Modification of a commercial dna extraction kit to simultaneously recover rna, safely and rapidly, and to assess molecular biomass of the total and the active part of microbial communities, from soils with diverse mineralogy and carbon content : S11.04-P -15

We have modified a commercial DNA extraction kit for soil to simultaneously co-extract RNA. In this new procedure RNA and DNA are separated by two selective purifications in cascade without the need of DNAase or RNAse digestion. Consequently DNA and RNA are respectively purified from the whole co-extraction solution. Nucleic acids extraction is based on the action of SDS coupled with an efficient bead-beating step, but it does not require any solvent. Avoiding the use of solvents, which are damaging for human health and environmental quality, was one of our most important motivations to develop this protocol. In a second time, we have optimized this protocol to improve the DNA and RNA yield, but kipping those yields below the saturation limit of the kit to assess and quantify the variations of molecular biomass of the total (DNA) and the active (RNA) part of microbial communities in natural samples. We have also introduced a first step of homogenization of soil sample in liquid nitrogen to improve the reliability of the fungal 18S gene sequence quantification. Finally, we have shown that this protocol can be applied to a wide diversity of soils whatever their mineralogy and metal content (2 Ferralsols, 1 Vertisol, 2 Andosols from Madagascar), texture or biomass content (1 poor sandy soil from Congo and one carbon rich temperate soil sample submitted or not to a 1 month cold stress). * E Tournier, L. Amenc and AL. Pablo contributed equally to this study. (Texte intégral

Ecological importance of soil bacterivores for ecosystem functions

BackgroundBacterivores, mostly represented by protists and nematodes, are a key component of soil biodiversity involved in soil fertility and plant productivity. In the current context of global change and soil biodiversity erosion, it becomes urgent to suitably recognize and quantify their ecological importance in ecosystem functioning.ScopeUsing meta-analysis tools, we aimed at providing a quantitative synthesis of the ecological importance of soil bacterivores on ecosystem functions. We also intended to produce an overview of the ecological factors that are expected to drive the magnitude of bacterivore effects on ecosystem functions.ConclusionsBacterivores in soil contributed significantly to numerous key ecosystem functions. We propose a new theoretical framework based on ecological stoichiometry stressing the role of C:N:P ratios in soil, microbial and plant biomass as important parameters driving bacterivore-effects on soil N and P availability for plants, immobilization of N and P in the bacterial biomass, and plant responses in nutrition and growth

Mullite interaction with bismuth oxide from minerals and sol-gel processes

International audienceThe high temperature treatment of kaolinite-muscovite alternate layers doped by bismuth oxide was studied by TGA and DTA, X ray diffraction, and electron microscopy (SEM). Thermal analyses shows that the two main transformation stages are the dehydroxylation of phyllosilicates and the structural reorganization of the whole assembly. During dehydroxylation, a progressive decrease of the structural order of kaolinite and muscovite occurs. It is more significant at temperature above 1000°C and mullite, glass and Alrich oxides are formed. Mullite exhibits an accentuated acicular morphology along 3 preferential orientations in relation to the remaining structure in the basal (001)musc planes of the former muscovite. With addition of bismuth oxide, SEM observations point to the strong accentuation of mullite growth along the c axis, at the very low temperature of 1050°C. This behavior was studied with various mullite-bismuth oxide compounds at temperatures ranging from 1000°C to 1400°C. Solgel processing were performed with TEOS (C2H5O)4Si, aluminum nitrate Al(NO3)3.9H2O and bismuth nitrate Bi(NO3)3. From Rietveld refinements of X ray diffraction patterns it was found that bismuth doesn't form a specific phase with mullite during the mullite nucleation and growth. At low Bi2O3 content, mullite coexists with amorphous silico-aluminate phases, even at high temperature. When the Bi2O3 content increases above 12mol%, mullite is no longer crystallized. Above 750°C, aluminum bismuth oxide coexists with silicon bismuth oxide. The liquidus temperature is below 1100°C and decreases with Bi2O3 additions. Above the liquidus, only corundum and a liquid coexist. A tentative mullite-Bi2O3 binary phase diagram is then proposed. These results evidence the Bi2O3 role on the early and large mullite growth in kaolinite-muscovite materials. Particularly, a very low quantity of a low viscous phase favor the local mobility of diffusing species and promotes the nucleation and growth of very large mullite crystals. In this way, highly textured and dense ceramics are obtained at low sintering temperature. Thin substrates (<500μm) present specific mechanical behaviors with the deviation of cracks along mullite layers

Aplicació de Twitter descentralitzat

Català: Agafant com a referència una aplicació de complexitat relativament baixa, com és en el nostre cas Twitter, mirar de re dissenyar-la per tal que estigui formada per un bon nombre de components de la granularitat més fina possible, per tal que desplegar-la en un entorn completament descentralitzat permeti un millor aprofitament dels recursos. En una societat tecnològica com l'actual, sempre hi ha demanda de serveis software. Aixó ha provocat que una tecnologia com és el Cloud Computing, l'objectiu de la qual és aconseguir una manera eficaç i eficient de respondre a aquesta demanda de serveis, ocupin gran part de la investigació i desenvolupament informàtics actuals. Així ha nascut la idea de CoDeS, un sistema de cloud desenvolupat per un equip universitari català, en el qual no hi ha màquines dedicades sino que s'aprofita al màxim els recursos que els usuaris cedeixen voluntàriament a la xarxa. Ens trobem davant d'una tendència en alça, i creiem que desenvolupar una aplicació d'aquestes característiques pot resultar en una bona oportunitat per a aprendre a desenvolupar un tipus de productes que, cada cop més, aniran sent productes informàtics quotidians

Numériser pour préserver et valoriser les patrimoines culturels

La Fédération Wallonie-Bruxelles a mis en place depuis une dizaine d’années le plan PEP’s (Préservation et Exploitation des PatrimoineS) qui consiste à donner un cadre financier et stratégique à l’action des pouvoir publics en mutualisant les moyens et en organisant la numérisation autour de standards communs : l’un des responsables du projet décrit les différentes étapes de ce plan, ses principaux résultats et les perspectives d’avenir concernant les nouveaux usages offerts notamment par le web sémantique