Magnetic order in the frustrated Ising-like chain compound Sr3_3NiIrO6_6

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 : l’utilisation croissante de cathéter veineux centraux (KTc) s’explique par l’intérêt d’avoir un accès veineux à long terme dans la prise en charge chronique des patients. Les bactériémies sur KTc sont responsables d’une morbi-mortalité importante et sont par conséquent une problématique hospitalière à l’origine d’une augmentation des durées d’hospitalisation et des dépenses de santé. Si la littérature internationale actuelle évoque largement les bactériémies sur KTc à Staphylococcus aureus (SA) et leurs complications (par endocardites infectieuses, thrombophlébites septiques, ou localisations septiques secondaires), les données concernant les complications des bactériémies sur KTc à autres germes restent pauvres. L’objectif principal de ce travail était de décrire les complications des bactériémies sur KTc survenues chez les patients hospitalisés au CHU de Bordeaux entre Octobre 2014 et Décembre 2016, selon le type de cathéter, le type de bactérie et le terrain du patient.Les objectifs secondaires étaient de décrire l’épidémiologie microbiologique et le profil de résistance aux antibiotiques des bactériémies liées aux KTc selon le type de KTc, le terrain du patient, et de décrire leur prise en charge. Patients et Méthodes : nous avons réalisé une étude rétrospective descriptive s’étendant d’Octobre 2014 à Décembre 2016. Nous avons retenu les patients majeurs ayant présenté durant cette période une bactériémie sur KTc documentée définie par des hémocultures sur KTc et périphériques poussant au même germe avec un délai différentiel de positivité entre les 2 ≥ 2h. Nous avons répertorié les caractéristiques des bactériémies sur KTc à l’aide du logiciel hospitalier DXcare (terrain du patient, microbiologie, caractéristiques du KTc, prise en charge, complications, évolution). Résultats : nous avons inclus 239 patients ayant présentés 254 bactériémies sur KTc à 285 bactéries. Parmi eux 131 étaient de sexe masculin. L’âge médian des patients étaient de 63,4 ans. Parmi les 254 bactériémies, 51,6% sont survenues sur CIP, 22,8% sur VVC non tunnélisée, 9,4% sur VVC tunnélisée, 13% sur piccline et 3,2 % sur cathéter de dialyse. Les principaux motifs de pose étaient une chimiothérapie (51,2% des cas), la nutrition (22,8% des cas), une antibiothérapie (5,5% des cas), et la dialyse (4,7% des cas). Les principales bactéries retrouvées étaient des entérobactéries (33%), des staphylocoques à coagulase négative (SCN) (28,8%), des SA (15,8%), et des bacilles gram négatif non fermentants (15,8%). Nous avions une proportion plus importante de SCN pour les KTc utilisés pour la nutrition, plus de SA pour les KTc utilisés pour la dialyse. Nous avions plus d’Entérobactéries chez les femmes et de SCN chez les hommes. Le délai médian de survenue d’une bactériémie tous types de KTc confondus a été de 1,2 mois. Une ablation du KTc a été réalisée dans 79,6% des cas, un verrou antibiotique dans 16,5% des cas, une antibiothérapie adaptée pour 95,3% des bactériémies. Des examens complémentaires à la recherche de complications ont été réalisés pour 117 bactériémies, essentiellement des échographies cardiaques (n=107), des TDM thoracoabdominopelviens (n=43), des dopplers veineux (n=21). Au moins une complication a été retrouvée pour 35 bactériémies (15 thrombophlébites septiques, 7 endocardites, 7 localisations osseuses, 6 localisations pulmonaires, 5 localisations cérébrales). Les bactériémies sur KTc à SA ont présenté le plus de complications (n=14, 31,1%), suivies des bactériémies à Pseudomonas aeruginosa (n=5, 16,7%), et des bactériémies à SCN (n=12, 14,6%). La dialyse a été retrouvé comme facteur de risque de complication. A l’inverse nous avons mis en avant qu’un traitement anticoagulant était protecteur sur la survenue de thrombophlébite septique. Enfin la survenue de complications a été associée à un risque plus important de bactériémi prolongée et de décès à 3 mois. Conclusion : les bactériémies sur KTc à SA ont présenté le plus fort taux de complications infectieuses. Des complications ont également été retrouvées pour les bactériémies à SCN et Pseudomonas aeruginosa. L’hémodialyse a été retrouvée comme facteur de risque de complication et un traitement par anticoagulant comme facteur protecteur. Enfin nous avons mis en évidence un impact de la survenue d’une complication sur la persistance d’hémoculture positive et sur la survenue d’un décès à 3 mois

Sequestration of Radionuclides Radium-226 and Strontium-90 by Cyanobacteria Forming Intracellular Calcium Carbonates

International audience$^{226}$Ra is a naturally occurring radionuclide with a half-life of 1600 y. In contrast, $^{90}$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 $G.\ lithophora$, capable of forming intracellular amorphous calcium carbonate inclusions, was investigated for its ability to uptake $^{226}$ Ra and $^{90}$Sr. In BG-11 medium, $G.\ lithophora$ accumulated 3.9 $\mu$g g$^{-1}$ $^{226}$Ra within 144 h and 47.9 ng g$^{-1}$ $^{90}$Sr within 1 h, corresponding to $\sim$99% removal of trace radionuclides. The presence of high concentration Ca$^{2+}$ in the background media solution did not inhibit $^{90}$Sr and $^{226}$Ra uptake by $G.\ lithophora$. In contrast, dead biomass of $G.\ lithophora$ accumulated 0.8 $\mu$g g$^{-1}$ $^{226}$Ra and 8.87 ng g$^{-1}$ $^{90}$Sr. Moreover, Synechocystis, a non-biomineralizing cyanobacteria removed only 14% and 25% of $^{226}$Ra and $^{90}$Sr, respectively. This suggested that sequestration of $^{90}$Sr and $^{226}$Ra was not intrinsic to all cyanobacteria but was likely a specific biological trait of $G.\ lithophora$ related to the formation of intracellular amorphous Ca-carbonates. The unique ability of $G.\ lithophora$ to uptake $^{90}$Sr and $^{226}$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