bluuebunny/crossref_metadata_2025_split huggingface dataset:
NopP, a phosphorylated effector of Rhizobium sp. strain NGR234, is a major determinant of nodulation of the tropical legumes Flemingia congesta and Tephrosia vogelii
Authors: Skorpil Peter , Saad Maged M. , Boukli Nawal M. , Kobayashi Hajime , Ares‐Orpel Florencia , Broughton William J. , Deakin William J. 
Published: August 2005

SummaryRhizobium sp. NGR234 nodulates many plants, some of which react to proteins secreted via a type three secretion system (T3SS) in a positive‐ (Flemingia congesta, Tephrosia vogelii) or negative‐ (Crotalaria juncea, Pachyrhizus tuberosus) manner. T3SSs are devices that Gram‐negative bacteria use to inject effector proteins into the cytoplasm of eukaryotic cells. The only two rhizobial T3SS effector proteins characterized to date are NopL and NopP of NGR234. NopL can be phosphorylated by plant kinases and we show this to be true for NopP as well. Mutation of nopP leads to a dramatic reduction in nodule numbers on F. congesta and T. vogelii. Concomitant mutation of nopL and nopP further diminishes nodulation capacity to levels that, on T. vogelii, are lower than those produced by the T3SS null mutant NGRΩrhcN. We also show that the T3SS of NGR234 secretes at least one additional effector, which remains to be identified. In other words, NGR234 secretes a cocktail of effectors, some of which have positive effects on nodulation of certain plants while others are perceived negatively and block nodulation. NopL and NopP are two components of this mix that extend the ability of NGR234 to nodulate certain legumes.
Positioning and the specific sequence of each 13‐mer motif are critical for activity of the plasmid RK2 replication origin
Authors: Kowalczyk Lukasz , Rajewska Magdalena , Konieczny Igor 
Published: August 2005

SummaryThe minimal replication origin of the broad‐host‐range plasmid RK2, oriV, contains five iterons which are binding sites for the plasmid‐encoded replication initiation protein TrfA, four DnaA boxes, which bind the host DnaA protein, and an AT‐rich region containing four 13‐mer sequences. In this study, 26 mutants with altered sequence and/or spacing of 13‐mer motifs have been constructed and analysed for replication activity in vivo and in vitro. The data show that the replacement of oriV 13‐mers by similar but not identical 13‐mer sequences from Escherichia coli oriC inactivates the origin. In addition, interchanging the positions of the oriV 13‐mers results in greatly reduced activity. Mutants with T/A substitutions are also inactive. Furthermore, introduction of single‐nucleotide substitutions demonstrates very restricted sequence requirements depending on the 13‐mer position. Only two of the mutants are host specific, functional in Pseudomonas aeruginosa but not in E. coli. Our experiments demonstrate considerable complexity in the plasmid AT‐rich region architecture required for functionality. It is evident that low internal stability of this region is not the only feature contributing to origin activity. Our studies suggest a requirement for sequence‐specific protein interactions within the 13‐mers during assembly of replication complexes at the plasmid origin.
The moonlighting protein Tsa1p is implicated in oxidative stress response and in cell wall biogenesis in Candida albicans
Authors: Urban Constantin , Xiong Xin , Sohn Kai , Schröppel Klaus , Brunner Herwig , Rupp Steffen 
Published: August 2005

SummaryCandida albicans is one of the most common fungal pathogens in humans. The cell wall is the first contact site between host and pathogen and thus is critical for colonization and infection of the host. We have identified Tsa1p, a protein that is differentially localized to the cell wall of C. albicans in hyphal cells but remains in the cytosol and nucleus in yeast‐form cells. This is different from Saccharomyces cerevisiae, where the homologous protein solely has been found in the cytoplasm. We report here that TSA1 confers resistance towards oxidative stress as well as is involved in the correct composition of hyphal cell walls. However, no significant change of the cell wall composition was observed in a TSA1 deletion strain in yeast‐form cells, which is in good agreement with the observation that Tsa1p is absent from the yeast‐form cell wall. This indicates that Tsa1p of C. albicans might represent a moonlighting protein with specific functions correlating to its respective localization. Furthermore, the translocation of Tsa1p to the hyphal cell wall of C. albicans depends on Efg1p, suggesting a contribution of the cAMP/PKA pathway to the localization of this protein. In a strain deleted for TUP1 that filaments constitutively Tsa1p can be found in the cell wall under all conditions tested, confirming the result that Tsa1p localization to the cell wall is correlated to the morphology of C. albicans.
Distinct mechanisms govern proteolytic shedding of a key invasion protein in apicomplexan pathogens
Authors: Howell Steven A. , Hackett Fiona , Jongco Artemio M. , Withers‐Martinez Chrislaine , Kim Kami , Carruthers Vern B. , Blackman Michael J. 
Published: August 2005

SummaryApical membrane antigen‐1 (AMA1) is a conserved apicomplexan protein that plays an important but undefined role in host cell invasion. We have studied the fate of Plasmodium falciparum AMA1 (PfAMA1) during erythrocyte invasion by the malaria merozoite, and compared it with that of the Toxoplasma gondii orthologue, TgAMA1. Shedding of the PfAMA1 ectodomain goes essentially to completion during invasion, and occurs predominantly or exclusively via juxtamembrane cleavage at the previously identified sheddase cleavage site, Thr517. Only the resulting juxtamembrane stub of the ectodomain is efficiently carried into the host cell, and this remains distributed around the plasma membrane of the intracellular ring‐stage parasite. Inhibition of normal shedding, however, results in proteolysis at an intramembrane, rhomboid‐like cleavage site, and PfAMA1 is susceptible to cleavage by Drosophila rhomboid‐1, showing that it can be a substrate for intramembrane cleavage but is not normally processed in this manner. In contrast, shedding of TgAMA1 from the surface of extracellular tachyzoites occurs exclusively via cleavage within the luminal half of its transmembrane domain by a rhomboid‐like protease. Also unlike PfAMA1, complete TgAMA1 shedding does not accompany Toxoplasma invasion as the intact protein was readily detected on the surface of newly invaded tachyzoites. This work reveals unexpected differences in the manner in which Plasmodium and Toxoplasma shed AMA1 from the surface of invasive zoites, and demonstrates the presence at the malaria merozoite surface of a rhomboid‐like protease.
The α‐toxin of Clostridium septicum is essential for virulence
Authors: Kennedy Catherine L. , Krejany Efrosinia O. , Young Lauren F. , O'Connor Jennifer R. , Awad Milena M. , Boyd Richard L. , Emmins John J. , Lyras Dena , Rood Julian I. 
Published: August 2005

SummaryClostridium septicum is the causative agent of spontaneous gas gangrene or atraumatic myonecrosis, a sudden and frequently fatal infection that is increasingly associated with malignancy of the colon. Little is known about the disease process although the focus of virulence studies has been the α‐toxin, a pore‐forming cytolysin that is encoded by the csa gene and secreted as an inactive protoxin. Until now a lack of techniques for the genetic manipulation of C. septicum has hindered the use of molecular approaches to understand pathogenesis. By introducing plasmids by conjugation from Escherichia coli, we have developed methods for the genetic manipulation of C. septicum and constructed a chromosomal csa mutant by allelic exchange. Virulence testing of an isogenic series of strains consisting of the wild type, the csa mutant, and a csa mutant complemented with the wild‐type csa gene revealed that the development of fulminant myonecrosis in mice was dependent on the ability to produce a functional haemolytic α‐toxin. Furthermore, the inhibition of leukocyte influx into the lesion, which is very typical of clostridial myonecrosis, was also dependent on the ability to produce α‐toxin. This study represents the first definitive identification of a virulence factor in this organism and opens the way for further studies that will delineate the role of other putative virulence factors in this significant pathogen.
VirR, a response regulator critical for Listeria monocytogenes virulence
Authors: Mandin Pierre , Fsihi Hafida , Dussurget Olivier , Vergassola Massimo , Milohanic Eliane , Toledo‐Arana Alejandro , Lasa Iñigo , Johansson Jörgen , Cossart Pascale 
Published: August 2005

SummarySignature‐tagged mutagenesis (STM) was used to identify new genes involved in the virulence of the Gram‐positive intracellular pathogen Listeria monocytogenes. One of the mutants isolated by this technique had the transposon inserted in virR, a gene encoding a putative response regulator of a two‐component system. Deletion of virR severely decreased virulence in mice as well as invasion in cell‐culture experiments. Using a transcriptomic approach, we identified 12 genes regulated by VirR, including the dlt‐operon, previously reported to be important for L. monocytogenes virulence. However, a strain lacking dltA, was not as impaired in virulence as the ΔvirR strain, suggesting a role in virulence for other members of the vir regulon. Another VirR‐regulated gene is homologous to mprF, which encodes a protein that modifies membrane phosphatidyl glycerol with l‐lysine and that is involved in resistance to human defensins in Staphylococcus aureus. VirR thus appears to control virulence by a global regulation of surface components modifications. These modifications may affect interactions with host cells, including components of the innate immune system. Surprisingly, although controlling the same set of genes as VirR, the putative cognate histidine kinase of VirR, VirS, encoded by a gene located three genes downstream of virR, was shown not to be essential for virulence. By monitoring the activity of VirR with a GFP reporter construct, we showed that VirR can be activated independently of VirS, for example through a mechanism involving variations in the level of intracellular acetyl phosphate. In silico analysis of the VirR‐regulated promoters revealed a VirR DNA‐binding consensus site and specific interaction between purified VirR protein and this consensus sequence was demonstrated by gel mobility shift assays. This study identifies a second key virulence regulon in L. monocytogenes, after the prfA regulon.
Novel gene functions required for melanization of the human pathogen Cryptococcus neoformans
Authors: Walton Felicia J. , Idnurm Alexander , Heitman Joseph 
Published: August 2005

SummaryThe ability to produce melanin is a key virulence factor in many fungal pathogens including the human basidiomycete pathogen Cryptococcus neoformans, a major cause of life‐threatening infections among immunocompromised persons. Despite the significance of melanin biosynthesis in virulence of C. neoformans, the cellular and molecular processes involved in this pathway have not yet been fully elucidated. Here, we used Agrobacterium to isolate insertional mutants and screened 12 000 mutants to uncover genes involved in melanin production in C. neoformans. Four new mutant alleles of the well‐known melanin biosynthesis gene, LAC1, which encodes laccase were identified, and the T‐DNA was shown to have a possible predisposition for insertion into the promoters of genes, in particular LAC1. Melanization in C. neoformans is dependent on five additional genes identified in this screen encoding homologues of the copper transporter Ccc2, the copper chaperone Atx1, the chitin synthase Chs3, the transcriptional coactivator Mbf1 and the chromatin‐remodelling enzyme Snf5. Illumination of the molecular and genetic components of this virulence pathway reveals potential novel targets for drug development against C. neoformans and provides further insight into the intimate relationship between metal ion homeostasis and melanin biosynthesis.
The Dif chemosensory pathway is directly involved in phosphatidylethanolamine sensory transduction in Myxococcus xanthus
Authors: Bonner Pamela J. , Xu Qian , Black Wesley P. , Li Zhuo , Yang Zhaomin , Shimkets Lawrence J. 
Published: August 2005

SummaryMyxococcus xanthus cells glide on solid surfaces and are chemotactically stimulated by certain phosphatidylethanolamine species. The dif gene cluster consists of six genes, difABCDEG, five of which encode proteins homologous to known chemotaxis proteins. DifA and DifE are required for the biosynthesis of fibrils, an extracellular matrix comprised of polysaccharide and protein. Chemotactic stimulation by 1,2‐O‐Bis[11‐(Z)‐hexadecenoyl]‐sn‐glycero‐3‐phosphatidylethanolamine (16:1 PE) and dilauroyl PE (12:0 PE) requires fibrils. Although previous work has shown that difA and difE mutants are not stimulated by 12:0 PE, these results do not distinguish between a dependence on fibrils or a direct role in chemosensory transduction. Here we provide evidence that the Dif chemosensory pathway directly mediates PE sensory transduction. First, stimulation by and adaptation to 16:1 PE requires all of the dif genes, including difBDG, which are not essential for fibril biogenesis. Second, a specific residue within the first putative methylation domain of DifA is required for stimulation by 16:1 PE but not fibril biogenesis. Transmembrane signalling through a chimeric NarX‐DifA chemoreceptor is required for fibril formation but not for stimulation by or adaptation to 16:1 PE. Third, difD and difE are required for stimulation by dioleoyl PE (18:1 PE) although the response does not require fibrils. Taken together these results argue that the Dif pathway mediates both matrix formation and lipid chemotaxis.
ANTI‐INFECTIVE THERAPY AT END OF LIFE: ETHICAL DECISION‐MAKING IN HOSPICE‐ELIGIBLE PATIENTS
Authors: FORD PAUL J. , FRASER THOMAS G. , DAVIS MELLAR P. , KODISH ERIC 
Published: August 2005

ABSTRACTClear guidelines addressing the ethically appropriate use of anti‐infectives in the setting of hospice care do not exist. There is lack of understanding about key treatment decisions related to infection treatment for patients who are eligible for hospice care. Ethical concerns about anti‐infective use at the end of life include: (1) delaying transition to hospice, (2) prolonging a dying process, (3) prescribing regimens incongruent with a short life expectancy and goals of care, (4) increasing the reservoir of potential resistant pathogens, (5) placing unreasonable costs on a capitated hospice system. Although anti‐infectives are thought to be relatively safe, they can place a burden on patients and be inconsistent to particular care plans. The current complex, and at times fragmented, medical care often fails to address these issues in decision‐making. In many ways, the ethics governing the end of life decisions related to dialysis, hydration/nutrition, and hypercalcemia parallel those of anti‐infectives. In this article we articulate important elements in ethical decision‐making in the application of anti‐infectives for patients who are eligible for hospice care, and we point to the need for prospective studies to help refine particular guidelines in these cases.
SOME ETHICAL ISSUES ARISING FROM POLIO ERADICATION PROGRAMMES IN INDIA
Authors: PAUL YASH , DAWSON ANGUS 
Published: August 2005

ABSTRACTThe World Health Organisation's programme for the eradication of poliomyelitis as currently practised in India raises many ethical issues. In this paper we concentrate on just two. The first is the balance to be struck between the risks and benefits generated by the eradication programme itself. The issue of risks and benefits arises in relation to the choice between two different vaccine types available for polio programmes: oral polio vaccine (OPV) and inactivated polio vaccine (IPV). OPV is the vaccine currently used in the eradication campaign in India. We argue that given the current risks/benefits profile of this vaccine, there is an urgent need to review the programme and take remedial action to address existing problems (at least in India). The second issue we discuss is the fact that there is little effort to gain the informed consent of the parents of vaccinated children, as they are not currently told about the potential limitations of OPV or the possibility of vaccine‐induced harm. We suggest that such a policy might be justifiable, given the importance of polio eradication, but only if there is a system of compensation for vaccine‐induced harm as part of the eradication programme itself. There is a real danger that if these issues are not addressed then public trust in the eradication programme and vaccination programmes as a whole will be lost.
PUBLIC COMMUNICATION, RISK PERCEPTION, AND THE VIABILITY OF PREVENTIVE VACCINATION AGAINST COMMUNICABLE DISEASES
Authors: MAY THOMAS 
Published: August 2005

ABSTRACTBecause of the nature of preventive vaccination programs, the viability of these public health interventions is particularly susceptible to public perceptions. This is because vaccination relies on a concept of ‘herd immunity’, achievement of which requires rational public behavior that can only be obtained through full and accurate communication about risks and benefits. This paper describes how irrational behavior that threatens the effectiveness of vaccination programs – both in crisis and non‐crisis situations – can be tied to public perceptions created by media portrayals of health risks. I concentrate on childhood vaccination as an exemplar of ‘non‐crisis’ preventive vaccination, and on the recent flu vaccine shortage as a ‘crisis’ situation. The paper concludes with an examination of the steps necessary to resolve these threats through better public communication.
PREPARING FOR AN INFLUENZA PANDEMIC: ETHICAL ISSUES
Authors: KOTALIK JARO 
Published: August 2005

ABSTRACTIn the near future, experts predict, an influenza pandemic will likely spread throughout the world. Many countries have been creating a contingency plan in order to mitigate the severe health and social consequences of such an event. Examination of the pandemic plans of Canada, the United Kingdom and the United States, from an ethical perspective, raises several concerns. One: scarcity of human and material resources is assumed to be severe. Plans focus on prioritization but do not identify resources that would be optimally required to reduce deaths and other serious consequences. Hence, these plans do not facilitate a truly informed choice at the political level where decisions have to be made on how much to invest now in order to reduce scarcity when a pandemic occurs. Two: mass vaccination is considered to be the most important instrument for reducing the impact of infection, yet pandemic plans do not provide concrete estimates of the benefits and burdens of vaccination to assure everyone that the balance is highly favorable. Three: pandemic plans make extraordinary demands on health care workers, yet professional organizations and unions may not have been involved in the plans’ formulation and they have not been assured that authorities will aim to protect and support health care workers in a way that corresponds to the demands made on them. Four: all sectors of society and all individuals will be affected by a pandemic and everyone's collaboration will be required. Yet, it appears that the various populations have been inadequately informed by occasional media reports. Hence, it is essential that plans are developed and communication programs implemented that will not only inform but also create an atmosphere of mutual trust and solidarity; qualities that at the time of a pandemic will be much needed.
Detection of Helicobacter pylori‐Specific Genes in the Oral Yeast
Authors: Siavoshi Farideh , Salmanian Ali Hatef , Kbari Fereshteh Akbari , Malekzadeh Reza , Massarrat Sadegh 
Published: August 2005

ABSTRACTBackgrounds.  Until today, human stomach is the only recognized habitat of Helicobacter pylori. However, recruitment of DNA‐based methods has made possible the detection of H. pylori in water and oral cavity, thus suggesting fecal–oral and oral–oral routes for transmission of H. pylori, respectively. In this study, yeast has been proposed as a common vector for transmission of H. pylori. Thus designed primers were recruited to target 16S rDNA and cagA genes in the oral yeasts by PCR.Materials and methods.  Eighteen yeasts were examined microscopically for the presence of bacterial‐like bodies. DNAs were extracted from oral yeasts using phenol–chloroform method. Amplification conditions were optimized as 33 cycles and annealing temperatures of 63 °C for 16S rDNA and 51 °C and 52 °C for cagA gene which was targeted in two steps. DNAs of H. pylori and Saccharomyces cerevisiae were used as controls. Polymerase chain reaction (PCR) products of two genes from one yeast and from H. pylori were cloned in pCAP and subsequently subcloned in pSK+ and were sequenced.Results.  Bacterial‐like bodies were observed in all oral yeasts. The amplified products of 16S rDNA from all oral yeasts were homologous in size with those of H. pylori. Fifteen out of eighteen (83%) yeasts contained cagA gene, homologous to H. pylori. CagA was not amplified from three yeasts and S. cerevisiae. Analysis of the sequenced products of 16S rDNA and cagA from one oral yeast showed 98% homology with those of H. pylori.Conclusions.  The presence of H. pylori inside the yeast was indicated by light microscopy and PCR. It appears that yeasts, which are abundant in nature and thrive the mucosal surfaces of human, might serve as reservoirs and vehicles of H. pylori.
Experimental Helicobacter pylori Infection Induces Antral‐Predominant, Chronic Active Gastritis in Hispid Cotton Rats (Sigmodon hispidus)
Authors: Mähler Michael , Heidtmann Wiebke , Niewiesk Stefan , Gruber Achim , Fossmark Reidar , Beil Winfried , Hedrich Hans , Wagner Siegfried 
Published: August 2005

ABSTRACTBackground.  The hispid cotton rat has proven to be an excellent animal model for a variety of human infectious disease agents. This study was performed to evaluate the use of the cotton rat as a model of Helicobacter pylori infection.Materials and methods.  Thirty‐eight inbred cotton rats were orogastrically inoculated with a human strain of H. pylori. Twenty‐eight control cotton rats were dosed with vehicle only. Animals were sacrificed at 2, 4, 12, 26, or 38 weeks after inoculation for bacterial and histologic and immunologic examinations.Results.  Helicobacter pylori was cultured from the glandular stomach of 89% of the infected cotton rats. The level of colonization was consistently high (approximately 104−6 colony‐forming units/g tissue). Histologically, the spiral bacteria were demonstrated on the epithelial surface and in the foveolae of the gastric mucosa with highest numbers in the antrum. H. pylori infection was associated with antral‐predominant, chronic active gastritis which progressively increased in severity over time. By week 26 of infection, moderate antral gastritis had developed with frequent involvement of the submucosa and formation of lymphocytic aggregates. Splenic T cells from infected cotton rats expressed mRNAs for interferon‐γ, interleukin‐4, interleukin‐6, and interleukin‐10 following in vitro stimulation with H. pylori. Serum levels of H. pylori‐specific immunoglobulin G were significantly elevated after 12 weeks of infection.Conclusions.  The H. pylori‐infected cotton rat represents a novel animal model that should prove useful for studies of H. pylori‐induced chronic active gastritis and factors affecting gastric colonization by this pathogen.