Deletion of flavoredoxin gene in Desulfovibrio gigas reveals its participation in thiosulfate reduction

Abstract: The gene encoding Desulfovibrio gigas flavoredoxin was deleted to elucidate its physiological role in the sulfate metabolism. Disruption of flr gene strongly inhibited the reduction of thiosulfate and exhibited a reduced growth in the presence of sulfite with lactate as electron donor. The growth with sulfate was not however affected by the lack of this protein. Additionally, flr mutant cells revealed a decrease of about 50% in the H-2 consumption rate using thiosulfate as electron acceptor. Altogether, our results show in vivo that during sulfite respiration, trithionate and thiosulfate are produced and that flavoredoxin is specific for thiosulfate reduction

Synthesis and characterization of Fe/Co/Ni alloys-MgO nanocomposite powders

A mixed oxalate β-Mg 0.896 Fe 0.047 Co 0.034 Ni 0.023 C 2 O 4 ·2H 2 O of well controlled size and morphology was prepared by coprecipitation. The corresponding quaternary solid solution between MgO, FeO, CoO and NiO was prepared by thermal decomposition and calcination in a H 2 /H 2 O/N 2 atmosphere. The selective reduction of the solid solution in an H 2 atmosphere was studied by a combination of X-ray diffraction, Mössbauer spectroscopy, transmission electron microscopy and associated analysis. This work has brought to light the very high stability of Fe 2+ , Co 2+ and notably Ni 2+ when substituted for Mg 2+ in the MgO rocksalt lattice. It is necessary to perform the reduction at 1300 °C fully to reduce the transition metal ions. The alloy particles are either distributed as relatively large particles (tens to hundreds of nanometers) at the surface of the MgO grains or as much smaller particles (≤20 nm) probably located inside the matrix grains and epitaxial with it. The composition distribution of the large surface particles is fairly broad when the reduction was performed at 1100 and 1300 °C. In contrast, it is much narrower in the powder prepared by reduction at 1200 °C, although the particles are still low in Ni compared to the target composition

Shewanella oneidensis: a new and efficient System for Expression and Maturation of heterologous [Fe-Fe] Hydrogenase from Chlamydomonas reinhardtii

<p>Abstract</p> <p>Background</p> <p>The eukaryotic green alga, <it>Chlamydomonas reinhardtii</it>, produces H₂ under anaerobic conditions, in a reaction catalysed by a [Fe-Fe] hydrogenase HydA1. For further biochemical and biophysical studies a suitable expression system of this enzyme should be found to overcome its weak expression in the host organism. Two heterologous expression systems used up to now have several advantages. However they are not free from some drawbacks. In this work we use bacterium <it>Shewanella oneidensis</it> as a new and efficient system for expression and maturation of HydA1 from <it>Chlamydomonas reinhardtii</it>.</p> <p>Results</p> <p>Based on codon usage bias and hydrogenase maturation ability, the bacterium <it>S. oneidensis</it>, which possesses putative [Fe-Fe] and [Ni-Fe] hydrogenase operons, was selected as the best potential host for <it>C. reinhardtii </it>[Fe-Fe] hydrogenase expression. Hydrogen formation by <it>S. oneidensis </it>strain AS52 (Δ<it>hydA</it>Δ<it>hyaB</it>) transformed with a plasmid bearing <it>Cr</it>HydA1 and grown in the presence of six different substrates for anaerobic respiration was determined. A significant increase in hydrogen evolution was observed for cells grown in the presence of trimethylamine oxide, dimethylsulfoxide and disodium thiosulfate, showing that the system of <it>S. oneidensis </it>is efficient for heterologous expression of algal [Fe-Fe] hydrogenase.</p> <p>Conclusion</p> <p>In the present work a new efficient system for heterologous expression and maturation of <it>C. reinhardtii </it>hydrogenase has been developed. HydA1 of <it>C. reinhardtii </it>was purified and shown to contain 6 Fe atoms/molecule of protein, as expected. Using DMSO, TMAO or thiosulfate as substrates for anaerobic respiration during the cell growth, 0.4 – 0.5 mg l^-1(OD₆₀₀= 1) of catalytically active HydA1 was obtained with hydrogen evolution rate of ~700 μmol H₂mg^-1min^-1.</p

Elaboration, microstructure and oxidation behavior of metal-alumina and metal-chromia nanocomposite powders.

Metal-Al203 and metal-Cr203 nanocomposite powders have been prepared by selective reduction in hydrogen of oxide solid solutions. The metallic phase (either Cr or an (Fe, Cr) alloy) is present in the form of nanometric particles inside and/or at the surface of the oxide matrix grains. The microstructure of the different composites has been compared and their air oxidation behavior has been investigated. The metal particles located in the open porosity of the matrix are totally oxidized at temperatures lower than 600°C, whereas those intragranularly located are stable up to 800°C. The oxidation behavior is generally complex and explanations in relation to the powder microstructure are proposed

Imagerie à travers la turbulence par déconvolution myope multi-trame

La déconvolution par analyse de fronts d'onde est une technique d'imagerie à haute résolution en présence de turbulence atmosphérique. Elle consiste en une déconvolution multi-trame d'images courte pose utilisant des mesures de fronts d'onde enregistrées simultanément. L'approche bayésienne proposée ici nous permet de construire un algorithme de déconvolution original pour prendre en compte le bruit sur les mesures de front d'onde. L'utilisation de connaissances a priori sur les objets observés et sur la statistique de la turbulence atmosphérique nous permet de plus de régulariser le problème. Une simulation numérique montre l'utilité de la régularisation sur les fronts d'onde

Combining Logic and Probabilities for Discovering Mappings between Taxonomies

Abstract. In this paper, we investigate a principled approach for defining and discovering probabilistic mappings between two taxonomies. First, we compare two ways of modeling probabilistic mappings which are compatible with the logical constraints declared in each taxonomy. Then we describe a generate and test algorithm which minimizes the number of calls to the probability estimator for determining those mappings whose probability exceeds a certain threshold. Finally, we provide an experimental analysis of this approach

Hyperbolic manifolds with convex boundary

Let $(M, \partial M)$ be a compact 3-manifold with boundary, which admits a convex co-compact hyperbolic metric. We consider the hyperbolic metrics on $M$ such that the boundary is smooth and strictly convex. We show that the induced metrics on the boundary are exactly the metrics with curvature $K>-1$, and that the third fundamental forms of \dr M are exactly the metrics with curvature $K2\pi$. Each is obtained exactly once. Other related results describe existence and uniqueness properties for other boundary conditions, when the metric which is achieved on \dr M is a linear combination of the first, second and third fundamental forms.Comment: Check the updated version(s) on http://picard.ups-tlse.fr/~schlenker/ Version 2: an error corrected. Version 3: simpler main statement, small corrections, more details on one technical statement. Version 5: one error correcte

The EAGLE instrument for the E-ELT: developments since delivery of Phase A

The EAGLE instrument is a Multi-Object Adaptive Optics (MOAO) fed, multiple Integral Field Spectrograph (IFS), working in the Near Infra-Red (NIR), on the European Extremely Large Telescope (E-ELT). A Phase A design study was delivered to the European Southern Observatory (ESO) leading to a successful review in October 2009. Since that time there have been a number of developments, which we summarize here. Some of these developments are also described in more detail in other submissions at this meeting. The science case for the instrument, while broad, highlighted in particular: understanding the stellar populations of galaxies in the nearby universe, the observation of the evolution of galaxies during the period of rapid stellar build-up between redshifts of 2-5, and the search for 'first light' in the universe at redshifts beyond 7. In the last 2 years substantial progress has been made in these areas, and we have updated our science case to show that EAGLE is still an essential facility for the E-ELT. This in turn allowed us to revisit the science requirements for the instrument, confirming most of the original decisions, but with one modification. The original location considered for the instrument (a gravity invariant focal station) is no longer in the E-ELT Construction Proposal, and so we have performed some preliminary analyses to show that the instrument can be simply adapted to work at the E-ELT Nasmyth platform. Since the delivery of the Phase A documentation, MOAO has been demonstrated on-sky by the CANARY experiment at the William Herschel Telescope.Comment: 10 pages, SPIE Conference proceedings, Amsterdam, July 201

Henipavirus and Tioman Virus Antibodies in Pteropodid Bats, Madagascar

Specimens were obtained from the 3 Malagasy fruit bats, Pteropus rufus, Eidolon dupreanum, and Rousettus madagascariensis. Antibodies against Nipah, Hendra, and Tioman viruses were detected by immunoassay in 23 and by serum neutralization tests in 3 of 427 serum samples, which suggests that related viruses have circulated in Madagascar