bluuebunny/crossref_metadata_2025_split huggingface dataset:
Essential Nature of the
mreC
Determinant of
Bacillus subtilis
Authors: Lee Joong-Chul , Stewart George C. 
Published: July 2003

ABSTRACT

The
mre
genes of
Escherichia coli
and
Bacillus subtilis
are cell shape determination genes. Mutants affected in
mre
function are spheres instead of the normal rods. Although the
mre
determinants are not required for viability in
E
.
coli
, the
mreB
determinant is an essential gene in
B
.
subtilis
. Conflicting results have been reported as to whether the two membrane-associated proteins MreC and MreD are essential proteins. Furthermore, although the MreB protein has been studied in some detail, the roles of the MreC and MreD proteins in cell shape determination are unknown. We constructed a strain of
B
.
subtilis
in which expression of the
mreC
determinant is dependent upon the addition of isopropyl-β-
d
-thiogalactopyranoside to the culture medium. Utilizing this conditional strain, it was shown that
mreC
is an essential gene in
B
.
subtilis
. Furthermore, it was shown that cells lacking sufficient quantities of MreC undergo morphological changes, namely, swelling and twisting of the cells, which is followed by cell lysis. Electron microscopy was utilized to demonstrate that a polymeric material accumulated at one side of the division septum of the cells and that the presence of this material correlated with the bending of the cell. The best explanation for the results is that the MreC protein is involved in the control of septal versus long-axis peptidoglycan synthesis, that cells lacking MreC perform aberrant septal peptidoglycan synthesis, and that lysis results from a deficiency in long-axis peptidoglycan synthesis.
Lateral Flagellar Gene System of
Vibrio parahaemolyticus
Authors: Stewart Bonnie J. , McCarter Linda L. 
Published: July 2003

ABSTRACT

Vibrio parahaemolyticus
possesses dual flagellar systems adapted for movement under different circumstances. A single polar flagellum propels the bacterium in liquid (i.e., swimming) with a motor that is powered by the sodium motive force. Multiple proton-driven lateral flagella enable translocation over surfaces (i.e., swarming). The polar flagellum is produced continuously, while production of lateral flagella is induced when the organism is grown on surfaces. This work describes the isolation of mutants with insertions in the structural and regulatory
laf
genes. A Tn
5
-based
lux
transcriptional reporter transposon was constructed and used for mutagenesis and subsequent transcriptional analysis of the
laf
regulon. Twenty-nine independent insertions were distributed within 16
laf
genes. DNA sequence analysis identified 38
laf
genes in two loci. Among the mutants isolated, 11 contained surface-induced
lux
fusions. A hierarchy of
laf
gene expression was established following characterization of the
laf
::
lux
transcriptional fusion strains and by mutational and primer extension analyses of the
laf
regulon. The
laf
system is like many enteric systems in that it is a proton-driven, peritrichous flagellar system; however,
laf
regulation was different from the
Salmonella
-
Escherichia coli
paradigm. There is no apparent
flhDC
counterpart that encodes master regulators known to control flagellar biosynthesis and swarming in many enteric bacteria. A potential σ
54
-dependent regulator, LafK, was demonstrated to control expression of early genes, and a lateral-specific σ
28
factor controls late flagellar gene expression. Another notable feature was the discovery of a gene encoding a MotY-like product, which previously had been associated only with the architecture of sodium-type polar flagellar motors.
Phase Variation in the Phage Growth Limitation System ofStreptomyces coelicolorA3(2)
Authors: Sumby Paul , Smith Margaret C. M. 
Published: July 2003

ABSTRACTThe phase-variable phage growth limitation (Pgl) system ofStreptomyces coelicolorA3(2) is an unusual bacteriophage resistance mechanism that confers protection against the temperate phage φC31 and homoimmune relatives. Pgl is subject to phase variation, and data presented here show that this is at least partially due to expansion and contraction of a polyguanine tract present within the putative adenine-specific DNA methyltransferase gene,pglX. Furthermore, thepglXparalogue SC6G9.02, here renamedpglS, was shown to be able to interfere with the Pgl phenotype, suggesting that PglS could provide an alternative activity to that conferred by PglX.
Isolation and Analysis of Mutants of Double-Stranded-RNA Bacteriophage φ6 with Altered Packaging Specificity
Authors: Qiao Jian , Qiao Xueying , Sun Yang , Mindich Leonard 
Published: July 2003

ABSTRACT

The genomes of bacteriophage φ6 and its relatives are packaged through a mechanism that involves the recognition and translocation of the three different plus strand transcripts of the segmented double-stranded RNA genomes into preformed polyhedral structures called procapsids or inner cores. This packaging requires hydrolysis of nucleoside triphosphates and takes place in the order S-M-L. Packaging is dependent on unique sequences of about 200 nucleotides near the 5′ ends of plus strand transcripts of the three genomic segments. Changes in the
pac
sequences lead to loss of packaging ability but can be suppressed by second-site changes in RNA or amino acid changes in protein P1, the major structural protein of the procapsid. It appears that P1 is the determinant of the RNA binding sites, and it is suggested that the binding sites overlap or are conformational changes of the same domains.
Molecular and Functional Analysis of thelepBGene, Encoding a Type I Signal Peptidase fromRickettsia rickettsiiandRickettsia typhi
Authors: Rahman M. Sayeedur , Simser Jason A. , Macaluso Kevin R. , Azad Abdu F. 
Published: July 2003

ABSTRACTThe type I signal peptidaselepBgenes fromRickettsia rickettsiiandRickettsia typhi, the etiologic agents of Rocky Mountain spotted fever and murine typhus, respectively, were cloned and characterized. Sequence analysis of the clonedlepBgenes fromR. rickettsiiandR. typhishows open reading frames of 801 and 795 nucleotides, respectively. Alignment analysis of the deduced amino acid sequences reveals the presence of highly conserved motifs that are important for the catalytic activity of bacterial type I signal peptidase. Reverse transcription-PCR and Northern blot analysis demonstrated that thelepBgene ofR. rickettsiiis cotranscribed in a polycistronic message with the putativenuoF(encoding NADH dehydrogenase I chain F),secF(encoding protein export membrane protein), andrnc(encoding RNase III) genes in asecF-nuoF-lepB-rnccluster. The clonedlepBgenes fromR. rickettsiiandR. typhihave been demonstrated to possess signal peptidase I activity inEscherichia colipreprotein processing in vivo by complementation assay.
Biochemical Function of
msl5
(
pks8
plus
pks17
) in
Mycobacterium tuberculosis
H37Rv: Biosynthesis of Monomethyl Branched Unsaturated Fatty Acids
Authors: Dubey Vinod S. , Sirakova Tatiana D. , Cynamon Michael H. , Kolattukudy Pappachan E. 
Published: July 2003

ABSTRACT

We show that the disruption of one of the mycocerosic acid synthase (
mas
)-like genes,
msl5
(
pks8
plus
pks17
) in
Mycobacterium tuberculosis
H37Rv generates a mutant incapable of producing monomethyl branched unsaturated C
16
to C
20
fatty acids that are minor constituents of acyltrehaloses and sulfolipids. The
msl5
mutation did not cause any significant change in the acyl lipid composition and also did not affect growth in culture, in mouse alveolar macrophage cell line MH-S, or in the murine lung.
A 65-Kilobase Pathogenicity Island Is Unique to Philadelphia-1 Strains of
Legionella pneumophila
Authors: Brassinga Ann Karen C. , Hiltz Margot F. , Sisson Gary R. , Morash Michael G. , Hill Nathan , Garduno Elizabeth , Edelstein Paul H. , Garduno Rafael A. , Hoffman Paul S. 
Published: July 2003

ABSTRACT

Nucleotide sequence analysis of an ∼80-kb genomic region revealed an ∼65-kb locus that bears hallmarks of a pathogenicity island. This locus includes homologues of a type IV secretion system, mobile genetic elements, and known virulence factors. Comparative studies with other
Legionella pneumophila
strains and serogroups indicated that this ∼65-kb locus is unique to
L
.
pneumophila
serogroup 1 Philadelphia-1 strains.
Microarray Transcription Analysis of Clinical
Staphylococcus aureus
Isolates Resistant to Vancomycin
Authors: Mongodin Emmanuel , Finan Jon , Climo Michael W. , Rosato Adriana , Gill Steven , Archer Gordon L. 
Published: July 2003

ABSTRACT

The transcriptomes of vancomycin intermediate-resistance
Staphylococcus aureus
(VISA) clinical isolates HIP5827 and Mu50 (MIC = 8 μg/ml) were compared to those of highly vancomycin-resistant
S. aureus
(VRSA; MIC = 32 μg/ml) passage derivatives by microarray. There were 35 genes with increased transcription and 16 genes with decreased transcription in common between the two VRSAs compared to those of their VISA parents. Of the 35 genes with increased transcription, 15 involved purine biosynthesis or transport, and the regulator (
purR
) of the major purine biosynthetic operon (
purE-purD
) was mutant. We hypothesize that increased energy (ATP) is required to generate the thicker cell walls that characterize resistant mutants.
Transcriptional Expression ofEscherichia coliGlutamate-Dependent Acid Resistance GenesgadAandgadBCin anhns rpoSMutant
Authors: Waterman Scott R. , Small P. L. C. 
Published: July 2003

ABSTRACTResistance to being killed by acidic environments with pH values lower than 3 is an important feature of both pathogenic and nonpathogenicEscherichia coli. The most potentE. coliacid resistance system utilizes two isoforms of glutamate decarboxylase encoded bygadAandgadBand a putative glutamate:γ-aminobutyric acid antiporter encoded bygadC. Thegadsystem is controlled by two repressors (H-NS and CRP), one activator (GadX), one repressor-activator (GadW), and two sigma factors (σSand σ70). In contrast to results of previous reports, we demonstrate thatgadtranscription can be detected in anhns rpoSmutant strain ofE. coliK-12, indicating thatgadpromoters can be initiated by σ70in the absence of H-NS.
Kinetic Models of Lipophilic Compound Uptake and Bioelimination in Amphibians During the Aquatic Stages
Authors: Venturino Andrés , Bergoc Rosa M. , Pechen Ana M. 
Published: July 2003

During embryonic development, amphibians are particularly sensitive to lipophilic toxic compounds, given their tendency to bioaccumulate from the aquatic environment. On the basis of a series of toxicokinetic experiments with the organophosphorus malathion, we have developed several biomathematical models to explain the behavior of the toxin in an aquatic environment, as well as its biotransformation in amphibian larval stages. Malathion in medium displayed uniexponential bioelimination, while it rapidly accumulated in larvae, decaying according to complex kinetics. Both kinetics were satisfactorily predicted by a model of two compartments in series. In the first compartment, which accounts for bioaccumulation in lipidic tissues, an exponential decline in capacity correlated with progressive depletion of larval lipid reserves was considered. In the second, metabolic biotransformation by several degradative enzymes was considered as a function of the mass of compound present in it. The rapid mass equilibrium between medium and lipidic compartment justifies the apparent uniexponential decay in the first, driven by the overall biotransformation rate constant from the metabolic compartment.
Time Felt, Time Understood
Authors:   Fraser
Published: July 2003

AbstractThe experience of time's passage is intimately familiar, the idea of time is strangely elusive. Mature, healthy humans find it is easy to act consistently with the notions of tomorrow, yesterday and today.Yet, explaining what is meant by future, past, and present, without assuming prior familiarity with time, seems impossible. The asymmetry between the obviousness of the experience of time, and the unobviousness of the idea of time, has been a source of perplexity to reflective thought for at least fourteen centuries. This essay sees the sources of that asymmetry in the evolutionary structuring of the cognitive capacities of the human brain. It draws attention to certain conflicts rooted in the differences between those cognitive capacities- copresent in the mind- and notes the importance of the humanities in the management of the conflicts.
Father Time, Speed, and the Temporality of Posters Around 1900
Authors: Iskin Ruth 
Published: July 2003

AbstractThe essay proposes that advertising posters around 1900 construct a popular-culture iconography of a modern temporality associated with new technologies. In addition, it proposes, posters themselves embody a new temporality as a medium. The essay analyses how posters portray time by focusing on several images, some of which depict an updated allegorical figure of Father Time in order to advertise a racing automobile or precision watch.The essay also addresses the temporality of posters as a medium by investigating their conditions of viewing and the role of their advertising function. The discussion of the media specificity of posters, their cultural context, and a detailed analysis of their imagery, concludes that posters both elicit a certain kind of temporal viewing and portray a conflictual transition between old and new temporalities.
Degrees of Separation in the Phaedo
Authors: Pakaluk Michael 
Published: July 2003

AbstractIt can be shown that, if we assume 'substance dualism', or the real distinctness of the soul from the body, then the standard objections to the Cyclical Argument in the Phaedo fail. So charity would presumably require that we take substance dualism to be presupposed by that argument. To do so would not beg any question, since substance dualism is a significantly weaker thesis than the immortality of the soul. Moreover, there is good textual evidence in favor of this presumption. A closer look at the immediately preceding passage, viz. "Socrates' Defense", reveals an argument for a real distinction between soul and body, not unlike Descartes' famous argument, based on the identification of an activity in which the soul can in principle engage on its own, without assistance from the body. The argumentative project of the Phaedo, on this reading, becomes: given that the soul is really distinct, show that it is immortal. And Plato aims to do this in two stages. The three initial arguments are meant to establish merely the minimal claim that the continued existence of the soul across cycles of reincarnation is the most plausible view to take, given substance dualism; and it is left to the Final Argument to argue for something that we might regard as immortality, that is, the imperishability of the soul, come what may.
Zeno on the Unity of Philosophy
Authors: Mansfeld Jaap 
Published: July 2003

AbstractThe formula 'the elements of logos' in the Zeno quotation by Epictetus at Arrian, Diss. 4.8.12 need not, pace e.g. von Arnim, pertain to the parts of speech, but more probably means the elements i.e. primary theorems of philosophical theory, or doctrine. Theory moreover should become internalized to the soul and 'lived': philosophy is also the so-called 'art of life'. These theorems are to be distinguished but should reciprocally entail each other. Philosophy according to Zeno is both tripartite and one, and tripartite especially in that its parts (and subparts) cannot be transferred simultaneously: of necessity these have to taught and learned one after the other.
Are Birds the Primary Selective Force Leading to Evolution of Mimicry and Aposematism in Butterflies? An Opposing Point of View
Authors: Kassarov Luka 
Published: July 2003

AbstractBirds are universally considered to be the primary selective force leading to the evolution of mimicry in butterflies and the evolution of aposematic coloration. This concept does not take into account the visual capabilities of birds. In this paper it is argued that the aerial hawker insectivorous birds, which are the primary predators of butterflies, are not able to differentiate the separate elements in the color patterns of flying butterflies. They cannot distinguish details in color of the markings or their shape, size, and distribution. As a consequence, birds cannot serve as a selective force for evolution of mimicry and aposematic coloration in these insects. Many aspects of vision, and especially vision in birds, on which my conclusions are based are discussed in detail. The different morphological and behavioral characteristics of butterflies, especially their flight characteristics, correlate with their profitability as a source of energy and nutrients. The flight pattern of the butterfly is the first stimulus that the bird sees, not the color pattern. It is this characteristic flight pattern, not the bright aposematic coloration pattern, that birds are able to recognize and then learn rapidly to associate visually with the profitability of the prey. The characteristic flight behavior signals to the bird whether the prey is energetically profitable or not, thus whether to attack or ignore a potential prey. The ability to distinguish prey types by flight pattern allows the bird to conserve energy and maximize its feeding efficiency.
Behavioural Responses by Red-backed Salamanders to Conspecific and Heterospecific Cues
Authors: Sullivan Aaron , Rohr Jason , Madison Dale 
Published: July 2003

AbstractChemical cues released from injured prey are thought to indicate the proximity of a predator or predation event, and therefore, an area of elevated predation risk. Prey often avoid chemical cues released from injured heterospecifics, but there is little evidence to determine whether this is due to homologous cues among phylogenetically related species, or avoidance of injured syntopic species that experience predation from the same predators. The purpose of this study was to examine the response of terrestrial red-backed salamanders (Plethodon cinereus) to chemical cues from non-injured and injured members of their prey guild that vary in their relatedness to P.cinereus. In the laboratory, P.cinereus avoided chemical cues from injured conspecifics, injured and non-injured slimy salamanders (P.glutinosus), and injured confamilial dusky salamanders (Desmognathus ochrophaeus). Red-backed salamanders did not avoid rinses from non-injured conspecifics and dusky salamanders, or cues from injured and non-injured earthworms (Lumbricus sp.), a more distantly related prey guild member. These results cannot be fully explained by either phylogenetic relatedness (among plethodontid salamanders) or prey guild membership alone. We suggest that a combination of these factors, and perhaps others, likely influenced the evolution of heterospecific alarm cue avoidance in the red-backed salamander.
Finite Element Modeling and Active Control of an Inflated Torus Using Piezoelectric Devices
Authors: Lewis Jackson A. , Inman Daniel J. 
Published: July 2003

Satellite antenna design requirements are driving the satellite size to dimensions that cannot be launched into space using current technology. In order to reduce the launch size and mass of satellites, inflatable structures, also known as gossamer structures, are being considered. Inflatable space-based structures are susceptible to vibration disturbance due to their low stiffness and damping. This paper discusses the structural dynamics and vibration suppression via piezoelectric actuators of an inflatable torus. A commercial finite element package, ANSYS, is used to model the inflated torus. The effect of torus aspect ratio and inflation pressure on the vibratory response of the structure is investigated. The interaction with the torus of the surface-mounted piezoelectric patches, made of PVDF, is modeled using Euler-Bernoulli beam theory. A state space representation is created of the model in modal space and modal truncation is performed. Traditional control tools are used to suppress vibration in the structure. First observer-based full state feedback is used, then direct output velocity feedback is explored.
Die Reaktion von Kaliumhydrogensulfid mit Ethylbromid in ethanolischen Lösungen ‐ ein geeignetes Beispiel zur Einführung des SN2‐Reaktionsmechanismus
Authors: Friedrich Jens , Brockmann Melanie , Jansen Walter 
Published: July 2003

AbstractDIE REAKTION VON KALIUMHYDROGENSULFID mit Ethylbromid in ethanolischer Lösung wurde kinetisch und analytisch untersucht. Abhängig von den Reaktionsbedingungen ist als Hauptprodukt Ethanthiol nachweisbar; Triethylsulfoniumbromid dürfte als Nebenprodukt vermutlich aus dem intermediär vorliegenden Diethylsulfid durch Reaktion mit Ethylbromid entstehen. Aus Leitfähigkeitsmessungen kann eine Kinetik 2. Ordnung ermittelt werden. Eine plausible Erklärung ist die bimolekulare Reaktion von Hydrogensulfid‐Ionen und Ethylbromid‐Molekülen. Zum Vergleich wurde die Reaktion von Kaliumsulfid mit Ethylbromid untersucht: In diesem Fall kann die Bildung von Diethylsulfid als Hauptprodukt sowie Ethanthiol und Triethylsulfoniumbromid als Nebenprodukte nachgewiesen werden. Die untersuchten Umwandlungen sind als mechanistische Modellrektionen für die nukleophile Substitution u.E. geeigneter als die Reaktion von Alkylhalogeniden mit Hydroxid‐Ionen. Informativ ist ein Vergleich zwischen Reaktionen der S‐Nukleophile und den bereits veröffentlichten Ergebnissen über O‐Nukleophile.
Gebacken ist nicht ungefährlich
Authors: Hardam Werner 
Published: July 2003

AbstractSEITDEM IM JAHRE 2001 die Substanz Acrylamid in alltäglichen Lebensmitteln entdeckt wurde, sind viele Verbraucher verunsichert; die Substanz soll besonders in Kartoffelchips, in Pommes frites, im Müsli, in Corn Flakes sowie in Keksen und Brot vorkommen [1, 2]. Es wurde herausgefunden, dass es sich bei den getesteten Produkten fast immer um pflanzliche Produkte handelt, die viele Kohlenhydrate enthalten und sehr stark gebacken, getoastet oder frittiert werden. In gekochten Speisen tritt die Substanz nicht auf. Insbesondere kommt in erhitzten Kartoffelerzeugnissen eine erhöhte Acrylamid‐Konzentration vor. Grob gilt: Je intensiver die Braunfärbung, desto höher die Acrylamid‐Belastung. Acrylamid gilt aufgrund von Tierversuchen (Ratten, Kaninchen) als krebserregend und erbgutschädigend; die Wirkung auf den menschlichen Organismus ist bisher unbekannt.
Effective radial Liapunov exponent for the radial diffusion of test electrons
Authors: Maluckov A. , Nakajima N. , Okamoto M. , Murakami S. , Kanno R. 
Published: July 2003

AbstractThe radial diffusion of test electrons in the bounded magnetic field region with irregularities is a realization of the magnetic (deterministic) and collisional (statistical) stochasticities. To clarify the development of stochasticities the effective radial Liapunov exponent Ler, the number of the electron trajectories (magnetic field lines) with positive radial Liapunov exponent Np, the distribution of the radial Liapunov exponent, Kolmogorov entropy and 3D Liapunov exponent are calculated numerically. In the absence of collisions the overlapping among magnetic islands (generation of the global stochasticity) is indicated by the qualitative change from negative to positive Ler in the long time limit. The fact that Np < N, where N is the number of test electrons, is the sign of sticking to the magnetic field structures. From the viewpoint of the radial Liapunov exponents both stochasticities manifest similarly. It is shown that the distribution of the radial Liapunov exponents is not the elementary one, except in the region of the extremely frequent collisions and partially destroyed magnetic field. Transition of the radial diffusion from the strange to the standard diffusion [1] is related with neglecting sticking of the electrons to the magnetic field structures by enough frequent collisions.