bluuebunny/crossref_metadata_2025 huggingface dataset:
α‐Tocopheryl succinate selectively induces apoptosis in neuroblastoma cells: potential therapy of malignancies of the nervous system?
Authors: Swettenham Emma , Witting Paul K. , Salvatore Brian A. , Neuzil Jiri
Published: December 2005

Vitamin E (VE) analogues, epitomized by α‐tocopheryl succinate (α‐TOS), are potent inducers of apoptosis and anti‐cancer agents. Here, we tested their effect on the highly malignant N‐type neuroblastoma (Nb) cells and their differentiated, neurone‐like counterparts. Nb cells were highly susceptible to several VE analogues, while differentiated Nb cells were relatively resistant to α‐TOS. The importance of caspase‐9 rather than caspase‐8, as judged by specific siRNAs studies, together with the loss of the inner mitochondrial potential, suggests that α‐TOS triggers apoptosis in Nb cells via the mitochondrial pathway. Cultured Nb cells were sensitized to α‐TOS by pre‐treatment with Bcl‐2, Bcl‐xL or Mcl‐1 siRNAs, while the malignant cell line was more resistant to the vitamin E analogue when Bax was knocked down. In contrast, overexpression of Bcl‐2 in Nb cells rendered them more resistant to α‐TOS‐induced apoptosis. The resistance of differentiated Nb cells to α‐TOS‐mediated apoptosis occurred via two modes: first, by up‐regulation of the anti‐apoptotic Bcl‐2 family proteins and second, by accumulation of decreased levels of reactive oxygen species when challenged with α‐TOS. We conclude that α‐TOS is highly selective in killing malignant brain cancer cells while relatively inert toward differentiated neuronal cells, and that vitamin E analogues may be novel therapeutics for the treatment of tumours such as neuroblastomas.
Evidence that protein kinase Cα interacts with and regulates the glial glutamate transporter GLT‐1
Authors: I. González Marco , Susarla Bala T. S. , Robinson Michael B.
Published: December 2005

Many of the sodium‐dependent neurotransmitter transporters are rapidly (within minutes) regulated by protein kinase C (PKC), with changes in activity being correlated with changes in transporter trafficking to or from the plasma membrane. Our recent studies suggest that one of the classical subtypes of PKC, PKCα, may selectively mediate redistribution of the neuronal glutamate transporter, excitatory amino acid carrier (EAAC)1, and show that PKCα can be co‐immunoprecipitated with EAAC1. When the glial glutamate transporter GLT‐1a is transfected into C6 glioma cells, this transporter is internalized in response to activation of PKC, but the PKC subtype involved in this regulation is unknown. In the present study, expression of the phorbol ester‐activated subtypes of PKC was examined in C6 glioma transfected with GLT‐1. Of the classical subtypes, only PKCα was detected, and of the non‐classical subtypes, PKCδ and PKCε were detected. In this system, phorbol ester‐dependent internalization of GLT‐1 was blocked by a general inhibitor of PKCs (bisindolylmaleimide II) and by concentrations of Gö6976 that selectively block classical PKCs, but not by an inhibitor of PKCδ (rottlerin). PKCα immunoreactivity was found in GLT‐1 immunoprecipitates obtained from transfected C6 cells and from crude rat brain synaptosomes, a milieu that better mimicsin vivoconditions. The amount of PKCα in both types of immunoprecipitate was modestly increased by phorbol ester, and this increase was blocked by a PKC antagonist. These studies suggest that PKCα may be required for the regulated redistribution of GLT‐1.
Establishing Representative No‐Take Areas in the Great Barrier Reef: Large‐Scale Implementation of Theory on Marine Protected Areas
Authors: FERNANDES LEANNE , DAY JON , LEWIS ADAM , SLEGERS SUZANNE , KERRIGAN BRIGID , BREEN DAN , CAMERON DARREN , JAGO BELINDA , HALL JAMES , LOWE DAVE , INNES JAMES , TANZER JOHN , CHADWICK VIRGINIA , THOMPSON LEANNE , GORMAN KERRIE , SIMMONS MARK , BARNETT BRYONY , SAMPSON KIRSTI , DE'ATH GLENN , MAPSTONE BRUCE , MARSH HELENE , POSSINGHAM HUGH , BALL IAN , WARD TREVOR , DOBBS KIRSTIN , AUMEND JAMES , SLATER DEB , STAPLETON KATE
Published: December 2005

Abstract:  The Great Barrier Reef Marine Park, an area almost the size of Japan, has a new network of no‐take areas that significantly improves the protection of biodiversity. The new marine park zoning implements, in a quantitative manner, many of the theoretical design principles discussed in the literature. For example, the new network of no‐take areas has at least 20% protection per “bioregion,” minimum levels of protection for all known habitats and special or unique features, and minimum sizes for no‐take areas of at least 10 or 20 km across at the smallest diameter. Overall, more than 33% of the Great Barrier Reef Marine Park is now in no‐take areas (previously 4.5%). The steps taken leading to this outcome were to clarify to the interested public why the existing level of protection was inadequate; detail the conservation objectives of establishing new no‐take areas; work with relevant and independent experts to define, and contribute to, the best scientific process to deliver on the objectives; describe the biodiversity (e.g., map bioregions); define operational principles needed to achieve the objectives; invite community input on all of the above; gather and layer the data gathered in round‐table discussions; report the degree of achievement of principles for various options of no‐take areas; and determine how to address negative impacts. Some of the key success factors in this case have global relevance and include focusing initial communication on the problem to be addressed; applying the precautionary principle; using independent experts; facilitating input to decision making; conducting extensive and participatory consultation; having an existing marine park that encompassed much of the ecosystem; having legislative power under federal law; developing high‐level support; ensuring agency priority and ownership; and being able to address the issue of displaced fishers.
The Acute Anticonvulsant Effects of Deoxycorticosterone in Developing Rats: Role of Metabolites and Mineralocorticoid‐receptor Responses
Authors: Edwards Heather E. , Vimal Sutha , Burnham W. McIntyre
Published: November 2005

Summary: Purpose:The mechanisms that mediate the acute anticonvulsant effects of deoxycorticosterone (DOC) were investigated in young rats.

Methods:Fifteen‐day‐old rats were pretreated with a variety of compounds, including (a) agonists of the receptors that bind DOC (mineralocorticoid receptors); (b) the DOC 5α− and 5α‐3α–reduced metabolites, plus agonists that bind the receptors of the 5α−reduced metabolite of DOC (progesterone receptors); and (c) DOC itself in the presence and absence of metabolism and receptor blockers. Fifteen minutes later, pentylenetetrazol (PTZ) was administered, and maximal pentylenetetrazol (MMT) seizure responses were scored.

Results:Agonists of mineralocorticoid receptors increased the latency to forelimb flexion in PTZ seizures and sometimes suppressed the seizures completely. At low, nonconvulsant doses, spironolactone (a mineralocorticoid‐receptor antagonist) blocked the anticonvulsant effects of a nonsedating, but not a sedating, dose of DOC. These data suggest the possible direct involvement of mineralocorticoid receptors in the anticonvulsant effects of DOC. At low, nonconvulsant doses, finasteride (which blocks the metabolism of DOC) partially blocked the protective effects of DOC, suggesting the contribution of metabolites to the anticonvulsant actions of DOC. Dihydrodeoxycorticosterone (DHDOC)—the first metabolite of DOC, an agonist at progesterone receptors, and an allosteric modulator of the γ‐aminobutyric acid (GABA)Areceptor—and tetrahydrodeoxycorticosterone, a secondary metabolite of DOC and an allosteric modulator of the GABAAreceptor, both blocked MMT seizures.

Conclusions:These findings suggest that both DOC and its metabolites may contribute to the anticonvulsant effects seen in young rats, perhaps acting via interactions with several different receptors.
Status Epilepticus and Frequent Seizures: Incidence and Clinical Characteristics in Pediatric Epilepsy Surgery Patients
Authors: Koh Susan , Mathern Gary W. , Glasser Gabrielle , Wu Joyce Y. , Shields W. Donald , Jonas Rinat , Yudovin Sue , Cepeda Carlos , Salamon Noriko , Vinters Harry V. , Sankar Raman
Published: November 2005

Summary: Purpose:The literature suggests that pediatric epilepsy surgery cases that present in status epilepticus (SE) are an unusual occurrence. However, this concept is based on case reports, and the incidence and clinical characteristics of these patients have not been systematically assessed.

Methods:The cohort consisted of resective epilepsy surgery cases from 2000 to 2005 (n = 115), and they were classified as presenting with continuous SE requiring medical suppression therapy (n = 6) or intermittent SE (greater than 3 seizures/hour; n = 17). The SE categories were compared with extratemporal surgery patients without SE (non‐SE; n = 64) for differences in clinical variables abstracted from the medical record.

Results:Continuous SE was noted in 5% and intermittent SE in 15% of resective surgery cases, and all had extratemporal cortical involvement. Compared with continuous SE and non‐SE cases, intermittent SE patients were younger at surgery with shorter duration of seizures, and had an increased incidence of active infantile spasms during video scalp EEG monitoring. Compared with non‐SE cases, the continuous and intermittent SE groups required a larger number of antiepileptic medications presurgery and 6‐months postsurgery, underwent hemispherectomy more frequently, and had an increased incidence of hemimegalencephaly and Rasmussen encephalitis and a lower occurrence of infarct/ischemia and infectious etiologies. Seizure control was over 71% up to 2 years postsurgery, and there were no differences between patient groups. Finally, seizure frequency per hour was greater in continuous SE cases compared with the intermittent SE group.

Conclusions:Children presenting with continuous or intermittent SE are not rare in pediatric epilepsy surgery centers, and such cases are more commonly associated with infantile spasms, Rasmussen's syndrome, and hemimegalencephaly pathologies. Seizure outcome after surgery was not altered in pediatric patients because they had presented with continuous or intermittent SE.
Employers' Attitudes to Employment of People with Epilepsy: Still the Same Old Story?
Authors: Jacoby Ann , Gorry Joanne , Baker Gus A.
Published: November 2005

Summary: Purpose:One area of life quality known to be compromised by having epilepsy is employment, and one factor contributing to the employment problems of people with epilepsy (PWE) is employer attitudes. Much research on this topic is now outdated and given the changing legal, medical, and social contexts in which PWE live, we therefore reexamined employer attitudes in the united Kingdom.

Method:A mail survey of a random sample of U.K. companies selected to be representative of the 14 U.K. economic regions and proportional to the number of employees.

Findings:The overall response rate was 41% (n = 204). Twenty‐six percent of respondents reported having experience of employing PWE. Sixteen percent considered that there were no jobs in their company suitable for PWE; 21% thought employing PWE would be “a major issue.” Employers were uniformly of the view that PWE, even when in remission, should disclose their condition to a prospective employer. Seizure severity, frequency, and controllability were all considered important features of epilepsy in the context of employment. Epilepsy created high concern to around half of employers, including the likelihood of it being linked to a work‐related accident. Employers were willing to make accommodations for PWE, in particular job sharing, temporary reassignment of duties, and flexible working hours. Attitudes to employment of PWE were influenced by company size and type and previous experience of doing so.

Conclusions:We conclude that it is still the same old story for employers' attitudes toward PWE, though happily for PWE, with some room for optimism.
Body Mass Index, Dieting, Romance, and Sexual Activity in Adolescent Girls: Relationships Over Time
Authors: Halpern Carolyn Tucker , King Rosalind Berkowitz , Oslak Selene G. , Udry J. Richard
Published: November 2005

Romantic relationships constitute an important, but understudied, developmental context for accommodation to pubertal change. Using a nationally representative sample of 5,487 black, white, and Hispanic adolescent females, this study examined associations among body mass index, current romantic involvement, and dieting. For each one point increase in body mass‐index (BMI), the probability of having a romantic relationship decreased by 6%. Further, involvement in a nonsexual romantic relationship—but not involvement in a sexual romantic relationship—was associated with a significant increase in the likelihood of dieting. Associations between relationship type and dieting did not vary by age, socioeconomic status, or race, but were stronger at higher BMIs. These findings confirm that weight has implications for romantic involvement, which is highly valued by adolescent girls, and that romantic relationships, in turn, are important contexts in which to consider psychological and behavioral accommodation to the physical changes of puberty.
Initiating Sexual Experiences: How Do Young Adolescents Make Decisions Regarding Early Sexual Activity?
Authors: Michels Tricia M. , Kropp Rhonda Y. , Eyre Stephen L. , Halpern‐Felsher Bonnie L.
Published: November 2005

Understanding how young adolescents make decisions to engage in early sexual activities is vital for intervention efforts aimed at fostering positive youth development and reducing the negative outcomes of adolescent sexual behavior. In‐depth interviews with 42 suburban, mostly White, ninth‐grade adolescents (52% females, mean age=14.1, SD=.45) elicited accounts of their early sexual decisions. We adapted grounded theory methodology to build a model of sexual decision making from the adolescents' narratives. Six dominant categories emerged: contextual factors (relationship and personal characteristics), consideration of risks and benefits, boundary setting, boundary communication, the sexual experience, and evaluation. Our model of early sexual decision‐making processes, developed from the perspectives of young adolescents, highlights active consideration of health and social risks and benefits, as well as the generation of options regarding sexual activity. The model also shows that young adolescents set clear boundaries of sexual limits and evaluate sexual experiences, suggesting a dynamic process of decision making.
Usefulness and Reliability of Tanner Pubertal Self‐Rating to Urban Black Adolescents in South Africa
Authors: Norris Shane A. , Richter Linda M.
Published: November 2005

Self‐rating of pubertal development is the recommended method to assess puberty in large community‐based surveys of adolescent development and behavior. The aim of this study was to validate for the first time pubertal self‐assessment using the sexual maturation scale developed by Tanner among Black South African adolescents (n=182) aged between 10 and 18 years who were recruited and assessed at public schools in Soweto—Johannesburg. There was significant concordance between adolescents' and same sex health professional's assessment of pubic hair growth and breast development in females (κ coefficients .71 and .76, respectively; p<.0005), and pubic hair growth and genital development in males (κ coefficients .63 and .60, respectively; p<.0005). We conclude that the Tanner pubertal self‐rating appears to be a reasonably valid instrument to use among black South African youth. The tool can be administered in school or other community‐based settings with moderate confidence provided the procedure is thoroughly explained to the participant through the developed tutorial in the language of choice, and privacy and confidentiality are assured.
Synthesis and Characterization of Porous Single‐Crystalline Titanium Dioxide Nanorods
Authors: Yang Songwang , Gao Lian
Published: December 2005

Porous single‐crystalline titanium dioxide (TiO2) nanorods were prepared though a solution aggregation‐based growth process followed by the calcination treatment. The products were characterized by X‐ray diffraction, transmission electron microscopy, and nitrogen adsorption–desorption isotherm analysis. The prepared nanorods were of the single‐crystalline nature and the mesoporosity characteristic. The prepared porous single‐crystalline TiO2 nanorods had high BET‐specific area, 70.3 m2/g. The formation mechanism of the porous single‐crystalline TiO2 nanorods was also investigated. The solution aggregation‐based growth of the nanoparticulates and the following calcination process may result in the formation of the porous single‐crystalline TiO2 nanorods.
Kinetics of Urea Decomposition in the Presence of Transition Metal Ions: Ni2+
Authors: Mavis Bora , Akinc Mufit
Published: December 2005

The literature on kinetics of the urea decomposition reaction was reviewed for the 333–373 K range of temperature. Possible reactions in the pH range of 5–9 were identified. Kinetic simulations indicated significant accumulation of the cyanate intermediate in the pH‐time–temperature range that was studied. The effects of Ni2+ hydrolysis and complexation with the urea decomposition products were incorporated into the simulations. The kinetic simulation of the rate of Ni2+ removal from the solutions was compared against the experimental data. The experimental results indicated an agglomerative growth mechanism for the precipitation process. Chemical analyses showed that the composition of the precipitate varies with digestion time, in agreement with the predictions of the kinetic simulation.
Structural Analysis of the Interaction Between the SNARE Tlg1 and Vps51
Authors: Fridmann‐Sirkis Yael , Kent Helen M. , Lewis Michael J. , Evans Philip R. , Pelham Hugh R. B.
Published: December 2005

Membrane fusion in cells involves the interaction of SNARE proteins on apposing membranes. Formation of SNARE complexes is preceded by tethering events, and a number of protein complexes that are thought to mediate this have been identified. The VFT or GARP complex is required for endosome‐Golgi traffic in yeast. It consists of four subunits, one of which, Vps51, has been shown to bind specifically to the SNARE Tlg1, which participates in the same fusion event. We have determined the structure of the N‐terminal domain of Tlg1 bound to a peptide from the N terminus of Vps51. Binding depends mainly on residues 18–30 of Vps51. These form a short helix which lies in a conserved groove in the three‐helix bundle formed by Tlg1. Surprisingly, although both Vps51 and Tlg1 are required for transport to the late Golgi from endosomes, removal of the Tlg1‐binding sequences from Vps51 does not block such traffic in vivo. Thus, this particular interaction cannot be crucial to the process of vesicle docking or fusion.
Emerging Markets as Learning Laboratories: Learning Behaviors of Local Firms and Foreign Entrants in Different Institutional Contexts
Authors: Hitt Michael A. , Li Haiyang , Worthington William J.
Published: December 2005

In this work, we examine and integrate the research streams on learning behaviours of both local firms and foreign entrants in emerging markets. We propose that local firms and foreign entrants differ in the types of learning pursued and in the learning processes used. While emerging market firms engage in a significant amount of exploratory learning, they also attempt to exploit the newly gained knowledge in their current markets. Furthermore, foreign entrants engage in exploitative learning as expected but also must participate in exploratory learning to acquire knowledge of culture, institutional norms, and important social relationships. While much of the learning occurs through cooperative processes with both partners, they also each engage in experiential learning. We argue that emerging markets also differ; firms in the more mature emerging markets seek different types of learning and the learning processes used vary compared to those in less mature emerging markets. Our research suggests that emerging markets represent learning laboratories and provide a base to catalyse future research.
Stillborn baby with partial monosomy of the short arm of chromosome 5 and partial trisomy of the short arm of chromosome 20
Authors: Okada Michiko , Usami Akemi , Okajima Kaori , Yamada Miwako , Yamaguchi Yuka , Umezaki Izumi , Matsuda Yoshio , Ohta Hiroaki
Published: November 2005

ABSTRACT  A stillborn baby with multiple malformations, including cardiac defects and cerebellar hypoplasia, is described. The abnormal features were ascribed to an unbalanced chromosome translocation, resulting in a partial deletion of the short arm of chromosome 5 and a partial trisomy of the short arm of chromosome 20. A parental balanced translocation t(5; 20)(p13.3; p11.23) was identified. The present case is the first case in Japan of monosomy of the short arm of chromosome 5 and trisomy of the short arm of chromosome 20.
Gender performances in a service orientated workplace in Aotearoa/New Zealand
Authors: Guyatt Victoria
Published: December 2005

Abstract:  This paper uses Butler's (1990) concept of performativity to explore the constructions of feminine and masculine identities integral to the gendered bodily performance in ‘interactive’ service economies. The empirical research for this paper is based on Fat Freddie's student pub in Aotearoa/New Zealand, and was collected over an eight‐week period using an ethnographic methodology. While Butler argues we ‘do’ gender, I explore how these ‘fabrications’ are naturalized, and the effect this has on the division of labour within Fat Freddie's. While these performances are regulatory, they are, however, unstable and alternate subject positionings can be adopted. I discuss how these subject positionings within Fat Freddie's can disrupt dichotomized gendered divisions and hegemonic understandings of appropriate gendered roles and identities.
Perspectives in Australian Global Education and Geography/Mätauranga Matawhenua
Authors: Bliss Susan
Published: December 2005

Abstract: In teaching and learning geography and global education in Australia, understanding a range of perspectives is important because content and practice are inextricably linked. Currently both geography and global education promote a ‘perspectives’ curricula approach requiring effective implementation of a range of perspectives theories such as positivism, multiculturalism, deep environmentalism, feminism and globalism. This paper outlines the philosophical basis of perspectivism, discusses some of the major perspectives theories and their backgrounds, and describes how they are applied in teaching geography and global education with particular reference to the Australian (principally New South Wales) and New Zealand curricula. It concludes with some comments on the current classroom reality of the ‘perspectives’ curricula approach.
Principles of Selective Ion Transport in Channels and Pumps
Authors: Gouaux Eric , MacKinnon Roderick
Published: December 2005

The transport of ions across the membranes of cells and organelles is a prerequisite for many of life's processes. Transport often involves very precise selectivity for specific ions. Recently, atomic-resolution structures have been determined for channels or pumps that are selective for sodium, potassium, calcium, and chloride: four of the most abundant ions in biology. From these structures we can begin to understand the principles of selective ion transport in terms of the architecture and detailed chemistry of the ion conduction pathways.
The Ins and Outs of DNA Transfer in Bacteria
Authors: Chen Inês , Christie Peter J. , Dubnau David
Published: December 2005

Transformation and conjugation permit the passage of DNA through the bacterial membranes and represent dominant modes for the transfer of genetic information between bacterial cells or between bacterial and eukaryotic cells. As such, they are responsible for the spread of fitness-enhancing traits, including antibiotic resistance. Both processes usually involve the recognition of double-stranded DNA, followed by the transfer of single strands. Elaborate molecular machines are responsible for negotiating the passage of macromolecular DNA through the layers of the cell surface. All or nearly all the machine components involved in transformation and conjugation have been identified, and here we present models for their roles in DNA transport.
ATP Signaling Is Crucial for Communication from Taste Buds to Gustatory Nerves
Authors: Finger Thomas E. , Danilova Vicktoria , Barrows Jennell , Bartel Dianna L. , Vigers Alison J. , Stone Leslie , Hellekant Goran , Kinnamon Sue C.
Published: December 2005

Taste receptor cells detect chemicals in the oral cavity and transmit this information to taste nerves, but the neurotransmitter(s) have not been identified. We report that adenosine 5′-triphosphate (ATP) is the key neurotransmitter in this system. Genetic elimination of ionotropic purinergic receptors (P2X
2
and P2X
3
) eliminates taste responses in the taste nerves, although the nerves remain responsive to touch, temperature, and menthol. Similarly, P2X-knockout mice show greatly reduced behavioral responses to sweeteners, glutamate, and bitter substances. Finally, stimulation of taste buds in vitro evokes release of ATP. Thus, ATP fulfils the criteria for a neurotransmitter linking taste buds to the nervous system.
Comment on "The Great Sumatra-Andaman Earthquake of 26 December 2004"
Authors: Neetu S. , Suresh I. , Shankar R. , Shankar D. , Shenoi S. S. C. , Shetye S.R. , Sundar D. , Nagarajan B.
Published: December 2005

Lay
et al
. (Research Articles, 20 May 2005, p. 1127) estimated a 600-km length for the tsunami source region. Adding tide-gauge data from Paradip, the northernmost of the Indian east-coast stations and therefore the most critical constraint on the northern extent of the source, we estimate that its length was greater by ∼30%.
Conformational Changes of Spo0F along the Phosphotransfer Pathway
Authors: Varughese Kottayil I.
Published: December 2005

Spo0F is a secondary messenger in the sporulation phosphorelay, and its structure has been characterized crystallographically in the apo-state, in the metal-bound state, and in an interacting state with a phosphotransferase. Additionally, the solution structure of the molecule has been characterized by nuclear magnetic resonance techniques in the unliganded state and in complex with beryllofluoride. Spo0F is a single-domain protein with a well-defined three-dimensional structure, but it is capable of adapting to specific conformations for catching and releasing the phosphoryl moiety. This commentary deals with the conformational fluctuations of the molecule as it moves from an apo-state to a metal-coordinated state, to a phosphorylated state, and then to a phosphoryl-transferring state.
Spatial Periodicity of
Escherichia coli
K-12 Biofilm Microstructure Initiates during a Reversible, Polar Attachment Phase of Development and Requires the Polysaccharide Adhesin PGA
Authors: Agladze Konstantin , Wang Xin , Romeo Tony
Published: December 2005

Using fast Fourier transform (FFT) analysis, we previously observed that cells within
Escherichia coli
biofilm are organized in nonrandom or periodic spatial patterns (K. Agladze et al., J. Bacteriol. 185:5632-5638, 2003). Here, we developed a gravity displacement assay for examining cell adherence and used it to quantitatively monitor the formation of two distinct forms of cell attachment, temporary and permanent, during early biofilm development. Temporarily attached cells were mainly surface associated by a cell pole; permanent attachments were via the lateral cell surface. While temporary attachment precedes permanent attachment, both forms can coexist in a population. Exposure of attached cells to gravity liberated an unattached population capable of rapidly reassembling a new monolayer, composed of temporarily attached cells, and possessing periodicity. A
csrA
mutant, which forms biofilm more vigorously than its wild-type parent, exhibited an increased proportion of permanently attached cells and a form of attachment that was not apparent in the parent strain, permanent polar attachment. Nevertheless, it formed periodic attachment patterns. In contrast, biofilm mutants with altered lipopolysaccharide synthesis (
waaG
) exhibited increased cell-cell interactions, bypassed the polar attachment step, and produced FFT spectra characteristic of aperiodic cell distribution. Mutants lacking the polysaccharide adhesin β-1,6-
N
-acetyl-
d
-glucosamine (
ΔpgaC
) also exhibited aperiodic cell distribution, but without apparent cell-cell interactions, and were defective in forming permanent attachments. Thus, spatial periodicity of biofilm microstructure is genetically determined and evident during the formation of temporary cell surface attachments.
Distribution and Expression of the ZmpA Metalloprotease in the
Burkholderia cepacia
Complex
Authors: Gingues S. , Kooi C. , Visser M. B. , Subsin B. , Sokol P. A.
Published: December 2005

The distribution of the metalloprotease gene
zmpA
was determined among strains of the
Burkholderia cepacia
complex (Bcc). The
zmpA
gene was present in
B. cepacia
,
B. cenocepacia
,
B. stabilis
,
B. ambifaria
and
B. pyrrocinia
but absent from
B. multivorans
,
B. vietnamiensis
,
B. dolosa
, and
B. anthina
. The presence of
zmpA
generally correlated with extracellular proteolytic activity with the exception of five strains, which had
zmpA
but had no detectable proteolytic activity when skim milk agar was used as a substrate (
zmpA
protease deficient). Western immunoblot experiments with anti-ZmpA antibodies suggest that the
zmpA
protease-deficient strains do not secrete or accumulate detectable ZmpA. Transcriptional
zmpA
::
lacZ
fusions were introduced in selected strains of the Bcc.
zmpA
::
lacZ
was expressed in all strains, but expression was generally lower in the
zmpA
protease-deficient strains than in the
zmpA
protease-proficient strains. Quantitative reverse transcriptase real-time PCR demonstrated that
zmpA
protease-deficient strains did express
zmpA
mRNA, although at various levels.
ZmpA
has previously been shown to be positively regulated by the CepIR quorum-sensing system. Addition of exogenous AHLs did not restore extracellular protease production to any of the
zmpA
protease-deficient strains; however, introduction of
cepR
in
trans
complemented protease activity in two of five strains. Extracellular proteolytic activity was restored by the presence of
zmpA
in
trans
in two of the five strains. These studies suggest that although some strains of the Bcc contain the
zmpA
gene, multiple factors may influence its expression.
F-Like Type IV Secretion Systems Encode Proteins with Thioredoxin Folds That Are Putative DsbC Homologues
Authors: Elton Trevor C. , Holland Samantha J. , Frost Laura S. , Hazes Bart
Published: December 2005

F and R27 are conjugative plasmids of enteric bacteria belonging to the IncF and IncHI1 plasmid incompatibility groups, respectively. Based on sequence analysis, two genes of the F transfer region,traFandtrbB, and three genes of the R27 transfer region,trhF,dsbC, andhtdT, are predicted to encode periplasmic proteins containing a C-terminal thioredoxin fold. The C-X-X-C active-site motif of thioredoxins is present in all of these proteins except TraFF.Escherichia colicarrying adsbAmutation, which is deficient in disulfide bond formation, cannot synthesize pili and exhibits hypersensitivity to dithiothreitol (DTT) as monitored by mating ability. Overproduction of theE. colidisulfide bond isomerase DsbC, TrbBF, DsbCR27, or HtdTR27, but not TraFFor TrhFR27, reverses this hypersensitivity to DTT. Site-directed mutagenesis established that the C-X-X-C motif was necessary for this activity. Secretion into the periplasm of the C-terminal regions of TrbBFand DsbCR27, containing putative thioredoxin folds, but not TrhFR27, partially complemented the hostdsbAmutation. AtrbBFdeletion mutant showed a 10-fold-lower mating efficiency in anE. coli dsbCnull strain but had no phenotype in wild-typeE. coli, suggesting redundancy in function between TrbBFandE. coliDsbC. Our results indicate that TrbBF, DsbCR27, and HtdTR27are putative disulfide bond isomerases for their respective transfer systems. TraFFis essential for conjugation but appears to have a function other than disulfide bond chemistry.
ExbBD-Dependent Transport of Maltodextrins through the Novel MalA Protein across the Outer Membrane ofCaulobacter crescentus
Authors: Neugebauer Heidi , Herrmann Christina , Kammer Winfried , Schwarz Gerold , Nordheim Alfred , Braun Volkmar
Published: December 2005

Analysis of the genome sequence ofCaulobacter crescentuspredicts 67 TonB-dependent outer membrane proteins. To demonstrate that among them are proteins that transport nutrients other than chelated Fe3+and vitamin B12—the substrates hitherto known to be transported by TonB-dependent transporters—the outer membrane protein profile of cells grown on different substrates was determined by two-dimensional electrophoresis. Maltose induced the synthesis of a hitherto unknown 99.5-kDa protein, designated here as MalA, encoded by the cc2287 genomic locus. MalA mediated growth on maltodextrins and transported [14C]maltodextrins from [14C]maltose to [14C]maltopentaose. [14C]maltose transport showed biphasic kinetics, with a fast initial rate and a slower second rate. The initial transport had aKdof 0.2 μM, while the second transport had aKdof 5 μM. It is proposed that the fast rate reflects binding to MalA and the second rate reflects transport into the cells. Energy depletion of cells by 100 μM carbonyl cyanide 3-chlorophenylhydrazone abolished maltose binding and transport. Deletion of themalAgene diminished maltose transport to 1% of the wild-typemalAstrain and impaired transport of the larger maltodextrins. ThemalAmutant was unable to grow on maltodextrins larger than maltotetraose. Deletion of twoC. crescentusgenes homologous to theexbB exbDgenes ofEscherichia coliabolished [14C]maltodextrin binding and transport and growth on maltodextrins larger than maltotetraose. These mutants also showed impaired growth on Fe3+-rhodotorulate as the sole iron source, which provided evidence of energy-coupled transport. Unexpectedly, a deletion mutant of atonBhomolog transported maltose at the wild-type rate and grew on all maltodextrins tested. Since Fe3+-rhodotorulate served as an iron source for thetonBmutant, an additional gene encoding a protein with a TonB function is postulated. Permeation of maltose and maltotriose through the outer membrane of theC. crescentus malAmutant was slower than permeation through the outer membrane of anE. coli lamBmutant, which suggests a low porin activity inC. crescentus. The pores of theC. crescentusporins are slightly larger than those ofE. coliK-12, since maltotetraose supported growth of theC. crescentus malAmutant but failed to support growth of theE. coli lamBmutant. The data are consistent with the proposal that binding of maltodextrins to MalA requires energy and MalA actively transports maltodextrins withKdvalues 1,000-fold smaller than those for the LamB porin and 100-fold larger than those for the vitamin B12and ferric siderophore outer membrane transporters. MalA is the first example of an outer membrane protein for which an ExbB/ExbD-dependent transport of a nutrient other than iron and vitamin B12has been demonstrated.
The Maltodextrin System ofEscherichia coli: Metabolism and Transport
Authors: Dippel Renate , Boos Winfried
Published: December 2005

The maltose/maltodextrin regulon ofEscherichia coliconsists of 10 genes which encode a binding protein-dependent ABC transporter and four enzymes acting on maltodextrins. Allmalgenes are controlled by MalT, a transcriptional activator that is exclusively activated by maltotriose. By the action of amylomaltase, we prepared uniformly labeled [14C]maltodextrins from maltose up to maltoheptaose with identical specific radioactivities with respect to their glucosyl residues, which made it possible to quantitatively follow the rate of transport for each maltodextrin. IsogenicmalQmutants lacking maltodextrin phosphorylase (MalP) or maltodextrin glucosidase (MalZ) or both were constructed. The resulting in vivo pattern of maltodextrin metabolism was determined by analyzing accumulated [14C]maltodextrins. MalP−MalZ+strains degraded all dextrins to maltose, whereas MalP+MalZ−strains degraded them to maltotriose. The labeled dextrins were used to measure the rate of transport in the absence of cytoplasmic metabolism. Irrespective of the length of the dextrin, the rates of transport at a submicromolar concentration were similar for the maltodextrins when the rate was calculated per glucosyl residue, suggesting a novel mode for substrate translocation. Strains lacking MalQ and maltose transacetylase were tested for their ability to accumulate maltose. At 1.8 nM external maltose, the ratio of internal to external maltose concentration under equilibrium conditions reached 106to 1 but declined at higher external maltose concentrations. The maximal internal level of maltose at increasing external maltose concentrations was around 100 mM. A strain lackingmalQ,malP, andmalZas well as glycogen synthesis and in which maltodextrins are not chemically altered could be induced by external maltose as well as by all other maltodextrins, demonstrating the role of transport per se for induction.
Catabolite Control Protein A (CcpA) Contributes to Virulence and Regulation of Sugar Metabolism in
Streptococcus pneumoniae
Authors: Iyer Ramkumar , Baliga Nitin S. , Camilli Andrew
Published: December 2005

We characterized the role of catabolite control protein A (
ccpA
) in the physiology and virulence of
Streptococcus pneumoniae. S. pneumoniae
has a large percentage of its genome devoted to sugar uptake and metabolism, and therefore, regulation of these processes is likely to be crucial for fitness in the nasopharynx and may play a role during invasive disease. In many bacteria, carbon catabolite repression (CCR) is central to such regulation, influencing hierarchical sugar utilization and growth rates. CcpA is the major transcriptional regulator in CCR in several gram-positive bacteria. We show that CcpA functions in CCR of lactose-inducible β-galactosidase activity in
S. pneumoniae
. CCR of maltose-inducible α-glucosidase, raffinose-inducible α-galactosidase, and cellobiose-inducible β-glucosidase is unaffected in the
ccpA
strain, suggesting that other regulators, possibly redundant with CcpA, control these systems. The
ccpA
strain is severely attenuated for nasopharyngeal colonization and lung infection in the mouse, establishing its role in fitness on these mucosal surfaces. Comparison of the cell wall fraction of the
ccpA
and wild-type strains shows that CcpA regulates many proteins in this compartment that are involved in central and intermediary metabolism, a subset of which are required for survival and multiplication in vivo. Both in vitro and in vivo defects were complemented by providing
ccpA
in
trans
. Our results demonstrate that CcpA, though not a global regulator of CCR in
S. pneumoniae
, is required for colonization of the nasopharynx and survival and multiplication in the lung.
Heme A Synthase Enzyme Functions Dissected by Mutagenesis ofBacillus subtilisCtaA
Authors: Hederstedt Lars , Lewin Anna , Throne-Holst Mimmi
Published: December 2005

Heme A, as a prosthetic group, is found exclusively in respiratory oxidases of mitochondria and aerobic bacteria.Bacillus subtilisCtaA and other heme A synthases catalyze the conversion of a methyl side group on heme O into a formyl group. The catalytic mechanism of heme A synthase is not understood, and little is known about the composition and structure of the enzyme. In this work, we have: (i) constructed actaAdeletion mutant and a system for overproduction of mutant variants of the CtaA protein inB. subtilis, (ii) developed anaffinity purification procedure for isolation of preparative amounts of CtaA, and (iii) investigated the functional roles of four invariant histidine residues in heme A synthase by in vivo and in vitro analyses of the properties of mutant variants of CtaA. Our results show an important function of three histidine residues for heme A synthase activity. Several of the purified mutant enzyme proteins contained tightly bound heme O. One variant also contained trapped hydroxylated heme O, which is a postulated enzyme reaction intermediate. The findings indicate functional roles for the invariant histidine residues and provide strong evidence that the heme A synthase enzyme reaction includes two consecutive monooxygenations.
Identification of a Twin-Arginine Translocation System in
Pseudomonas syringae
pv. tomato DC3000 and Its Contribution to Pathogenicity and Fitness
Authors: Bronstein Philip A. , Marrichi Matthew , Cartinhour Sam , Schneider David J. , DeLisa Matthew P.
Published: December 2005

The bacterial plant pathogen
Pseudomonas syringae
pv. tomato DC3000 (DC3000) causes disease in
Arabidopsis thaliana
and tomato plants, and it elicits the hypersensitive response in nonhost plants such as
Nicotiana tabacum
and
Nicotiana benthamiana
. While these events chiefly depend upon the type III protein secretion system and the effector proteins that this system translocates into plant cells, additional factors have been shown to contribute to DC3000 virulence and still many others are likely to exist. Therefore, we explored the contribution of the twin-arginine translocation (Tat) system to the physiology of DC3000. We found that a
tatC
mutant strain of DC3000 displayed a number of phenotypes, including loss of motility on soft agar plates, deficiency in siderophore synthesis and iron acquisition, sensitivity to copper, loss of extracellular phospholipase activity, and attenuated virulence in host plant leaves. In the latter case, we provide evidence that decreased virulence of
tatC
mutants likely arises from a synergistic combination of (i) compromised fitness of bacteria in planta; (ii) decreased efficiency of type III translocation; and (iii) cytoplasmically retained virulence factors. Finally, we demonstrate a novel broad-host-range genetic reporter based on the green fluorescent protein for the identification of Tat-targeted secreted virulence factors that should be generally applicable to any gram-negative bacterium. Collectively, our evidence supports the notion that virulence of DC3000 is a multifactorial process and that the Tat system is an important virulence determinant of this phytopathogenic bacterium.
Genetic Characterization ofPseudomonas fluorescensSBW25rspGene Expression in the Phytosphere and In Vitro
Authors: Jackson Robert W. , Preston Gail M. , Rainey Paul B.
Published: December 2005

The plant-colonizingPseudomonas fluorescensstrain SBW25 harbors a gene cluster (rsp) whose products show similarity to type III protein secretion systems found in plant and animal pathogens. Here we report a detailed analysis of the expression and regulation of theP. fluorescens rsppathway, both in the phytosphere and in vitro. A combination of chromosomally integrated transcriptional reporter fusions, overexpressed regulatory genes, and specific mutants reveal that promoters controlling expression ofrspare actively transcribed in the plant rhizosphere but not (with the exception of therspCpromoter) in the phyllosphere. In synthetic medium, regulatory (rspLandrspR) and structural (rspU, plus the putative effectorropE) genes are poorly expressed; therspCpromoter is subject to an additional level of regulatory control. Ectopic expression of regulatory genes in wild-type and mutant backgrounds showed that RspR controls transcription of the alternate sigma factor,rspL, and that RspL controls expression of gene clusters encoding structural genes. Mutation ofrspVdid not affect RspR-mediated expression ofrspU. A search for additional regulators revealed two candidates—one with a role in the conversion of alanine to pyruvate—suggesting that expression ofrspis partly dependent upon the metabolic status of the cell. Mutations inrspregulators resulted in a significant reduction in competitive colonization of the root tips of sugar beet seedlings but also caused a marked increase in the lag phase of laboratory-grown cultures, indicating thatrspregulatory genes play a more significant general role in the function ofP. fluorescensSBW25 than previously appreciated.
FpvA-Mediated Ferric Pyoverdine Uptake in
Pseudomonas aeruginosa:
Identification of Aromatic Residues in FpvA Implicated in Ferric Pyoverdine Binding and Transport
Authors: Shen Jiang-Sheng , Geoffroy Valérie , Neshat Shadi , Jia Zongchao , Meldrum Allison , Meyer Jean-Marie , Poole Keith
Published: December 2005

A number of aromatic residues were seen to cluster in the upper portion of the three-dimensional structure of the FpvA ferric pyoverdine receptor of
Pseudomonas aeruginosa
, reminiscent of the aromatic binding pocket for ferrichrome in the FhuA receptor of
Escherichia coli
. Alanine substitutions in three of these, W362, W391, and F795, markedly compromised ferric pyoverdine binding and transport, consistent with a role of FpvA in ferric pyoverdine recognition.
SigF, a New Sigma Factor Required for a Motility System of
Myxococcus xanthus
Authors: Ueki Toshiyuki , Xu Chun-Ying , Inouye Sumiko
Published: December 2005

A new sigma factor, SigF, was identified from the social and developmental bacterium
Myxococcus xanthus
. SigF is required for fruiting body formation during development as well as social motility during vegetative growth. Analysis of gene expression indicates that it is possible that the
sigF
gene is involved in regulation of an unidentified gene for social motility.
Synthesis of Peptidoglycan Units with UDP at the Anomeric Position
Authors: Lioux Thierry , Busson Roger , Rozenski Jef , Nguyen-Distèche Martine , Frère Jean-Marie , Herdewijn Piet
Published: November 2005

A series of UDP-disaccharide peptide compounds were synthesized as synthetic substrate analogues or potential inhibitors of glycosyl transferase. Fluorescent compounds have been prepared with the aim of developing a screening method for selecting transglycosylase inhibitors.
Experimental Evidence for a Dual Site Mechanism in Sn-Beta and Sn-MCM-41 Catalysts for the Baeyer-Villiger Oxidation
Authors: Corma Avelino , Renz Michael
Published: November 2005

It is postulated that the catalytic active centre in Sn-Beta and Sn-MCM-41 zeolites for Baeyer-Villiger oxidations involves not only the framework Sn sites but also an associated "basic" oxygen that stabilises the reaction transition state through hydrogen bonding. The presence of these "basic" sites has been studied by cross-polarization MAS NMR H → Sn, and by carrying out the condensation of ketones with malononitrile. The reaction proceeds highly selectively and the reactivity of the substrates corresponds to that of the ketones in the Baeyer-Villiger oxidation with hydrogen peroxide, catalysed with tin-containing molecular sieves.