bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modulation of Antioxidant Defense in
Aspergillus parasiticus
Is Involved in Aflatoxin Biosynthesis: a Role for the Ap
yapA
Gene
Authors: Reverberi Massimo , Zjalic Slaven , Ricelli Alessandra , Punelli Federico , Camera Emanuela , Fabbri Claudia , Picardo Mauro , Fanelli Corrado , Fabbri Anna A. 
Published: April 2008

ABSTRACT

Oxidative stress is recognized as a trigger of different metabolic events in all organisms. Various factors correlated with oxidation, such as the β-oxidation of fatty acids and their enzymatic or nonenzymatic by-products (e.g., precocious sexual inducer factors and lipoperoxides) have been shown to be involved in aflatoxin formation. In the present study, we found that increased levels of reactive oxygen species (ROS) were correlated with increased levels of aflatoxin biosynthesis in
Aspergillus parasiticus
. To better understand the role of ROS formation in toxin production, we generated a mutant (ΔAp
yapA
) having the Ap
yapA
gene deleted, given that Ap
yapA
orthologs have been shown to be part of the antioxidant response in other fungi. Compared to the wild type, the mutant showed an increased susceptibility to extracellular oxidants, as well as precocious ROS formation and aflatoxin biosynthesis. Genetic complementation of the ΔAp
yapA
mutant restored the timing and quantity of toxin biosynthesis to the levels found in the wild type. The presence of putative AP1 (ApYapA orthologue) binding sites in the promoter region of the regulatory gene
aflR
further supports the finding that ApYapA plays a role in the regulation of aflatoxin biosynthesis. Overall, our results show that the lack of Ap
yapA
leads to an increase in oxidative stress, premature conidiogenesis, and aflatoxin biosynthesis.
RscS Functions Upstream of SypG To Control the
syp
Locus and Biofilm Formation in
Vibrio fischeri
Authors: Hussa Elizabeth A. , Darnell Cynthia L. , Visick Karen L. 
Published: April 2008

ABSTRACT

Two-component signal transduction systems, composed of sensor kinase (SK) and response regulator (RR) proteins, allow bacterial cells to adapt to changes such as environmental flux or the presence of a host. RscS is an SK required for
Vibrio fischeri
to initiate a symbiotic partnership with the Hawaiian squid
Euprymna scolopes
, likely due to its role in controlling the symbiosis polysaccharide (
syp
) genes and thus biofilm formation. To determine which RR(s) functions downstream of RscS, we performed epistasis experiments with a library of 35 RR mutants. We found that several RRs contributed to RscS-mediated biofilm formation in
V. fischeri
. However, only the
syp
-encoded symbiosis regulator SypG was required for both biofilm phenotypes and
syp
transcription induced by RscS. These data support the hypothesis that RscS functions upstream of SypG to induce biofilm formation. In addition, this work also revealed a role for the
syp
-encoded RR SypE in biofilm formation. To our knowledge, no other study has used a large-scale epistasis approach to elucidate two-component signaling pathways. Therefore, this work both contributes to our understanding of regulatory pathways important for symbiotic colonization by
V. fischeri
and establishes a paradigm for evaluating two-component pathways in the genomics era.
Streptococcal Antagonism in Oral Biofilms:Streptococcus sanguinisandStreptococcus gordoniiInterference withStreptococcus mutans
Authors: Kreth Jens , Zhang Yongshu , Herzberg Mark C. 
Published: April 2008

ABSTRACTBiofilms are polymicrobial, with diverse bacterial species competing for limited space and nutrients. Under healthy conditions, the different species in biofilms maintain an ecological balance. This balance can be disturbed by environmental factors and interspecies interactions. These perturbations can enable dominant growth of certain species, leading to disease. To model clinically relevant interspecies antagonism, we studied three well-characterized and closely related oral species,Streptococcus gordonii, Streptococcus sanguinis, and cariogenicStreptococcus mutans. S. sanguinisandS. gordoniiused oxygen availability and the differential production of hydrogen peroxide (H2O2) to compete effectively againstS. mutans. Interspecies antagonism was influenced by glucose with reduced production of H2O2. Furthermore, aerobic conditions stimulated the competence system and the expression of the bacteriocin mutacin IV ofS. mutans, as well as the H2O2-dependent release of heterologous DNA from mixed cultures ofS. sanguinisandS. gordonii. These data provide new insights into ecological factors that determine the outcome of competition between pioneer colonizing oral streptococci and the survival mechanisms ofS. mutansin the oral biofilm.
Roles of Pneumococcal DivIB in Cell Division
Authors: Le Gouëllec Audrey , Roux Laure , Fadda Daniela , Massidda Orietta , Vernet Thierry , Zapun André 
Published: April 2008

ABSTRACTDivIB, also known as FtsQ in gram-negative organisms, is a division protein that is conserved in most eubacteria. DivIB is localized at the division site and forms a complex with two other division proteins, FtsL and DivIC/FtsB. The precise function of these three bitopic membrane proteins, which are central to the division process, remains unknown. We report here the characterization of adivIBdeletion mutant ofStreptococcus pneumoniae, which is a coccus that divides with parallel planes. Unlike its homologue FtsQ inEscherichia coli, pneumococcal DivIB is not required for growth in rich medium, but the ΔdivIBmutant forms chains of diplococci and a small fraction of enlarged cells with defective septa. However, the deletion mutant does not grow in a chemically defined medium. In the absence of DivIB and protein synthesis, the partner FtsL is rapidly degraded, whereas other division proteins are not affected, pointing to a role of DivIB in stabilizing FtsL. This is further supported by the finding that an additional copy offtsLrestores growth of the ΔdivIBmutant in defined medium. Functional mapping of the three distinct α, β, and γ domains of the extracellular region of DivIB revealed that a complete β domain is required to fully rescue the deletion mutant. DivIB with a truncated β domain reverts only the chaining phenotype, indicating that DivIB has distinct roles early and late in the division process. Most importantly, the deletion ofdivIBincreases the susceptibility to β-lactams, more evidently in a resistant strain, suggesting a function in cell wall synthesis.
Regulatory Network Controlling Extracellular Proteins inErwinia carotovorasubsp.carotovora: FlhDC, the Master Regulator of Flagellar Genes, ActivatesrsmBRegulatory RNA Production by AffectinggacAandhexA(lrhA) Expression
Authors: Cui Yaya , Chatterjee Asita , Yang Hailian , Chatterjee Arun K. 
Published: April 2008

ABSTRACTErwinia carotovorasubsp.carotovoraproduces an array of extracellular proteins (i.e., exoproteins), including plant cell wall-degrading enzymes and Harpin, an effector responsible for eliciting hypersensitive reaction. Exoprotein genes are coregulated by the quorum-sensing signal,N-acyl homoserine lactone, plant signals, an assortment of transcriptional factors/regulators (GacS/A, ExpR1, ExpR2, KdgR, RpoS, HexA, and RsmC) and posttranscriptional regulators (RsmA,rsmBRNA).rsmBRNA production is positively regulated by GacS/A, a two-component system, and negatively regulated by HexA (PecT inErwinia chrysanthemi; LrhA [LysR homolog A] inEscherichia coli) and RsmC, a putative transcriptional adaptor. While free RsmA, an RNA-binding protein, promotes decay of mRNAs of exoprotein genes, binding of RsmA withrsmBRNA neutralizes the RsmA effect. In the course of studies of GacA regulation, we discovered that a locus bearing strong homology to theflhDCoperon ofE. colialso controls extracellular enzyme production. A transposon insertion FlhDC−mutant produces very low levels of pectate lyase, polygalacturonase, cellulase, protease, andE. carotovorasubsp.carotovoraHarpin (HarpinEcc) and is severely attenuated in its plant virulence. The production of these exoproteins is restored in the mutant carrying an FlhDC+plasmid. Sequence analysis and transcript assays disclosed that theflhDoperon ofE. carotovorasubsp.carotovora, like those of other enterobacteria, consists offlhDandflhC. Complementation analysis revealed that the regulatory effect requires functions of bothflhDandflhCproducts. The data presented here show that FlhDC positively regulatesgacA,rsmC, andfliAand negatively regulateshexA(lrhA). Evidence shows that FlhDC controls extracellular protein production through cumulative effects onhexAandgacA. Reduced levels of GacA and elevated levels of HexA in the FlhDC−mutant are responsible for the inhibition ofrsmBRNA production, a condition conducive to the accumulation of free RsmA. Indeed, studies with an RsmA−FlhDC−double mutant and multiple copies ofrsmB+DNA establish that the negative effect of FlhDC deficiency is exerted via RsmA. The FlhDC-mediated regulation offliAhas no bearing on exoprotein production inE. carotovorasubsp.carotovora. Our observations for the first time establish a regulatory connection between FlhDC, HexA, GacA, andrsmBRNA in the context of the exoprotein production and virulence ofE. carotovorasubsp.carotovora.
A Genomic Islet Mediates Flagellar Phase Variation in
Escherichia coli
Strains Carrying the Flagellin-Specifying Locus
flk
Authors: Feng Lu , Liu Bin , Liu Yanqun , Ratiner Yuli A. , Hu Bo , Li Dan , Zong Xiaolin , Xiong Wei , Wang Lei 
Published: April 2008

ABSTRACT

The occurrence of unilateral flagellar phase variation was previously demonstrated in
Escherichia coli
strains carrying the non-
fliC
flagellin-specifying locus
flk
. In this study, we investigated the mechanism involved in this process. By using sequencing and sequence analysis, the
flk
region between the chromosomal genes
yhaC
and
rnpB
was characterized in all described
flk
-positive
E. coli
strains, including the H35 strain identified in this study (the other strains used are H3, H36, H47, and H53 strains), and this region was found to contain a putative integrase gene and flanking direct repeats in addition to the
flk
flagellin-specifying gene
flkA
and a
fliC
repressor gene,
flkB
, indicating that there is a typical genomic islet (GI), which was designated the
flk
GI. The horizontal transfer potential of the
flk
GI was indicated by detection of the excised extrachromosomal circular form of the
flk
GI. By generating
fliC
-expressing variants of H3 and H47 strains, unilateral flagellar phase variation in
flk
-positive strains was shown to be mediated by excision of the
flk
GI. The function of the proposed integrase gene was confirmed by deletion and a complementation test. The potential integration sites of the
flk
GI were identified. A general model for flagellar phase variation in
flk
-positive
E. coli
strains can be expressed as
fliC
off
+
flkA
on
→
fliC
on
+
flkA
none
. This is the first time that a molecular mechanism for flagellar phase variation has been reported for
E. coli
.
Signal Pathway in Salt-Activated Expression of theSalmonellaPathogenicity Island 1 Type III Secretion System inSalmonella entericaSerovar Typhimurium
Authors: Mizusaki Hideaki , Takaya Akiko , Yamamoto Tomoko , Aizawa Shin-Ichi 
Published: April 2008

ABSTRACTSalmonella entericaserovar Typhimurium secretes virulence factors for invasion called Sip proteins or Sips into its hosts through a type III secretion system (T3SS). In the absence of a host,S. entericainduces Sip secretion in response to sucrose or simple salts, such as NaCl. We analyzed induction of host-independent Sip secretion by monitoring protein secretion by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), assembly of needle complexes by electron microscopy, and transcription of virulence regulatory genes by quantitative reverse transcriptase PCR (real-time PCR). SDS-PAGE showed that addition of sucrose or simple salts, such as NaCl, to the growth medium induced Sip secretion without altering flagellar protein secretion, which requires a distinct T3SS. Electron microscopy confirmed that the amount of secreted Sips increased as the number of assembled needle complexes increased. Real-time PCR revealed that added sucrose or NaCl enhanced transcription ofhilA,hilC, andhilD, which encode known regulators ofSalmonellavirulence. However, epistasis analysis implicated HilD and HilA, but not HilC, in the direct pathway from the salt stimulus to the Sip secretion response. Further analyses showed that the BarA/SirA two-component signal transduction pathway, but not the two-component sensor kinase EnvZ, directly activatedhilDandhilAtranscription and thus Sip secretion in response to either sucrose or NaCl. Finally, real-time PCR showed that salt does not influence transcription of the BarA/SirA-dependentcsrBandcsrCgenes. A model is proposed for the major pathway in which sucrose or salt signals to enhance virulence gene expression.
Evidence for an Elongated Dimeric Structure of Heparin-Binding Hemagglutinin from
Mycobacterium tuberculosis
Authors: Esposito Carla , Pethoukov Maxim V. , Svergun Dmitri I. , Ruggiero Alessia , Pedone Carlo , Pedone Emilia , Berisio Rita 
Published: April 2008

ABSTRACT
Heparin-binding hemagglutinin (HBHA) is a virulence factor of tuberculosis which is responsible for extrapulmonary dissemination of this disease. A thorough biochemical characterization of HBHA has provided experimental evidence of a coiled-coil nature of HBHA. These data, together with the low-resolution structures of a full-length form and a truncated form of HBHA obtained by small-angle X-ray scattering, have unambiguously indicated that HBHA has a dimeric structure with an elongated shape.
Clinical prioritisations of healthcare for the aged—professional roles
Authors: Nortvedt P , Pedersen R , Grøthe K H , Nordhaug M , Kirkevold M , Slettebø Å , Brinchmann B S , Andersen B 
Published: April 2008

Background:Although fair distribution of healthcare services for older patients is an important challenge, qualitative research exploring clinicians’ considerations in clinical prioritisation within this field is scarce.Objectives:To explore how clinicians understand their professional role in clinical prioritisations in healthcare services for old patients.Design:A semi-structured interview-guide was employed to interview 45 clinicians working with older patients. The interviews were analysed qualitatively using hermeneutical content analysis.Participants:20 physicians and 25 nurses working in public hospitals and nursing homes in different parts of Norway.Results and interpretations:The clinicians struggle with not being able to attend to the comprehensive needs of older patients, and being unfaithful to professional ideals and expectations. There is a tendency towards lowering the standards and narrowing the role of the clinician. This is done in order to secure the vital needs of the patient, but is at the expense of good practice and holistic role modelling. Increased specialisation, advances and increase in medical interventions, economical incentives, organisational structures, and biomedical paradigms, may all contribute to a narrowing of the clinicians’ role.Conclusion:Distributing healthcare services in a fair way is generally not described as integral to the clinicians’ role in clinical prioritisations. If considerations of justice are not included in clinicians’ role, it is likely that others will shape major parts of their roles and responsibilities in clinical prioritisations. Fair distribution of healthcare services for older patients is possible only if clinicians accept responsibility in these questions.
Evaluation of three polymerase chain reaction techniques for detection ofBrucellaDNA in peripheral human blood
Authors: Baddour Manal M. , Alkhalifa Dalal H. 
Published: April 2008

Brucellosis is a widespread zoonosis. Currently the diagnosis of this zoonosis is based on microbiological and serological laboratory tests. Polymerase chain reaction (PCR) has been used to detect DNA from Brucella . Different target genes, primer pairs, PCR techniques, and extraction procedures have previously been published for Brucella detection. But only a few of these primers have been used in human samples, and only one study has been carried out to compare sensitivity between them. In the present study, 3 sets of primers and 3 different PCR protocols amplifying 3 different regions of the Brucella genome were compared for detection of Brucella DNA in a peripheral-blood PCR assay to conclude which is most suitable for the clinical diagnostic laboratory. These 3 pairs of primers amplify 3 different fragments included in (i) a gene encoding a 31 kDa Brucella abortus antigen (B4/B5), (ii) a sequence 16S rRNA of B. abortus (F4/R2), and (iii) a gene encoding an outer membrane protein (omp-2) (JPF/JPR). Some modifications on the reported techniques were applied during the present work to improve the outcome. The results showed that the B4/B5 primer pair had the highest sensitivity for detection of positive samples (98%), the JPF/JPR primer pair detected 88.4% of positive samples, whereas F4/R2 primer pair was the least sensitive, being able to detect only 53.1% of positive samples. The specificity of the 3 techniques was 100%. The B4/B5 primer pair was also able to detect the smallest number of bacteria (700 cfu/mL), whereas JPF/JPR was able to detect 7 × 105 cfu/mL and F4/R2 was able to detect 7 × 107cfu/mL. It is thus concluded that using the B4/B5 primer PCR with the suggested modifications is a robust assay, which meets the sensitivity requirements to be used for testing of human blood samples for brucellosis in the diagnostic laboratory.
Aspergillus flavus aflatoxin occurrence and expression of aflatoxin biosynthesis genes in soil
Authors: Accinelli Cesare , Abbas H.K. , Zablotowicz R.M. , Wilkinson J.R. 
Published: April 2008

The carcinogen aflatoxin B1 (AFB1) produced by Aspergillus flavus is a major food safety concern in crops. However, information on AFB1 occurrence in soil and crop residue is scarce. A series of experiments investigated the occurrence of AFB1 in soil and corn residues and ascertained the ecology of A. flavus in a Dundee silt loam soil. Samples of untilled soil (0–2 cm) and residues were collected in March 2007 from plots previously planted with a corn isoline containing the Bacillus thuringiensis (Bt) endotoxin gene or the parental non-Bt isoline. AFB1 levels were significantly different in various corn residues. The highest AFB1 levels were observed in cobs containing grain, with 145 and 275 ng·g–1in Bt and non-Bt, respectively (P ≥ F = 0.001). Aflatoxin levels averaged 3.3 and 9.6 ng·g–1in leaves and (or) stalks and cobs without grain, respectively. All soils had AFB1 ranging from 0.6 to 5.5 ng·g–1with similar levels in plots from Bt and non-Bt corn. Based on cultural methods, soil contained from log103.1 to 4.5 A. flavus cfu·g–1with about 60% of isolates producing aflatoxin. Laboratory experiments demonstrated that AFB1 is rapidly degraded in soil at 28 °C (half-life ≤ 5 days). The potential of the soil A. flavus to produce aflatoxins was confirmed by molecular methods. Transcription of 5 aflatoxin biosynthesis genes, including aflD, aflG, aflP, aflR, and aflS, were detected by reverse transcription – polymerase chain reaction analysis in soil. Although AFB1 appears to be transient in soils, it is clear that AFB1 is produced in surface soil in the presence of corn residues, as indicated by A. flavus cfu levels, AFB1 detection, and expression of aflatoxin biosynthetic genes.
The Future of Site Investigation
Authors: Craig C. 
Published: April 2008

Abstract
A review of the recent past leads one to conclude that the UK has an over capacity in terms of consultancy, specialist contracting and professional staff. This will have to be brought into balance.
Factors likely to affect the future are discussed—technological breakthrough, legislation, certification, litigation, and market attitude.
The fragmented organisation of the five basic activities of SI are considered and it is suggested that there is much to recommend the appointment of an independent geotechnical consultant, who would accept total responsibility for the SI.
Effects of Stress Path and Stress History on the Stiffness of Reconstituted London Clay
Authors: Atkinson J. H. , Evans J. S. , Richardson D. 
Published: April 2008

Abstract
Soil behaviour is stress history dependent and stress path dependent and soil parameters, particularly those for stress-strain behaviour, measured in conventional triaxial tests may not represent the behaviour of soil in many civil engineering works.

To obtain more realistic parameters it may be necessary to conduct laboratory tests which more closely represent
in situ
conditions before and during construction.

The paper describes equipment developed at The City University to carry out stress path tests simply and economically. A series of CU triaxial tests and stress path tests on reconstituted soil illustrate the dependence of measured soil parameters on stress history and stress path.
An Assessment of the British Code of Practice for Site Investigations for Hong Kong Conditions
Authors: Borrie G. W. , Cipullo A. , Massey J. B. 
Published: April 2008

Abstract
The Geotechnical Control Office has undertaken the preparation of two separate, complementary guides on “Rock and Soil Description ” and “Site Investigation ”, as companion documents to BS 5930:1981 for use in Hong Kong. This paper examines the need for a separate guidance document on site investigation for Hong Kong conditions. The predominance of heterogeneous weathered soil profiles and colluvium in Hong Kong presents particular problems, both in their description and investigation, which are not covered adequately by BS 5930:1981.
Emphasis in this paper is placed on highlighting the shortcomings or inappropriateness of some of the BS 5930:1981 site investigation techniques when applied to Hong Kong conditions. For example, the British Code of Practice discusses techniques which are not used in Hong Kong, such as light cable percussive drilling; techniques and good practice associated with rotary core drilling are amplified instead. Similar treatment is given to the commonly installed open hydraulic (Casagrande) piezometers.

Particular problems and interpretation of frequently performed field tests such as dynamic probing, the standard penetration test,
in-situ
vane shear test and impression packer surveys are also discussed.
Recent Techniques in Geophysics with Special Applications to Engineering Geology
Authors: Caldwell R. A. 
Published: April 2008

Abstract and Introduction
Geophysical field measurements are now more frequently employed to gain information about the ground conditions, so that construction projects can be economically and safely designed. This is especially the case for offshore structures and nuclear power plants or where the ground conditions are poor.
Large scale structures require aseismic design and this area of application has been greatly improved, as we can accurately analyse the dynamic properties of the ground. Instruments are also available to monitor the ground behaviour during and after construction so that the new stress conditions can be evaluated.

The fields which have been improved recently are: the seismic reflection technique for shallow exploration, the measurement of shear wave velocity to determine dynamic modulus, borehole measurement of all types and most recently radar to give a continuous high resolution section of the near surface. All these techniques have been improved by new technology enhancing the display and plotting capability and
S/N
ratio, as well as continued development of the theoretical problem.