bluuebunny/crossref_metadata_2025 huggingface dataset:
The development of scales to measure teacher and school executive occupational satisfaction
Authors: Scott Catherine , Dinham Stephen
Published: February 2003

Interest in teacher “stress” and its relationship to teacher well‐being has a long and distinguished history. However, there has been criticism of this research endeavour for its conceptual narrowness and lack of psychometric rigour. An international project investigating teacher and school executive career satisfaction, motivation and mental health is initiated. This project sought to develop a model of teachers’ occupational well‐being that was wider than a focus on “stress”, and, as noted, included occupational motivation and satisfaction. This paper reports on a sub‐aspect of that research, the development of scales to measure teacher and school executive satisfaction with the work of teaching and its context carried out in Australia, England, New Zealand and the USA. Separate teams recruited participants in each of the four countries, giving a final sample of 3,000 teachers and school executive. Exploratory and confirmatory factor analyses of the Australian data resulted in a ten factor model, which was validated on the English and New Zealand data. Analyses of the US data resulted in a 16 factor model. As well as revealing relative satisfaction with various facets of the teaching role, these scales also prove useful in explaining how teachers and school executive view the construction of their respective educational and social contexts.
An analysis of enabling and mindful school structures
Authors: Hoy Wayne K.
Published: February 2003

This inquiry is a theoretical analysis that attempts to identify the features of school structure that efficiently promote positive outcomes of organization, while limiting negative consequences that are often associated with bureaucratic structures. To that end, the concepts of enabling structures and mindful organizations are developed, contrasted, and synthesized. Then, the research and practical implications of enabling and mindful school structures are proposed and discussed.
A STEP BEYOND KNESER'S THEOREM FOR ABELIAN FINITE GROUPS
Authors: DESHOUILLERS JEAN-MARC , FREIMAN GREGORY A.
Published: February 2003

A precise description of a subset $\mathcal{A}$ of $\mathbb{Z} / n \mathbb{Z}$ satisfying

$$ | \mathcal{A} + \mathcal{A} | \leq 2.04 | \mathcal{A} | $$

is given. Basically, there exists a subgroup $\mathcal{H}$ of $\mathbb{Z} / n \mathbb{Z}$ such that $\mathcal{A}$ is included in an arithmetic progression of $\ell$ cosets modulo $\mathcal{H}$ and

$$(\ell - 1) | \mathcal{H} | \leq | \mathcal{A} + \mathcal{A} | - | \mathcal{A} |.$$

2000 Mathematical Subject Classification: 11B50, 11B83, 20E34.
RECTIFIABILITY OF MEASURES WITH LOCALLY UNIFORM CUBE DENSITY
Authors: LORENT ANDREW
Published: February 2003

The conjecture that Radon measures in Euclidean space with positive finite density are rectifiable was a central problem in Geometric Measure Theory for fifty years. This conjecture was positively resolved by Preiss in 1986, using methods entirely dependent on the symmetry of the Euclidean unit ball. Since then, due to reasons of isometric immersion of metric spaces into $l_{\infty}$ and the uncommon nature of the sup norm even in finite dimensions, a popular model problem for generalising this result to non-Euclidean spaces has been the study of 2-uniform measures in $l^{3}_{\infty}$. The rectifiability or otherwise of these measures has been a well-known question.

In this paper the stronger result that locally 2-uniform measures in $l^{3}_{\infty}$ are rectifiable is proved. This is the first result that proves rectifiability, from an initial condition about densities, for general Radon measures of dimension greater than 1 outside Euclidean space.

2000 Mathematical Subject Classification: 28A75.
EQUIVARIANT PRINCIPAL BUNDLES OVER SPHERES AND COHOMOGENEITY ONE MANIFOLDS
Authors: HAMBLETON IAN , HAUSMANN JEAN-CLAUDE
Published: February 2003

We classify smooth ${\rm SO}(n)$-equivariant principal bundles over $S^n$ in terms of their isotropy representations over the north and south poles. This is an example of a general result classifying equivariant $(\Pi, G)$-bundles over manifolds with cohomogeneity 1.

2000 Mathematical Subject Classification: 55R91.
CRYSTAL BASES FOR QUANTUM AFFINE ALGEBRAS AND COMBINATORICS OF YOUNG WALLS
Authors: KANG SEOK-JIN
Published: February 2003

In this paper we give a realization of crystal bases for quantum affine algebras using some new combinatorial objects which we call the Young walls. The Young walls consist of colored blocks with various shapes that are built on a given ground-state wall and can be viewed as generalizations of Young diagrams. The rules for building Young walls and the action of Kashiwara operators are given explicitly in terms of combinatorics of Young walls. The crystal graph of a basic representation is characterized as the set of all reduced proper Young walls. The character of a basic representation can be computed easily by counting the number of colored blocks that have been added to the ground-state wall.

2000 Mathematical Subject Classification: 17B37, 17B65, 81R50, 82B23.
DILATATION AND ORDER OF CONTACT FOR HOLOMORPHIC SELF-MAPS OF STRONGLY CONVEX DOMAINS
Authors: BRACCI FILIPPO
Published: February 2003

Let $D$ be a bounded strongly convex domain and let $f$ be a holomorphic self-map of $D$. In this paper we introduce and study the dilatation $\alpha (f)$ of $f$ defined, if $f$ has no fixed points in $D$, as the usual boundary dilatation coefficient of $f$ at its Wolff point, or, if $f$ has some fixed points in $D$, as the ratio of shrinking of the Kobayashi balls around a fixed point of $f$. In particular, we show that the map $\alpha$, defined as $\alpha : f \mapsto \alpha (f) \in [0,1]$, is lower semicontinuous. Among other things, this allows us to study the limits of a family of holomorphic self-maps of $D$. In the case of an inner fixed point, the dilatation is an intrinsic measure of the order of contact of $f(D)$ to $\partial D$.

Finally, using complex geodesics, we define and study a directional dilatation, which is a measure of the shrinking of the domain along a given direction. Again, results of semicontinuity are given and applied to a family of holomorphic self-maps.

2000 Mathematical Subject Classification: primary 32H99; secondary 30F99, 32H15.
BROUÉ'S CONJECTURE FOR THE HALL–JANKO GROUP AND ITS DOUBLE COVER
Authors: HOLLOWAY MILES
Published: February 2003

Broué's abelian defect conjecture suggests a deep link between the module categories of a block of a group algebra and its Brauer correspondent, viz. that they should be derived equivalent. We are able to verify Broué's conjecture for the Hall–Janko group, even its double cover $2.J_2$, as well as for $U_3(4)$ and ${\rm Sp}_4(4)$. In fact we verify Rickard's refinement to Broué's conjecture and show that the derived equivalence can be chosen to be a splendid equivalence for these examples.

2000 Mathematical Subject Classification: 20C20, 20C34.
DUNKL OPERATORS FOR COMPLEX REFLECTION GROUPS
Authors: DUNKL C. F. , OPDAM E. M.
Published: February 2003

Dunkl operators for complex reflection groups are defined in this paper. These commuting operators give rise to a parameterized family of deformations of the polynomial De Rham complex. This leads to the study of the polynomial ring as a module over the ‘rational Cherednik algebra’, and a natural contravariant form on this module. In the case of the imprimitive complex reflection groups $G(m, p, N)$, the set of singular parameters in the parameterized family of these structures is described explicitly, using the theory of non-symmetric Jack polynomials.

2000 Mathematical Subject Classification: 20F55 (primary), 52C35, 05E05, 33C08 (secondary).
Inhibition of Hepatitis B Virus Replication by Drug-Induced Depletion of Nucleocapsids
Authors: Deres Karl , Schröder Claus H. , Paessens Arnold , Goldmann Siegfried , Hacker Hans Jörg , Weber Olaf , Krämer Thomas , Niewöhner Ulrich , Pleiss Ulrich , Stoltefuss Jürgen , Graef Erwin , Koletzki Diana , Masantschek Ralf N. A. , Reimann Anja , Jaeger Rainer , Groß Rainer , Beckermann Bernhard , Schlemmer Karl-Heinz , Haebich Dieter , Rübsamen-Waigmann Helga
Published: February 2003

Chronic hepatitis B virus (HBV) infection is a major cause of liver disease. Only interferon-α and the nucleosidic inhibitors of the viral polymerase, 3TC and adefovir, are approved for therapy. However, these therapies are limited by the side effects of interferon and the substantial resistance of the virus to nucleosidic inhibitors. Potent new antiviral compounds suitable for monotherapy or combination therapy are highly desired. We describe non-nucleosidic inhibitors of HBV nucleocapsid maturation that possess in vitro and in vivo antiviral activity. These inhibitors have potential for future therapeutic regimens to combat chronic HBV infection.
Lipid-Like Material as the Source of the Uncharacterized Organic Carbon in the Ocean?
Authors: Hwang Jeomshik , Druffel Ellen R. M.
Published: February 2003

The composition and formation mechanisms of the uncharacterized fraction of oceanic particulate organic carbon (POC) are not well understood. We isolated biologically important compound classes and the acid-insoluble fraction, a proxy of the uncharacterized fraction, from sinking POC in the deep Northeast Pacific and measured carbon isotope ratios to constrain the source(s) of the uncharacterized fraction. Stable carbon and radiocarbon isotope signatures of the acid-insoluble fraction were similar to those of the lipid fraction, implying that the acid-insoluble fraction might be composed of selectively accumulated lipid-like macromolecules.
Eocene El Niño: Evidence for Robust Tropical Dynamics in the "Hothouse"
Authors: Huber Matthew , Caballero Rodrigo
Published: February 2003

Much uncertainty surrounds the interactions between the El Niño–Southern Oscillation (ENSO) and long-term global change. Past periods of extreme global warmth, exemplified by the Eocene (55 to 35 million years ago), provide a good testing ground for theories for this interaction. Here, we compare Eocene coupled climate model simulations with annually resolved variability records preserved in lake sediments. The simulations show Pacific deep-ocean and high-latitude surface warming of ∼10°C but little change in the tropical thermocline structure, atmosphere-ocean dynamics, and ENSO, in agreement with proxies. This result contrasts with theories linking past and future “hothouse” climates with a shift toward a permanent El Niño–like state.
Extracting Work from a Single Heat Bath via Vanishing Quantum Coherence
Authors: Scully Marlan O. , Zubairy M. Suhail , Agarwal Girish S. , Walther Herbert
Published: February 2003

We present here a quantum Carnot engine in which the atoms in the heat bath are given a small bit of quantum coherence. The induced quantum coherence becomes vanishingly small in the high-temperature limit at which we operate and the heat bath is essentially thermal. However, the phase φ, associated with the atomic coherence, provides a new control parameter that can be varied to increase the temperature of the radiation field and to extract work from a single heat bath. The deep physics behind the second law of thermodynamics is not violated; nevertheless, the quantum Carnot engine has certain features that are not possible in a classical engine.
Carbon Nanotube Flow Sensors
Authors: Ghosh Shankar , Sood A. K. , Kumar N.
Published: February 2003

We report that the flow of a liquid on single-walled carbon nanotube bundles induces a voltage in the sample along the direction of the flow. The voltage that was produced fit a logarithmic velocity dependence over nearly six decades of velocity. The magnitude of the voltage depended sensitively on the ionic conductivity and on the polar nature of the liquid. Our measurements suggest that the dominant mechanism responsible for this highly nonlinear response involves a direct forcing of the free charge carriers in the nanotubes by the fluctuating Coulombic field of the liquid flowing past the nanotubes. We propose an explanation based on pulsating asymmetric ratchets. Our work highlights the device potential for nanotubes as sensitive flow sensors and for energy conversion.
Design and Chemical Synthesis of a Homogeneous Polymer-Modified Erythropoiesis Protein
Authors: Kochendoerfer Gerd G. , Chen Shiah-Yun , Mao Feng , Cressman Sonya , Traviglia Stacey , Shao Haiyan , Hunter Christie L. , Low Donald W. , Cagle E. Neil , Carnevali Maia , Gueriguian Vincent , Keogh Peter J. , Porter Heather , Stratton Stephen M. , Wiedeke M. Con , Wilken Jill , Tang Jie , Levy Jay J. , Miranda Les P. , Crnogorac Milan M. , Kalbag Suresh , Botti Paolo , Schindler-Horvat Janice , Savatski Laura , Adamson John W. , Kung Ada , Kent Stephen B. H. , Bradburne James A.
Published: February 2003

We report the design and total chemical synthesis of “synthetic erythropoiesis protein” (SEP), a 51-kilodalton protein-polymer construct consisting of a 166-amino–acid polypeptide chain and two covalently attached, branched, and monodisperse polymer moieties that are negatively charged. The ability to control the chemistry allowed us to synthesize a macromolecule of precisely defined covalent structure. SEP was homogeneous as shown by high-resolution analytical techniques, with a mass of 50,825 ±10 daltons by electrospray mass spectrometry, and with a pI of 5.0. In cell and animal assays for erythropoiesis, SEP displayed potent biological activity and had significantly prolonged duration of action in vivo. These chemical methods are a powerful tool in the rational design of protein constructs with potential therapeutic applications.
Atomic-Resolution Imaging of Oxygen in Perovskite Ceramics
Authors: Jia C. L. , Lentzen M. , Urban K.
Published: February 2003

Using an imaging mode based on the adjustment of a negative value of the spherical-aberration coefficient of the objective lens of a transmission electron microscope, we successfully imaged all types of atomic columns in the dielectric SrTiO
3
and the superconductor YBa
2
Cu
3
O
7
. In particular, we were able to view the oxygen atoms which, due to their low scattering power, were not previously accessible, and this allowed us to detect local nonstoichiometries or the degree of oxygen-vacancy ordering. This technique offers interesting opportunities for research into oxides, minerals, and ceramics. In particular, this holds for the huge group of perovskite-derived electroceramic materials in which the local oxygen content sensitively controls the electronic properties.
Carbon Tunneling from a Single Quantum State
Authors: Zuev Peter S. , Sheridan Robert S. , Albu Titus V. , Truhlar Donald G. , Hrovat David A. , Borden Weston Thatcher
Published: February 2003

We observed ring expansion of 1-methylcyclobutylfluorocarbene at 8 kelvin, a reaction that involves carbon tunneling. The measured rate constants were 4.0 × 10
−6
per second in nitrogen and 4 × 10
−5
per second in argon. Calculations indicated that at this temperature the reaction proceeds from a single quantum state of the reactant so that the computed rate constant has achieved a temperature-independent limit. According to calculations, the tunneling contribution to the rate is 152 orders of magnitude greater than the contribution from passage over the barrier. We discuss environmental effects of the solid-state inert-gas matrix on the reaction rate.
Mitochondrial Biogenesis in Mammals: The Role of Endogenous Nitric Oxide
Authors: Nisoli Enzo , Clementi Emilio , Paolucci Clara , Cozzi Valeria , Tonello Cristina , Sciorati Clara , Bracale Renata , Valerio Alessandra , Francolini Maura , Moncada Salvador , Carruba Michele O.
Published: February 2003

Nitric oxide was found to trigger mitochondrial biogenesis in cells as diverse as brown adipocytes and 3T3-L1, U937, and HeLa cells. This effect of nitric oxide was dependent on guanosine 3′,5′-monophosphate (cGMP) and was mediated by the induction of peroxisome proliferator–activated receptor γ coactivator 1α, a master regulator of mitochondrial biogenesis. Moreover, the mitochondrial biogenesis induced by exposure to cold was markedly reduced in brown adipose tissue of endothelial nitric oxide synthase null-mutant (eNOS
–/–
) mice, which had a reduced metabolic rate and accelerated weight gain as compared to wild-type mice. Thus, a nitric oxide–cGMP–dependent pathway controls mitochondrial biogenesis and body energy balance.
Rest in Plastic
Authors: Herscovitch Penny
Published: February 2003

Body Worlds
The Anatomical Exhibition of Real Human Bodies. Gunther von Hagens, Curator. Atlantis Gallery, 146 Brick Lane, London, E1 6QL, UK. Through 9 February 2003.
www.bodyworlds.com

Körperwelten
Fascination Beneath the Surface. Gunther von Hagens, Curator. München Arena, Munich, Germany. 22 February to 9 March, and 21 March to 15 June 2003.

Von Hagen's controversial exhibition, which has also been presented in Germany and elsewhere as Körperwelten, features plasticized anatomical and whole-body specimens.
Angiogenesis-Independent Endothelial Protection of Liver: Role of VEGFR-1
Authors: LeCouter Jennifer , Moritz Dirk R. , Li Bing , Phillips Gail Lewis , Liang Xiao Huan , Gerber Hans-Peter , Hillan Kenneth J. , Ferrara Napoleone
Published: February 2003

The vascular endothelium was once thought to function primarily in nutrient and oxygen delivery, but recent evidence suggests that it may play a broader role in tissue homeostasis. To explore the role of sinusoidal endothelial cells (LSECs) in the adult liver, we studied the effects of vascular endothelial growth factor (VEGF) receptor activation on mouse hepatocyte growth. Delivery of VEGF-A increased liver mass in mice but did not stimulate growth of hepatocytes in vitro, unless LSECs were also present in the culture. Hepatocyte growth factor (HGF) was identified as one of the LSEC-derived paracrine mediators promoting hepatocyte growth. Selective activation of VEGF receptor–1 (VEGFR-1) stimulated hepatocyte but not endothelial proliferation in vivo and reduced liver damage in mice exposed to a hepatotoxin. Thus, VEGFR-1 agonists may have therapeutic potential for preservation of organ function in certain liver disorders.
Nota Bene: The Art of the Oldest Science
Authors: Smith Orla
Published: February 2003

Dream Anatomy
. Michael Sappol, Curator. National Library of Medicine, Bethesda, MD. Through 31 July 2003.
www.nlm.nih.gov/dreamanatomy

This small exhibition surveys the visual representations of human anatomy ranging from engraved drawings of the 15th century to photographs and computer models of today.
A War on Obesity, Not the Obese
Authors: Friedman Jeffrey M.
Published: February 2003

In their efforts to lose weight, obese individuals may be fighting a powerful set of evolutionary forces honed in an environment drastically different from that of today.
Obesity and the Environment: Where Do We Go from Here?
Authors: Hill James O. , Wyatt Holly R. , Reed George W. , Peters John C.
Published: February 2003

The obesity epidemic shows no signs of abating. There is an urgent need to push back against the environmental forces that are producing gradual weight gain in the population. Using data from national surveys, we estimate that affecting energy balance by 100 kilocalories per day (by a combination of reductions in energy intake and increases in physical activity) could prevent weight gain in most of the population. This can be achieved by small changes in behavior, such as 15 minutes per day of walking or eating a few less bites at each meal. Having a specific behavioral target for the prevention of weight gain may be key to arresting the obesity epidemic.
Au
20
: A Tetrahedral Cluster
Authors: Li Jun , Li Xi , Zhai Hua-Jin , Wang Lai-Sheng
Published: February 2003

Photoelectron spectroscopy revealed that a 20-atom gold cluster has an extremely large energy gap, which is even greater than that of C
60
, and an electron affinity comparable with that of C
60
. This observation suggests that the Au
20
cluster should be highly stable and chemically inert. Using relativistic density functional calculations, we found that Au
20
possesses a tetrahedral structure, which is a fragment of the face-centered cubic lattice of bulk gold with a small structural relaxation. Au
20
is thus a unique molecule with atomic packing similar to that of bulk gold but with very different properties.
GUN4, a Regulator of Chlorophyll Synthesis and Intracellular Signaling
Authors: Larkin Robert M. , Alonso Jose M. , Ecker Joseph R. , Chory Joanne
Published: February 2003

Nuclear genes control plastid differentiation in response to developmental signals, environmental signals, and retrograde signals from plastids themselves. In return, plastids emit signals that are essential for proper expression of many nuclear photosynthetic genes. Accumulation of magnesium-protoporphyrin IX (Mg-Proto), an intermediate in chlorophyll biosynthesis, is a plastid signal that represses nuclear transcription through a signaling pathway that, in
Arabidopsis
, requires the
GUN4
gene. GUN4 binds the product and substrate of Mg- chelatase, an enzyme that produces Mg-Proto, and activates Mg-chelatase. Thus, GUN4 participates in plastid-to-nucleus signaling by regulating Mg-Proto synthesis or trafficking.
Myc-Induced T Cell Leukemia in Transgenic Zebrafish
Authors: Langenau David M. , Traver David , Ferrando Adolfo A. , Kutok Jeffery L. , Aster Jon C. , Kanki John P. , Lin Shuo , Prochownik Ed , Trede Nikolaus S. , Zon Leonard I. , Look A. Thomas
Published: February 2003

The zebrafish is an attractive model organism for studying cancer development because of its genetic accessibility. Here we describe the induction of clonally derived T cell acute lymphoblastic leukemia in transgenic zebrafish expressing mouse c-
myc
under control of the zebrafish
Rag2
promoter. Visualization of leukemic cells expressing a chimeric transgene encoding Myc fused to green fluorescent protein (GFP) revealed that leukemias arose in the thymus, spread locally into gill arches and retro-orbital soft tissue, and then disseminated into skeletal muscle and abdominal organs. Leukemic cells homed back to the thymus in irradiated fish transplanted with GFP-labeled leukemic lymphoblasts. This transgenic model provides a platform for drug screens and for genetic screens aimed at identifying mutations that suppress or enhance c-
myc
– induced carcinogenesis.
Formation of Electron Holes and Particle Energization During Magnetic Reconnection
Authors: Drake J. F. , Swisdak M. , Cattell C. , Shay M. A. , Rogers B. N. , Zeiler A.
Published: February 2003

Three-dimensional particle simulations of magnetic reconnection reveal the development of turbulence driven by intense electron beams that form near the magnetic x-line and separatrices. The turbulence collapses into localized three-dimensional nonlinear structures in which the electron density is depleted. The predicted structure of these electron holes compares favorably with satellite observations at Earth's magnetopause. The birth and death of these electron holes and their associated intense electric fields lead to strong electron scattering and energization, whose understanding is critical to explaining why magnetic explosions in space release energy so quickly and produce such a large number of energetic electrons.
Phytolith Evidence for Early Holocene
Cucurbita
Domestication in Southwest Ecuador
Authors: Piperno Dolores R. , Stothert Karen E.
Published: February 2003

Cucurbita
(squash and gourd) phytoliths recovered from two early Holocene archaeological sites in southwestern Ecuador and directly dated to 10,130 to 9320 carbon-14 years before the present (about 12,000 to 10,000 calendar years ago) are identified as derived from domesticated plants because they are considerably larger than those from modern wild taxa. The beginnings of plant husbandry appear to have been preceded by the exploitation of a wild species of
Cucurbita
during the terminal Pleistocene. These data provide evidence for an independent emergence of plant food production in lowland South America that was contemporaneous with or slightly before that in highland Mesoamerica.
Yield Effects of Genetically Modified Crops in Developing Countries
Authors: Qaim Matin , Zilberman David
Published: February 2003

Onfarm field trials carried out with
Bacillus thuringiensis
(Bt) cotton in different states of India show that the technology substantially reduces pest damage and increases yields. The yield gains are much higher than what has been reported for other countries where genetically modified crops were used mostly to replace and enhance chemical pest control. In many developing countries, small-scale farmers especially suffer big pest-related yield losses because of technical and economic constraints. Pest-resistant genetically modified crops can contribute to increased yields and agricultural growth in those situations, as the case of Bt cotton in India demonstrates.
Passage of Heme-Iron Across the Envelope of
Staphylococcus aureus
Authors: Mazmanian Sarkis K. , Skaar Eric P. , Gaspar Andrew H. , Humayun Munir , Gornicki Piotr , Jelenska Joanna , Joachmiak Andrzej , Missiakas Dominique M. , Schneewind Olaf
Published: February 2003

The cell wall envelope of Gram-positive pathogens functions as a scaffold for the attachment of virulence factors and as a sieve that prevents diffusion of molecules. Here the
isd
genes (iron-regulated surface determinant) of
Staphylococcus aureus
were found to encode factors responsible for hemoglobin binding and passage of heme-iron to the cytoplasm, where it acts as an essential nutrient. Heme-iron passage required two sortases that tether Isd proteins to unique locations within the cell wall. Thus, Isd appears to act as an import apparatus that uses cell wall–anchored proteins to relay heme-iron across the bacterial envelope.
Fat in Control
Authors: Himes Christine L.
Published: February 2003

Female Fertility and the Body Fat Connection
. Rose E. Frisch. University of Chicago Press, Chicago, 2002. 206 pp. $20. ISBN 0-226-26545-5.

Frisch's account for a popular audience weaves together a review of research on the relation between body composition and fertility and the story of her own work in this field.
A Clinical View of the Obesity Problem
Authors: Pi-Sunyer Xavier
Published: February 2003

The increased rate of obesity in the past decade is caused by a larger rate of energy input than energy expenditure. But this simple explanation belies the complexity of the possible solutions: Education about obesity needs to improve for both the medical community and the public. Successful treatment will require reforms of medical practice as well as more research to facilitate the development of new drugs.
Identification and Localization of Flagellins FlaA and FlaB3 within Flagella ofMethanococcus voltae
Authors: Bardy Sonia L. , Mori Takahisa , Komoriya Kaoru , Aizawa Shin-Ichi , Jarrell Ken F.
Published: February 2003

Methanococcus voltaepossesses four flagellin genes, two of which (flaB1andflaB2) have previously been reported to encode major components of the flagellar filament. The remaining two flagellin genes,flaAandflaB3, are transcribed at lower levels, and the corresponding proteins remained undetected prior to this work. Electron microscopy examination of flagella isolated by detergent extraction of whole cells revealed a curved, hook-like region of varying length at the end of a long filament. Enrichment of the curved region of the flagella resulted in the identification of FlaB3 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and N-terminal sequencing, and the localization of this flagellin to the cell-proximal portion of the flagellum was confirmed through immunoblotting and immunoelectron microscopy with FlaB3-specific antibodies, indicating that FlaB3 likely composes the curved portion of the flagella. This could represent a unique case of a flagellin performing the role of the bacterial hook protein. FlaA-specific antibodies were used in immunoblotting to determine that FlaA is found throughout the flagellar filament. M. voltaecells were transformed with a modifiedflaAgene containing a hemagglutinin (HA) tag introduced into the variable region. Transformants that had replaced the wild-type copy of theflaAgene with the HA-tagged version incorporated the HA-tagged version of FlaA into flagella which appeared normal by electron microscopy.
Identification of GtgE, a Novel Virulence Factor Encoded on the Gifsy-2 Bacteriophage ofSalmonella entericaSerovar Typhimurium
Authors: Ho Theresa D. , Figueroa-Bossi Nara , Wang Minhua , Uzzau Sergio , Bossi Lionello , Slauch James M.
Published: February 2003

The Gifsy-2 temperate bacteriophage ofSalmonella entericaserovar Typhimurium contributes significantly to the pathogenicity of strains that carry it as a prophage. Previous studies have shown that Gifsy-2 encodes SodCI, a periplasmic Cu/Zn superoxide dismutase, and at least one additional virulence factor. Gifsy-2 encodes aSalmonellapathogenicity island 2 type III secreted effector protein. Sequence analysis of the Gifsy-2 genome also identifies several open reading frames with homology to those of known virulence genes. However, we found that null mutations in these genes did not individually have a significant effect on the ability ofS. entericaserovar Typhimurium to establish a systemic infection in mice. Using deletion analysis, we have identified a gene,gtgE, which is necessary for the full virulence ofS. entericaserovar Typhimurium Gifsy-2 lysogens. Together, GtgE and SodCI account for the contribution of Gifsy-2 toS. entericaserovar Typhimurium virulence in the murine model.
fleQ
, the Gene Encoding the Major Flagellar Regulator of
Pseudomonas aeruginosa
, Is σ
70
Dependent and Is Downregulated by Vfr, a Homolog of
Escherichia coli
Cyclic AMP Receptor Protein
Authors: Dasgupta Nandini , Ferrell Evan P. , Kanack Kristen J. , West Susan E. H. , Ramphal Reuben
Published: February 2003

The flagellar transcriptional regulator FleQ appears to be the highest-level regulator in the hierarchical regulatory cascade of flagellar biogenesis in
Pseudomonas aeruginosa
. Except for the posttranslational downregulation of FleQ activity by FleN, an antiactivator, not much is known about the regulation of the
fleQ
gene or its gene product. Some FleQ homologs in other bacterial species either are positively regulated by another regulator (e.g., CtrA, the master regulator regulating FlbD in
Caulobacter crescentus
) or are expressed from a σ
70
-dependent promoter (e.g., FlgR of
Helicobacter pylori
). In this study we demonstrated that Vfr, an
Escherichia coli
CRP homolog known to function as an activator for various genes, including
lasR
,
regA
, and
toxA
, in
P. aeruginosa
, is capable of repressing
fleQ
transcription by binding to its consensus sequence in the
fleQ
promoter. In a DNase I footprint assay, purified Vfr protected the sequence 5′-AATTGACTAATCGTTCACATTTG-3′. When this putative Vfr binding site in the
fleQ
promoter was mutated, Vfr was unable to bind the
fleQ
promoter fragment and did not repress
fleQ
transcription effectively. Primer extension analysis of the
fleQ
transcript revealed two transcriptional start sites, t1 and t2, that map within the Vfr binding site. A putative −10 region (TAAAAT) for the t2 transcript, with a five-of-six match with the
E. coli
σ
70
binding consensus, overlaps with one end of the Vfr binding site. A 4-bp mutation and an 8-bp mutation in this −10 region markedly reduced the activity of the
fleQ
promoter. The same mutations led to the disappearance of the 203-nucleotide
fleQ
transcript in an in vitro transcription assay. Vfr probably represses
fleQ
transcription by binding to the Vfr binding site in the
fleQ
promoter and preventing the sigma factor from binding to the −10 region to initiate transcription.
FleQ, the Major Flagellar Gene Regulator in
Pseudomonas aeruginosa
, Binds to Enhancer Sites Located Either Upstream or Atypically Downstream of the RpoN Binding Site
Authors: Jyot Jeevan , Dasgupta Nandini , Ramphal Reuben
Published: February 2003

In
Pseudomonas aeruginosa
, flagellar genes are regulated in a cascade headed by FleQ, an NtrC/NifA-type activator. FleQ and RpoN positively regulate expression of
flhA
,
fliE
,
fliL
, and
fleSR
genes, among others. Direct interaction of FleQ with
flhA
,
fliE
,
fliL
, and
fleSR
promoters was demonstrated by gel shift assay, along with experiments to conclusively determine the specificity of its binding. DNase I footprinting was performed to determine the FleQ binding sites on
flhA
,
fliE
,
fliL
, and
fleSR
promoters. No sequence conservation among these binding sites was observed. Primer extension analysis revealed the transcription start sites (TSSs) to be localized above the FleQ binding sites in
flhA
,
fliE
, and
fliL
promoters. Analysis of the above data revealed FleQ binding to be in the leader sequence of these promoters, whereas FleQ binding was 67 bp upstream of the TSS in the
fleSR
promoter. Mutagenesis of the FleQ binding site in the
flhA
promoter confirmed its functionality in vivo. Deletion of the
flhA
promoter upstream of the RNA polymerase binding site did not result in a significant loss of promoter activity. These results point to two modes of regulation by an NtrC-type regulator in the flagellar hierarchy in
P. aeruginosa
, the first being the typical model of activation from a distance via looping in the
fleSR
promoter and the second involving
flhA
,
fliE
, and
fliL
promoters, where FleQ binds in the downstream vicinity of the promoter and activates transcription without looping.
Metabolism of Dichloromethylcatechols as Central Intermediates in the Degradation of Dichlorotoluenes byRalstoniasp. Strain PS12
Authors: Pollmann Katrin , Kaschabek Stefan , Wray Victor , Reineke Walter , Pieper Dietmar H.
Published: February 2003

Ralstoniasp. strain PS12 is able to use 2,4-, 2,5-, and 3,4-dichlorotoluene as growth substrates. Dichloromethylcatechols are central intermediates that are formed by TecA tetrachlorobenzene dioxygenase-mediated activation at two adjacent unsubstituted carbon atoms followed by TecB chlorobenzene dihydrodiol dehydrogenase-catalyzed rearomatization and then are channeled into a chlorocatecholorthocleavage pathway involving a chlorocatechol 1,2-dioxygenase, chloromuconate cycloisomerase, and dienelactone hydrolase. However, completely different metabolic routes were observed for the three dichloromethylcatechols analyzed. Whereas 3,4-dichloro-6-methylcatechol is quantitatively transformed into one dienelactone (5-chloro-2-methyldienelactone) and thus is degraded via a linear pathway, 3,5-dichloro-2-methylmuconate formed from 4,6-dichloro-3-methylcatechol is subject to both 1,4- and 3,6-cycloisomerization and thus is degraded via a branched metabolic route. 3,6-Dichloro-4-methylcatechol, on the first view, is transformed predominantly into one (2-chloro-3-methyl-trans-) dienelactone. In situ1H nuclear magnetic resonance analysis revealed the intermediate formation of 2,5-dichloro-4-methylmuconolactone, showing that both 1,4- and 3,6-cycloisomerization occur with this muconate and indicating a degradation of the muconolactone via a reversible cycloisomerization reaction and the dienelactone-forming branch of the pathway. Diastereomeric mixtures of two dichloromethylmuconolactones were prepared chemically to proof such a hypothesis. Chloromuconate cycloisomerase transformed 3,5-dichloro-2-methylmuconolactone into a mixture of 2-chloro-5-methyl-cis- and 3-chloro-2-methyldienelactone, affording evidence for a metabolic route of 3,5-dichloro-2-methylmuconolactone via 3,5-dichloro-2-methylmuconate into 2-chloro-5-methyl-cis-dienelactone. 2,5-Dichloro-3-methylmuconolactone was transformed nearly exclusively into 2-chloro-3-methyl-trans-dienelactone.
Cold Shock Response in SporulatingBacillus subtilisand Its Effect on Spore Heat Resistance
Authors: Movahedi Sara , Waites William
Published: February 2003

Cold shock and ethanol and puromycin stress responses in sporulatingBacillus subtiliscells have been investigated. We show that a total of 13 proteins are strongly induced after a short cold shock treatment of sporulating cells. The cold shock pretreatment affected the heat resistance of the spores formed subsequently, with spores heat killed at 85 or 90°C being more heat resistant than the control spores while they were more heat sensitive than controls that were heat treated at 95 or 100°C. However,B. subtilisspores with mutations in the main cold shock proteins, CspB, -C, and -D, did not display decreased heat resistance compared to controls, indicating that these proteins are not directly responsible for the increased heat resistance of the spores. The disappearance of the stress proteins later in sporulation suggests that they cannot be involved in repairing heat damage during spore germination and outgrowth but must alter spore structure in a way which increases or decreases heat resistance. Since heat, ethanol, and puromycin stress produce similar proteins and similar changes in spore heat resistance while cold shock is different in both respects, these alterations appear to be very specific.
A New Modified
ortho
Cleavage Pathway of 3-Chlorocatechol Degradation by
Rhodococcus opacus
1CP: Genetic and Biochemical Evidence
Authors: Moiseeva Olga V. , Solyanikova Inna P. , Kaschabek Stefan R. , Gröning Janosch , Thiel Monika , Golovleva Ludmila A. , Schlömann Michael
Published: February 2003

The 4-chloro- and 2,4-dichlorophenol-degrading strain
Rhodococcus opacus
1CP has previously been shown to acquire, during prolonged adaptation, the ability to mineralize 2-chlorophenol. In addition, homogeneous chlorocatechol 1,2-dioxygenase from 2-chlorophenol-grown biomass has shown relatively high activity towards 3-chlorocatechol. Based on sequences of the N terminus and tryptic peptides of this enzyme, degenerate PCR primers were now designed and used for cloning of the respective gene from genomic DNA of strain 1CP. A 9.5-kb fragment containing nine open reading frames was obtained on pROP1. Besides other genes, a gene cluster consisting of four chlorocatechol catabolic genes was identified. As judged by sequence similarity and correspondence of predicted N termini with those of purified enzymes, the open reading frames correspond to genes for a second chlorocatechol 1,2-dioxygenase (ClcA2), a second chloromuconate cycloisomerase (ClcB2), a second dienelactone hydrolase (ClcD2), and a muconolactone isomerase-related enzyme (ClcF). All enzymes of this new cluster are only distantly related to the known chlorocatechol enzymes and appear to represent new evolutionary lines of these activities. UV overlay spectra as well as high-pressure liquid chromatography analyses confirmed that 2-chloro-
cis
,
cis
-muconate is transformed by ClcB2 to 5-chloromuconolactone, which during turnover by ClcF gives
cis
-dienelactone as the sole product.
cis
-Dienelactone was further hydrolyzed by ClcD2 to maleylacetate. ClcF, despite its sequence similarity to muconolactone isomerases, no longer showed muconolactone-isomerizing activity and thus represents an enzyme dedicated to its new function as a 5-chloromuconolactone dehalogenase. Thus, during 3-chlorocatechol degradation by
R. opacus
1CP, dechlorination is catalyzed by a muconolactone isomerase-related enzyme rather than by a specialized chloromuconate cycloisomerase.
ilvIH
Operon Expression in
Escherichia coli
Requires Lrp Binding to Two Distinct Regions of DNA
Authors: Jafri Samina , Chen Shaolin , Calvo Joseph M.
Published: February 2003

The leucine-responsive regulatory protein Lrp regulates the expression of a number of operons in
Escherichia coli
, including the
ilvIH
operon. Earlier in vitro experiments showed purified Lrp binding to two regions of DNA proximal to the
ilvIH
promoter, an upstream region (−260 to −190) and a downstream region (−150 to −40). The effect of mutations in these regions on
ilvIH
promoter expression in vivo led to the proposal that activation of transcription required Lrp binding to downstream sites 3, 4, 5, and 6. Binding of Lrp to upstream sites 1 and 2 seemed to enhance promoter expression but was not absolutely required (Q. Wang and J. M. Calvo, J. Mol. Biol. 229:306-318, 1993). Here we present data that require a reevaluation of the above conclusion. Constructs having either a deletion of DNA or a 100-bp substitution of DNA upstream of position −160 showed no
ilvIH
promoter activity in vivo. These results unambiguously establish that DNA at or upstream of position −160 is required for
ilvIH
promoter expression. Together with previous results, we conclude that Lrp bound at downstream sites is necessary but not sufficient for promoter activation. In addition, insertion of 4, 6, 8, or 10 bp between the upstream and downstream regions also resulted in a very strong reduction of in vivo promoter expression, even though the binding of Lrp in vitro was not greatly affected by these mutations. Closer inspection showed that the affinity of Lrp for the upstream region of all of these constructs was about the same but that Lrp bound to the downstream region of the wild-type construct with a higher degree of cooperativity than in the case of the others. These mutations may have reduced promoter activity in vivo by eliminating a binding site for some transcription factor other than Lrp. Alternatively, the small-addition mutations may have affected the geometry of these complexes, preventing either an interaction between Lrps bound at upstream and downstream sites (which might be necessary for promoter expression) or preventing the positioning of Lrp bound at upstream sites for productive interaction with the promoter.
Regulatory Response of
Methanococcus maripaludis
to Alanine, an Intermediate Nitrogen Source
Authors: Lie Thomas J. , Leigh John A.
Published: February 2003

In the methanogenic archaeon
Methanococcus maripaludis
, growth with ammonia results in conditions of nitrogen excess. Complete repression of nitrogen fixation (
nif
) gene transcription occurs, and glutamine synthetase (
glnA
) gene transcription falls to a basal constitutive level. In addition, ammonia completely switches off nitrogenase enzyme activity. In contrast, growth with dinitrogen as the sole nitrogen source results in nitrogen starvation, full expression of
nif
and
glnA
, and high activity of nitrogenase. Here we report that a third nitrogen source, alanine, results in an intermediate regulatory response. Growth with alanine resulted in intermediate transcription of
nif
and
glnA
, and addition of alanine to a nitrogen-fixing (diazotrophic) culture caused partial switch-off of nitrogenase. This uniformity of response occurred despite differences in regulatory mechanisms. Nitrogenase switch-off requires the nitrogen sensor homologs NifI
1
and NifI
2
, while transcriptional regulation of
nif
and
glnA
relies on a different, unknown sensor mechanism. In addition, although
nif
and
glnA
transcription are governed by a common repressor, the numbers and arrangements of repressor binding sites differ. Thus, the
nif
promoter region contains two operators situated downstream of the transcription start site, while the
glnA
promoter region contains only one operator just upstream of two closely spaced transcription start sites. In a previous study of
nif
expression using ammonia, we were able to detect a role only for the first
nif
operator in repression. Here we show that
nif
repression by alanine requires the second operator as well. In contrast, in the case of
glnA
the single operator was sufficient for repression by ammonia or alanine. These results suggest a uniform cellular response to nitrogen that is mediated by a different mechanism in each case.
Adaptation of Sucrose Metabolism in the
Escherichia coli
Wild-Type Strain EC3132†
Authors: Jahreis Knut , Bentler Lars , Bockmann Jürgen , Hans Stephan , Meyer Astrid , Siepelmeyer Jörg , Lengeler Joseph W.
Published: February 2003

Although
Escherichia coli
strain EC3132 possesses a chromosomally encoded sucrose metabolic pathway, its growth on low sucrose concentrations (5 mM) is unusually slow, with a doubling time of 20 h. In this report we describe the subcloning and further characterization of the corresponding
csc
genes and adjacent genes. The
csc
regulon comprises three genes for a sucrose permease, a fructokinase, and a sucrose hydrolase (genes
cscB
,
cscK
, and
cscA
, respectively). The genes are arranged in two operons and are negatively controlled at the transcriptional level by the repressor CscR. Furthermore,
csc
gene expression was found to be cyclic AMP-CrpA dependent. A comparison of the genomic sequences of the
E. coli
strains EC3132, K-12, and O157:H7 in addition to
Salmonella enterica
serovar Typhimurium LT2 revealed that the
csc
genes are located in a hot spot region for chromosomal rearrangements in enteric bacteria. The comparison further indicated that the
csc
genes might have been transferred relatively recently to the
E. coli
wild-type EC3132 at around the time when the different strains of the enteric bacteria diverged. We found evidence that a mobile genetic element, which used the gene
argW
for site-specific integration into the chromosome, was probably involved in this horizontal gene transfer and that the
csc
genes are still in the process of optimal adaptation to the new host. Selection for such adaptational mutants growing faster on low sucrose concentrations gave three different classes of mutants. One class comprised
cscR
(Con) mutations that expressed all
csc
genes constitutively. The second class constituted a
cscKo
operator mutation, which became inducible for
csc
gene expression at low sucrose concentrations. The third class was found to be a mutation in the sucrose permease that caused an increase in transport activity.
Structural Maintenance of Chromosomes Protein of
Bacillus
subtilis
Affects Supercoiling In Vivo
Authors: Lindow Janet C. , Britton Robert A. , Grossman Alan D.
Published: February 2003

Structural maintenance of chromosomes (SMC) proteins are found in nearly all organisms. Members of this protein family are involved in chromosome condensation and sister chromatid cohesion.
Bacillus
subtilis
SMC protein (BsSMC) plays a role in chromosome organization and partitioning. To better understand the function of BsSMC, we studied the effects of an
smc
null mutation on DNA supercoiling in vivo. We found that an
smc
null mutant was hypersensitive to the DNA gyrase inhibitors coumermycin A1 and norfloxacin. Furthermore, depleting cells of topoisomerase I substantially suppressed the partitioning defect of an
smc
null mutant. Plasmid DNA isolated from an
smc
null mutant was more negatively supercoiled than that from wild-type cells. In vivo cross-linking experiments indicated that BsSMC was bound to the plasmid. Our results indicate that BsSMC affects supercoiling in vivo, most likely by constraining positive supercoils, an activity which contributes to chromosome compaction and organization.
MazG, a Nucleoside Triphosphate Pyrophosphohydrolase, Interacts with Era, an Essential GTPase inEscherichia coli
Authors: Zhang Junjie , Inouye Masayori
Published: February 2003

Era is an essential GTPase inEscherichia coli, and Era has been implicated in a number of cellular functions. Homologues of Era have been identified in various bacteria and some eukaryotes. Using theeragene as bait in the yeast two-hybrid system to screenE. coligenomic libraries, we discovered that Era interacts with MazG, a protein of unknown function which is highly conserved among bacteria. The direct interaction between Era and MazG was also confirmed in vitro, being stronger in the presence of GDP than in the presence of GTPγS. MazG was characterized as a nucleoside triphosphate pyrophosphohydrolase which can hydrolyze all eight of the canonical ribo- and deoxynucleoside triphosphates to their respective monophosphates and PPi, with a preference for deoxynucleotides. AmazGdeletion strain ofE. coliwas constructed by replacing themazGgene with a kanamycin resistance gene. UnlikemutT, a gene for another conserved nucleotide triphosphate pyrophosphohydrolase that functions as a mutator gene, themazGdeletion did not result in a mutator phenotype inE. coli.