Role of the cabins as shelters for the lesser horseshoe bat

Dans le cadre d’un programme coordonné par le Parc naturel régional du Luberon, l’expertise présentée ici a porté sur l’inventaire des colonies de Petits Rhinolophes (Rhinolophus hipposideros) présentes dans le petit patrimoine bâti. Au total, sur les 561 cabanons et maisonnettes répertoriés, seuls 120 sont inhabités et présentent un état compatible avec l’accueil de Petits Rhinolophes. Les auteurs ont mis en évidence que seule la toiture en tuile « canal » est une caractéristique architecturale favorable à l’installation d’une colonie de reproduction, mais que cela ne se vérifie pas pour une simple fréquentation de l’espèce. Aucune relation statistiquement signifi cative n’a été découverte pour les critères d’état général du bâti ou le nombre de niveaux. Une relative plasticité écologique du Petit rhinolophe vis-à-vis du choix de son gîte en est déduite, mais lors de la mise-bas, l’espèce montre des besoins particuliers, probablement relatifs à la température. La population des cabanons représente plus du quart de la population reproductrice totale des communes inspectées. Il est donc primordial de mettre en œuvre les mesures nécessaires au maintien de ce réseau de gîtes.Within the context of a programme coordinated by the regional nature Park of Luberon, the expert evaluation presented here is focused on the inventory of the colony of Lesser Horseshoe Bats (Rhinolophus hipposideros) present in the little built patrimony. In total, over the 561 cabins and little houses itemized, only 120 are uninhabited and present a compatible state for the accomodation of this bat. The authors have put in evidence that only the “canal” tile roof is a favourable architectural characteristic for the installation of a reproductive colony, but that is not verified for the simple frequenting of the species. No significant relation has been discovered for the general state criterion of the frame or the number of levels. The authors deduct a relative ecological plasticity of the Lesser Horseshoe Bat concerning the choice of its shelter, but during birth, the species shows special needs, probably relative to temperature. The population of the cabins represents more than the quarter of the total reproductive population of the inspected district. Therefore it is essential to take the measures necessary to maintain this network of shelters

Relationship between the occurrence of filamentous bacteria on Bathymodiolus azoricus shell and the physiological and toxicological status of the vent mussel

En libre-accès sur Archimer : http://archimer.ifremer.fr/doc/2009/publication-6821.pdfInternational audienceThe edifice walls of the Eiffel Tower hydrothermal vent site (Mid-Atlantic Ridge, Lucky Strike vent field) are populated with dense communities of dual symbioses harboring vent mussel Bathymodiolus azoricus, some of which are covered by white filamentous mats belonging to sulfur-oxidizing bacteria. Mussels were collected in both the presence and absence of the filamentous bacteria. A sample of the filamentous bacteria was collected and water measurements of temperature, CH4 and H2S were recorded at the collection area. The whole soft tissues were analyzed for total lipid, carbohydrate and total protein. Metallothioneins and metals (Cu, Fe and Zn) levels were determined in the major organs. The results showed no significant physiological and toxicological evidence that emphasizes the influence of associated sulfur-oxidizing filamentous bacteria on B. azoricus mussel shells. However, B. azoricus mussel seems to be well adapted to the assorted physico-chemical characteristics from the surrounding environment since it is able to manage the constant fluctuation of physico-chemical compounds

Establishment and Validation of Whole-Cell Based Fluorescence Assays to Identify Anti-Mycobacterial Compounds Using the Acanthamoeba castellanii - Mycobacterium marinum Host-Pathogen System

Tuberculosis is considered to be one of the world's deadliest disease with 2 million deaths each year. The need for new antitubercular drugs is further exacerbated by the emergence of drug-resistance strains. Despite multiple recent efforts, the majority of the hits discovered by traditional target-based screening showed low efficiency in vivo. Therefore, there is heightened demand for whole-cell based approaches directly using host-pathogen systems. The phenotypic host-pathogen assay described here is based on the monitoring of GFP-expressing Mycobacterium marinum during infection of the amoeba Acanthamoeba castellanii. The assay showed straight-forward medium-throughput scalability, robustness and ease of manipulation, demonstrating its qualities as an efficient compound screening system. Validation with a series of known antitubercular compounds highlighted the advantages of the assay in comparison to previously published macrophage-Mycobacterium tuberculosis-based screening systems. Combination with secondary growth assays based on either GFP-expressing D. discoideum or M. marinum allowed us to further fine-tune compound characterization by distinguishing and quantifying growth inhibition, cytotoxic properties and antibiotic activities of the compounds. The simple and relatively low cost system described here is most suitable to detect anti-infective compounds, whether they present antibiotic activities or not, in which case they might exert anti-virulence or host defense boosting activities, both of which are largely overlooked by classical screening approaches

5-ethyl-2'-deoxyuridine fragilizes Klebsiella pneumoniae outer wall and facilitates intracellular killing by phagocytic cells

Klebsiella pneumoniae is the causative agent of a variety of severe infections. Many K. pneumoniae strains are resistant to multiple antibiotics, and this situation creates a need for new antibacterial molecules. K. pneumoniae pathogenicity relies largely on its ability to escape phagocytosis and intracellular killing by phagocytic cells. Interfering with these escape mechanisms may allow to decrease bacterial virulence and to combat infections. In this study, we used Dictyostelium discoideum as a model phagocyte to screen a collection of 1,099 chemical compounds. Phg1A KO D. discoideum cells cannot feed upon K. pneumoniae bacteria, unless bacteria bear mutations decreasing their virulence. We identified 3 non-antibiotic compounds that restored growth of phg1A KO cells on K. pneumoniae, and we characterized the mode of action of one of them, 5-ethyl-2'-deoxyuridine (K2). K2-treated bacteria were more rapidly killed in D. discoideum phagosomes than non-treated bacteria. They were more sensitive to polymyxin and their outer membrane was more accessible to a hydrophobic fluorescent probe. These results suggest that K2 acts by rendering the membrane of K. pneumoniae accessible to antibacterial effectors. K2 was effective on three different K. pneumoniae strains, and acted at concentrations as low as 3 μM. K2 has previously been used to treat viral infections but its precise molecular mechanism of action in K. pneumoniae remains to be determined

En quoi l'étude des îlots forestiers permet-elle de mieux connaître le fonctionnement de la forêt tropicale ?

Small forested islands isolated from surrounding tropical forest by new reservoirs provide a norm for interpreting the effects of fragmentating the forest by intervening agriculture and pasture, and an effective means of investigating the ecological organization of the mainland forest. Water is a more effective barrier to immigration and a more neutral matrix than field or pasture. On forest fragments isolated by water, the effects of fragmentation are minimally confounded with effects of the matrix, while forest fragments surrounded by fields and pastures may suffer intrusions from tire, domestic animals, and other pests. On small islands, some species will go extinct. If the extinction of a species is followed by increase in its prey or competitors, we may provisionally assume that on the mainland, these prey and competitors are lirnited by the species now absent from the island. If, when a tree's seed disperser disappears, new seedlings of that tree no longer appear, that tree's regeneration presumably depends on its seed disperser. Islands in new reservoirs are the tropical forest ecologist's closest analogue to the exclusion experiments so effective in understanding the ecology of intertidal comrnunities. Small islands in reservoirs can also serve as systems of replicates for experimental analysis of the causes of regulation of selected populations. We review work on small islands isolated in 1914 by Panama's Gatun Lake, islands isolated in 1986 by Venezuela's Lake Guri, and islets isolated in 1994 at Saint-Eugène in French Guiana. The more recently the islands have been isolated, the more can be Jeamed from them. The Saint-Eugène Fragmentation Project is particularly important because it is only one of the three in true rainforest and studies there have been done before and after fragmentationLes petites îles boisées qui sont isolées de la forêt tropicale voisine après la mise en eau de réservoirs en amont des barrages hydroélectriques constituent des modèles pour l'étude de la fragmentation forestière après mise en agriculture ou pâturage. Elles offrent ainsi aux écologistes un protocole expérimental pour l'étude des processus écologiques de la forêt de terre ferme. L'eau est une barrière plus efficace et joue un rôle plus neutre contre l'immigration que les champs ou les pâturages. Sur des fragments forestiers isolés par une matrice aquatique, les effets de la matrice, qui sont souvent confondus avec ceux de la fragmentation, sont ici minimaux, alors que des fragments forestiers entourés de champs et de pâturages ont à supporter les feux intrusifs et l'invasion des animaux domestiques et autres pestes. Sur les petites îles, quelques espèces vont disparaître. Si l'extinction d'une espèce y est suivie de l'augmentation de la population de ses proies ou d'autres espèces compétitrices, on peut provisoirement supposer que, sur le continent, ces proies et compétiteurs sont limités par cette espèce qui a aujourd'hui disparu sur l'île. Si, lorsque l'agent disséminateur des graines d'un arbre disparaît et que les jeunes plantules de cet arbre ne sont plus présentes, c'est que la régénération de l'arbre en était fortement dépendante. Les îles des récents réservoirs sont, pour les écologistes, des systèmes expérimentaux analogues aux expériences d'exclusion qui sont si utiles pour comprendre l'écologie des communautés, des zones intertidales en particulier. Les îlots des réservoirs peuvent également servir comme système de réplicats pour l'analyse des causes de la régulation de certaines populations. Dans cet article, nous présentons une revue des études menées sur les petites îles isolées en 1914 par les eaux du lac Gatun au Panama, les îles isolées en 1986 par le lac Guri au Vénézuela, et les îlots formés en 1994 à Saint-Eugène en Guyane française. Plus les îles se sont formées récemment, plus les enseignements qui en découlent sont riches. Le Projet Fragmentation de Saint-Eugène est particulièrement important car c'est le seul des trois sites cités a être réalisé dans une vraie forêt tropicale humide, et les études y ont été menées avant et après la fragmentatio

Resistance of Dictyostelium discoideum membranes to saponin permeabilization

<p>Abstract</p> <p>Background</p> <p>Saponin is a mild detergent commonly used to permeabilize cells prior to immunofluorescence labeling of intracellular proteins. It has previously been used to that effect in <it>Dictyostelium discoideum </it>amoebae.</p> <p>Findings</p> <p>We show that saponin, contrary to Triton X-100 or alcohol, permeabilizes at best incompletely membranes of <it>Dictyostelium</it>. In cells exposed to osmotic stress, almost complete resistance to saponin permeabilization was observed.</p> <p>Conclusions</p> <p>Saponin should be used with special care to permeabilize <it>Dictyostelium </it>membranes. This unsusual property is presumably linked to the specific sterol composition of <it>Dictyostelium </it>membranes. It may also represent an adaptation of <it>Dictyostelium </it>to harsh conditions or to natural compounds encountered in its natural environment.</p