bluuebunny/crossref_metadata_2025_split huggingface dataset:
The ObgE/CgtA GTPase influences the stringent response to amino acid starvation in Escherichia coli
Authors: Persky Nicole S. , Ferullo Daniel J. , Cooper Deani L. , Moore Hayley R. , Lovett Susan T. 
Published: June 2009

SummaryThe stringent response is important for bacterial survival under stressful conditions, such as amino acid starvation, and is characterized by the accumulation of ppGpp and pppGpp. ObgE (CgtA, YhbZ) is an essential conserved GTPase in Escherichia coli and several observations have implicated the protein in the control of the stringent response. However, consequences of the protein on specific responses to amino acid starvation have not been noted. We show that ObgE binds to ppGpp with biologically relevant affinity in vitro, implicating ppGpp as an in vivo ligand of ObgE. ObgE mutants increase the ratio of pppGpp to ppGpp within the cell during the stringent response. These changes are correlated with a delayed inhibition of DNA replication by the stringent response, delayed resumption of DNA replication after release, as well as a decreased survival after amino acid deprivation. With these data, we place ObgE as an active effector of the response to amino acid starvation in vivo. Our data correlate the pppGpp/ppGpp ratio with DNA replication control under bacterial starvation conditions, suggesting a possible role for the relative balance of these two nucleotides.
Unexpected chemoreceptors mediate energy taxis towards electron acceptors in Shewanella oneidensis
Authors: Baraquet Claudine , Théraulaz Laurence , Iobbi‐Nivol Chantal , Méjean Vincent , Jourlin‐Castelli Cécile 
Published: June 2009

Summary Shewanella oneidensis uses a wide range of terminal electron acceptors for respiration. In this study, we show that the chemotactic response of S. oneidensis to anaerobic electron acceptors requires functional electron transport systems. Deletion of the genes encoding dimethyl sulphoxide and trimethylamine N‐oxide reductases, or inactivation of these molybdoenzymes as well as nitrate reductase by addition of tungstate, abolished electron acceptor taxis. Moreover, addition of nigericin prevented taxis towards trimethylamine N‐oxide, dimethyl sulphoxide, nitrite, nitrate and fumarate, showing that this process depends on the ΔpH component of the proton motive force. These data, together with those concerning response to metals (Bencharit and Ward, 2005), support the idea that, in S. oneidensis, taxis towards electron acceptors is governed by an energy taxis mechanism. Surprisingly, energy taxis in S. oneidensis is not mediated by the PAS‐containing chemoreceptors but rather by a chemoreceptor (SO2240) containing a Cache domain. Four other chemoreceptors also play a minor role in this process. These results indicate that energy taxis can be mediated by new types of chemoreceptors.
Listeria monocytogenesl‐forms respond to cell wall deficiency by modifying gene expression and the mode of division
Authors: Dell'Era Simone , Buchrieser Carmen , Couvé Elisabeth , Schnell Barbara , Briers Yves , Schuppler Markus , Loessner Martin J. 
Published: June 2009

SummaryCell wall‐deficient bacteria referred to as l‐forms have lost the ability to maintain or build a rigid peptidoglycan envelope. We have generated stable, non‐reverting l‐form variants of the Gram‐positive pathogen Listeria monocytogenes, and studied the cellular and molecular changes associated with this transition. Stable l‐form cells can occur as small protoplast‐like vesicles and as multinucleated, large bodies. They have lost the thick, multilayered murein sacculus and are surrounded by a cytoplasmic membrane only, although peptidoglycan precursors are still produced. While they lack murein‐associated molecules including Internalin A, membrane‐anchored proteins such as Internalin B are retained. Surprisingly, l‐forms were found to be able to divide and propagate indefinitely without a wall. Time‐lapse microscopy of fluorescently labelled l‐forms indicated a switch to a novel form of cell division, where genome‐containing membrane vesicles are first formed within enlarged l‐forms, and subsequently released by collapse of the mother cell. Array‐based transcriptomics of parent and l‐form cells revealed manifold differences in expression of genes associated with morphological and physiological functions. The l‐forms feature downregulated metabolic functions correlating with the dramatic shift in surface to volume ratio, whereas upregulation of stress genes reflects the difficulties in adapting to this unusual, cell wall‐deficient lifestyle.
Mycobacteriophage Lysin B is a novel mycolylarabinogalactan esterase
Authors: Payne Kimberly , Sun Qingan , Sacchettini James , Hatfull Graham F. 
Published: June 2009

SummaryMycobacteriophages encounter a unique problem among phages of Gram‐positive bacteria, in that lysis must not only degrade the peptidoglycan layer but also circumvent a mycolic acid‐rich outer membrane covalently attached to the arabinogalactan–peptidoglycan complex. Mycobacteriophages accomplish this by producing two lysis enzymes, Lysin A (LysA) that hydrolyses peptidoglycan, and Lysin B (LysB), a novel mycolylarabinogalactan esterase, that cleaves the mycolylarabinogalactan bond to release free mycolic acids. The D29 LysB structure shows an α/β hydrolase organization with a catalytic triad common to cutinases, but which contains an additional four‐helix domain implicated in the binding of lipid substrates. Whereas LysA is essential for mycobacterial lysis, a Giles ΔlysB mutant mycobacteriophage is viable, but defective in the normal timing, progression and completion of host cell lysis. We propose that LysB facilitates lysis by compromising the integrity of the mycobacterial outer membrane linkage to the arabinogalactan–peptidoglycan layer.
In vivo localizations of membrane stress controllers PspA and PspG in Escherichia coli
Authors: Engl Christoph , Jovanovic Goran , Lloyd Louise J. , Murray Heath , Spitaler Martin , Ying Liming , Errington Jeff , Buck Martin 
Published: June 2009

SummaryThe phage shock protein (Psp) response in Gram‐negative bacteria counteracts membrane stress. Transcription of the PspF regulon (pspABCDE and pspG) in Escherichia coli is induced upon stresses that dissipate the proton motive force (pmf). Using GFP fusions we have visualized the subcellular localizations of PspA (a negative regulator and effector of Psp) and PspG (an effector of Psp). It has previously been proposed that PspA evenly coates the inner membrane of the cell. We now demonstrate that instead of uniformly covering the entire cell, PspA (and PspG) is highly organized into what appear to be distinct functional classes (complexes at the cell pole and the lateral cell wall). Real‐time observations revealed lateral PspA and PspG complexes are highly mobile, but absent in cells lacking MreB. Without the MreB cytoskeleton, induction of the Psp response is still observed, yet these cells fail to maintain pmf under stress conditions. The two spatial subspecies therefore appear to be dynamically and functionally distinct with the polar clusters being associated with sensory function and the mobile complexes with maintenance of pmf.
Identification of small RNAs in Mycobacterium tuberculosis
Authors: Arnvig Kristine B. , Young Douglas B. 
Published: June 2009

SummaryIn spite of being one of our most prominent bacterial pathogens, the presence of small regulatory RNAs (sRNAs) has not previously been investigated in Mycobacterium tuberculosis. Post‐transcriptional regulation of gene expression by sRNA molecules has been demonstrated in a wide range of pathogenic bacteria and has been shown to play a significant role in the control of virulence. By screening cDNA libraries prepared from low‐molecular weight RNA from M. tuberculosis we have identified nine putative sRNA molecules, including cis‐encoded antisense transcripts from within open reading frames and trans‐encoded transcripts from intergenic regions. sRNAs displayed differential expression between exponential and stationary phase, and during a variety of stress conditions. Two of the cis‐encoded sRNAs were associated with genes encoding enzymes involved in lipid metabolism, desA1 and pks12. These sRNAs showed complementarity to multiple M. tuberculosis genes, suggesting the potential to act as both cis‐encoded and trans‐encoded sRNAs. Overexpression of selected trans‐encoded sRNAs had profound impact on growth of M. tuberculosis and M. smegmatis. This is the first experimental evidence of sRNAs in M. tuberculosis and it will be important to consider the potential influence of sRNA regulation when studying the transcriptome and the proteome of M. tuberculosis during infection.
Mycobacterium tuberculosis Entry into Mast Cells Through Cholesterol‐rich Membrane Microdomains
Authors: Muñoz S. , Rivas‐Santiago B. , Enciso J. A. 
Published: June 2009

AbstractCholesterol‐enriched membrane microdomains (lipid rafts) play a role in the uptake of many pathogens. Mycobacteria are one of the intracellular pathogens that utilize lipid rafts in order to invade both phagocytic and non‐phagocytic cells. However, the mechanism of Mycobacterium tuberculosis uptake by mast cell is not known. To address this issue, we investigated the interaction of M. tuberculosis (H37Rv strain) with mast cells. Confocal microscopy showed that interaction of mycobacterium with mast cell resulted in changes in the mast cell surface, with formation of pseudopod‐like structure and activation with visibly extruded granules. Moreover, infection of mast cells with Mycobacteria induced cholesterol accumulation at the site of bacterial entry and around intracellular mycobacteria. Disruption of mast cells lipid rafts by cholesterol depletion markedly inhibited the mycobacterium entry. Intracellular multiplication of M. tuberculosis within mast cells was also observed. Overall, our results indicate that M. tuberculosis employs a cholesterol‐dependent pathway to infect mast cells, which leads to degranulation and mast cell morphological changes. These results suggest that although mast cells are capable to respond to M. tuberculosis infection, entry of mycobacterium through lipid rafts may allow replication within mast cells.
A Systematic Review and Meta‐analysis of the Efficacy and Safety of Etanercept for Treating Rheumatoid Arthritis
Authors: Wiens Astrid , Correr Cassyano Januario , Pontarolo Roberto , Venson Rafael , Quinalha Juliana Vasconcelos , Otuki Michel Fleith 
Published: June 2009

AbstractThe aim of this study was to evaluate the efficacy and safety of etanercept (ETA) for treating rheumatoid arthritis. A systematic review was performed to search for randomized clinical trials comparing subcutaneous doses of ETA at 25 mg twice a week or 50 mg weekly to a placebo group, with or without methotrexate. Studies of low quality (less than 3 points on Jadad’s scale) were excluded. The efficacy was assessed by using the criteria of the American College of Rheumatology (ACR). Safety data were evaluated based on serious adverse events, serious infections, malignancy and deaths. Withdrawals as a result of adverse events or lack of efficacy were also evaluated. Eight studies met the inclusion criteria, comprising 2385 patients. In the efficacy meta‐analysis, a greater number of ETA‐treated patients achieved the efficacy criteria within 6 months of treatment, where the relative risk (RR) was 2.94 [2.27, 3.81] for achieving ACR20, 5.28 [3.12, 8.92] for ACR50 and 4.83 [1.74, 13.47] for ACR70. After 1 year, the RR for achieving ACR20, ACR50 and ACR70 were 1.14 [1.07, 1.23], 1.36 [1.21, 1.53] and 1.56 [1.30, 1.88], respectively. This response rates were higher for ETA‐treated patients in comparison with control group patients. For safety, there were no statistically significant differences between treated patients and controls. This was also confirmed by withdrawals as a result of adverse events, which were not statistically different between the two groups. However, more patients withdrew from control groups because of a lack of efficacy as compared with ETA groups (RR = 0.48 [0.30, 0.78]).
Reduced Apoptosis of Mouse Macrophages Induced by yscW Mutant of Yersinia pestis Results from the Reduced Secretion of YopJ and Relates to Caspase‐3 Signal Pathway
Authors: Bi Y. , Du Z. , Yang H. , Guo Z. , Tan Y. , Zhu Z. , Yang Ruifu 
Published: June 2009

AbstractThe virulence of the pathogenic Yersinia species depends on a plasmid‐encoded type III secretion system (T3SS) that injects six Yersinia outer protein (Yop) effector proteins into the cytosol of macrophages, leading to disruption of host defence mechanisms. Here, we report that a T3SS structural protein YscW of Yersinia pestis contributed to the induction of apoptosis of murine macrophages. The apoptotic percentage of macrophages, from both mouse peritoneal cavity and spleen, and of RAW264.7 cell line, caused by the yscW mutant strain was significantly lower than that by wild type (WT) Y. pestis and yscW complemented strain. Meanwhile, detection of caspase‐3 activity in macrophages, a key apoptosis‐inducing protein, showed coincident results with the changes of macrophage apoptosis induced by WT, yscW mutant and complemented strains, indicating that macrophage apoptosis was related to caspase‐3 signal pathways. However, ectopic expression of YscW in RAW264.7 cells cannot increase the macrophage apoptosis and death, suggesting that YscW itself could not induce macrophage apoptosis directly. To get insight into the mechanism of this phenomenon, we investigated the secretion of YopJ, which has been thought to be the only Yop effector related to apoptosis, in WT, mutant and complemented strains, respectively. Results showed that in yscW mutant strain, secretion of YopJ was decreased significantly in the supernatant than that in WT or complemented strain. This means although YscW does not induce apoptosis directly, it can indirectly affect apoptosis through reducing the secretion of YopJ.
Studies on the Mechanism by Which Antigen‐Specific IgG Suppresses Primary Antibody Responses: Evidence for Epitope Masking and Decreased Localization of Antigen in the Spleen
Authors: Getahun A. , Heyman B. 
Published: June 2009

AbstractImmunoglobulin (IgG) has the ability to suppress the Ab response against the Ag to which it binds. Although the mechanism remains unclear, this phenomenon has physiological relevance and is used clinically in Rh prophylaxis. As suppression works well in mice lacking the inhibitory FcγRIIB, the two most likely explanations are that IgG masks epitopes and/or that IgG increases the clearance of Ag. In the present study, mice were immunized with sheep red blood cells (SRBC) to which the hapten 5‐iodo‐4‐hydroxyl‐3‐nitrophenacetyl (NIP) was conjugated at high or low density and the ability of IgG anti‐NIP to suppress the Ab response to NIP and SRBC was assayed. Only the NIP‐specific response was suppressed when mice were immunized with SRBC‐NIPlow, whereas both NIP‐ and SRBC‐specific responses were suppressed when SRBC‐NIPhigh was used. This is best explained by epitope masking; at high epitope density, IgG also blocks neighbouring epitopes from recognition by B cells. We also examined the effects of IgG‐mediated suppression on T‐cell responses directly in vivo. While IgG anti‐SRBC administered with sheep red blood cells ovalbumin (SRBC‐OVA) almost completely suppressed the anti‐SRBC and anti‐OVA Ab responses, the OVA‐specific T‐cell response was still 50% of that observed in control mice. This is probably the result of decreased Ag exposure as IgG‐bound SRBC were cleared faster from the bloodstream and were found at lower concentration in the spleen than unbound SRBC. These results suggest that both Ag clearance and epitope masking occurs during IgG‐mediated suppression, but that under physiological circumstances epitope masking is the predominant mechanism.
HIV Induces both a Down‐Regulation of IRAK‐4 that Impairs TLR Signalling and an Up‐regulation of the Antibiotic Peptide Dermcidin in Monocytic Cells
Authors: Pathak S. , De Souza G. A. , Salte T. , Wiker H. G. , Åsjö B. 
Published: June 2009

AbstractHIV‐infected individuals have an increased risk of invasive bacterial infections, even at early clinical stages with relatively normal CD4+ T‐cell counts. The pathogenic mechanisms behind this are not fully understood. However, an increasing number of studies indicate that HIV may impair the innate immunity to bacteria by infecting key cells of the monocyte/macrophage lineage. In this study, the effects of HIV infection on the protein profile of undifferentiated monocyte‐like THP‐1 cells were examined by a mass spectrometric approach based on stable isotope labelling with amino acid in cell culture (SILAC). We identified 651 proteins, of which nine proteins were down‐regulated and 17 proteins were up‐regulated in HIV‐infected THP‐1 cells as compared to uninfected controls. Most remarkably, the IL‐1 receptor associated kinase 4 (IRAK‐4), which is essential for virtually all TLR signalling, was suppressed, whereas the precursor for the antibiotic peptide Dermcidin was up‐regulated in HIV‐infected cells. Upon stimulation of either TLR2 or TLR4, the HIV‐infected THP‐1 cells displayed reduced TNF‐α secretion. The HIV‐induced down‐regulation of IRAK‐4 was reconfirmed in monocyte‐derived macrophage cell cultures. These data suggests that HIV may impair the TLR signalling cascade for pathogen recognition in cells of the monocyte/macrophage lineage and thus, may reduce the ability of the innate immune system to sense invading pathogens and initiate appropriate responses.
MHC II and the Endocytic Pathway: Regulation by Invariant Chain
Authors: Landsverk O. J. B. , Bakke O. , Gregers T. F. 
Published: June 2009

AbstractThe major histocompatibility complex (MHC) class I and II molecules perform vital functions in innate and adaptive immune responses towards invading pathogens. MHC class I molecules load peptides in the endoplasmatic reticulum (ER) and display them to the T cell receptors (TcR) on CD8+ T lymphocytes. MHC class II molecules (MHC II) acquire their peptides in endosomes and present these to the TcR on CD4+ T lymphocytes. They are vital for the generation of humoral immune responses. MHC II assembly in the ER and trafficking to endosomes is guided by a specialized MHC II chaperone termed the invariant chain (Ii). Ii self‐associates into a trimer in the ER, this provides a scaffold for the assembly of three MHC II heterodimers and blocks their peptide binding grooves, thereby avoiding premature peptide binding. Ii then transports the nascent MHC II to more or less specialized compartment where they can load peptides derived from internalized pathogens.
Increased Expression of Activation‐Induced Cytidine Deaminase is Associated with Anti‐CCP and Rheumatoid Factor in Rheumatoid Arthritis
Authors: Xu X. , Hsu H.‐C. , Chen J. , Grizzle W. E. , Chatham W. W. , Stockard C. R. , Wu Q. , Yang P. A. , Holers V. M. , Mountz J. D. 
Published: June 2009

AbstractRheumatoid arthritis (RA) is associated with higher levels of autoantibodies and IL‐17. Here, we investigated if ectopic lymphoid follicles and peripheral blood mononuclear cells (PBMCs) from RA patients exhibit increased activation‐induced cytidine deaminase (AID), and if increased AID is correlated with serum levels of autoantibodies and IL‐17. The results of immunohistochemical staining showed that organized AID+ germinal centres were observed in six of the 12 RA synovial samples, and AID+ cells were found almost exclusively in the B‐cell areas of these follicles. Aggregated but not organized lymphoid follicles were found in only one OA synovial sample without AID+ cells. Significantly higher levels of AID mRNA (Aicda) detected by RT‐PCR were found in the PBMCs from RA patients than PBMCs from normal controls (P < 0.01). In the PBMCs from RA patients, AID was expressed predominately by the CD10+IgM+CD20+ B‐cell population and the percentage of these cells that expressed AID was significantly higher than in normal controls (P < 0.01). AID expression in the PBMCs correlated significantly and positively with the serum levels of rheumatoid factor (RF) (P ≤ 0.0001) and anti‐cyclic citrullinated peptide (CCP) (P = 0.0005). Serum levels of IFN‐γ (P = 0.0005) and IL‐17 (P = 0.007), but not IL‐4, also exhibited positive correlation with the expression of AID. These results suggest that the higher levels of AID expression in B cells of RA patients correlate with, and may be associated with the higher levels of T helper cell cytokines IFN‐γ and IL‐17, leading to the development of anti‐CCP and RF.
Diagnosis of antiretroviral therapy failure in Malawi: poor performance of clinical and immunological WHO criteria
Authors: Van Oosterhout Joep J.G. , Brown Lillian , Weigel Ralf , Kumwenda Johnstone J. , Mzinganjira Dalitso , Saukila Nasinuku , Mhango Brian , Hartung Thomas , Phiri Sam , Hosseinipour Mina C. 
Published: June 2009

SummaryObjectives  In antiretroviral therapy (ART) scale‐up programmes in sub‐Saharan Africa viral load monitoring is not recommended. We wanted to study the impact of only using clinical and immunological monitoring on the diagnosis of virological ART failure under routine circumstances.Methods  Clinicians in two urban ART clinics in Malawi used clinical and immunological monitoring to identify adult patients for switching to second‐line ART. If patients met clinical and/or immunological failure criteria of WHO guidelines and had a viral load <400 copies/ml there was misclassification of virological ART failure.Results  Between January 2006 and July 2007, we identified 155 patients with WHO criteria for immunological and/or clinical failure. Virological ART failure had been misclassified in 66 (43%) patients. Misclassification was significantly higher in patients meeting clinical failure criteria (57%) than in those with immunological criteria (30%). On multivariate analysis, misclassification was associated with being on ART <2 years [OR = 7.42 (2.63, 20.95)] and CD4 > 200 cells/μl [OR = 5.03 (2.05, 12.34)]. Active tuberculosis and Kaposi’s sarcoma were the most common conditions causing misclassification of virological ART failure.Conclusion  Misclassification of virological ART failure occurs frequently using WHO clinical and immunological criteria of ART failure for poor settings. A viral load test confirming virological ART failure is therefore advised to avoid unnecessary switching to second‐line regimens.
Outbreak of leptospirosis in New Caledonia: diagnosis issues and burden of disease
Authors: Goarant C. , Laumond‐Barny S. , Perez J. , Vernel‐Pauillac F. , Chanteau S. , Guigon A. 
Published: June 2009

SummaryA leptospirosis epidemic affected New Caledonia during the first semester of 2008. A total of 135 cases were diagnosed with a relatively low fatality rate of 3.7%. Heavy rainfalls, related to La Niña, favoured this epidemic. The PCR, routinely used, confirmed 54% of the cases, and the microagglutination test 56%. Epidemiological and economical data on this epidemic are presented and discussed.