorelay mechanism to the response regulator protein LuxO. Genetic evidence suggests that LuxO-phosphate negatively regulates the expression of luminescence at low cell density in the absence of autoinducers. At high cell density, interaction of the sensors with their cognate autoinducers results in dephosphorylation and inactivation of the LuxO repressor. In the present report, we show that LuxN and LuxQ channel sensory information to LuxO via a newly identified phosphorelay protein that we have named LuxU. LuxU shows sequence similarity to other described phosphorelay proteins, including BvgS, ArcB, and Ypd1. A critical His residue (His 58) of LuxU is required for phosphorelay function. PMID:9922254

  12. The Physarum polycephalum Genome Reveals Extensive Use of Prokaryotic Two-Component and Metazoan-Type Tyrosine Kinase Signaling

    PubMed Central

    Schaap, Pauline; Barrantes, Israel; Minx, Pat; Sasaki, Narie; Anderson, Roger W.; Bénard, Marianne; Biggar, Kyle K.; Buchler, Nicolas E.; Bundschuh, Ralf; Chen, Xiao; Fronick, Catrina; Fulton, Lucinda; Golderer, Georg; Jahn, Niels; Knoop, Volker; Landweber, Laura F.; Maric, Chrystelle; Miller, Dennis; Noegel, Angelika A.; Peace, Rob; Pierron, Gérard; Sasaki, Taeko; Schallenberg-Rüdinger, Mareike; Schleicher, Michael; Singh, Reema; Spaller, Thomas; Storey, Kenneth B.; Suzuki, Takamasa; Tomlinson, Chad; Tyson, John J.; Warren, Wesley C.; Werner, Ernst R.; Werner-Felmayer, Gabriele; Wilson, Richard K.; Winckler, Thomas; Gott, Jonatha M.; Glöckner, Gernot; Marwan, Wolfgang

    2016-01-01

    Physarum polycephalum is a well-studied microbial eukaryote with unique experimental attributes relative to other experimental model organisms. It has a sophisticated life cycle with several distinct stages including amoebal, flagellated, and plasmodial cells. It is unusual in switching between open and closed mitosis according to specific life-cycle stages. Here we present the analysis of the genome of this enigmatic and important model organism and compare it with closely related species. The genome is littered with simple and complex repeats and the coding regions are frequently interrupted by introns with a mean size of 100 bases. Complemented with extensive transcriptome data, we define approximately 31,000 gene loci, providing unexpected insights into early eukaryote evolution. We describe extensive use of histidine kinase-based two-component systems and tyrosine kinase signaling, the presence of bacterial and plant type photoreceptors (phytochromes, cryptochrome, and phototropin) and of plant-type pentatricopeptide repeat proteins, as well as metabolic pathways, and a cell cycle control system typically found in more complex eukaryotes. Our analysis characterizes P. polycephalum as a prototypical eukaryote with features attributed to the last common ancestor of Amorphea, that is, the Amoebozoa and Opisthokonts. Specifically, the presence of tyrosine kinases in Acanthamoeba and Physarum as representatives of two distantly related subdivisions of Amoebozoa argues against the later emergence of tyrosine kinase signaling in the opisthokont lineage and also against the acquisition by horizontal gene transfer. PMID:26615215

  13. Two-Component Fitting of Coronal-Hole and Quiet-Sun He I 1083 Spectra

    NASA Technical Reports Server (NTRS)

    Jones, Harrison P.; Malanushenko, Elena V.; Fisher, Richard R. (Technical Monitor)

    2001-01-01

    We present reduction techniques and first results for detailed fitting of solar spectra obtained with the NASA/National Solar Observatory Spectromagnetograph (NASA/NSO SPM over a 2 nm bandpass centered on the He 1 1083 nm line. The observation for this analysis was a spectra-spectroheliogram obtained at the NSO/Kitt Peak Vacuum Telescope (KPVT) on 00 Apr 17 at 21:46 UT spanning an area of 512 x 900 arc-seconds; the field of view included a coronal hole near disk center as well as surrounding quiet sun. Since the He I line is very weak and blended with nearby solar and telluric lines, accurate determination of the continuum intensity as a function of wavelength is crucial. We have modified the technique of Malanushenko {\\it et al.) (1992; {\\it AA) (\\bf 259), 567) to tie regions of continuua and the wings of spectral lines which show little variation over the image to standard reference spectra such as the NSO Fourier Transform Spectrometer atlas (Wallace {\\it et al). 1993; NSO Tech Report \\#93-001). We performed detailed least-squares fits of spectra from selected areas, accounting for all the known telluric and solar absorbers in the spectral bandpass. The best physically consistent fits to the Helium lines were obtained with Gaussian profiles from two components (one ''cool'', characteristic of the upper chromosphere; one ''hot'', representing the cool transition region at 2-3 x 10$^{4)$ K). In the coronal hole, the transition-region component, shifted by 6-7 km/s to the blue, is mildly dominant, consistent with mass outflow as suggested by Dupree {\\it et all. (1996; {\\it Ap. J.}-{\\bf 467), 121). In quiet-sun spectra there is less evidence of outward flow, and the chromospheric component is more important. All our fitted spectra show a very weak unidentified absorption feature at 1082.880 nm in the red wing of the nearby Si I line.

  14. Short and medium range order in two-component silica glasses by positron annihilation spectroscopy

    SciTech Connect

    Inoue, K.; Kataoka, H.; Nagai, Y.; Hasegawa, M.; Kobayashi, Y.

    2014-05-28

    The dependence of chemical composition on the average sizes of subnanometer-scale intrinsic structural open spaces surrounded by glass random networks in two-component silica-based glasses was investigated systematically using positronium (Ps) confined in the open spaces. The average sizes of the open spaces for SiO{sub 2}-B{sub 2}O{sub 3} and SiO{sub 2}-GeO{sub 2} glasses are only slightly dependent on the chemical compositions because the B{sub 2}O{sub 3} and GeO{sub 2} are glass network formers that are incorporated into the glass network of the base SiO{sub 2}. However, the open space sizes for all SiO{sub 2}-R{sub 2}O (R = Li, Na, K) glasses, where R{sub 2}O is a glass network modifier that occupies the open spaces, decrease rapidly with an increase in the R{sub 2}O concentration. Despite the large difference in the ionic radii of the alkali metal (R) atoms, the open space sizes decrease similarly for all the alkali metal atoms studied. This dependence of the chemical composition on the open space sizes in SiO{sub 2}-R{sub 2}O observed by Ps shows that the alkali metal atoms do not randomly occupy the structural open spaces, but filling of the open spaces by R{sub 2}O proceeds selectively from the larger to the smaller open spaces as the R{sub 2}O concentrations are increased.

  15. A two-component generalized extreme value distribution for precipitation frequency analysis

    NASA Astrophysics Data System (ADS)

    Rulfová, Zuzana; Buishand, Adri; Roth, Martin; Kyselý, Jan

    2016-03-01

    A two-component generalized extreme value (TCGEV) distribution is introduced based on the assumption that the annual maxima for convective and stratiform precipitation follow two separate generalized extreme value (GEV) distributions. The regional TCGEV model is used to analyze 6-h precipitation data for 11 stations in the Czech Republic over 1982-2010 subdivided into predominantly convective and stratiform precipitation. For each type of precipitation, the shape parameter and the ratio of the scale parameter and the location parameter of the underlying GEV distributions are assumed to be constant over the region. The validity of this homogeneity assumption is explored with a bootstrap procedure and the goodness-of-fit is tested with the Anderson-Darling statistic both for each individual station and for all stations simultaneously. The return levels from the regional TCGEV distribution are compared with those obtained with the common method of fitting a regional GEV distribution to the overall annual maxima, ignoring their convective or stratiform origin. The differences are generally small, but they increase with return period and are larger at lowland stations where the proportion of convective precipitation extremes is greater. High return levels based on a GEV fit to the overall annual maxima for these stations tend to be smaller than those for the convective component owing to the heavier upper tail of the distribution of convective extremes. Results from the TCGEV distribution are consistent, i.e., the estimated return levels of the overall annual maxima cannot be smaller than those for the convective and stratiform components obtained from the GEV distribution.

  16. Perturbative treatment of spin-orbit coupling within spin-free exact two-component theory

    SciTech Connect

    Cheng, Lan; Gauss, Jürgen

    2014-10-28

    This work deals with the perturbative treatment of spin-orbit-coupling (SOC) effects within the spin-free exact two-component theory in its one-electron variant (SFX2C-1e). We investigate two schemes for constructing the SFX2C-1e SOC matrix: the SFX2C-1e+SOC [der] scheme defines the SOC matrix elements based on SFX2C-1e analytic-derivative theory, hereby treating the SOC integrals as the perturbation; the SFX2C-1e+SOC [fd] scheme takes the difference between the X2C-1e and SFX2C-1e Hamiltonian matrices as the SOC perturbation. Furthermore, a mean-field approach in the SFX2C-1e framework is formulated and implemented to efficiently include two-electron SOC effects. Systematic approximations to the two-electron SOC integrals are also proposed and carefully assessed. Based on benchmark calculations of the second-order SOC corrections to the energies and electrical properties for a set of diatomic molecules, we show that the SFX2C-1e+SOC [der] scheme performs very well in the computation of perturbative SOC corrections and that the “2eSL” scheme, which neglects the (SS|SS)-type two-electron SOC integrals, is both efficient and accurate. In contrast, the SFX2C-1e+SOC [fd] scheme turns out to be incompatible with a perturbative treatment of SOC effects. Finally, as a first chemical application, we report high-accuracy calculations of the {sup 201}Hg quadrupole-coupling parameters of the recently characterized ethylmercury hydride (HHgCH{sub 2}CH{sub 3}) molecule based on SFX2C-1e coupled-cluster calculations augmented with second-order SOC corrections obtained at the Hartree-Fock level using the SFX2C-1e+SOC [der]/2eSL scheme.

  17. Isomerization and dissociation in competition: The two-component dissociation rates of methyl propionate ions

    SciTech Connect

    Mazyar, O.A.; Baer, T.

    1999-03-04

    Threshold photoelectron-photoion coincidence (TPEPICO) spectroscopy has been used to investigate the unimolecular chemistry of gas-phase methyl propionate ions. This ion undergoes isomerization to a lower energy enol structure, CH{sub 3}CHC(OH)OCH{sub 3}{sup {sm_bullet}+}, via two different pathways involving two distonic isomers, {sup {sm_bullet}}CH{sub 2}CH{sub 2}C{sup +}(OH)OCH{sub 3} and CH{sub 3}CH{sub 2}C{sup +}(OH)OCH{sub 2}{sup {sm_bullet}}. This isomerization reaction is in competition with the direct CH{sub 3}O{sup {sm_bullet}} loss reaction, which leads to two-component dissociation rates of the methyl propionate ions. Detailed modeling of this complex reaction permitted the extraction of the dissociative photoionization threshold for methyl propionate, which at 0 K is 10.83 {+-} 0.01 eV, as well as the isomerization barrier between the distonic CH{sub 3}CH{sub 2}C{sup +}(OH)OCH{sub 2}{sup {sm_bullet}} and enol CH{sub 3}CHC(OH)OCH{sub 3}{sup {sm_bullet}+} ions of 8.5 kcal/mol (relative to the methyl propionate ion). By combining this with the 0 K heats of formation of methyl propionate and the methoxy radical, the authors derive a 0 K heat of formation of the product propanoyl ion of 147 kcal/mol. Also measured was the adiabatic ionization energy of methyl propionate, 10.03 {+-} 0.05 eV.

  18. TWO-COMPONENT GALACTIC BULGE PROBED WITH RENEWED GALACTIC CHEMICAL EVOLUTION MODEL

    SciTech Connect

    Tsujimoto, Takuji; Bekki, Kenji

    2012-03-10

    Results of recent observations of the Galactic bulge demand that we discard a simple picture of its formation, suggesting the presence of two stellar populations represented by two peaks of stellar metallicity distribution (MDF) in the bulge. To assess this issue, we construct Galactic chemical evolution models that have been updated in two respects: first, the delay time distribution of Type Ia supernovae (SNe Ia) recently revealed by extensive SN Ia surveys is incorporated into the models. Second, the nucleosynthesis clock, the s-processing in asymptotic giant branch stars, is carefully considered in this study. This novel model first shows that the Galaxy feature tagged by the key elements, Mg, Fe, and Ba, for the bulge as well as thin and thick disks is compatible with a short-delay SN Ia. We present a successful modeling of a two-component bulge including the MDF and the evolutions of [Mg/Fe] and [Ba/Mg], and reveal its origin as follows. A metal-poor component (([Fe/H]) {approx} -0.5) is formed with a relatively short timescale of {approx}1 Gyr. These properties are identical to the thick disk's characteristics in the solar vicinity. Subsequently from its remaining gas mixed with a gas flow from the disk outside the bulge, a metal-rich component (([Fe/H]) {approx} +0.3) is formed with a longer timescale ({approx}4 Gyr) together with a top-heavy initial mass function that might be identified with the thin disk component within the bulge.

  19. Large-scale Models Reveal the Two-component Mechanics of Striated Muscle

    PubMed Central

    Jarosch, Robert

    2008-01-01

    This paper provides a comprehensive explanation of striated muscle mechanics and contraction on the basis of filament rotations. Helical proteins, particularly the coiled-coils of tropomyosin, myosin and α-actinin, shorten their H-bonds cooperatively and produce torque and filament rotations when the Coulombic net-charge repulsion of their highly charged side-chains is diminished by interaction with ions. The classical “two-component model” of active muscle differentiated a “contractile component” which stretches the “series elastic component” during force production. The contractile components are the helically shaped thin filaments of muscle that shorten the sarcomeres by clockwise drilling into the myosin cross-bridges with torque decrease (= force-deficit). Muscle stretch means drawing out the thin filament helices off the cross-bridges under passive counterclockwise rotation with torque increase (= stretch activation). Since each thin filament is anchored by four elastic α-actinin Z-filaments (provided with force-regulating sites for Ca2+ binding), the thin filament rotations change the torsional twist of the four Z-filaments as the “series elastic components”. Large scale models simulate the changes of structure and force in the Z-band by the different Z-filament twisting stages A, B, C, D, E, F and G. Stage D corresponds to the isometric state. The basic phenomena of muscle physiology, i. e. latency relaxation, Fenn-effect, the force-velocity relation, the length-tension relation, unexplained energy, shortening heat, the Huxley-Simmons phases, etc. are explained and interpreted with the help of the model experiments. PMID:19330099

  20. Remarkable regioisomer control in the hydrogel formation from a two-component mixture of pyridine-end oligo(p-phenylenevinylene)s and N-decanoyl-L-alanine.

    PubMed

    Bhattacharjee, Subham; Datta, Sougata; Bhattacharya, Santanu

    2013-12-01

    N-Decanoyl-L-alanine (DA) was mixed with either colorless 4,4'-bipyridine (BP) or various derivatives such as chromogenic oligo(p-phenylenevinylene) (OPV) functionalized with isomeric pyridine termini in specific molar ratios. This mixtures form salt-type gels in a water/ethanol (2:1, v/v) mixture. The gelation properties of these two-component mixtures could be modulated by variation of the position of the ''N'' atom of the end pyridyl groups in OPVs. The presence of acid-base interactions in the self-assembly of these two-component systems leading to gelation was probed in detail by using stoichiometry-dependent UV/Vis and FTIR spectroscopy. Furthermore, temperature-dependent UV/Vis and fluorescence spectroscopy clearly demonstrated a J-type aggregation mode of these gelator molecules during the sol-to-gel transition process. Morphological features and the arrangement of the molecules in the gels were examined by using scanning electron microscopy (SEM), atomic force microscopy (AFM), and X-ray diffraction (XRD) techniques. Calculation of the length of each molecular system by energy minimization in its extended conformation and comparison with the XRD patterns revealed that this class of gelator molecules adopts lamellar organizations. Rheological properties of these two-component systems provided clear evidence that the flow behavior could be modulated by varying the acid/amine ratio. Polarized optical microscopy (POM), differential scanning calorimetry (DSC), and XRD results revealed that the solid-phase behavior of such two-component mixtures (acid/base=2:1) varied significantly upon changing the proton-acceptor part from BP to OPV. Interestingly, the XRD pattern of these acid/base mixtures after annealing at their associated isotropic temperature was significantly different from that of their xerogels. PMID:24194380

  1. Laplace-transformed atomic orbital-based Møller-Plesset perturbation theory for relativistic two-component Hamiltonians

    NASA Astrophysics Data System (ADS)

    Helmich-Paris, Benjamin; Repisky, Michal; Visscher, Lucas

    2016-07-01

    We present a formulation of Laplace-transformed atomic orbital-based second-order Møller-Plesset perturbation theory (MP2) energies for two-component Hamiltonians in the Kramers-restricted formalism. This low-order scaling technique can be used to enable correlated relativistic calculations for large molecular systems. We show that the working equations to compute the relativistic MP2 energy differ by merely a change of algebra (quaternion instead of real) from their non-relativistic counterparts. With a proof-of-principle implementation we study the effect of the nuclear charge on the magnitude of half-transformed integrals and show that for light elements spin-free and spin-orbit MP2 energies are almost identical. Furthermore, we investigate the effect of separation of charge distributions on the Coulomb and exchange energy contributions, which show the same long-range decay with the inter-electronic/atomic distance as for non-relativistic MP2. A linearly scaling implementation is possible if the proper distance behavior is introduced to the quaternion Schwarz-type estimates as for non-relativistic MP2.

  2. Characterization of GX 339-4 outburst of 2010-11: analysis by XSPEC using two component advective flow model

    NASA Astrophysics Data System (ADS)

    Debnath, Dipak; Mondal, Santanu; Chakrabarti, Sandip K.

    2015-02-01

    We study spectral properties of GX 339-4 during its 2010-11 outburst with two component advective flow (TCAF) model after its inclusion in XSPEC as a table model. We compare results fitted by TCAF model with combined disc blackbody and power-law model. For a spectral fit, we use 2.5-25 keV spectral data of the Proportional Counter Array instrument onboard RXTE satellite. From our fit, accretion flow parameters such as Keplerian (disc) rate, sub-Keplerian (halo) rate, location and strength of shock are extracted. We quantify how the disc and the halo rates vary during the entire outburst. We study how the halo to disc accretion rate ratio (ARR), quasi-periodic oscillations (QPOs), shock locations and its strength vary when the system passes through hard, hard-intermediate, soft-intermediate and soft states. We find pieces of evidence of monotonically increasing and decreasing nature of QPO frequencies depending on the variation of ARR during rising and declining phases. Interestingly, on days of transition from hard state to hard-intermediate spectral state (during the rising phase) or vice-versa (during decline phase), ARR is observed to be locally maximum. Non-constancy of ARR while obtaining reasonable fits points to the presence of two independent components in the flow.

  3. Interface and vortex motion in the two-component complex dissipative Ginzburg-Landau equation in two-dimensional space

    NASA Astrophysics Data System (ADS)

    Yabunaka, Shunsuke

    2014-10-01

    We study interface and vortex motion in the two-component dissipative Ginzburg-Landau equation in two-dimensional space. We consider cases where the whole system is divided into several domains, and we assume that these domains are separated by interfaces and each domain contains quantized vortices. The equations for interface and vortex motion will be derived by means of a variational approach by Kawasaki. These equations indicate that, along an interface, the phase gradient fields of the complex order parameters is parallel to the interface. They also indicate that the interface motion is driven by the curvature and the phase gradient fields along the interface, and vortex motion is driven by the phase gradient field around the vortex. With respect to the static interactions between defects, we find an analogy between quantized vortices in a domain and electric charges in a vacuum domain surrounded by a metallic object in electrostatic. This analogy indicates that there is an attractive interaction between an interface and a quantized vortex with any charge. We also discuss several examples of interface and vortex motion.

  4. Laplace-transformed atomic orbital-based Møller-Plesset perturbation theory for relativistic two-component Hamiltonians.

    PubMed

    Helmich-Paris, Benjamin; Repisky, Michal; Visscher, Lucas

    2016-07-01

    We present a formulation of Laplace-transformed atomic orbital-based second-order Møller-Plesset perturbation theory (MP2) energies for two-component Hamiltonians in the Kramers-restricted formalism. This low-order scaling technique can be used to enable correlated relativistic calculations for large molecular systems. We show that the working equations to compute the relativistic MP2 energy differ by merely a change of algebra (quaternion instead of real) from their non-relativistic counterparts. With a proof-of-principle implementation we study the effect of the nuclear charge on the magnitude of half-transformed integrals and show that for light elements spin-free and spin-orbit MP2 energies are almost identical. Furthermore, we investigate the effect of separation of charge distributions on the Coulomb and exchange energy contributions, which show the same long-range decay with the inter-electronic/atomic distance as for non-relativistic MP2. A linearly scaling implementation is possible if the proper distance behavior is introduced to the quaternion Schwarz-type estimates as for non-relativistic MP2. PMID:27394099

  5. Large effect of membrane tension on the fluid–solid phase transitions of two-component phosphatidylcholine vesicles

    PubMed Central

    Chen, Dong; Santore, Maria M.

    2014-01-01

    Model phospholipid membranes and vesicles have long provided insight into the nature of confined materials and membranes while also providing a platform for drug delivery. The rich thermodynamic behavior and interesting domain shapes in these membranes have previously been mapped in extensive studies that vary temperature and composition; however, the thermodynamic impact of tension on bilayers has been restricted to recent reports of subtly reduced fluid–fluid transition temperatures. In two-component phosphatidylcholine unilamellar vesicles [1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC)/1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC)], we report a dramatic influence of tension on the fluid–solid transition and resulting phases: At fixed composition, systematic variations in tension produce differently shaped solid domains (striped or irregular hexagons), shift fluid–solid transition temperatures, and produce a triple-point–like intersection of coexistence curves at elevated tensions, about 3 mN/m for 30% DOPC/70% DPPC. Tension therefore represents a potential switch of microstructure in responsive engineered materials; it is an important morphology-determining variable in confined systems, and, in biological membranes, it may provide a means to regulate dynamic structure. PMID:24344297

  6. A Two-Component Mixing Model for Predicting Regional Episodic Acidification of Surface Waters During Spring Snowmelt Periods

    NASA Astrophysics Data System (ADS)

    Eshleman, Keith N.; Davies, Trevor D.; Tranter, Martyn; Wigington, Parker J.

    1995-04-01

    A two-component mixing model of acid neutralizing capacity (ANC) is proposed for explaining two observed features related to the episodic acidification of surface waters during snowmelt periods: (1) maximum episodic declines in ANC are largest in high ANC systems and increase linearly with antecedent ANC and (2) relative depressions in ANC attributable to increases in nitric acid concentrations are larger in low ANC systems, while relative depressions in ANC attributable to dilution of base cations are larger in high ANC systems. Conceptually, the model represents the physical mixing of two hydrochemical end-members within a surface water environment, although the physical sources of water in the model are undefined. The model is shown to explain 55-72% of the total variation of these characteristics among various surface water systems within the Catskill and Adirondack mountain regions of New York. In addition, the model also explains 11-47% of the relative depression in ANC attributable to natural organic acidity in surface waters in these regions. The model is subsequently linked to an empirical equilibrium acidification model for predicting the long-term episodic acidification response of Adirondack lakes during snowmelt periods. Model predictions suggest that percentage decreases in sulfuric acid concentrations of the magnitude mandated by the 1990 Clean Air Act Amendments (40%) will not restore to positive values the ANC of all Adirondack lakes which are currently acidic (ANC < 0) during spring snowmelt periods. Long-term increases in nitric acid concentrations may counterbalance the expected increases in ANC attributable to reductions in sulfur deposition.

  7. Evidence against a simple two-component model for the far-infrared emission from galaxies

    NASA Technical Reports Server (NTRS)

    Eales, Stephen A.; Devereux, Nicholas A.

    1990-01-01

    Two of the first Infrared Astronomy Satellite (IRAS) results were that galaxies have a wide range of values for the ratio of 60 micron to 100 micron flux density (0.2 less than or equal to S sub 60/S sub 100 less than or equal to 1.0) and that this ratio is correlated with L sub fir, L sub b, L sub fir being the total far-infrared luminosity and L sub b being the luminosity at visible wavelengths (de Jong et al. 1984; Soifer et al. 1984). From these results arose the following simple model for the far-infrared emission from galaxies (de Jong et al. 1984), which has remained the standard model ever since. In this model, the far-infrared emission comes from two dust components: warm dust (T approx. equals 50 K) intermingled with, and heated by, young massive OB stars in molecular clouds and HII regions, and colder dust (T approx. equals 20 K) associated with the diffuse atomic hydrogen in the interstellar medium and heated by the general interstellar radiation field. As the number of young stars in a galaxy increases, S sub 60/S sub 100 increases, because there is a greater proportion of warm dust, and so does L sub fir/L sub b, because most of the radiation from the young stars is absorbed by the dust, leading to a swifter increase in far-infrared emission than in visible light. Although this model explains the basic IRAS results, it is inelegant. It uses two free parameters to fit two data (the 60 and 100 micron flux densities)-and there are now several observations that contradict it. Despite these major problems with the two-component model, it is not clear what should be put in its place. When considering possible models for the far-infrared emission from galaxies, the observational evidence for our own galaxy must be considered. Researchers suspect that the study by Boulanger and Perault (1988) of the far-infrared properties of the local interstellar medium may be particularly relevant. They showed that molecular clouds are leaky - that most of the light from

  8. Wind Variability of B Supergiants. No. 2; The Two-component Stellar Wind of gamma Arae

    NASA Technical Reports Server (NTRS)

    Prinja, R. K.; Massa, D.; Fullerton, A. W.; Howarth, I. D.; Pontefract, M.

    1996-01-01

    The stellar wind of the rapidly rotating early-B supergiant, gamma Ara, is studied using time series, high-resolution IUE spectroscopy secured over approx. 6 days in 1993 March. Results are presented based on an analysis of several line species, including N(N), C(IV), Si(IV), Si(III), C(II), and Al(III). The wind of this star is grossly structured, with evidence for latitude-dependent mass loss which reflects the role of rapid rotation. Independent, co-existing time variable features are identified at low-velocity (redward of approx. -750 km/s) and at higher-speeds extending to approx. -1500 km/s. The interface between these structures is 'defined' by the appearance of a discrete absorption component which is extremely sharp (in velocity space). The central velocity of this 'Super DAC' changes only gradually, over several days, between approx. -400 and -750 km/s in most of the ions. However, its location is shifted redward by almost 400 km/s in Al(III) and C(II), indicating that the physical structure giving rise to this feature has a substantial velocity and ionization jump. Constraints on the relative ionization properties of the wind structures are discussed, together with results based on SEI line-profile-fitting methods. The overall wind activity in gamma Ara exhibits a clear ion dependence, such that low-speed features are promoted in low-ionization species, including Al(III), C(II), and Si(III). We also highlight that - in contrast to most OB stars - there are substantial differences in the epoch-to-epoch time-averaged wind profiles of gamma Ara. We interpret the results in terms of a two-component wind model for gamma Ara, with an equatorially compressed low ionization region, and a high speed, higher-ionization polar outflow. This picture is discussed in the context of the predicted bi-stability mechanism for line-driven winds in rapidly rotating early-B type stars, and the formation of compressed wind regions in rapidly rotating hot stars. The apparent

  9. Two components of postseismic gravity changes of megathrust earthquakes from satellite gravimetry

    NASA Astrophysics Data System (ADS)

    Tanaka, Y.; Heki, K.

    2013-12-01

    There are several reports of the observations of gravity changes due to megathrust earthquakes with data set of Gravity Recovery And Climate Experiment (GRACE) satellite. We analyzed the co- and postseismic gravity changes of the three magnitude 9 class earthquakes, the 2004 Sumatra-Andaman, the 2010 Chile (Maule), and the 2011 Tohoku-Oki earthquakes, using the newly released data (Release 05 data) set. In addition to the coseismic steps, these earthquakes showed a common feature that the postseismic changes include two components with different polarity and time constants, i.e. rapid decreases over a few months, followed by slow increases lasting for years. This is shown in the auxiliary figure of this abstract. In this figure, the white circles are the data whose seasonal and secular changes were removed. The vertical translucent lines denote the earthquake occurrence times. All the three earthquakes suggest the existence of two postseismic gravity change components with two distinct time constants. The first (short-term) component showed geographical distribution similar to the coseismic changes, but the position of the largest gravity decrease shifted toward the trench. The short-term components can be related to afterslip, but their time constants and distributions showed significant deviation from gravity changes predicted by the afterslip models. The second (long-term) components are characterized by positive gravity changes with the peak close to the trench axis. The long-term components should be attributed to different or multiple mechanisms, e.g. viscous relaxation of rocks in the upper mantle [Han and Simons, 2008; Panet et al., 2007] and diffusion of supercritical water around the down-dip end of the ruptured fault [Ogawa and Heki, 2007]. Both of the two mechanisms can explain the postseismic gravity increase in this timescale to some extent, but there have been no decisive evidence to prove or disprove either one of these. But generally speaking

  10. Evidence against a simple two-component model for the far-infrared emission from galaxies

    NASA Astrophysics Data System (ADS)

    Eales, Stephen A.; Devereux, Nicholas A.

    1990-07-01

    Two of the first Infrared Astronomy Satellite (IRAS) results were that galaxies have a wide range of values for the ratio of 60 micron to 100 micron flux density (0.2 less than or equal to S60/S sub 100 less than or equal to 1.0) and that this ratio is correlated with Lfir, Lb, Lfir being the total far-infrared luminosity and Lb being the luminosity at visible wavelengths (de Jong et al. 1984; Soifer et al. 1984). From these results arose the following simple model for the far-infrared emission from galaxies (de Jong et al. 1984), which has remained the standard model ever since. In this model, the far-infrared emission comes from two dust components: warm dust (T approx. equals 50 K) intermingled with, and heated by, young massive OB stars in molecular clouds and HII regions, and colder dust (T approx. equals 20 K) associated with the diffuse atomic hydrogen in the interstellar medium and heated by the general interstellar radiation field. As the number of young stars in a galaxy increases, S60/S sub 100 increases, because there is a greater proportion of warm dust, and so does Lfir/L sub b, because most of the radiation from the young stars is absorbed by the dust, leading to a swifter increase in far-infrared emission than in visible light. Although this model explains the basic IRAS results, it is inelegant. It uses two free parameters to fit two data (the 60 and 100 micron flux densities)-and there are now several observations that contradict it. Despite these major problems with the two-component model, it is not clear what should be put in its place. When considering possible models for the far-infrared emission from galaxies, the observational evidence for our own galaxy must be considered. Researchers suspect that the study by Boulanger and Perault (1988) of the far-infrared properties of the local interstellar medium may be particularly relevant. They showed that molecular clouds are leaky - that most of the light from OB stars in molecular clouds does

  11. The Two Components of the Evolved Massive Binary LZ Cephei: Testing the Effects of Binarity on Stellar Evolution

    NASA Technical Reports Server (NTRS)

    Mahy, L.; Martins, F.; Donati, J.-F.; Bouret, J.-C.

    2011-01-01

    We present an in-dep(h study of the two components of the binary system LZ Cep to constrain the effects of binarity on the evolution of massive stars. Methods. We analyzed a set of high-resolution, high signal-to-noise ratio optical spectra obtained over the orbital period of the system to perform a spectroscopic disentangling and derive an orbital solution. We subsequently determine the stellar properties of each component by means of an analysis with the CMFGEN atmosphere code. Finally, with the derived stellar parameters, we model the Hipparcos photometric light curve using the program NIGHTFALL to obtain the orbit inclination and the stellar masses. Results.LZ Cep is a O9III+ON9.7V binary. It is as a semi-detailed system in which either the primary or the secondary star almost fills up its Roche lobe. The dynamical masses are about 16.0 Stellar Mass (primary) and 6.5 Stellar Mass (secondary). The latter is lower than the typical mass of late-type O stars. The secondary component is chemically more evolved than the primary (which barely shows any sign of CNO processing), with strong helium and nitrogen enhancements as well as carbon and oxygen depletions. These properties (surface abundances and mass) are typical of Wolf-Rayet stars, although the spectral type is ON9.7V. The luminosity of the secondary is consistent with that of core He-burning objects. The preferred, tentative evolutionary scenario to explain abe observed properties involves mass transfer from the secondary - which was initially more massive- towards the primary. The secondary is now almost a core He-burning object, probably with only a thin envelope of H-rich and CNO processed material. A very inefficient mass transfer is necessary to explain the chemical appearance of the primary. Alternative scenarios are discussed but they are affected by greater uncertainties.

  12. Atomic resolution imaging of the two-component Dirac-Landau levels in a gapped graphene monolayer

    NASA Astrophysics Data System (ADS)

    Wang, Wen-Xiao; Yin, Long-Jing; Qiao, Jia-Bin; Cai, Tuocheng; Li, Si-Yu; Dou, Rui-Fen; Nie, Jia-Cai; Wu, Xiaosong; He, Lin

    2015-10-01

    The wave function of Dirac fermions is a two-component spinor. In graphene, a one-atom-thick film showing two-dimensional Dirac-like electronic excitations, the two-component representation, reflects the amplitude of the electron wave function on the A and B sublattices. This unique property provides unprecedented opportunities to image the two components of Dirac fermions spatially. Here, we report atomic resolution imaging of two-component Dirac-Landau levels in gapped graphene monolayers by scanning tunneling microscopy and spectroscopy. A gap of about 20 meV, driven by inversion symmetry breaking by the substrate potential, is observed in the graphene sheets on both SiC and graphite substrates. Such a gap splits the n =0 Landau level (LL) into two levels, 0+ and 0-. We demonstrate that the amplitude of the wave function of the 0+ LL is mainly on the A sites and that of the 0- LL is mainly on the B sites of graphene, characterizing the internal structure of the spinor of the n =0 LL. This provides direct evidence of the two-component nature of Dirac fermions.

  13. A Principle of Corresponding States for Two-Component, Self-Gravitating Fluids

    NASA Astrophysics Data System (ADS)

    Caimmi, R.

    2010-06-01

    Macrogases are defined as two-component, large-scale celestial objects where the subsystems interact only via gravitation. The macrogas equation of state is formulated and compared to the van der Waals (VDW) equation of state for ordinary gases. By analogy, it is assumed that real macroisothermal curves in macrogases occur as real isothermal curves in ordinary gases, where a phase transition (vapour-liquid observed in ordinary gases and gas-stars assumed in macrogases) takes place along a horizontal line in the macrovolume-macropressure (O X_{V} X_{p}) plane. The intersections between real and theoretical (deduced from the equation of state) macroisothermal curves, make two regions of equal surface as for ordinary gases obeying the VDW equation of state. A numerical algorithm is developed for determining the following points of a selected theoretical macroisothermal curve on the (O X_{V} X_{p}) plane: the three intersections with the related real macroisothermal curve, and the two extremum points (one maximum and one minimum). Different kinds of macrogases are studied in detail: UU, where U density profiles are flat, to be conceived as a simple guidance case; HH, where H density profiles obey the Hernquist (1990) law, which satisfactorily fits the observed spheroidal components of galaxies; HN/NH, where N density profiles obey the Navarro-Frenk-White (1995, 1996, 1997) law, which satisfactorily fits the simulated nonbaryonic dark matter haloes. A different trend is shown by theoretical macroisothermal curves on the (O X_{V} X_{p}) plane, according to whether density profiles are sufficiently mild (UU) or sufficiently steep (HH, HN/NH). In the former alternative, no critical macroisothermal curve exists, below or above which the trend is monotonous. In the latter alternative, a critical macroisothermal curve exists, as shown by VDW gases, where the critical point may be defined as the horizontal inflexion point. In any case, by analogy with VDW gases, the first

  14. Screening of an electrically charged particle in a two-dimensional two-component plasma at Γ = 2

    NASA Astrophysics Data System (ADS)

    Ferrero, Alejandro; Téllez, Gabriel

    2014-11-01

    We consider the thermodynamic effects of an electrically charged impurity immersed in a two-dimensional two-component plasma, composed of particles with charges ±e, at temperature T, at coupling Γ = e2/(kBT) = 2, confined in a large disk of radius R. In particular, we focus on the analysis of the charge density, the correlation functions and the grand potential. Our analytical results show how the charges are redistributed in the circular geometry considered here. When we consider a positively charged impurity, the negative ions accumulate close to the impurity leaving an excess of positive charge that accumulates at the boundary of the disk. Due to the symmetry under charge exchange, the opposite effect takes place when we place a negative impurity. Both cases in which the impurity charge is an integer multiple of the particle charges in the plasma, ±e, and where a fraction of them are considered, require a slightly different mathematical treatment, showing the effect of the quantization of plasma charges. The bulk and the tension effects in the plasma described by the grand potential are not modified by the introduction of the charged particle. Apart from the effects due to the collapse coming from the attraction between oppositely charged ions, an additional topological term appears in the grand potential, proportional to -n2 ln(mR), with n the dimensionless charge of the particle. This term modifies the central charge of the system, from c = 1 to c = 1 - 6n2, when considered in the context of conformal field theories.

  15. Five new Fast Radio Bursts from the HTRU high latitude survey at Parkes: first evidence for two-component bursts

    NASA Astrophysics Data System (ADS)

    Champion, D. J.; Petroff, E.; Kramer, M.; Keith, M. J.; Bailes, M.; Barr, E. D.; Bates, S. D.; Bhat, N. D. R.; Burgay, M.; Burke-Spolaor, S.; Flynn, C. M. L.; Jameson, A.; Johnston, S.; Ng, C.; Levin, L.; Possenti, A.; Stappers, B. W.; van Straten, W.; Thornton, D.; Tiburzi, C.; Lyne, A. G.

    2016-04-01

    The detection of five new fast radio bursts (FRBs) found in the 1.4-GHz High Time Resolution Universe high latitude survey at Parkes, is presented. The rate implied is 7^{+5}_{-3}× 10^3 (95%) FRBs sky-1 day-1 above a fluence of 0.13 Jy ms for an FRB of 0.128 ms duration to 1.5 Jy ms for 16 ms duration. One of these FRBs has a two-component profile, in which each component is similar to the known population of single component FRBs and the two components are separated by 2.4 ± 0.4 ms. All the FRB components appear to be unresolved following deconvolution with a scattering tail and accounting for intra-channel smearing. The two-component burst, FRB 121002, also has the highest dispersion measure (1629 pc cm-3) of any FRB to-date. Many of the proposed models to explain FRBs use a single high energy event involving compact objects (such as neutron star mergers) and therefore cannot easily explain a two-component FRB. Models that are based on extreme versions of flaring, pulsing or orbital events however could produce multiple component profiles. The compatibility of these models and the FRB rate implied by these detections is discussed.

  16. Anaerobically controlled expression system derived from the arcDABC operon of Pseudomonas aeruginosa: application to lipase production.

    PubMed Central

    Winteler, H V; Schneidinger, B; Jaeger, K E; Haas, D

    1996-01-01

    The anaerobically inducible arcDABC operon encodes the enzymes of the arginine deiminase pathway in Pseudomonas aeruginosa. Upon induction, the arcAB mRNAs and proteins reach high intracellular levels, because of a strong anaerobically controlled promoter and mRNA processing in arcD, leading to stable downstream transcripts. We explored the usefulness of this system for the construction of expression vectors. The lacZ gene of Escherichia coli was expressed to the highest levels when fused close to the arc promoter. Insertion of lacZ further downstream into arcA or arcB did not stabilize the intrinsically unstable lacZ mRNA. On the contrary, lacZ mRNA appeared to be a vulnerable endonuclease target destabilizing arcAB mRNAs in the 5'-to-3' direction in P. aeruginosa. The native arc promoter was modified for optional expression in the -10 sequence and in the -40 region, which is a binding site for the anaerobic regulator ANR. In P. aeruginosa grown either anaerobically or with oxygen limitation in unshaken cultures, this promoter was stronger than the induced tac promoter. The P. aeruginosa lipAH genes, which encode extracellular lipase and lipase foldase, respectively, were fused directly to the modified arc promoter in an IncQ vector plasmid. Semianaerobic static cultures of P. aeruginosa PAO1 carrying this recombinant plasmid overproduced extracellular lipase 30-fold during stationary phase compared with the production by strain PAO1 without the plasmid. Severe oxygen limitation, in contrast, resulted in poor lipase productivity despite effective induction of the ANR-dependent promoter, suggesting that secretion of active lipase is blocked by the absence of oxygen. In conclusion, the modified arc promoter is useful for driving the expression of cloned genes in P. aeruginosa during oxygen-limited growth and stationary phase. PMID:8795231

  17. Bose–Einstein condensation in a two-component Bose gas with harmonic oscillator interaction

    NASA Astrophysics Data System (ADS)

    Abulseoud, A. A.; Abbas, A. H.; Galal, A. A.; El-Sherbini, Th M.

    2016-07-01

    In this article a system containing two species of identical bosons interacting via a harmonic oscillator potential is considered. It is assumed that the number of bosons of each species is the same and that bosons belonging to the same species repel each other while those belonging to different species attract. The Hamiltonian is diagonalized and the energy spectrum of the system is written down. The behaviour of the system in the thermodynamic limit is studied within the framework of the grand canonical ensemble, and thermodynamic parameters, such as the internal energy, entropy and specific heat capacity are calculated. It is shown that the system exhibits a single species Bose–Einstein condensation when the coupling strengths are equal and a dual species condensation when they are different.

  18. Two-Component Signaling Regulates Osmotic Stress Adaptation via SskA and the High-Osmolarity Glycerol MAPK Pathway in the Human Pathogen Talaromyces marneffei.

    PubMed

    Boyce, Kylie J; Cao, Cunwei; Andrianopoulos, Alex

    2016-01-01

    For successful infection to occur, a pathogen must be able to evade or tolerate the host's defense systems. This requires the pathogen to first recognize the host environment and then signal this response to elicit a complex adaptive program in order to activate its own defense strategies. In both prokaryotes and eukaryotes, two-component signaling systems are utilized to sense and respond to changes in the external environment. The hybrid histidine kinases (HHKs) at the start of the two-component signaling pathway have been well characterized in human pathogens. However, how these HHKs regulate processes downstream currently remains unclear. This study describes the role of a response regulator downstream of these HHKs, sskA, in Talaromyces marneffei, a dimorphic human pathogen. sskA is required for asexual reproduction, hyphal morphogenesis, cell wall integrity, osmotic adaptation, and the morphogenesis of yeast cells both in vitro at 37°C and during macrophage infection, but not during dimorphic switching. Comparison of the ΔsskA mutant with a strain in which the mitogen-activated protein kinase (MAPK) of the high-osmolarity glycerol pathway (SakA) has been deleted suggests that SskA acts upstream of this pathway in T. marneffei to regulate these morphogenetic processes. This was confirmed by assessing the amount of phosphorylated SakA in the ΔsskA mutant, antifungal resistance due to a lack of SakA activation, and the ability of a constitutively active sakA allele (sakA(F316L) ) to suppress the ΔsskA mutant phenotypes. We conclude that SskA regulates morphogenesis and osmotic stress adaptation in T. marneffei via phosphorylation of the SakA MAPK of the high-osmolarity glycerol pathway. IMPORTANCE This is the first study in a dimorphic fungal pathogen to investigate the role of a response regulator downstream of two-component signaling systems and its connection to the high-osmolarity glycerol pathway. This study will inspire further research into the

  19. Two-Component Signaling Regulates Osmotic Stress Adaptation via SskA and the High-Osmolarity Glycerol MAPK Pathway in the Human Pathogen Talaromyces marneffei

    PubMed Central

    Cao, Cunwei; Andrianopoulos, Alex

    2016-01-01

    ABSTRACT For successful infection to occur, a pathogen must be able to evade or tolerate the host’s defense systems. This requires the pathogen to first recognize the host environment and then signal this response to elicit a complex adaptive program in order to activate its own defense strategies. In both prokaryotes and eukaryotes, two-component signaling systems are utilized to sense and respond to changes in the external environment. The hybrid histidine kinases (HHKs) at the start of the two-component signaling pathway have been well characterized in human pathogens. However, how these HHKs regulate processes downstream currently remains unclear. This study describes the role of a response regulator downstream of these HHKs, sskA, in Talaromyces marneffei, a dimorphic human pathogen. sskA is required for asexual reproduction, hyphal morphogenesis, cell wall integrity, osmotic adaptation, and the morphogenesis of yeast cells both in vitro at 37°C and during macrophage infection, but not during dimorphic switching. Comparison of the ΔsskA mutant with a strain in which the mitogen-activated protein kinase (MAPK) of the high-osmolarity glycerol pathway (SakA) has been deleted suggests that SskA acts upstream of this pathway in T. marneffei to regulate these morphogenetic processes. This was confirmed by assessing the amount of phosphorylated SakA in the ΔsskA mutant, antifungal resistance due to a lack of SakA activation, and the ability of a constitutively active sakA allele (sakAF316L) to suppress the ΔsskA mutant phenotypes. We conclude that SskA regulates morphogenesis and osmotic stress adaptation in T. marneffei via phosphorylation of the SakA MAPK of the high-osmolarity glycerol pathway. IMPORTANCE This is the first study in a dimorphic fungal pathogen to investigate the role of a response regulator downstream of two-component signaling systems and its connection to the high-osmolarity glycerol pathway. This study will inspire further research into

  20. Direct-View Multi-Point Two-Component Interferometric Rayleigh Scattering Velocimeter

    NASA Technical Reports Server (NTRS)

    Bivolaru, Daniel; Danehy, Paul M.; Gaffney, Richard L., Jr.; Cutler, Andrew D.

    2008-01-01

    This paper describes an instantaneous velocity measurement system based on the Doppler shift of elastically scattered laser light from gas molecules (Rayleigh scattering) relative to an incident laser. The system uses a pulsed laser as the light source, direct-viewing optics to collect the scattered light, an interferometer to analyze spectrally the scattered light mixed with the incident laser light, and a CCD camera to capture the resulting interferogram. The system is capable of simultaneous, spatially (approximately 0.2 mm(exp 3)) and temporally (approximately 40 ns) resolved, multiple point measurements of two orthogonal components of flow velocity in the presence of background scattered light, acoustic noise and vibrations, and flow particulates. Measurements in a large-scale axi-symmetric Mach 1.6 H2-air combustion-heated jet running at a flow sensible enthalpy specific to Mach 5.5 hypersonic flight are performed to demonstrate the technique. The measurements are compared with CFD calculations using a finite-volume discretization of the Favre-averaged Navier-Stokes equations (VULCAN code).

  1. A high-resolution study of surfactant partitioning and kinetic limitations for two-component internally mixed aerosols

    NASA Astrophysics Data System (ADS)

    Suda, S. R.; Petters, M. D.

    2013-12-01

    Atmospheric aerosols serve as cloud condensation nuclei (CCN), altering cloud properties and ultimately affecting climate through their effect on the radiative balance. Aerosol CCN activity depends in part on aerosol composition and surfactant compounds are of particular interest because surfactants are enriched at the water/air interface, resulting in a radial concentration gradient within the aqueous droplet. Accurate treatment of the surfactant concentration gradient complicates the otherwise straightforward predictions of CCN activity for aerosols of known composition. To accurately evaluate predictions made by theory, laboratory studies investigating the relationship between critical supersaturation and dry diameter of particles that include surfactants require significant reduction in measurement uncertainty for both water-uptake and CCN measurements. Furthermore, uncertainties remain regarding kinetic limitations to surfactant partitioning that could result in deviation from predictions based on equilibrium thermodynamics. This study attempts to address some of these issues through high-resolution analysis of CCN activity of two-component mixed surfactant/non-surfactant aerosols at different internal mixing ratios performed with and without a water-uptake time delay to ascertain whether or not the observed effects are kinetically limited. We present new data for the aerosols consisting of 1) the ionic surfactant sodium dodecyl sulfate (SDS) with ammonium sulfate, 2) SDS with sodium chloride and 3) the strong non-ionic fluorosurfactant Zonyl with an organic proxy glucose. As a point of reference we also evaluated the mixture of ammonium sulfate with glucose. Aerosol activation diameters were determined using CCN analysis in conjunction with scanning mobility size classification and high sheath-to-aerosol flow ratios. This resulted in CCN-derived kappa values that could be determined within +/-5% relative error. To test whether dynamic surfactant partitioning

  2. Spatially resolved imaging of the two-component η Crv debris disk with Herschel

    SciTech Connect

    Duchêne, G.; Arriaga, P.; Kalas, P.; Wyatt, M.; Kennedy, G.; Sibthorpe, B.; Lisse, C.; Holland, W.; Wisniewski, J.; Clampin, M.; Pinte, C.; Booth, M.; Horner, J.; Matthews, B.; Greaves, J.

    2014-04-01

    We present far-infrared and submillimeter images of the η Crv debris disk system obtained with Herschel and SCUBA-2, as well as Hubble Space Telescope visible and near-infrared coronagraphic images. In the 70 μm Herschel image, we clearly separate the thermal emission from the warm and cold belts in the system, find no evidence for a putative dust population located between them, and precisely determine the geometry of the outer belt. We also find marginal evidence for azimuthal asymmetries and a global offset of the outer debris ring relative to the central star. Finally, we place stringent upper limits on the scattered light surface brightness of the outer ring. Using radiative transfer modeling, we find that it is impossible to account for all observed properties of the system under the assumption that both rings contain dust populations with the same properties. While the outer belt is in reasonable agreement with the expectations of steady-state collisional cascade models, albeit with a minimum grain size that is four times larger than the blow-out size, the inner belt appears to contain copious amounts of small dust grains, possibly below the blow-out size. This suggests that the inner belt cannot result from a simple transport of grains from the outer belt and rather supports a more violent phenomenon as its origin. We also find that the emission from the inner belt has not declined over three decades, a much longer timescale than its dynamical timescale, which indicates that the belt is efficiently replenished.

  3. Dark-dark solitons and modulational instability in miscible two-component Bose-Einstein condensates

    SciTech Connect

    Hoefer, M. A.; Chang, J. J.; Hamner, C.; Engels, P.

    2011-10-15

    We investigate the dynamics of two miscible superfluids experiencing fast counterflow in a narrow channel. The superfluids are formed by two distinguishable components of a trapped dilute-gas Bose-Einstein condensate (BEC). The onset of counterflow-induced modulational instability throughout the cloud is observed and shown to lead to the proliferation of dark-dark vector solitons. These solitons do not exist in single-component systems, exhibit intriguing beating dynamics, and can experience a transverse instability leading to vortex line structures. Experimental results and multidimensional numerical simulations are presented.

  4. Noncommutative Path Integral for Spinless Relativistic Equation in the Two-Component Theory

    NASA Astrophysics Data System (ADS)

    Benzair, H.; Merad, M.; Boudjedaa, T.

    2013-09-01

    In this paper, we have constructed the Green function of the Feshbach-Villars (FV) spinless particle in a noncommutative (NC) phase-space coordinates, where the Pauli matrices describing the charge symmetry are replaced by the Grassmannian odd variables. Subsequently, for the perform calculations, we diagonalize the Hamiltonian governing the dynamics of the system via the Foldy-Wouthuysen (FW) canonical transformation. The exact calculations have been done in the cases of free particle and magnetic field interaction. In both cases, the energy eigenvalues and their corresponding eigenfunctions are deduced.

  5. Correlated random walk on lattices. II. Tracer diffusion through a two-component dynamic background

    NASA Astrophysics Data System (ADS)

    Tahir-Kheli, R. A.

    1983-06-01

    A detailed calculation of frequency- and wave-vector-dependent correlation functions for an arbitrary tracer diffusing in a regular crystal against a background of hopping classical particles has recently been given by Tahir-Kheli and Elliott

    [Phys. Rev. B 27, 844 (1983)]
    . Here we present an important generalization of this work to a system with a dynamic background consisting of two arbitrary species of particles. In particular, the generalization includes a system where the tracer concentration itself is finite while an arbitrary concentration of other atoms is also present in the dynamic stream. The theory is exact to the leading nontrivial order in particle concentration xA and xB. In the intermediate-concentration regime, the theory incorporates dominant fluctuations from the mean field. The present model can serve to usefully describe incoherent neutron scattering in metal-hydride interstitial solutions such as MAxABxB with A,B≡H, D, and T and M≡Pd and Ti. Moreover, it can be used to treat tracer diffusion dynamics in nonstoichiometric metal oxides and, somewhat more simplistically, ionic conduction in the superionic state.

  6. Temporal Evolution of Photons Emerging out of Two Component Advective Disks

    NASA Astrophysics Data System (ADS)

    Chatterjee, Arka; Chakrabarti, Sandip Kumar; Ghosh, Himadri

    2016-07-01

    For outbursting cases, time lead and lag for hard photons to that of soft photons carries major information about the geometry of the system and the process that photons have undergone before they reach the detector. We construct a standard Keplerian disk as the source of soft photons which are Comptonized inside relativistic thick disks used as a proxy of the CENtrifugal BOundary supported Layer or CENBOL. Comptonization is computed by Monte-Carlo method. Finally, when the Comptonized photons leave the system and detected by a distant observer, their paths are guided by null geodesic equations. Time stamps on generated photons are put for different energy bands. We present difference of time in the arrival of soft photons to that of hard photons for various sizes of accretion disks. We compare our simulated results with the observational data available in literature. We also study the effects of inclination angle. Our aim is to develop a total time dependent outburst scenario to study the temporal properties of the observed photons.

  7. FRAN and RBF-PSO as two components of a hyper framework to recognize protein folds.

    PubMed

    Abbasi, Elham; Ghatee, Mehdi; Shiri, M E

    2013-09-01

    In this paper, an intelligent hyper framework is proposed to recognize protein folds from its amino acid sequence which is a fundamental problem in bioinformatics. This framework includes some statistical and intelligent algorithms for proteins classification. The main components of the proposed framework are the Fuzzy Resource-Allocating Network (FRAN) and the Radial Bases Function based on Particle Swarm Optimization (RBF-PSO). FRAN applies a dynamic method to tune up the RBF network parameters. Due to the patterns complexity captured in protein dataset, FRAN classifies the proteins under fuzzy conditions. Also, RBF-PSO applies PSO to tune up the RBF classifier. Experimental results demonstrate that FRAN improves prediction accuracy up to 51% and achieves acceptable multi-class results for protein fold prediction. Although RBF-PSO provides reasonable results for protein fold recognition up to 48%, it is weaker than FRAN in some cases. However the proposed hyper framework provides an opportunity to use a great range of intelligent methods and can learn from previous experiences. Thus it can avoid the weakness of some intelligent methods in terms of memory, computational time and static structure. Furthermore, the performance of this system can be enhanced throughout the system life-cycle. PMID:23930812

  8. Unstaggered-staggered solitons in two-component discrete nonlinear Schrödinger lattices

    NASA Astrophysics Data System (ADS)

    Malomed, Boris A.; Kaup, D. J.; van Gorder, Robert A.

    2012-02-01

    We present stable bright solitons built of coupled unstaggered and staggered components in a symmetric system of two discrete nonlinear Schrödinger equations with the attractive self-phase-modulation nonlinearity, coupled by the repulsive cross-phase-modulation interaction. These mixed modes are of a “symbiotic” type, as each component in isolation may only carry ordinary unstaggered solitons. The results are obtained in an analytical form, using the variational and Thomas-Fermi approximations (VA and TFA), and the generalized Vakhitov-Kolokolov (VK) criterion for the evaluation of the stability. The analytical predictions are verified against numerical results. Almost all the symbiotic solitons are predicted by the VA quite accurately and are stable. Close to a boundary of the existence region of the solitons (which may feature several connected branches), there are broad solitons which are not well approximated by the VA and are unstable.

  9. The Intracellular Concentration of Acetyl Phosphate in Escherichia coli Is Sufficient for Direct Phosphorylation of Two-Component Response Regulators▿

    PubMed Central

    Klein, Adam H.; Shulla, Ana; Reimann, Sylvia A.; Keating, David H.; Wolfe, Alan J.

    2007-01-01

    Acetyl phosphate, the intermediate of the AckA-Pta pathway, acts as a global signal in Escherichia coli. Although acetyl phosphate clearly signals through two-component response regulators, it remains unclear whether acetyl phosphate acts as a direct phospho donor or functions through an indirect mechanism. We used two-dimensional thin-layer chromatography to measure the relative concentrations of acetyl phosphate, acetyl coenzyme A, ATP, and GTP over the course of the entire growth curve. We estimated that the intracellular concentration of acetyl phosphate in wild-type cells reaches at least 3 mM, a concentration sufficient to activate two-component response regulators via direct phosphoryl transfer. PMID:17545286

  10. Recovering four-component solutions by the inverse transformation of the infinite-order two-component wave functions

    SciTech Connect

    Barysz, Maria; Mentel, Lukasz; Leszczynski, Jerzy

    2009-04-28

    The two-component Hamiltonian of the infinite-order two-component (IOTC) theory is obtained by a unitary block-diagonalizing transformation of the Dirac-Hamiltonian. Once the IOTC spin orbitals are calculated, they can be back transformed into four-component solutions. The transformed four component solutions are then used to evaluate different moments of the electron density distribution. This formally exact method may, however, suffer from certain approximations involved in its numerical implementation. As shown by the present study, with sufficiently large basis set of Gaussian functions, the Dirac values of these moments are fully recovered in spite of using the approximate identity resolution into eigenvectors of the p{sup 2} operator.

  11. Effects of transverse trapping on the ground state of a cigar-shaped two-component Bose—Einstein condensate

    NASA Astrophysics Data System (ADS)

    Cui, Guo-Dong; Sun, Jian-Fang; Jiang, Bo-Nan; Qian, Jun; Wang, Yu-Zhu

    2013-09-01

    We derive the coupled nonpolynomial nonlinear Schrödinger equations for a two-component Bose—Einstein condensate in a quasi-one-dimension geometry and investigate the effects of a tightly transverse trapping on the ground state and the miscibility—immiscibility threshold. We find that the density profile of the matter wavepacket is remarkably dependent on the transverse width and the effective one-dimension nonlinear coupling strengths in miscible and immiscible regimes.

  12. Approaching Phosphorescence Lifetimes in Solution: The Two-Component Polarizable-Embedding Approximate Coupled-Cluster Method.

    PubMed

    Krause, Katharina; Bauer, Mirko; Klopper, Wim

    2016-06-14

    Theoretical description of phosphorescence lifetimes in the condensed phase requires a method that takes into account both spin-orbit coupling and solvent-solute interactions. To obtain such a method, we have coupled our recently developed two-component coupled-cluster method with singles and approximated doubles to a polarizable environment. With this new method, we investigate how different solvents effect the electronic phosphorescence energies and lifetimes of 4H-pyran-4-thione. PMID:27158835

  13. Rabi-coupled two-component Bose-Einstein condensates: Classification of the ground states, defects, and energy estimates

    NASA Astrophysics Data System (ADS)

    Aftalion, Amandine; Mason, Peter

    2016-08-01

    We classify the ground states and topological defects of two-component Bose-Einstein condensates under the effect of internal coherent Rabi coupling. We present numerical phase diagrams which show the boundaries between symmetry-breaking components and various vortex patterns (triangular, square, bound state between vortices). We estimate the Rabi energy in the Thomas-Fermi limit which allows us to have an analytical description of the point energy leading to the formation of the various vortex patterns.

  14. A comparative experimental evaluation of uncertainty estimation methods for two-component PIV

    NASA Astrophysics Data System (ADS)

    Boomsma, Aaron; Bhattacharya, Sayantan; Troolin, Dan; Pothos, Stamatios; Vlachos, Pavlos

    2016-09-01

    Uncertainty quantification in planar particle image velocimetry (PIV) measurement is critical for proper assessment of the quality and significance of reported results. New uncertainty estimation methods have been recently introduced generating interest about their applicability and utility. The present study compares and contrasts current methods, across two separate experiments and three software packages in order to provide a diversified assessment of the methods. We evaluated the performance of four uncertainty estimation methods, primary peak ratio (PPR), mutual information (MI), image matching (IM) and correlation statistics (CS). The PPR method was implemented and tested in two processing codes, using in-house open source PIV processing software (PRANA, Purdue University) and Insight4G (TSI, Inc.). The MI method was evaluated in PRANA, as was the IM method. The CS method was evaluated using DaVis (LaVision, GmbH). Utilizing two PIV systems for high and low-resolution measurements and a laser doppler velocimetry (LDV) system, data were acquired in a total of three cases: a jet flow and a cylinder in cross flow at two Reynolds numbers. LDV measurements were used to establish a point validation against which the high-resolution PIV measurements were validated. Subsequently, the high-resolution PIV measurements were used as a reference against which the low-resolution PIV data were assessed for error and uncertainty. We compared error and uncertainty distributions, spatially varying RMS error and RMS uncertainty, and standard uncertainty coverages. We observed that qualitatively, each method responded to spatially varying error (i.e. higher error regions resulted in higher uncertainty predictions in that region). However, the PPR and MI methods demonstrated reduced uncertainty dynamic range response. In contrast, the IM and CS methods showed better response, but under-predicted the uncertainty ranges. The standard coverages (68% confidence interval) ranged from

  15. Phase equilibria in DOPC/DPPC: Conversion from gel to subgel in two component mixtures.

    PubMed

    Schmidt, Miranda L; Ziani, Latifa; Boudreau, Michelle; Davis, James H

    2009-11-01

    Biological membranes contain a mixture of phospholipids with varying degrees of hydrocarbon chain unsaturation. Mixtures of long chain saturated and unsaturated lipids with cholesterol have attracted a lot of attention because of the formation of two coexisting fluid bilayer phases in such systems over a broad range of temperature and composition. Interpretation of the phase behavior of such ternary mixtures must be based on a thorough understanding of the phase behavior of the binary mixtures formed with the same components. This article describes the phase behavior of mixtures of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) with 1,2-di-d(31)-palmitoyl-sn-glycero-3-phosphocholine (DPPC) between -20 and 50 degrees C. Particular attention has been paid to the phase coexistence below about 16 degrees C where the subgel phase appears. The changes in the shape of the spectrum (and its spectral moments) during the slow transformation process leads to the conclusion that below 16 degrees C the gel phase is metastable and the gel component of the two-phase mixture slowly transforms to the subgel phase with a slightly different composition. This results in a line of three-phase coexistence near 16 degrees C. Analysis of the transformation of the metastable gel domains into the subgel phase using the nucleation and growth model shows that the subgel domain growth is a two dimensional process. PMID:19895044

  16. Fourth Moment Sum Rule for the Charge Correlations of a Two-Component Classical Plasma

    NASA Astrophysics Data System (ADS)

    Alastuey, Angel; Fantoni, Riccardo

    2016-05-01

    We consider an ionic fluid made with two species of mobile particles carrying either a positive or a negative charge. We derive a sum rule for the fourth moment of equilibrium charge correlations. Our method relies on the study of the system response to the potential created by a weak external charge distribution with slow spatial variations. The induced particle densities, and the resulting induced charge density, are then computed within density functional theory, where the free energy is expanded in powers of the density gradients. The comparison with the predictions of linear response theory provides a thermodynamical expression for the fourth moment of charge correlations, which involves the isothermal compressibility as well as suitably defined partial compressibilities. The familiar Stillinger-Lovett condition is also recovered as a by-product of our method, suggesting that the fourth moment sum rule should hold in any conducting phase. This is explicitly checked in the low density regime, within the Abe-Meeron diagrammatical expansions. Beyond its own interest, the fourth-moment sum rule should be useful for both analyzing and understanding recently observed behaviours near the ionic critical point.

  17. VLT spectroscopy of XTE J2123-058 during quiescence: the masses of the two components

    NASA Astrophysics Data System (ADS)

    Casares, J.; Dubus, G.; Shahbaz, T.; Zurita, C.; Charles, P. A.

    2002-01-01

    We present Very Large Telescope (VLT) low-resolution spectroscopy of the neutron star X-ray transient XTE J2123-058 during its quiescent state. Our data reveal the presence of a K7V companion which contributes 77 per cent to the total flux at λ6300 and orbits the neutron star at K2=287+/-12kms-1. Contrary to other soft X-ray transients (SXTs), the Hα emission is almost exactly in antiphase with the velocity curve of the optical companion. Using the light-centre technique we obtain K1=140+/-27kms-1 and hence q=K1/K2=M2/M1=0.49+/-0.10. This, combined with a previous determination of the inclination angle (i=73°+/-4°) yields M1=1.55+/-0.31Msolar and M2=0.76+/-0.22Msolar. M2 agrees well with the observed spectral type. Doppler tomography of the Hα emission shows a non-symmetric accretion disc distribution mimicking that seen in SW Sex stars. Although we find a large systemic velocity of - 110+/-8kms-1 this value is consistent with the galactic rotation velocity at the position of J2123-058, and hence a halo origin. The formation scenario of J2123-058 is still unresolved.

  18. Solvation effects with a photoresponsive two-component 12-hydroxystearic acid-azobenzene additive organogel.

    PubMed

    Delbecq, Frederic; Kaneko, Nobuhiro; Endo, Hiroshi; Kawai, Takeshi

    2012-10-15

    A "light-triggerable" azobenzene amine derivative (additive 1) was synthesized and then introduced into organogels of 12-hydroxystearic acid (HSA) in the molar ratio of 1:3. The organogels (HSA/1) consisting of additive 1 and HSA were analyzed by (1)H nuclear magnetic resonance (NMR), Fourier transform-infrared (FT-IR), and X-ray diffraction (XRD). The homogeneity of the gel networks was observed using field emission scanning electron microscopy (FE-SEM). Additive 1 formed a complex with HSA in HSA organogels due to salification between the terminal amine group of additive 1 and the carboxylic acid group of HSA. Additive 1 in the gels of HSA/1 showed the potential for photo-isomerization, and we achieved a reversible control of HSA/1 sol-gel transition in toluene by the alternating irradiation with UV and visible light. Interestingly, the opposite phenomenon was observed in CHCl(3) system, namely, the orange solution of HSA/1 in CHCl(3) was turned to a red-transparent gel by exposure to UV light. PMID:22819394

  19. A two-component volatile atmosphere for Pluto. I. The bulk