bluuebunny/crossref_metadata_2025 huggingface dataset:
Cell volume homeostatic mechanisms: effectors and signalling pathways
Authors: Hoffmann E. K. , Pedersen S. F.
Published: September 2010

Cell volume homeostasis and its fine‐tuning to the specific physiological context at any given moment are processes fundamental to normal cell function. The understanding of cell volume regulation owes much to August Krogh, yet has advanced greatly over the last decades. In this review, we outline the historical context of studies of cell volume regulation, focusing on the lineage started by Krogh, Bodil Schmidt‐Nielsen, Hans‐Henrik Ussing, and their students. The early work was focused on understanding the functional behaviour, kinetics and thermodynamics of the volume‐regulatory ion transport mechanisms. Later work addressed the mechanisms through which cellular signalling pathways regulate the volume regulatory effectors or flux pathways. These studies were facilitated by the molecular identification of most of the relevant channels and transporters, and more recently also by the increased understanding of their structures. Finally, much current research in the field focuses on the most up‐ and downstream components of these paths: how cells sense changes in cell volume, and how cell volume changes in turn regulate cell function under physiological and pathophysiological conditions.
Most Influential Parameters for the Bed‐Load Sediment Flux Equations Used in Alluvial Rivers1
Authors: Khorram Saeed , Ergil Mustafa
Published: September 2010

Khorram, Saeed and Mustafa Ergil, 2010. Most Influential Parameters for the Bed‐Load Sediment Flux Equations Used in Alluvial Rivers. Journal of the American Water Resources Association (JAWRA): 46(6):1065–1090. DOI: 10.1111/j.1752‐1688.2010.00468.x

Abstract:  Problems of bed‐load sediment transport equations in alluvial rivers are addressed in this study where user‐friendly parameters were developed. To determine the influences of 300 parameters on the final result, 52 selected bed‐load equations for noncohesive particles (sand and gravel separately) were gathered and individually investigated. The influences of discrepancies among the computed and measured datasets were obtained by sensitivity analysis through multilinear regression method. The most influential parameters for the bed‐load sediment flux equations used to describe sand particles in alluvial rivers are: the gravitational power due to Shields’ parameter with an energy slope, the universal stream power due to critical Shields’ parameter with an energy slope, the Shields’ parameter ratio, the critical unit stream power, and the Shields’ parameter with energy slope. For gravel particles, the most influential parameters are: the universal stream power due to critical Shields’ parameter with an energy slope, the Shields’ parameter ratio, the gravitational power due to Shields’ parameter with an energy slope, the Shields’ parameter with an energy slope, and the Froude number of the channel. It is expected that researchers working in this field will be able to use these predicted parameters to generate new bed‐load sediment flux equations that give results that more closely agree with the actual values measured in alluvial rivers.
Permanent Genetic Resources added to Molecular Ecology Resources Database 1 June 2010 – 31 July 2010
Authors:   Molecular Ecology Resources Primer Development Consortium, ANDRIS MALVINA , ARADOTTIR GUDBJORG I. , ARNAU G. , AUDZIJONYTE ASTA , BESS EMILIE C. , BONADONNA FRANCESCO , BOURDEL G. , BRIED JOËL , BUGBEE GREGORY J. , BURGER P. A. , CHAIR H. , CHARRUAU P. C. , CIAMPI A. Y. , COSTET L. , DeBARRO PAUL J. , DELATTE H. , DUBOIS MARIE‐PIERRE , ELDRIDGE MARK D. B. , ENGLAND PHILLIP R. , ENKHBILEG D. , FARTEK B. , GARDNER MICHAEL G. , GRAY KAREN‐ANN , GUNASEKERA RASANTHI M. , HANLEY STEVEN J. , HAVIL NATHAN , HEREWARD JAMES P. , HIRASE SHOTARO , HONG YAN , JARNE PHILIPPE , JIANFEI QI , JOHNSON REBECCA N. , KANNO MANAMI , KIJIMA AKIHIRO , KIM HYUN C. , KIM KWAN S. , KIM WOO‐JIN , LaRUE ELIZABETH , LEE JANG W. , LEE JEONG‐HO , LI CHUNHONG , LIAO MINGHUI , LO NATHAN , LOWE ANDREW J. , MALAUSA THIBAUT , MALÉ PIERRE‐JEAN G. , MARKO MICHELLE D. , MARTIN JEAN‐FRANÇOIS , MESSING RUSSELL , MILLER KAREN J. , MIN BYEONG‐WHA , MYEONG JEONG‐IN , NIBOUCHE S. , NOACK ANN E. , NOH JAE K. , ORIVEL JÉRÔME , PARK CHOUL‐JI , PETRO D. , PRAPAYOTIN‐RIVEROS KITTIPATH , QUILICHINI ANGÉLIQUE , REYNAUD B. , RIGINOS CYNTHIA , RISTERUCCI A. M. , ROSE HARLEY A. , SAMPAIO I. , SILBERMAYR K. , SILVA M. B. , TERO N. , THUM RYAN A. , VINSON C. C. , VORSINO ADAM , VOSSBRINCK CHARLES R. , WALZER C. , WHITE JASON C. , WIECZOREK ANIA , WRIGHT MARK
Published: September 2010

This article documents the addition of 205 microsatellite marker loci to the Molecular Ecology Resources Database. Loci were developed for the following species: Bagassa guianensis, Bulweria bulwerii, Camelus bactrianus, Chaenogobius annularis, Creontiades dilutus, Diachasmimorpha tryoni, Dioscorea alata, Euhrychiopsis lecontei, Gmelina arborea, Haliotis discus hannai, Hirtella physophora, Melanaphis sacchari, Munida isos, Thaumastocoris peregrinus and Tuberolachnus salignus. These loci were cross‐tested on the following species: Halobaena caerulea, Procellaria aequinoctialis, Oceanodroma monteiroi, Camelus ferus, Creontiades pacificus, Dioscorea rotundata, Dioscorea praehensilis, Dioscorea abyssinica, Dioscorea nummularia, Dioscorea transversa, Dioscorea esculenta, Dioscorea pentaphylla, Dioscorea trifida, Hirtella bicornis, Hirtella glandulosa, Licania alba, Licania canescens, Licania membranaceae, Couepia guianensis and 7 undescribed Thaumastocoris species.
Uniqueness of MoravaK-theory
Authors: Angeltveit Vigleik
Published: September 2010

We show that there is an essentially uniqueS-algebra structure on the MoravaK-theory spectrumK(n), whileK(n) has uncountably manyMUor$\widehat {E(n)}$-algebra structures. Here$\widehat {E(n)}$is theK(n)-localized Johnson–Wilson spectrum. To prove this we set up a spectral sequence computing the homotopy groups of the moduli space ofA∞structures on a spectrum, and use the theory ofS-algebrak-invariants for connectiveS-algebras found in the work of Dugger and Shipley [Postnikov extensions of ring spectra, Algebr. Geom. Topol.6(2006), 1785–1829 (electronic)] to show that all the uniqueness obstructions are hit by differentials.
Topological complexity of collision-free motion planning on surfaces
Authors: Cohen Daniel C. , Farber Michael
Published: September 2010

The topological complexity$\mathsf {TC}(X)$is a numerical homotopy invariant of a topological spaceXwhich is motivated by robotics and is similar in spirit to the classical Lusternik–Schnirelmann category ofX. Given a mechanical system with configuration spaceX, the invariant$\mathsf {TC}(X)$measures the complexity of motion planning algorithms which can be designed for the system. In this paper, we compute the topological complexity of the configuration space ofndistinct ordered points on an orientable surface, for both closed and punctured surfaces. Our main tool is a theorem of B. Totaro describing the cohomology of configuration spaces of algebraic varieties. For configuration spaces of punctured surfaces, this is used in conjunction with techniques from the theory of mixed Hodge structures.
A Finite Element Method for Three-Dimensional Analysis of Thermo-acoustic Combustion Instability
Authors: Camporeale S. M. , Fortunato B. , Campa G.
Published: September 2010

A method for predicting the onset of acoustically driven combustion instabilities in gas turbine combustor is examined. The basic idea is that the governing equations of the acoustic waves can be coupled with a flame heat release model and solved in the frequency domain. The paper shows that a complex eigenvalue problem is obtained that can be solved numerically by implementing the governing equations in a finite element code. This procedure allows one to identify the frequencies at which thermo-acoustic instabilities are expected and the growth rate of the pressure oscillations, at the onset of instability, when the hypothesis of linear behavior of the acoustic waves can be applied. The method can be applied virtually to any three-dimensional geometry, provided the necessary computational resources that are, anyway, much less than those required by computational fluid dynamics methods proposed for analyzing the combustion chamber under instability condition. Furthermore, in comparison with the “lumped” approach that characterizes popular acoustics networks, the proposed method allows one for much more flexibility in defining the geometry of the combustion chamber. The paper shows that different types of heat release laws, for instance, heat release concentrated in a flame sheet, as well as distributed in a larger domain, can be adopted. Moreover, experimentally or numerically determined flame transfer functions, giving the response of heat release to acoustic velocity fluctuations, can be incorporated in the model. To establish proof of concept, the method is validated at the beginning against simple test cases taken from literature. Over the frequency range considered, frequencies and growth rates both of stable and unstable eigenmodes are accurately evaluated. Then the method is applied to a much more complex annular combustor geometry in order to evaluate frequencies and growth rates of the unstable modes and to show how the variation in the parameters of the heat release law can influence the transition to instability.
The Effects of Diesel Injector Needle Motion on Spray Structure
Authors: Powell C. F. , Kastengren A. L. , Liu Z. , Fezzaa K.
Published: September 2010

The internal structure of diesel fuel injectors is known to have a significant impact on the steady-state fuel distribution within the spray. However, little experimental or computational work has been performed on the dynamics of fuel injectors. Recent studies have shown that it is possible to measure the three-dimensional geometry of the injector nozzle, and to track changes in that geometry as the needle opens and closes in real time. This has enabled the dynamics of the injector to be compared with the dynamics of the spray, and allows computational fluid dynamics (CFD) simulations to use realistic time-dependent flow passage geometries. In this study, X-ray phase-enhanced imaging has been used to perform time-resolved imaging of the needle seat area in several common-rail diesel injection nozzles. The fuel distributions of the sprays emitted by these injectors were also studied with fast X-ray radiography. Correlations between eccentric motions of the injector needle valve and oscillations in the fuel density as it emerges from the nozzle are examined. CFD modeling is used to interpret the effect of needle motion on fuel flow.
Nonlinear Contact Analysis of Different API Line Pipe Coupling Modifications
Authors: Van Wittenberghe Jeroen , De Baets Patrick , De Waele Wim
Published: September 2010

Threaded pipe couplings are used to join pipelines when they have to be uncoupled frequently or as an easy to assemble alternative to welding. A large variety of patented coupling modifications are available, but little is known about their influence on the connection’s behavior. In this study, the finite element model of an API line pipe threaded pipe connection is presented and its nonlinearities in material properties and contact behavior are discussed. Test results obtained from a four-point bending fatigue experiment are in good agreement with the results of the numerical simulations. A series of modifications of the standard connection are simulated to gain a better understanding in the influence of geometrical and material parameters on the connection’s performance. It was found that not all existing coupling modifications are improving the connection’s performance. It can be concluded that critical evaluation of the performance of existing coupling modifications is necessary and finite element analyses are proven to be a useful tool for this.
Measurement of Decompression Wave Speed in Rich Gas Mixtures at High Pressures (370 bars) Using a Specialized Rupture Tube
Authors: Botros K. K. , Geerligs J. , Eiber R. J.
Published: September 2010

Measurements of decompression wave speed in conventional and rich natural gas mixtures following rupture of a high-pressure pipe have been conducted. A high-pressure stainless steel rupture tube (internal diameter=38.1 mm and 42 m long) has been constructed and instrumented with 16 high frequency-response pressure transducers mounted very close to the rupture end and along the length of the tube to capture the pressure-time traces of the decompression wave. Tests were conducted for initial pressures of 33–37 MPa-a and a temperature range of 21–68°C. The experimentally determined decompression wave speeds were compared with both GASDECOM and PIPEDECOM predictions with and without nonequilibrium condensation delays at phase crossing. The interception points of the isentropes representing the decompression process with the corresponding phase envelope of each mixture were correlated with the respective plateaus observed in the decompression wave speed profiles. Additionally, speeds of sound in the undisturbed gas mixtures at the initial pressures and temperatures were compared with predictions by five equations of state, namely, BWRS, AGA-8, Peng–Robinson, Soave–Redlich–Kwong, and Groupe Européen de Recherches Gaziéres. The measured gas decompression curves were used to predict the fracture arrest toughness needed to assure fracture control in natural gas pipelines. The rupture tube test results have shown that the Charpy fracture arrest values predicted using GASEDCOM are within +7% (conservative) and −11% (nonconservative) of the rupture tube predicted values. Similarly, PIPEDECOM with no temperature delay provides fracture arrest values that are within +13% and −20% of the rupture tube predicted values, while PIPEDECOM with a 1°C temperature delay provides fracture arrest values that are within 0% and −20% of the rupture tube predicted values. Ideally, it would be better if the predicted values by the equations of state were above the rupture tube predicted values to make the predictions conservative but that was not always the case.
Damage Evolution and Life Prediction of a P91 Longitudinal Welded Tube Under Internal Pressure Creep
Authors: Ogata Takashi , Sakai Takayuki , Yaguchi Masatsugu
Published: September 2010

The clarification of creep damage mechanism and the establishment of remaining life prediction methods of longitudinal welded piping of P91 steel are important subjects to maintain a reliable operation of boilers in thermal power plants. Internal pressure creep tests were conducted on P91 steel longitudinal welded tubes to characterize the evolution of creep damage with time and to evaluate a life prediction method. Interrupted creep tests were performed for damage observation in addition to rupture tests. Three dimensional finite element creep analyses of the longitudinal welded tube specimens were conducted to identify the stress and creep strain distributions within the specimen during creep. Failure occurred at a heat affected zone (HAZ) without a significant macroscopic deformation. It was found that the initiation of creep voids had concentrated at the midthickness region in the HAZ rather than in the surface. The creep analysis results indicated that the triaxial tensile stress yielded at the midthickness region in the HAZ due to difference of creep deformation property among the base metal, the HAZ, and the weld metal. It was suggested that the triaxial stress state caused acceleration of the creep damage evolution in the HAZ, resulting in internal failure of the tube specimens. A rupture time prediction method of the welded tube is proposed based on the maximum principal stress and the triaxial stress factor in the HAZ. The void growth behavior in the HAZ was well predicted by the previously proposed void growth simulation method by introducing a void initiation function to the method.
Three-Dimensional Modeling for Wet Compression in a Single Stage Compressor Including Liquid Particle Erosion Analysis
Authors: Khan Jobaidur R. , Wang Ting
Published: September 2010

Gas turbine inlet fog/overspray cooling is considered as a simple and effective method to increase power output. To help understand the water mist transport in the compressor flow passage, this study conducts a 3D computational simulation of wet compression in a single rotor-stator compressor stage using the commercial code FLUENT. A sliding mesh scheme is used to simulate the stator-rotor interaction in a rotating frame. Eulerian–Lagrangian method is used to calculate the continuous phase and track the discrete (droplet) phase. Models to simulate droplet breakup and coalescence are incorporated to take into consideration the effect of local acceleration and deceleration on water droplet dynamics. Analysis on the droplet history (trajectory and size) with stochastic tracking is employed to interpret the mechanism of droplet dynamics under the influence of local turbulence, acceleration, diffusion, and body forces. A liquid-droplet erosion model is included. The sensitivity of the turbulence models on the results is conducted by employing six different turbulence models and four different time constants. The result shows that the local thermal equilibrium is not always achieved due to short residence time and high value of latent heat of water. Local pressure gradients in both the rotor and stator flow passages drive up the droplet slip velocity during compression. The erosion model predicts that the most eroded area occurs in the leading edge and one spot of the trailing edge of the rotor suction side.
Vibration Test of a 1/10 Reduced Scale Model of Cylindrical Water Storage Tank
Authors: Maekawa Akira , Shimizu Yasutaka , Suzuki Michiaki , Fujita Katsuhisa
Published: September 2010

This paper describes the results of vibration tests using a 1/10 reduced scale model of large-scale cylindrical water storage tanks to clarify their dynamic behavior under seismic excitation. The thin sidewall of the tanks is not so rigid that the vibration modes (sloshing and bulging) induced by earthquake can affect the distribution of their liquid pressure and seismic load. It is, therefore, important for the seismic design of water storage tanks to consider such elastic deformation theoretically and experimentally. In this study, vibration tests by shaking table are conducted using a reduced scale tank model partially filled with water to investigate the dynamic fluid pressure behavior and seismic-proof safety of the tanks. A small sinusoidal excitation test, large amplitude sinusoidal excitation test and seismic excitation test are conducted. The measured values are compared with the calculated ones by some conventional seismic design methods. The results reveal that the distribution shape and magnitude of the dynamic fluid pressure are different between under positive and negative pressures and depend on the magnitude of input acceleration. Further examination concludes that the oval-type vibration, which is a high-order vibration mode, occurring on the sidewall of the tanks affects the distribution shape and magnitude of dynamic fluid pressure. However, it is demonstrated that the vibration does not act as a seismic load in the conventional evaluation of seismic-proof safety.
Application of Fiber-Optical Microphone for Thermo-Acoustic Measurements
Authors: Konle Holger J. , Paschereit Christian O. , Röhle Ingo
Published: September 2010

A high temperature resistant fiber-optical microphone (FOM) was developed and successfully applied in a combustion chamber at a thermal power of 8.4 kW to measure thermo-acoustic oscillations at a frequency of 85 Hz and a sound pressure level of 154 dB. The sensor head temperature was estimated to ∼1000 K. The core of the optical setup used for the FOM is a Fabry–Perot interferometer. To create an acoustical sensor based on this type of interferometer, a new method of generation and postprocessing of the interference signal was developed. The simple replaceability of the sensor membrane reduces the requirements concerning the sensor handling compared with conventional condenser microphones and allows the adaptation of the sensor sensitivity to its application case changing the membrane stiffness.
A Novel Approach of Retrofitting a Combined Cycle With Post Combustion CO2 Capture
Authors: Jonshagen Klas , Sipöcz Nikolett , Genrup Magnus
Published: September 2010

Most state-of-the-art natural gas-fired combined cycle (NGCC) plants are triple-pressure reheat cycles with efficiencies close to 60%. However, with carbon capture and storage, the efficiency will be penalized by almost 10% units. To limit the energy consumption for a carbon capture NGCC plant, exhaust gas recirculation (EGR) is necessary. Utilizing EGR increases the CO2 content in the gas turbine exhaust while it reduces the flue gas flow to be treated in the capture plant. Nevertheless, due to EGR, the gas turbine will experience a different media with different properties compared with the design case. This study looks into how the turbomachinery reacts to EGR. The work also discusses the potential of further improvements by utilizing pressurized water rather than extraction steam as the heat source for the CO2 stripper. The results show that the required low-pressure level should be elevated to a point close to the intermediate-pressure to achieve optimum efficiency, hence, one pressure level can be omitted. The main tool used for this study is an in-house off-design model based on fully dimensionless groups programmed in the commercially available heat and mass balance program IPSEPRO. The model is based on a GE 109FB machine with a triple-pressure reheat steam cycle.
Structural and electrical properties of Cu2O thin films deposited on ZnO by metal organic chemical vapor deposition
Authors: Jeong SeongHo , Aydil Eray S.
Published: September 2010

Cu 2 O thin films were deposited on ZnO coated glass substrates by metal organic chemical vapor deposition from copper(II) hexafluoroacetylacetonate [Cu(C5HF6O2)2], oxygen gas, and water vapor. The dependence of the structural and electrical properties of Cu2O films on deposition temperature and film thickness was investigated. X-ray diffraction showed that Cu2O thin films grow on ZnO with preferred (220)Cu2O∥(0002)ZnO orientation. The grain size and stress in Cu2O films increase with increasing substrate temperature but decrease with increasing film thickness. The carrier mobility increases with increasing grain size indicating that the carrier transport is limited by scattering from the grain boundaries. Single-phase epitaxial p-type Cu2O films with hole mobilities exceeding 30 cm2/V s are obtained at a deposition temperature of 400 °C.
Genetic and Biological Analysis of ColombianPhthorimaea operculellaGranulovirus Isolated fromTecia solanivora(Lepidoptera: Gelechiidae)
Authors: Espinel-Correal Carlos , Léry Xavier , Villamizar Laura , Gómez Juliana , Zeddam Jean Louis , Cotes Alba Marina , López-Ferber Miguel
Published: September 2010

Tecia solanivora(Lepidoptera: Gelechiidae) is an invasive potato pest of the north of South America that recently colonized zones wherePhthorimaea operculella(Lepidoptera: Gelechiidae), a taxonomically related insect, was established. Nowadays, both species can be found in most areas in different proportions. ThePhthorimaea operculella granulovirus(PhopGV) was found to efficiently controlP. operculellaand was used as a biopesticide in storage conditions. However, no appropriate biological control methods exist forT. solanivora, and the use of granulovirus isolates would provide a solution. The Colombian Corporation for Agricultural Research (CORPOICA) carried out severalT. solanivoralarva samplings in Colombia with the aim of finding potential isolates. Five geographical granulovirus isolates fromT. solanivora(VG001, VG002, VG003, VG004, and VG005) were found, and molecular analysis by REN profiles shows three different genotypic variants in Colombia. Analysis of their genomes revealed their relatedness to PhopGV. Two isolates exhibited submolar bands in their REN patterns, suggesting a mixture of viral genotypes. These data were confirmed by PCR amplification and sequencing of particular regions of the viral genomes. Their biological activity was assayed on both hosts,T. solanivoraandP. operculella. A significantly higher pathogenicity in both hosts was observed with isolates VG001 and VG005 than with isolate VG003 or a Peruvian isolate (fromP. operculella) used as a reference in the bioassay. Based on their molecular and biological activity characteristics, VG001 and VG005 isolates should be selected for further analysis in order to establish their potential as biological control agents.
Molecular Characterization of
Cryptosporidium molnari
Reveals a Distinct Piscine Clade
Authors: Palenzuela Oswaldo , Alvarez-Pellitero Pilar , Sitjà-Bobadilla Ariadna
Published: September 2010

Multilocus phylogenetic analysis of small-subunit (SSU) rRNA and actin from
Cryptosporidium molnari
clustered this species with the
C. molnari
-like genotype of an isolate from the guppy, although the two fish isolates seem to be distinct species. The analysis of available piscine genotypes provides some support for cladistic congruence of the genus
Piscicryptosporidium
, but additional piscine genotypes are needed.
Identification and Characterization of a Novel CprA Reductive Dehalogenase Specific to Highly Chlorinated Phenols from
Desulfitobacterium hafniense
Strain PCP-1
Authors: Bisaillon Ariane , Beaudet Réjean , Lépine François , Déziel Eric , Villemur Richard
Published: September 2010

Desulfitobacterium hafniense
strain PCP-1 reductively dechlorinates pentachlorophenol (PCP) to 3-chlorophenol and a variety of halogenated aromatic compounds at the
ortho
,
meta
, and
para
positions. Several reductive dehalogenases (RDases) are thought to be involved in this cascade of dehalogenation. We partially purified a novel RDase involved in the dechlorination of highly chlorinated phenols from strain PCP-1 cultivated in the presence of 2,4,6-trichlorophenol. The RDase was membrane associated, and the activity was sensitive to oxygen, with a half-life of 128 min upon exposure to air. The pH and temperature optima were 7.0 and 55°C, respectively. Several highly chlorinated phenols were dechlorinated at the
ortho
positions. The highest dechlorinating activity levels were observed with PCP, 2,3,4,5-tetrachlorophenol, and 2,3,4-trichlorophenol. 3-Chloro-4-hydroxyphenylacetate, 3-chloro-4-hydroxybenzoate, dichlorophenols, and monochlorophenols were not dechlorinated. The apparent

K
m

value for PCP was 46.7 μM at a methyl viologen concentration of 2 mM. A mixture of iodopropane and titanium citrate caused a light-reversible inhibition of the dechlorinating activity, suggesting the involvement of a corrinoid cofactor. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the partially purified preparation revealed 2 bands with apparent molecular masses of 42 and 47 kDa. Mass spectrometry analysis using Mascot to search the genome sequence of
D. hafniense
strain DCB-2 identified the 42-kDa band as NADH-quinone oxidoreductase, subunit D, and the 47-kDa band as the putative chlorophenol RDase CprA3. This is the first report of an RDase with high affinity and high dechlorinating activity toward PCP.
Elimination of Lyme Disease Spirochetes from Ticks Feeding on Domestic Ruminants
Authors: Richter Dania , Matuschka Franz-Rainer
Published: September 2010

To determine whether and which spirochetes are cleared from
Ixodes ricinus
ticks during feeding on ruminants, ticks were removed from goats and cattle grazing on tick-infested pastures. Although about a quarter of ticks questing on the pasture were infected by spirochetes, no molted ticks that had previously engorged to repletion on ruminants harbored Lyme disease spirochetes.
Borrelia miyamotoi
spirochetes, however, appear not to be eliminated. Thus, the more subadult ticks are diverted from reservoir-competent hosts to zooprophylactic ruminants, the smaller the risk of infection by Lyme disease spirochetes is.
Elimination ofd-Lactate Synthesis Increases Poly(3-Hydroxybutyrate) and Ethanol Synthesis from Glycerol and Affects Cofactor Distribution in RecombinantEscherichia coli
Authors: Nikel Pablo I. , Giordano Andrea M. , de Almeida Alejandra , Godoy Manuel S. , Pettinari M. Julia
Published: September 2010

The effect of eliminatingd-lactate synthesis in poly(3-hydroxybutyrate) (PHB)-accumulating recombinantEscherichia coli(K24K) was analyzed using glycerol as a substrate. K24KL, anldhAderivative, produced more biomass and had altered carbon partitioning among the metabolic products, probably due to the increased availability of carbon precursors and reducing power. This resulted in a significant increase of PHB and ethanol synthesis and a decrease in acetate production. Cofactor measurements revealed that cultures of K24K and K24KL had a high intracellular NADPH content and that the NADPH/NADP+ratio was higher than the NADH/NAD+ratio. TheldhAmutation affected cofactor distribution, resulting in a more reduced intracellular state, mainly due to a further increase in NADPH/NADP+. In 60-h fed-batch cultures, K24KL reached 41.9 g·liter−1biomass and accumulated PHB up to 63% ± 1% (wt/wt), with a PHB yield on glycerol of 0.41 ± 0.03 g·g−1, the highest reported using this substrate.
Characterization of a New Bacteriocin, Carocin D, from
Pectobacterium carotovorum
subsp.
carotovorum
Pcc21
Authors: Roh Eunjung , Park Tae-Ho , Kim Myung-il , Lee Seungdon , Ryu Sangryeol , Oh Chang-Sik , Rhee Sangkee , Kim Doo-Ho , Park Beom-Seok , Heu Sunggi
Published: September 2010

Two different bacteriocins, carotovoricin and carocin S1, had been found in
Pectobacterium carotovorum
subsp.
carotovorum
, which causes soft-rot disease in diverse plants. Previously, we reported that the particular strain Pcc21, producing only one high-molecular-weight bacteriocin, carried a new antibacterial activity against the indicator strain Pcc3. Here, we report that this new antibacterial activity is due to a new bacteriocin produced by strain Pcc21 and named carocin D. Carocin D is encoded by the
caro
DK gene located in the genomic DNA together with the
caro
DI gene, which seems to encode an immunity protein. N-terminal amino acid sequences of purified carocin D were determined by Edman degradation. In comparison with the primary translation product of
caro
DK, it was found that 8 amino acids are missing at the N terminus. This finding proved that carocin D is synthesized as a precursor peptide and that 8 amino acids are removed from its N terminus during maturation. Carocin D has two putative translocation domains; the N-terminal and C-terminal domains are homologous to those of
Escherichia coli
colicin E3 and
Pseudomonas aeruginosa
S-type pyocin, respectively. When
caro
DK and
caro
DI genes were transformed into carocin D-sensitive bacteria such as Pcc3, the bacteria became resistant to this bacteriocin. Carocin D has one putative DNase domain at the extreme C terminus and showed DNase activity
in vitro
. This bacteriocin had slight tolerance to heat but not to proteases. The
caro
DK gene was present in only 5 of 54 strains of
P. carotovorum
subsp.
carotovorum
. These results indicate that carocin D is a third bacteriocin found in
P. carotovorum
subsp.
carotovorum
, and this bacteriocin can be readily expressed in carocin D-sensitive nonpathogenic bacteria, which may have high potential as a biological control agent in the field.
Reorganization of the Growth Pattern of Schizosaccharomyces pombe in Invasive Filament Formation
Authors: Dodgson James , Brown William , Rosa Carlos A. , Armstrong John
Published: September 2010

The organization and control of polarized growth through the cell cycle of
Schizosaccharomyces pombe
, a single-celled eukaryote, have been studied extensively. We have investigated the changes in these processes when
S. pombe
differentiates to form multicellular invasive mycelia and have found striking alterations to the behavior of some of the key regulatory proteins. Cells at the tips of invading filaments are considerably more elongated than cells growing singly and grow at one pole only. The filament tip follows a strict direction of growth through multiple cell cycles. A group of proteins involved in the growth process and actin regulation, comprising Spo20, Bgs4, activated Cdc42, and Crn1, are all concentrated at the growing tip, unlike their distribution at both ends of single cells. In contrast, several proteins implicated in microtubule-dependent organization of growth, including Tea1, Tea4, Mod5, and Pom1, all show the opposite effect and are relatively depleted at the growing end and enriched at the nongrowing end, although Tea1 appears to continue to be delivered to both ends. A third group acting at different stages of the cell cycle, including Bud6, Rga4, and Mid1, localize similarly in filaments and single cells, while Nif1 shows a reciprocal localization to Pom1.
A Possible Role for Exocytosis in Aflatoxin Export in Aspergillus parasiticus
Authors: Chanda Anindya , Roze Ludmila V. , Linz John E.
Published: September 2010

Filamentous fungi synthesize bioactive secondary metabolites with major human health and economic impacts. Little is known about the mechanisms that mediate the export of these metabolites to the cell exterior.
Aspergillus parasiticus
synthesizes aflatoxin, a secondary metabolite that is one of the most potent naturally occurring carcinogens known. We previously demonstrated that aflatoxin is synthesized and compartmentalized in specialized vesicles called aflatoxisomes and that these subcellular organelles also play a role in the export process. In the current study, we tested the hypothesis that aflatoxisomes fuse with the cytoplasmic membrane to facilitate the release of aflatoxin into the growth environment. Microscopic analysis of
A. parasiticus
grown under aflatoxin-inducing and non-aflatoxin-inducing conditions generated several lines of experimental evidence that supported the hypothesis. On the basis of the evidence, we propose that export of the mycotoxin aflatoxin in
Aspergillus parasiticus
occurs by exocytosis, and we present a model to illustrate this export mechanism.
α-1,6-Mannosylation of N-Linked Oligosaccharide Present on Cell Wall Proteins Is Required for Their Incorporation into the Cell Wall in the Filamentous Fungus Neurospora crassa
Authors: Maddi Abhiram , Free Stephen J.
Published: September 2010

The enzyme α-1,6-mannosyltransferase (OCH-1) is required for the synthesis of galactomannans attached to the N-linked oligosaccharides of
Neurospora crassa
cell wall proteins. The
Neurospora crassa
och-1
mutant has a tight colonial phenotype and a defective cell wall. A carbohydrate analysis of the
och-1 mutant
cell wall revealed a 10-fold reduction in the levels of mannose and galactose and a total lack of 1,6-linked mannose residues. Analysis of the integral cell wall protein from wild-type and
och-1
mutant cells showed that the mutant cell wall had reduced protein content. The
och-1
mutant was found to secrete 18-fold more protein than wild-type cells. Proteomic analysis of the proteins released by the mutant into the growth medium identified seven of the major cell wall proteins. Western blot analysis of ACW-1 and GEL-1 (two glycosylphosphatidylinositol [GPI]-anchored proteins that are covalently integrated into the wild-type cell wall) showed that high levels of these proteins were being released into the medium by the
och-1
mutant. High levels of ACW-1 and GEL-1 were also released from the
och-1
mutant cell wall by subjecting the wall to boiling in a 1% SDS solution, indicating that these proteins are not being covalently integrated into the mutant cell wall. From these results, we conclude that N-linked mannosylation of cell wall proteins by OCH-1 is required for their efficient covalent incorporation into the cell wall.
α-Tubulin Mutations Alter Oryzalin Affinity and Microtubule Assembly Properties To Confer Dinitroaniline Resistance
Authors: Lyons-Abbott Sally , Sackett Dan L. , Wloga Dorota , Gaertig Jacek , Morgan Rachel E. , Werbovetz Karl A. , Morrissette Naomi S.
Published: September 2010

Plant and protozoan microtubules are selectively sensitive to dinitroanilines, which do not disrupt vertebrate or fungal microtubules.
Tetrahymena thermophila
is an abundant source of dinitroaniline-sensitive tubulin, and we have modified the single
T. thermophila
α-tubulin gene to create strains that solely express mutant α-tubulin in functional dimers. Previous research identified multiple α-tubulin mutations that confer dinitroaniline resistance in the human parasite
Toxoplasma gondii
, and when two of these mutations (L136F and I252L) were introduced into
T. thermophila
, they conferred resistance in these free-living ciliates. Purified tubulin heterodimers composed of L136F or I252L α-tubulin display decreased affinity for the dinitroaniline oryzalin relative to wild-type
T. thermophila
tubulin. Moreover, the L136F substitution dramatically reduces the critical concentration for microtubule assembly relative to the properties of wild-type
T. thermophila
tubulin. Our data provide additional support for the proposed dinitroaniline binding site on α-tubulin and validate the use of
T. thermophila
for expression of genetically homogeneous populations of mutant tubulins for biochemical characterization.
Regulation of the Hypoxic Response in Candida albicans
Authors: Synnott John M. , Guida Alessandro , Mulhern-Haughey Siobhan , Higgins Desmond G. , Butler Geraldine
Published: September 2010

The regulation of the response ofCandida albicansto hypoxic (low-oxygen) conditions is poorly understood. We used microarray and other transcriptional analyses to investigate the role of the Upc2 and Bcr1 transcription factors in controlling expression of genes involved in cell wall metabolism, ergosterol synthesis, and glycolysis during adaptation to hypoxia. Hypoxic induction of the ergosterol pathway is mimicked by treatment with sterol-lowering drugs (ketoconazole) and requiresUPC2. Expression of three members of the family CFEM (common in severalfungalextracellularmembranes) of cell wall genes (RBT5,PGA7, andPGA10) is also induced by hypoxia and ketoconazole and requires bothUPC2andBCR1. Expression of glycolytic genes is induced by hypoxia but not by treatment with sterol-lowering drugs, whereas expression of respiratory pathway genes is repressed. However, Upc2 does not play a major role in regulating expression of genes required for central carbon metabolism. Our results indicate that regulation of gene expression in response to hypoxia inC. albicansis complex and is signaled both via lowered sterol levels and other unstudied mechanisms. We also show that induction of filamentation under hypoxic conditions requires the Ras1- and Cdc35-dependent pathway.
Fitness Effects of Replichore Imbalance in
Salmonella enterica
Authors: Matthews T. David , Maloy Stanley
Published: September 2010

A fitness cost due to imbalanced replichores has been proposed to provoke chromosome rearrangements in
Salmonella enterica
serovars. To determine the impact of replichore imbalance on fitness, the relative fitness of isogenic
Salmonella
strains containing transposon-held duplications of various sizes and at various chromosomal locations was determined. Although duplication of certain genes influenced fitness, a replichore imbalance of up to 16° did not affect fitness.
Chlamydia trachomatisSerovar L2 Can Utilize Exogenous Lipoic Acid through the Action of the Lipoic Acid Ligase LplA1
Authors: Ramaswamy Aishwarya V. , Maurelli Anthony T.
Published: September 2010

Lipoic acid is an essential protein bound cofactor that is vital for the functioning of several important enzymes involved in central metabolism. Genomes of all sequenced chlamydiae show the presence of two genes encoding lipoic acid ligases and one gene encoding a lipoate synthase. However, the roles of these proteins in lipoic acid utilization or biosynthesis have not yet been characterized. The two distinct lipoic acid ligases inChlamydia trachomatisserovar L2, LplA1Ctand LplA2Ct(encoded by the open reading framesctl0537andctl0761) display moderate identity withEscherichia coliLplA (30 and 27%, respectively) but possess amino acid sequence motifs that are well conserved among all lipoyl protein ligases. The putative lipoic acid synthase LipACt, encoded byctl0815,is ca. 43% identical to theE. coliLipA homolog. We demonstrate here the presence of lipoylated proteins inC. trachomatisserovar L2 and show that the lipoic acid ligase LplA1Ctis capable of utilizing exogenous lipoic acid for the lipoylation Therefore, host-derived lipoic acid may be important for intracellular growth and development. Based on genetic complementation in a surrogate host, our study also suggests that theC. trachomatisserovar L2 LipA homolog may not be functionalin vivo.
Identification of YsrT and Evidence that YsrRST Constitute a Unique Phosphorelay System inYersinia enterocolitica
Authors: Walker Kimberly A. , Obrist Markus W. , Mildiner-Earley Shirly , Miller Virginia L.
Published: September 2010

Two-component systems (TCS) and phosphorelay systems are mechanisms used by bacteria and fungi to quickly adapt to environmental changes to produce proteins necessary for survival in new environments. Bacterial pathogens use TCS and phosphorelay systems to regulate genes necessary to establish infection within their hosts, including type III secretion systems (T3SS). TheYersinia enterocolitica ysaT3SS is activated in response to NaCl by YsrS and YsrR, a putative hybrid sensor kinase and a response regulator, respectively. Hybrid TCS consist of a sensor kinase that typically has three well-conserved sites of phosphorylation: autophosphorylation site H1, D1 within a receiver domain, and H2 in the histidine phosphotransferase (HPt) domain. From H2, the phosphoryl group is transferred to D2 on the response regulator. A curious feature of YsrS is that it lacks the terminal HPt domain. We report here the identification of the HPt-containing protein (YsrT) that provides this activity for the Ysr system. YsrT is an 82-residue protein predicted to be cytosolic and α-helical in nature and is encoded by a gene adjacent toysrS. To demonstrate predicted functions of YsrRST as a phosphorelay system, we introduced alanine substitutions at H1, D1, H2, and D2 and tested the mutant proteins for the ability to activate aysaE-lacZreporter. As expected, substitutions at H1, H2, and D2 resulted in a loss of activation ofysaEexpression. This indicates an interruption of normal protein function, most likely from loss of phosphorylation. A similar result was expected for D1; however, an intriguing “constitutive on” phenotype was observed. In addition, the unusual feature of a separate HPt domain led us to compare the sequences surrounding theysrS-ysrTjunction in severalYersiniastrains. In every strain examined,ysrTis a separate gene, leading to speculation that there is a functional advantage to YsrT being an independent protein.
Coxiella burnetii
Expresses a Functional Δ24 Sterol Reductase
Authors: Gilk Stacey D. , Beare Paul A. , Heinzen Robert A.
Published: September 2010

Coxiella burnetii
, the etiological agent of human Q fever, occupies a unique niche inside the host cell, where it replicates in a modified acidic phagolysosome or parasitophorous vacuole (PV). The PV membrane is cholesterol-rich, and inhibition of host cholesterol metabolism negatively impacts PV biogenesis and pathogen replication. The precise source(s) of PV membrane cholesterol is unknown, as is whether the bacterium actively diverts and/or modifies host cell cholesterol or sterol precursors.
C. burnetii
lacks enzymes for
de novo
cholesterol biosynthesis; however, the organism encodes a eukaryote-like Δ24 sterol reductase homolog, CBU1206. Absent in other prokaryotes, this enzyme is predicted to reduce sterol double bonds at carbon 24 in the final step of cholesterol or ergosterol biosynthesis. In the present study, we examined the functional activity of CBU1206. Amino acid alignments revealed the greatest sequence identity (51.7%) with a Δ24 sterol reductase from the soil amoeba
Naegleria gruberi.
CBU1206 activity was examined by expressing the protein in a
Saccharomyces cerevisiae erg4
mutant under the control of a galactose-inducible promoter. Erg4 is a yeast Δ24 sterol reductase responsible for the final reduction step in ergosterol synthesis. Like Erg4-green fluorescent protein (GFP), a CBU1206-GFP fusion protein localized to the yeast endoplasmic reticulum. Heterologous expression of CBU1206 rescued
S. cerevisiae erg4
sensitivity to growth in the presence of brefeldin A and cycloheximide and resulted in new synthesis of ergosterol. These data indicate CBU1206 is an active sterol reductase and suggest the enzyme may act on host sterols during
C. burnetii
intracellular growth.
The
Staphylococcus aureus
Autoinducer-2 Synthase LuxS Is Regulated by Ser/Thr Phosphorylation
Authors: Cluzel Marie-Eve , Zanella-Cléon Isabelle , Cozzone Alain J. , Fütterer Klaus , Duclos Bertrand , Molle Virginie
Published: September 2010

The
Staphylococcus aureus
autoinducer-2 (AI-2) producer protein LuxS is phosphorylated by the Ser/Thr kinase Stk1 at a unique position, Thr14. The enzymatic activity of the phosphorylated isoform of LuxS was abrogated compared to that of nonphosphorylated LuxS, thus providing the first evidence of an AI-2-producing enzyme regulated by phosphorylation and demonstrating that
S. aureus
possesses an original and specific system for controlling AI-2 synthesis.
Interaction of the Colicin K Bactericidal Toxin with Components of Its Import Machinery in the Periplasm ofEscherichia coli
Authors: Barnéoud-Arnoulet Aurélie , Gavioli Marthe , Lloubès Roland , Cascales Eric
Published: September 2010

Colicins are bacterial antibiotic toxins produced byEscherichia colicells and are active againstE. coliand closely related strains. To penetrate the target cell, colicins bind to an outer membrane receptor at the cell surface and then translocate their N-terminal domain through the outer membrane and the periplasm. Once fully translocated, the N-terminal domain triggers entry of the catalytic C-terminal domain by an unknown process. Colicin K uses the Tsx nucleoside-specific receptor for binding at the cell surface, the OmpA protein for translocation through the outer membrane, and the TolABQR proteins for the transit through the periplasm. Here, we initiated studies to understand how the colicin K N-terminal domain (KT) interacts with the components of its transit machine in the periplasm. We first produced KT fused to a signal sequence for periplasm targeting. Upon production of KT in wild-type strains, cells became partly resistant to Tol-dependent colicins and sensitive to detergent, released periplasmic proteins, and outer membrane vesicles, suggesting that KT interacts with and titrates components of its import machine. Using a combination ofin vivocoimmunoprecipitations andin vitropulldown experiments, we demonstrated that KT interacts with the TolA, TolB, and TolR proteins. For the first time, we also identified an interaction between the TolQ protein and a colicin translocation domain.