bluuebunny/crossref_metadata_2025_split huggingface dataset:
Transition from reversible to irreversible attachment during biofilm formation by Pseudomonas fluorescens WCS365 requires an ABC transporter and a large secreted protein
Authors: Hinsa Shannon M. , Espinosa‐Urgel Manuel , Ramos Juan L. , O'Toole George A. 
Published: July 2003

SummaryWe report the identification of an ATP‐binding cassette (ABC) transporter and an associated large cell‐surface protein that are required for biofilm formation by Pseudomonas fluorescens WCS365. The genes coding for these proteins are designated lap for large adhesion protein. The LapA protein, with a predicted molecular weight of ∼900 kDa, is found to be loosely associated with the cell surface and present in the culture supernatant. The LapB, LapC and LapE proteins are predicted to be the cytoplasmic membrane‐localized ATPase, membrane fusion protein and outer membrane protein component, respectively, of an ABC transporter. Consistent with this prediction, LapE, like other members of this family, is localized to the outer membrane. We propose that the lapEBC‐encoded ABC transporter participates in the secretion of LapA, as strains with mutations in the lapEBC genes do not have detectable LapA associated with the cell surface or in the supernatant. The lap genes are conserved among environmental pseudomonads such as P. putida KT2440, P. fluorescens PfO1 and P. fluorescens WCS365, but are absent from pathogenic pseudomonads such as P. aeruginosa and P. syringae. The wild‐type strain of P. fluorescens WCS365 and its lap mutant derivatives were assessed for their biofilm forming ability in static and flow systems. The lap mutant strains are impaired in an early step in biofilm formation and are unable to develop the mature biofilm structure seen for the wild‐type bacterium. Time‐lapse microscopy studies determined that the lap mutants are unable to progress from reversible (or transient) attachment to the irreversible attachment stage of biofilm development. The lap mutants were also found to be defective in attachment to quartz sand, an abiotic surface these organisms likely encounter in the environment.
Pathogenic Leptospira species express surface‐exposed proteins belonging to the bacterial immunoglobulin superfamily
Authors: Matsunaga James , Barocchi Michele A. , Croda Julio , Young Tracy A. , Sanchez Yolanda , Siqueira Isadora , Bolin Carole A. , Reis Mitermayer G. , Riley Lee W. , Haake David A. , Ko Albert I. 
Published: July 2003

SummaryProteins with bacterial immunoglobulin‐like (Big) domains, such as the Yersinia pseudotuberculosis invasin and Escherichia coli intimin, are surface‐expressed proteins that mediate host mammalian cell invasion or attachment. Here, we report the identification and characterization of a new family of Big domain proteins, referred to as Lig (leptospiral Ig‐like) proteins, in pathogenic Leptospira. Screening of L. interrogans and L. kirschneri expression libraries with sera from leptospirosis patients identified 13 lambda phage clones that encode tandem repeats of the 90 amino acid Big domain. Two lig genes, designated ligA and ligB, and one pseudogene, ligC, were identified. The ligA and ligB genes encode amino‐terminal lipoprotein signal peptides followed by 10 or 11 Big domain repeats and, in the case of ligB, a unique carboxy‐terminal non‐repeat domain. The organization of ligC is similar to that of ligB but contains mutations that disrupt the reading frame. The lig sequences are present in pathogenic but not saprophytic Leptospira species. LigA and LigB are expressed by a variety of virulent leptospiral strains. Loss of Lig protein and RNA transcript expression is correlated with the observed loss of virulence during culture attenuation of pathogenic strains. High‐pressure freeze substitution followed by immunocytochemical electron microscopy confirmed that the Lig proteins were localized to the bacterial surface. Immunoblot studies with patient sera found that the Lig proteins are a major antigen recognized during the acute host infection. These observations demonstrate that the Lig proteins are a newly identified surface protein of pathogenic Leptospira, which by analogy to other bacterial immunoglobulin superfamily virulence factors, may play a role in host cell attachment and invasion during leptospiral pathogenesis.
Characterization of the roles of NikR, a nickel‐responsive pleiotropic autoregulator of Helicobacter pylori
Authors: Contreras Monica , Thiberge Jean‐Michel , Mandrand‐Berthelot Marie‐Andrée , Labigne Agnès 
Published: July 2003

SummaryThe Helicobacter pylori genome contains a gene (hp1338 or nikR) that encodes a nickel‐dependent regulator that is homologous to the Escherichia coli nickel‐responsive regulator, NikR. The H. pylori nikR product acts as a pleiotropic metal‐dependent regulator. We constructed a non‐polar isogenic mutant deleted for the nikR gene. NikR was essential for the survival of H. pylori in the presence of high nickel and cobalt ion concentrations in vitro. We screened a DNA macroarray for genes that were differentially expressed in parental and nikR‐deficient H. pylori strains grown in the presence of excess nickel. We found that H. pylori NikR mediates the expression of nickel‐activated and ‐repressed genes. In the presence of excess nickel, NikR activated the transcription of ureA‐ureB (hp72–73), nixA (hp1077 ), copA2 (hp1072), hpn (hp1427 ) and hpn‐like (hp1432) genes and repressed the expression of genes encoding proteins involved in ferric iron uptake and storage [pfr (hp0653), fur (hp1027 ), frpB4 (hp1512), exbB/exbD (hp1339–1340), ceuE (hp1561)], motility [cheV (hp616), flaA (hp0601), flaB (hp0115 )], stress responses [hrcA‐grpE‐dnaK (hp111–110–109)] and encoding outer‐membrane proteins [omp11(hp0472), omp31 (hp1469), omp32 (hp1501)]. Slot blot DNA/RNA hybridization experiments using RNA from three independent bacterial cultures confirmed the transcriptome data for 10 selected genes. The results of gel shift experiments using purified native NikR, β‐galactosidase assays with the region between nikR and the exbB/exbD divergent operon, and the study of exbB gene expression using a gentamicin/apramycin reporter gene in H. pylori indicated that NikR is an autorepressor that binds to this intergenic region and also controls the expression of the exbB/exbD/tonB operon, which provides energy for ferric iron uptake. Thus, as previously suggested for Fur in H. pylori, NikR appears to be a global regulator of the metabolism of some divalent cations within a highly complex regulated network.
Regulation of fungal gene expression via short open reading frames in the mRNA 5′untranslated region
Authors: Vilela Cristina , McCarthy John E. G. 
Published: July 2003

SummaryWe review how the expression of fungal mRNAs can be controlled by ribosome interactions with short upstream open reading frames (uORFs) within the 5′untranslated region. The efficiency of uAUG recognition modulates the impact of a uORF but steps during and after translation of the uORF also influence uORF function. The post‐termination behaviour of ribosomes, therefore, plays a major role in determining the expression level of these main ORFs. Translation of a uORF can produce a cis‐acting peptide that causes effector molecule‐dependent stalling of the ribosomes at the end of the uORF. In other cases it is the length or position, or other features of the uORF, rather than the peptide it encodes, that determine the efficiency with which ribosomes reinitiate translation downstream of it. Whether the form of the ribosome that resumes scanning after termination is the 40S subunit alone or the entire 80S ribosome is not known. Translation of the uORF can also control gene expression by affecting the stability of the mRNA. Finally, trans‐acting factors may participate in the regulatory mechanisms. Future work will need not only to provide more information on the mechanisms underlying the known cases of uORF‐mediated control but also to define the full complement of uORF‐containing mRNAs in at least one fungal organism.
Three pathways for trehalose metabolism in Corynebacterium glutamicum ATCC13032 and their significance in response to osmotic stress
Authors: Wolf Andreas , Krämer Reinhard , Morbach Susanne 
Published: July 2003

SummaryGenome scanning of Corynebacterium glutamicum ATCC13032 revealed the presence of five different genes encoding enzymes belonging to three putative trehalose biosynthesis pathways (OtsAB, TreYZ, TreS). The function of the different pathways and of trehalose as an osmoprotectant was studied by characterizing several strains defective for individual trehalose biosynthetic routes. Trehalose synthesis was shown to increase upon hyperosmotic conditions. Cytoplasmic trehalose levels varied considerably depending on kind and accessibility of carbon and nitrogen sources. In contrast to other organisms, osmoregulated trehalose synthesis in C. glutamicum is mediated by the TreYZ and not by the OtsAB pathway. Irrespective of their significance for the osmotic response, otsA and treS were upregulated at the transcriptional level after hyperosmotic shock. In vivo, TreS‐mediated trehalose synthesis only occurred if maltose was used as the carbon source. In vitro, TreS catalysed the conversion of maltose into trehalose and, conversely, trehalose into maltose. As the reaction seems to be near equilibrium, TreS appears to be important for trehalose degradation rather than synthesis because a 1000‐fold excess of trehalose to maltose was detected in the cytoplasm. Also, evidence is given that both the OtsAB and the TreYZ pathways are involved, but not essential, in supplying trehalose for mycolic acid biosynthesis.
Touch and go: tying TonB to transport
Authors: Postle Kathleen , Kadner Robert J. 
Published: July 2003

SummaryThe TonB system of Gram‐negative bacteria appears to exist for the purpose of transducing the protonmotive force energy from the cytoplasmic membrane, where it is generated, to the outer membrane, where it is needed for active transport of iron siderophores, vitamin B12 and, in pathogens, iron from host‐binding proteins. In this review, we bring the reader up to date on the developments in the field since the authors each wrote reviews in this journal in 1990.
Effects of drought on nitrogen fixation in soybean root nodules
Authors: STREETER J. G. 
Published: July 2003

ABSTRACTSoybean plants [Glycine max (L.) Merr.] were grown in silica sand and were drought stressed for a 4 week period during reproductive development and without any mineral N supply in order to maximize demand for fixed nitrogen. A strain of Bradyrhizobium japonicum that forms large quantities of polysaccharide in nodules was used to determine whether or not the supply of reduced carbon to bacteroids limits nitrogenase activity. A depression of 30–40% in nitrogen content in leaves and pods of stressed plants indicated a marked decline in nitrogen fixation activity during the drought period. A 50% increase in the accumulation of bacterial polysaccharide in nodules accompanied this major decrease in nitrogen fixation activity and this result indicates that the negative impact of drought on nodules was not due to a depression of carbon supply to bacteroids. The drought treatment resulted in a statistically significant increase in N concentration in leaves and pods. Because N concentration and chlorophyll concentration in leaves were not depressed, there was no evidence of nitrogen deficiency in drought‐stressed plants, and this result indicates that the negative impact of drought on nodule function was not the cause of the depression of shoot growth. At the end of the drought period, the concentration of carbohydrates, amino nitrogen, and ureides was significantly increased in nodules on drought‐stressed plants. The overall results support the view that, under drought conditions, nitrogen fixation activity in nodules was depressed because demand for fixed N to support growth was lower.
Ethylene is required in tobacco to successfully compete with proximate neighbours
Authors: PIERIK R. , VISSER E. J. W. , DE KROON H. , VOESENEK L. A. C. J. 
Published: July 2003

ABSTRACTPlants sense neighbours even before these cause a decrease in photosynthetic light availability. Light reflected by proximate neighbours signals a plant to adjust growth and development, in order to avoid suppression by neighbour plants. These phenotypic changes are known as the shade‐avoidance syndrome and include enhanced shoot elongation and more upright‐positioned leaves. In the present study it was shown that these shade‐avoidance traits in tobacco (Nicotiana tabacum) are also induced by low concentrations of ethylene. Furthermore, it was shown that transgenic plants, insensitive to ethylene, have a delayed appearance of shade‐avoidance traits. The increase in both leaf angles and stem elongation in response to neighbours are delayed in ethylene‐insensitive plants. These data show that ethylene is an important component in the regulation of neighbour‐induced, shade‐avoidance responses. Consequently, ethylene‐insensitive plants lose competition with wild‐type neighbours, demonstrating that sensing of ethylene is required for a plant to successfully compete for light.
A test of the hydraulic limitation hypothesis in fast‐growingEucalyptus saligna
Authors: BARNARD H. R. , RYAN M. G. 
Published: July 2003

ABSTRACTThe hydraulic limitation hypothesis proposes that (1) reduced growth in taller trees is caused by decreased photosynthesis resulting from a decrease in hydraulic conductance promoted by a longer root‐to‐leaf flow path, and (2) this mechanism reduces stand productivity after canopy closure. This hypothesis was tested by comparing the physiology of 7 m (1 year) and 26 m (5 year)Eucalyptus salignaplantations where above‐ground productivity for the 26 m trees was approximately 69% of that for the 7 m trees, and water and nutrients were not limiting. The study compared whole tree physiology [water flux (Ql), average crown conductance (GT), crown hydraulic conductance per unit leaf area (KL), carbon isotope discrimination (δ13C)] and leaf physiology under light saturation (leaf water potential at the canopy top (ΨLEAF), photosynthetic capacity (Amax), and photosynthesis (A) and stomatal conductance (gs).KLwas 50% lower in the taller trees, but whole treeQlandGTwere the same for the 7 m and 26 m trees. Photosynthetic capacity was the same for leaves at the canopy top, butδ13C was −1.8‰ lower for the 26 m trees.Aandgswere either lower in the taller trees or equal, depending on sampling date. The taller trees maintained 0.8 MPa lowerΨLEAFduring the day and had 2.6‐times higher sapwood area per unit leaf area; these factors compensated for the effects of increased height and gravitational potential in the taller trees to maintain higherGT. The hydraulic limitation hypothesis (as originally stated) failed to explain the sharp decline in net primary productivity after canopy closure in this study. The effects of increased height appear to be a universal hydraulic problem for trees, but compensation mitigated these effects and maintainedQlandGTin the present study. Compensation may induce other problems (such as lowerΨLEAFor higher respiratory costs) that could reduce carbon gain or shift carbon allocation, and future studies of hydraulic limitation should consider compensation and associated carbon costs. In this study, the combination of similarGTand lowerδ13C for the 26 m trees suggests that total crown photosynthesis was lower for the 26 m trees, perhaps a result of the lowerΨLEAF.
Stomatal sensitivity to vapour pressure difference over a subambient to elevated CO2 gradient in a C3/C4 grassland
Authors: MAHERALI H. , JOHNSON H. B. , JACKSON R. B. 
Published: July 2003

ABSTRACTIn the present study the response of stomatal conductance (gs) to increasing leaf‐to‐air vapour pressure difference (D) in early season C3 (Bromus japonicus) and late season C4 (Bothriochloa ischaemum) grasses grown in the field across a range of CO2 (200–550 µmol mol−1) was examined. Stomatal sensitivity to D was calculated as the slope of the response of gs to the natural log of externally manipulated D (dgs/dlnD). Increasing D and CO2 significantly reduced gs in both species. Increasing CO2 caused a significant decrease in stomatal sensitivity to D in Br. japonicus, but not in Bo. ischaemum. The decrease in stomatal sensitivity to D at high CO2 for Br. japonicus fit theoretical expectations of a hydraulic model of stomatal regulation, in which gs varies to maintain constant transpiration and leaf water potential. The weaker stomatal sensitivity to D in Bo. ischaemum suggested that stomatal regulation of leaf water potential was poor in this species, or that non‐hydraulic signals influenced guard cell behaviour. Photosynthesis (A) declined with increasing D in both species, but analyses of the ratio of intercellular to atmospheric CO2 (Ci/Ca) suggested that stomatal limitation of A occurred only in Br. japonicus. Rising CO2 had the greatest effect on gs and A in Br. japonicus at low D. In contrast, the strength of stomatal and photosynthetic responses to CO2 were not affected by D in Bo. ischaemum. Carbon and water dynamics in this grassland are dominated by a seasonal transition from C3 to C4 photosynthesis. Interspecific variation in the response of gs to D therefore has implications for predicting seasonal ecosystem responses to CO2.
Abscisic acid activates ATPase in developing apple fruit especially in fruit phloem cells
Authors: PENG Y.‐B. , LU Y.‐F. , ZHANG D.‐P. 
Published: July 2003

ABSTRACTAbscisic acid (ABA) improves the sink strength by promoting the phloem unloading and regulating the assimilate metabolism in the economic sink organs of crops, although its mechanism remains unknown. The present experiment, using the techniques of the in vivo injection of ABA into the intact apple fruit attached to a growing apple tree and the in vivo incubation of the fruit tissue in the ABA‐contained medium, showed that ABA strongly activated the fruit ATPase especially P‐ATPase, of which the activity was doubled by ABA treatment. This ATPase activation was shown to be in vivo tissue‐dependent. The ABA‐induced P‐ATPase activation was fruit developmental stage‐, ABA dose‐, medium pH‐ and incubation time‐dependent. Physiological active (+)ABA was shown more effective to stimulate P‐ATPase activity than (+/–)ABA, and two ABA analogues (–)ABA and trans‐ABA, had no effect on P‐ATPase activation, indicating that only physiologically active cis(+)ABA can induce the enzyme activation, and so the ABA‐induced effects are stereospecific. The protein synthesis inhibitor cycloheximide was shown to have no effect on P‐ATPase activation by ABA, suggesting that synthesis of new proteins was not involved in the enzyme activation. The cytochemical assay revealed that P‐ATPase was activated by ABA in both the phloem and its surrounding flesh parenchyma cells, and that the most strongly P‐ATPase activation was observed in the plasma membrane of sieve element/companion cell complex. These data suggest that the improvement of phloem unloading by ABA previously reported in this fruit as in other crop sink organs may be attributed, at least partly, to the ABA‐induced ATPase activation especially in phloem cells.
Optimizing conditions for growth and sporulation of Pyrenophora semeniperda
Authors: Campbell M. A. , Medd R. W. , Brown J. B. 
Published: July 2003

The effects of photoperiod, light quality, wounding and sealing of culture plates on in vitro growth and sporulation of Pyrenophora semeniperda were examined to define conditions conducive to the abundant and rapid production of conidia. For maximum growth and sporulation, the leaf‐spotting and seedborne plant pathogen required an alternating light/dark sequence. Fewer conidia were produced under conditions of constant illumination or constant darkness. Growth was enhanced by light of wavelengths longer than 500 nm, while sporulation was enhanced by light of wavelengths shorter than 500 nm. Sporulation was enhanced under conditions of alternating temperature with a diurnal photoperiod and by mycelial wounding. Sealing of Petri plates had an inhibitory effect on sporulation. Significantly more conidia of higher quality formed when unsealed cultures, wounded after 7 days, were exposed to 23°C during the light phase and 19°C during darkness. Under these optimal conditions, conidial numbers were increased by 800% or more compared with unwounded cultures grown at constant 25°C in 12 h alternating cool‐white light.
Ciclopirox for the treatment of superficial fungal infections: a review
Authors: Gupta Aditya K. , Skinner Alayne R. 
Published: July 2003

AbstractCiclopirox is a broad‐spectrum antifungal agent that also exhibits anti‐inflammatory and antibacterial activity. The lotion and cream formulations of ciclopirox are effective in many types of infection, including tinea corporis/cruris, tinea pedis, cutaneous candidiasis, pityriasis (tinea) versicolor, and seborrheic dermatitis. The new ciclopirox gel 0.77% formulation is also indicated for the treatment of seborrheic dermatitis of the scalp, interdigital tinea pedis and tinea corporis.
Ciclopirox gel for seborrheic dermatitis of the scalp
Authors: Aly Raza , Katz H. Irving , Kempers Steven E. , Lookingbill Donald P. , Lowe Nicholas , Menter Alan , Morman Manuel , Savin Ronald C. , Wortzman Mitchell 
Published: July 2003

AbstractBackground  Seborrheic dermatitis is a common inflammatory skin disorder that usually occurs in patients with pre‐existing seborrhea. The etiology of seborrheic dermatitis is uncertain. Typically, sites dense with sebaceous glands support growth of the lipophilic yeast Malassezia furfur. Ciclopirox (Loprox®) gel is a hydroxypyridone, broad‐spectrum antifungal agent proven effective against the yeast M. furfur.Objective  A multicenter, randomized, double‐blind, vehicle controlled study of 178 subjects evaluated the efficacy of ciclopirox gel in treating seborrheic dermatitis of the scalp.Methods  One hundred and seventy‐eight subjects were randomized to apply either ciclopirox gel 0.77% twice daily, or vehicle twice daily for 28 days. Subjects’ signs and symptoms of severity (erythema, scaling, pruritus and burning) were rated on a scale of 0–3 (none to severe); for inclusion, a minimum score of 4, for the sum of the individual ratings was required. Efficacy evaluations were performed at baseline, days 4, 8, 15, 22, 29, and at end‐point (final visit, up to day 33). The primary efficacy variable was clinical response assessed by a global improvement, based on a scale of 0–5 (100% clearance to flare of treatment area). Changes in signs/symptoms severity scores within the target lesion were also evaluated.Results  Global evaluation scores demonstrated that significantly more ciclopirox‐treated subjects achieved over 75% improvement compared with vehicle at days 22, 29, and endpoint (P < 0.01). Change‐from‐baseline mean score for total signs and symptoms was significantly greater in ciclopirox subjects compared with vehicle subjects at the same time points as above (P < 0.001), as well as day 15 (P < 0.01). Twenty‐nine percent of subjects rated ciclopirox as having excellent cosmetic acceptability. There were only mild adverse events, with the most common being burning sensation in 13% of ciclopirox subjects and 9% of vehicle subjects.Conclusion  Ciclopirox gel is effective and safe in the treatment of seborrheic dermatitis of the scalp.