Toward visualization of nanomachines in their native cellular environment

The cellular nanocosm is made up of numerous types of macromolecular complexes or biological nanomachines. These form functional modules that are organized into complex subcellular networks. Information on the ultra-structure of these nanomachines has mainly been obtained by analyzing isolated structures, using imaging techniques such as X-ray crystallography, NMR, or single particle electron microscopy (EM). Yet there is a strong need to image biological complexes in a native state and within a cellular environment, in order to gain a better understanding of their functions. Emerging methods in EM are now making this goal reachable. Cryo-electron tomography bypasses the need for conventional fixatives, dehydration and stains, so that a close-to-native environment is retained. As this technique is approaching macromolecular resolution, it is possible to create maps of individual macromolecular complexes. X-ray and NMR data can be ‘docked’ or fitted into the lower resolution particle density maps to create a macromolecular atlas of the cell under normal and pathological conditions. The majority of cells, however, are too thick to be imaged in an intact state and therefore methods such as ‘high pressure freezing’ with ‘freeze-substitution followed by room temperature plastic sectioning’ or ‘cryo-sectioning of unperturbed vitreous fully hydrated samples’ have been introduced for electron tomography. Here, we review methodological considerations for visualizing nanomachines in a close-to-physiological, cellular context. EM is in a renaissance, and further innovations and training in this field should be fully supported

Réduction de la production des boues à l'aide d'ultrasons

The study presented here has taken place in the light of a LIFE Environment project directed by the Water and Waste Water Service of Angers Loire Metropole. The treatment of a part stream of recycled sludge (Waste water treatment plants of 6300 population equivalents) has reduced sludge production by about 26 %. The treatment by ultrasounds seems to have no impact on the water treatment performance, on the quality of thickened sludge, neither on the direct emission of greenhouse gases. The only exception is a decrease of the treatment performance of phosphorus. The treatment is not valuable from an economical point for this small waste water treatment plant with low sludge handling costs (10 /ton). Extrapolation of the results show that after some modifications, the process could be economically feasible for waste water treatment plants with a sizee 100 000 population equivalent and with final sludge eliminution costs > 11 /ton (DM 20%). If a digestor is present, it is preferable to apply ultrasounds to the sludge file in order to increase biogas production. This final application has proved itself all over the world (Hein, 2008; Nickel, 2008)

Evaluation de la performance des dispositifs de décantation des eaux de ruissellement

Colloque avec actes et comité de lecture. internationale.International audienceDe nombreux dispositifs de décantation des eaux de ruissellement sont mis en place à l’exutoire des réseaux pluviaux en vue de protéger le milieu récepteur (décanteurs lamellaires ou alvéolaires, débourbeurs, séparateurs, etc.). Cependant il n’existe actuellement aucune méthode permettant d’évaluer les performances en décantation de tels dispositifs. Plusieurs solutions sont disponibles: une évaluation expérimentale sur site(possible mais avec un contrôle difficile des conditions du test), une évaluation expérimentale en laboratoire(possible mais coûteuse) ou une évaluation numérique. Cet article s’attache justement à présenter un outil numérique développé dans ce sens. Après une présentation du fonctionnement de l’outil de calcul, celui-ci est validé par confrontation avec des données expérimentales collectées sur modèle réduit.L’outil numérique développé est capable d’évaluer les performances d’un ouvrage de décantation avec une précision de l’ordre de 5% à 10%. Dans un second temps, l’outil est appliqué à un séparateur particulaire à l’échelle1afin d’évaluer l’efficacité de l’ouvrage et d’optimiser celui-cipour y maximiser la décantatio