Taxonomic distribution of large DNA viruses in the sea

Phylogenetic mapping of metagenomics data reveals the taxonomic distribution of large DNA viruses in the sea, including giant viruses of the Mimiviridae family

Horizontal gene transfer and nucleotide compositional anomaly in large DNA viruses

<p>Abstract</p> <p>Background</p> <p>DNA viruses have a wide range of genome sizes (5 kb up to 1.2 Mb, compared to 0.16 Mb to 1.5 Mb for obligate parasitic bacteria) that do not correlate with their virulence or the taxonomic distribution of their hosts. The reasons for such large variation are unclear. According to the traditional view of viruses as gifted "gene pickpockets", large viral genome sizes could originate from numerous gene acquisitions from their hosts. We investigated this hypothesis by studying 67 large DNA viruses with genome sizes larger than 150 kb, including the recently characterized giant mimivirus. Given that horizontally transferred DNA often have anomalous nucleotide compositions differing from the rest of the genome, we conducted a detailed analysis of the inter- and intra-genome compositional properties of these viruses. We then interpreted their compositional heterogeneity in terms of possible causes, including strand asymmetry, gene function/expression, and horizontal transfer.</p> <p>Results</p> <p>We first show that the global nucleotide composition and nucleotide word usage of viral genomes are species-specific and distinct from those of their hosts. Next, we identified compositionally anomalous (cA) genes in viral genomes, using a method based on Bayesian inference. The proportion of cA genes is highly variable across viruses and does not exhibit a significant correlation with genome size. The vast majority of the cA genes were of unknown function, lacking homologs in the databases. For genes with known homologs, we found a substantial enrichment of cA genes in specific functional classes for some of the viruses. No significant association was found between cA genes and compositional strand asymmetry. A possible exogenous origin for a small fraction of the cA genes could be confirmed by phylogenetic reconstruction.</p> <p>Conclusion</p> <p>At odds with the traditional dogma, our results argue against frequent genetic transfers to large DNA viruses from their modern hosts. The large genome sizes of these viruses are not simply explained by an increased propensity to acquire foreign genes. This study also confirms that the anomalous nucleotide compositions of the cA genes is sometimes linked to particular biological functions or expression patterns, possibly leading to an overestimation of recent horizontal gene transfers.</p

Marine mimivirus relatives are probably large algal viruses

<p>Abstract</p> <p>Background</p> <p><it>Acanthamoeba polyphaga </it>mimivirus is the largest known ds-DNA virus and its 1.2 Mb-genome sequence has revealed many unique features. Mimivirus occupies an independent lineage among eukaryotic viruses and its known hosts include only species from the <it>Acanthamoeba </it>genus. The existence of mimivirus relatives was first suggested by the analysis of the Sargasso Sea metagenomic data.</p> <p>Results</p> <p>We now further demonstrate the presence of numerous "mimivirus-like" sequences using a larger marine metagenomic data set. We also show that the DNA polymerase sequences from three algal viruses (CeV01, PpV01, PoV01) infecting different marine algal species (<it>Chrysochromulina ericina</it>, <it>Phaeocystis pouchetii</it>, <it>Pyramimonas orientalis</it>) are very closely related to their homolog in mimivirus.</p> <p>Conclusion</p> <p>Our results suggest that the numerous mimivirus-related sequences identified in marine environments are likely to originate from diverse large DNA viruses infecting phytoplankton. Micro-algae thus constitute a new category of potential hosts in which to look for new species of <it>Mimiviridae</it>.</p

Design and baseline characteristics of the finerenone in reducing cardiovascular mortality and morbidity in diabetic kidney disease trial

Background: Among people with diabetes, those with kidney disease have exceptionally high rates of cardiovascular (CV) morbidity and mortality and progression of their underlying kidney disease. Finerenone is a novel, nonsteroidal, selective mineralocorticoid receptor antagonist that has shown to reduce albuminuria in type 2 diabetes (T2D) patients with chronic kidney disease (CKD) while revealing only a low risk of hyperkalemia. However, the effect of finerenone on CV and renal outcomes has not yet been investigated in long-term trials. Patients and Methods: The Finerenone in Reducing CV Mortality and Morbidity in Diabetic Kidney Disease (FIGARO-DKD) trial aims to assess the efficacy and safety of finerenone compared to placebo at reducing clinically important CV and renal outcomes in T2D patients with CKD. FIGARO-DKD is a randomized, double-blind, placebo-controlled, parallel-group, event-driven trial running in 47 countries with an expected duration of approximately 6 years. FIGARO-DKD randomized 7,437 patients with an estimated glomerular filtration rate >= 25 mL/min/1.73 m(2) and albuminuria (urinary albumin-to-creatinine ratio >= 30 to <= 5,000 mg/g). The study has at least 90% power to detect a 20% reduction in the risk of the primary outcome (overall two-sided significance level alpha = 0.05), the composite of time to first occurrence of CV death, nonfatal myocardial infarction, nonfatal stroke, or hospitalization for heart failure. Conclusions: FIGARO-DKD will determine whether an optimally treated cohort of T2D patients with CKD at high risk of CV and renal events will experience cardiorenal benefits with the addition of finerenone to their treatment regimen. Trial Registration: EudraCT number: 2015-000950-39; ClinicalTrials.gov identifier: NCT02545049

Étude d'interprétation structurale de macles de l'anatase

Des pseudo˗éléments de symétrie d'une tranche de la structure atomique cristalline correspondant aux éléments de macle parallèles au P. C. O. (plan de composition originel) sont utilisés pour obtenir les positions relatives des atomes des deux individus dans chacun des types de macles étudiés. On admet que la croissance des formes auxquelles appartiennent les P. C. O. de ces macles s'effectue, pour chacune des faces, par croissance de couches successives. Les éléments de symétrie de macle se trouvent entre deux couches contiguës appartenant l'une au premier, l'autre au second individu. On fait le bilan des liaisons du cristal perturbées dans les édifices maclés. L'énergie d'adhésion, par molécule TiO₂, d'un germe bidimensionnel sur une face (011) est calculée par la méthode de Madelung et celle de Hartman ; on obtient — 0,827 e² Å⁻¹ dans le cas du cristal, — 0,432 e² Å⁻¹ dans celui de la macle (112) par pénétration et — 0,375 e² Å⁻¹ dans le cas de la macle (011) par contact beaucoup plus rare que la précédente.Frey Michel, Monier Jean-Claude. Étude d'interprétation structurale de macles de l'anatase. In: Bulletin de la Société française de Minéralogie et de Cristallographie, volume 87, 1, 1964. pp. 39-47

Approches moléculaires pour l’étude de la diversité taxonomique et fonctionnelle microbienne

National audienc

Étude du composé d'addition Hg(CN)2.0,80 tétrahydrofuranne. Morphologie et données préliminaires sur la structure cristalline

Numerous studies have been made in order to determine the part played by adsorption on crystalline morphology and to deduce the structural mechanisms which may occur during growth in a solution. As a contribution to those works a study of solvate Hg (CN)₂ .0,80 tetrahydrofuran has been undertaken. The morphology of this compound is given, as well as a preliminary study of its structure (of unit cell parameters, space group, position of mercury atoms).De nombreuses études ont été effectuées pour déterminer le rôle de l'adsorption sur la morphologie cristalline et déduire les mécanismes structuraux qui peuvent intervenir lors de la croissance en solution. Dans le cadre d'une contribution à ces travaux, nous avons entrepris l'étude du solvate Hg (CN)₂ . 0,80 tétrahydrofuranne. On indique la morphologie de ce composé ainsi que l'étude préliminaire de sa structure (caractéristiques de la maille, groupe spatial, positions des atomes de mercure) .Ledésert Margaret, Frey Michel, Monier Jean-Claude. Étude du composé d'addition Hg(CN)2.0,80 tétrahydrofuranne. Morphologie et données préliminaires sur la structure cristalline. In: Bulletin de la Société française de Minéralogie et de Cristallographie, volume 90, 1, 1967. pp. 36-40

Progress in Microbial Fuel Cells Energy Production

International audienceBiological fuel cells are devices capable of directly transforming chemical to electrical energy via electrochemical reactions involving biochemical pathways. Among others, microbial fuel cells (MFCs) use bacterial metabolism at the anode to produce electricity from a wide range of organic substrate. While the idea of harvesting energy produced by MFCs is sprouting, two major issues need to be addressed: low power densities and high manufacturing cost. A typical 1 liter reactor produces no more than 10mW of electrical power, while the costs of the materials to manufacture it is above 30€. High price is caused by the use of nafion and platinum respectively in the membrane and the cathode. A lowcost (and low power density) MFC was built. Earthen membrane replaced nafion and biocathode replaced platinum cathode. Other more common works investigate single chamber air-cathode reactors where the membrane and the cathode are combined. Recent multidisciplinary works on reactor designs, electrodes, substrate and bacterial communities address price and performance issues altogether. In the near future, electrical engineers will contribute by designing adapted power management modules to capture and make use of the harvested energy. The way is long before MFCs can reach the present competitiveness of other renewable energy sources like photovoltaic modules. First applications of MFCs will most likely be to power micro-sensors in remote areas

Récupération de l'énergie électrique produite par les piles à combustibles microbiennes

Les Piles à Combustibles Microbiennes (PCMs) produisent de l'électricité à partir de la dégradation de matière organique par des bactéries. Pour récupérer l'énergie électrique produite, des architectures mettant en jeux plusieurs piles seront préférées à des architectures basées sur une pile unique de taille importante. Par ailleurs la nécessité d'élever les tensions, de mutualiser les puissances et d'adapter la charge à la source passent par le choix et le dimensionnement d'une chaîne judicieuse de convertisseurs de puissance spécifiques (faible tension d'entrée et basse puissance) au sein d'un réseau de PCMs. Le nombre de micro-sources considérées conduit naturellement à envisager la cellularisation de la conversion avec mise en réseau série et/ou parallèle des convertisseurs. Une récupération efficace de l'énergie passe également par l'intégration de la fonctionnalité MPPT (Maximum Power Point Tracking) qui permet d'adapter la charge à la pile