75 research outputs found
Magnetic order in the frustrated Ising-like chain compound SrNiIrO
We have studied the field and temperature dependence of the magnetization of
single crystals of Sr3NiIrO6. These measurements evidence the presence of an
easy axis of anisotropy and two anomalies in the magnetic susceptibility.
Neutron powder diffraction realized on a polycrystalline sample reveals the
emergence of magnetic reflections below 75 K with magnetic propagation vector k
~ (0, 0, 1), undetected in previous neutron studies [T.N. Nguyen and H.-C zur
Loye, J. Solid State Chem., 117, 300 (1995)]. The nature of the magnetic ground
state, and the presence of two anomalies common to this family of material, are
discussed on the basis of the results obtained by neutron diffraction,
magnetization measurements, and symmetry arguments
Influence of Uranium on Bacterial Communities: A Comparison of Natural Uranium-Rich Soils with Controls
This study investigated the influence of uranium on the indigenous bacterial community structure in natural soils with high uranium content. Radioactive soil samples exhibiting 0.26% - 25.5% U in mass were analyzed and compared with nearby control soils containing trace uranium. EXAFS and XRD analyses of soils revealed the presence of U(VI) and uranium-phosphate mineral phases, identified as sabugalite and meta-autunite. A comparative analysis of bacterial community fingerprints using denaturing gradient gel electrophoresis (DGGE) revealed the presence of a complex population in both control and uranium-rich samples. However, bacterial communities inhabiting uraniferous soils exhibited specific fingerprints that were remarkably stable over time, in contrast to populations from nearby control samples. Representatives of Acidobacteria, Proteobacteria, and seven others phyla were detected in DGGE bands specific to uraniferous samples. In particular, sequences related to iron-reducing bacteria such as Geobacter and Geothrix were identified concomitantly with iron-oxidizing species such as Gallionella and Sideroxydans. All together, our results demonstrate that uranium exerts a permanent high pressure on soil bacterial communities and suggest the existence of a uranium redox cycle mediated by bacteria in the soil
Two-component spike nanoparticle vaccine protects macaques from SARS-CoV-2 infection
Brouwer et al. present preclinical evidence in support of a COVID-19 vaccine candidate, designed as a self-assembling two-component protein nanoparticle displaying multiple copies of the SARS-CoV-2 spike protein, which induces strong neutralizing antibody responses and protects from high-dose SARS-CoV-2 challenge.The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic is continuing to disrupt personal lives, global healthcare systems, and economies. Hence, there is an urgent need for a vaccine that prevents viral infection, transmission, and disease. Here, we present a two-component protein-based nanoparticle vaccine that displays multiple copies of the SARS-CoV-2 spike protein. Immunization studies show that this vaccine induces potent neutralizing antibody responses in mice, rabbits, and cynomolgus macaques. The vaccine-induced immunity protects macaques against a high-dose challenge, resulting in strongly reduced viral infection and replication i
Bactériémies liées aux cathéters veineux centraux : épidémiologie, microbiologie, complications et prise en charge thérapeutique
Introduction : lâutilisation croissante de cathĂ©ter veineux centraux (KTc) sâexplique par lâintĂ©rĂȘt dâavoir un accĂšs veineux Ă long terme dans la prise en charge chronique des patients. Les bactĂ©riĂ©mies sur KTc sont responsables dâune morbi-mortalitĂ© importante et sont par consĂ©quent une problĂ©matique hospitaliĂšre Ă lâorigine dâune augmentation des durĂ©es dâhospitalisation et des dĂ©penses de santĂ©. Si la littĂ©rature internationale actuelle Ă©voque largement les bactĂ©riĂ©mies sur KTc Ă Staphylococcus aureus (SA) et leurs complications (par endocardites infectieuses, thrombophlĂ©bites septiques, ou localisations septiques secondaires), les donnĂ©es concernant les complications des bactĂ©riĂ©mies sur KTc Ă autres germes restent pauvres. Lâobjectif principal de ce travail Ă©tait de dĂ©crire les complications des bactĂ©riĂ©mies sur KTc survenues chez les patients hospitalisĂ©s au CHU de Bordeaux entre Octobre 2014 et DĂ©cembre 2016, selon le type de cathĂ©ter, le type de bactĂ©rie et le terrain du patient.Les objectifs secondaires Ă©taient de dĂ©crire lâĂ©pidĂ©miologie microbiologique et le profil de rĂ©sistance aux antibiotiques des bactĂ©riĂ©mies liĂ©es aux KTc selon le type de KTc, le terrain du patient, et de dĂ©crire leur prise en charge. Patients et MĂ©thodes : nous avons rĂ©alisĂ© une Ă©tude rĂ©trospective descriptive sâĂ©tendant dâOctobre 2014 Ă DĂ©cembre 2016. Nous avons retenu les patients majeurs ayant prĂ©sentĂ© durant cette pĂ©riode une bactĂ©riĂ©mie sur KTc documentĂ©e dĂ©finie par des hĂ©mocultures sur KTc et pĂ©riphĂ©riques poussant au mĂȘme germe avec un dĂ©lai diffĂ©rentiel de positivitĂ© entre les 2 â„ 2h. Nous avons rĂ©pertoriĂ© les caractĂ©ristiques des bactĂ©riĂ©mies sur KTc Ă lâaide du logiciel hospitalier DXcare (terrain du patient, microbiologie, caractĂ©ristiques du KTc, prise en charge, complications, Ă©volution). RĂ©sultats : nous avons inclus 239 patients ayant prĂ©sentĂ©s 254 bactĂ©riĂ©mies sur KTc Ă 285 bactĂ©ries. Parmi eux 131 Ă©taient de sexe masculin. LâĂąge mĂ©dian des patients Ă©taient de 63,4 ans. Parmi les 254 bactĂ©riĂ©mies, 51,6% sont survenues sur CIP, 22,8% sur VVC non tunnĂ©lisĂ©e, 9,4% sur VVC tunnĂ©lisĂ©e, 13% sur piccline et 3,2 % sur cathĂ©ter de dialyse. Les principaux motifs de pose Ă©taient une chimiothĂ©rapie (51,2% des cas), la nutrition (22,8% des cas), une antibiothĂ©rapie (5,5% des cas), et la dialyse (4,7% des cas). Les principales bactĂ©ries retrouvĂ©es Ă©taient des entĂ©robactĂ©ries (33%), des staphylocoques Ă coagulase nĂ©gative (SCN) (28,8%), des SA (15,8%), et des bacilles gram nĂ©gatif non fermentants (15,8%). Nous avions une proportion plus importante de SCN pour les KTc utilisĂ©s pour la nutrition, plus de SA pour les KTc utilisĂ©s pour la dialyse. Nous avions plus dâEntĂ©robactĂ©ries chez les femmes et de SCN chez les hommes. Le dĂ©lai mĂ©dian de survenue dâune bactĂ©riĂ©mie tous types de KTc confondus a Ă©tĂ© de 1,2 mois. Une ablation du KTc a Ă©tĂ© rĂ©alisĂ©e dans 79,6% des cas, un verrou antibiotique dans 16,5% des cas, une antibiothĂ©rapie adaptĂ©e pour 95,3% des bactĂ©riĂ©mies. Des examens complĂ©mentaires Ă la recherche de complications ont Ă©tĂ© rĂ©alisĂ©s pour 117 bactĂ©riĂ©mies, essentiellement des Ă©chographies cardiaques (n=107), des TDM thoracoabdominopelviens (n=43), des dopplers veineux (n=21). Au moins une complication a Ă©tĂ© retrouvĂ©e pour 35 bactĂ©riĂ©mies (15 thrombophlĂ©bites septiques, 7 endocardites, 7 localisations osseuses, 6 localisations pulmonaires, 5 localisations cĂ©rĂ©brales). Les bactĂ©riĂ©mies sur KTc Ă SA ont prĂ©sentĂ© le plus de complications (n=14, 31,1%), suivies des bactĂ©riĂ©mies Ă Pseudomonas aeruginosa (n=5, 16,7%), et des bactĂ©riĂ©mies Ă SCN (n=12, 14,6%). La dialyse a Ă©tĂ© retrouvĂ© comme facteur de risque de complication. A lâinverse nous avons mis en avant quâun traitement anticoagulant Ă©tait protecteur sur la survenue de thrombophlĂ©bite septique. Enfin la survenue de complications a Ă©tĂ© associĂ©e Ă un risque plus important de bactĂ©riĂ©mi prolongĂ©e et de dĂ©cĂšs Ă 3 mois. Conclusion : les bactĂ©riĂ©mies sur KTc Ă SA ont prĂ©sentĂ© le plus fort taux de complications infectieuses. Des complications ont Ă©galement Ă©tĂ© retrouvĂ©es pour les bactĂ©riĂ©mies Ă SCN et Pseudomonas aeruginosa. LâhĂ©modialyse a Ă©tĂ© retrouvĂ©e comme facteur de risque de complication et un traitement par anticoagulant comme facteur protecteur. Enfin nous avons mis en Ă©vidence un impact de la survenue dâune complication sur la persistance dâhĂ©moculture positive et sur la survenue dâun dĂ©cĂšs Ă 3 mois
Sequestration of Radionuclides Radium-226 and Strontium-90 by Cyanobacteria Forming Intracellular Calcium Carbonates
International audienceRa is a naturally occurring radionuclide with a half-life of 1600 y. In contrast, Sr is a radionuclide of sole anthropogenic origin, produced by nuclear fission reactions and has a half-life of 29 y; each of these radionuclides poses potential threats to 16 human and ecosystem health. Here, the cyanobacterium , capable of forming intracellular amorphous calcium carbonate inclusions, was investigated for its ability to uptake Ra and Sr. In BG-11 medium, accumulated 3.9 g g Ra within 144 h and 47.9 ng g Sr within 1 h, corresponding to 99% removal of trace radionuclides. The presence of high concentration Ca in the background media solution did not inhibit Sr and Ra uptake by . In contrast, dead biomass of accumulated 0.8 g g Ra and 8.87 ng g Sr. Moreover, Synechocystis, a non-biomineralizing cyanobacteria removed only 14% and 25% of Ra and Sr, respectively. This suggested that sequestration of Sr and Ra was not intrinsic to all cyanobacteria but was likely a specific biological trait of related to the formation of intracellular amorphous Ca-carbonates. The unique ability of to uptake Sr and Ra at high rates makes it an attractive candidate for further studies involving bioremediation of these radionuclides
Assessment of U and Th (bio)availability within a former U mine-impacted wetland
International audienceAssessment of the impact of naturally occurring radionuclides (NOR) within terrestrial biotopes of uraniferous territories is a sound issue. Among others, it requires deep understanding of NOR transfer within the soil-water-microorganisms/plants continuum. In this study, part of RADONORM (european-funded) and Needs-Environment INSPECT projects, we combined in-situ and lab characterization of samples taken from a small wetland downstream a former U-mine (Rophin site, France). Soil cores and co-located plants (Caltha palustris, Scirpus sylvaticus) were sampled in 2 zones, where a layer of U-rich materials originated from decantation pound leakage is present or not (control) in the root-colonized horizons. Samples were characterized for U and Th contents. Environmental availability and bioavailability were assessed in some soil layers respectively by successive batch desorption and by the ISO normalized RHIZOtest with ryegrass as test plant.U has an heterogenous distribution within the soil profile with higher concentration in the U-rich materials layer. In situ-U Transfer Factors ([U]leaves/[U]soil) were not different between the 2 zones despite contrasted soil and plant concentrations. For Th, plant concentrations and TF values were lower in the control zone than in the impacted one despite similar concentrations in soil. Environmental availability of U (0.3 to 3%) and Th (<0.1%) was low in all soil layers, with higher values in organic surface horizons of both zones for Th. These values differ from those of bioavailable U and Th assessed by the RHIZOtest experiments. The latter are lower than the environmental available ones for U in the mine layer and in organic layers for Th, whereas the opposite is observed for U in both horizons of the control zone and for Th in the deeper horizons of both zones. Results highlight the complex link between element speciation, solution/root relationships and transfer intensity and illustrate the remaining challenge to link availability/bioavailability experiments
Alteration of a Single Tryptophan Residue of the Cellulose-binding Domain Blocks Secretion of the Erwinia chrysanthemi Cel5 Cellulase (ex-EGZ) via the Type II System
International audienceCel5 (formerly known as endoglucanase Z) of Erwinia chrysanthemi is secreted by the Out type II pathway. Previous studies have shown that the catalytic domain (CD), linker region (LR) and cellulose-binding domain (CBD) each contain information needed for secretion. The aim of this work was to further investigate the secretion-related information present in the CBD(Cel5). Firstly(, )deleting a surface-exposed flexible loop had no effect on secretion. This indicated that some structural freedom is tolerated by the type II system. Secondly, mutation of a single tryptophan residue, previously shown to be important for binding to cellulose, i.e. Trp43, was found also to impair secretion. This indicated that the flat cellulose-binding surface of CBD(Cel5 )contains secretion-related information. Thirdly, CBD(Cel5) was substituted by the CBD(EGG) of Alteromonas haloplanctis endoglucanase G, yielding a hybrid protein CD(Cel5)-LR(Cel5)-CBD(EGG) that exhibited 90 % identity with Cel5, including the Trp43 residue. The hybrid protein was not secreted. This indicated that the Trp43 residue is necessary but not sufficient for secretion. Here we propose a model in which the secretion of Cel5 involves a transient intramolecular interaction between the cellulose-binding surface of CBD(Cel5) and a region close to the entry into the active site in CD(Cel5). Once secreted, the protein may then open out to allow the cellulose-binding surface of CBD(Cel5 )to interact with the surface of the cellulose substrate. An implication of this model is that protein molecules fold to a specific secretion-competent conformation prior to secretion that is different from the folding state of the secreted species
Exploration of Deinococcus-Thermus molecular diversity by novel group-specific PCR primers
International audienceThe deeply branching Deinococcus-Thermus lineage is recognized as one of the most extremophilic phylum of bacteria. In previous studies, the presence of Deinococcus-related bacteria in the hot arid Tunisian desert of Tataouine was demonstrated through combined molecular and culture-based approaches. Similarly , Thermus-related bacteria have been detected in Tunisian geothermal springs. The present work was conducted to explore the molecular diversity within the Deinococcus-Thermus phylum in these extreme environments. A set of specific primers was designed in silico on the basis of 16S rRNA gene sequences, validated for the specific detection of reference strains, and used for the polymerase chain reaction (PCR) amplification of metagenomic DNA retrieved from the Tataouine desert sand and Tunisian hot spring water samples. These analyses have revealed the presence of previously undescribed Deino-coccus-Thermus bacterial sequences within these extreme environments. The primers designed in this study thus represent a powerful tool for the rapid detection of Deinococcus-Thermus in environmental samples and could also be applicable to clarify the biogeography of the Deinococcus-Thermus phylum
Assessment of U and Th (bio)availability within a former U mine-impacted wetland
International audienceAssessment of the impact of naturally occurring radionuclides (NOR) within terrestrial biotopes of uraniferous territories is a sound issue. Among others, it requires deep understanding of NOR transfer within the soil-water-microorganisms/plants continuum. In this study, part of RADONORM (european-funded) and Needs-Environment INSPECT projects, we combined in-situ and lab characterization of samples taken from a small wetland downstream a former U-mine (Rophin site, France). Soil cores and co-located plants (Caltha palustris, Scirpus sylvaticus) were sampled in 2 zones, where a layer of U-rich materials originated from decantation pound leakage is present or not (control) in the root-colonized horizons. Samples were characterized for U and Th contents. Environmental availability and bioavailability were assessed in some soil layers respectively by successive batch desorption and by the ISO normalized RHIZOtest with ryegrass as test plant.U has an heterogenous distribution within the soil profile with higher concentration in the U-rich materials layer. In situ-U Transfer Factors ([U]leaves/[U]soil) were not different between the 2 zones despite contrasted soil and plant concentrations. For Th, plant concentrations and TF values were lower in the control zone than in the impacted one despite similar concentrations in soil. Environmental availability of U (0.3 to 3%) and Th (<0.1%) was low in all soil layers, with higher values in organic surface horizons of both zones for Th. These values differ from those of bioavailable U and Th assessed by the RHIZOtest experiments. The latter are lower than the environmental available ones for U in the mine layer and in organic layers for Th, whereas the opposite is observed for U in both horizons of the control zone and for Th in the deeper horizons of both zones. Results highlight the complex link between element speciation, solution/root relationships and transfer intensity and illustrate the remaining challenge to link availability/bioavailability experiments
Correction to âSequestration of Radionuclides Radium-226 and Strontium-90 by Cyanobacteria Forming Intracellular Calcium Carbonatesâ
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