Fruit consumption, seed dispersal and seed fate in the vine Strychnos erichsonii in a French Guianan forest

La consommation des fruits et la dissémination des graines ont été analysées chez trois individus de la liane Strychnos erichsonii (Loganiaceae) en forêt mature de Guyane française, pendant la saison de production minimale en fleurs et fruits. Cinq espèces consommatrices, oiseaux ou mammifères diurnes ou nocturnes, ont été observées, alors qu'un rongeur terrestre a été capturé dans des pièges appâtés avec de la pulpe de fruits ou des graines de S. erichsonii. Un mammifère diurne et un nocturne ont dispersé les graines à grande distance. Les frugivores arboricoles consommaient les fruits à mesure de leur apparition, et mangeaient également des fruits immatures. L'utilisation de collecteurs a montré que le taux de prélèvement de fruits était plus élevé la nuit chez les lianes les plus productives (productivité « instantanée »). Plus des deux-tiers des graines échantillonnées sur des transects jusqu'à 30 m du pied-mère étaient mortes ou parasitées, sans qu'une relation claire ait pu être établie avec leur localisation (sous ou au-delà de la couronne). La densité de graines chutait dans les premiers mètres à partir du pied-mère, mais restait non négligeable jusqu'à 15 m de la couronne sur certains transects. Les quelques plantules trouvées étaient réparties indépendamment de leur position sous ou au-delà de la couronne. Une mortalité élevée des graines et un faible nombre en même temps qu'un renouvellement rapide des plantules sous et à proximité du pied-mère suggèrent que la dispersion des graines à grande distance est primordiale pour la régénération de la plante. La dispersion à grande distance semble assurée par un petit nombre d'espèces variées. Par sa fructification régulière pendant la période de disponibilité minimale en fleurs et fruits et par sa place privilégiée dans le régime alimentaire de plusieurs mammifères frugivores, S. erichsonii constitue probablement une ressource importante pour ces espèces pendant la saison de faible disponibilité alimentaire

A combinatorial algorithm for microbial consortia synthetic design

International audienceSynthetic biology has boomed since the early 2000s when it started being shown that it was possible to efficiently synthetize compounds of interest in a much more rapid and effective way by using other organisms than those naturally producing them. However, to thus engineer a single organism, often a microbe, to optimise one or a collection of metabolic tasks may lead to difficulties when attempting to obtain a production system that is efficient, or to avoid toxic effects for the recruited microorganism. The idea of using instead a microbial consortium has thus started being developed in the last decade. This was motivated by the fact that such consortia may perform more complicated functions than could single populations and be more robust to environmental fluctuations. Success is however not always guaranteed. In particular, establishing which consortium is best for the production of a given compound or set thereof remains a great challenge. This is the problem we address in this paper. We thus introduce an initial model and a method that enable to propose a consortium to synthetically produce compounds that are either exogenous to it, or are endogenous but where interaction among the species in the consortium could improve the production line. Synthetic biology has been defined by the European Commission as " the application of science, technology, and engineering to facilitate and accelerate the design, manufacture, and/or modification of genetic materials in living organisms to alter living or nonliving materials ". It is a field that has boomed since the early 2000s when in particular Jay Keasling showed that it was possible to efficiently synthetise a compound–artemisinic acid–which after a few more tricks then leads to an effective anti-malaria drug, artemisini

The Radish Gene Reveals a Memory Component with Variable Temporal Properties

Memory phases, dependent on different neural and molecular mechanisms, strongly influence memory performance. Our understanding, however, of how memory phases interact is far from complete. In Drosophila, aversive olfactory learning is thought to progress from short-term through long-term memory phases. Another memory phase termed anesthesia resistant memory, dependent on the radish gene, influences memory hours after aversive olfactory learning. How does the radish-dependent phase influence memory performance in different tasks? It is found that the radish memory component does not scale with the stability of several memory traces, indicating a specific recruitment of this component to influence different memories, even within minutes of learning

Low Background Signal Readout Electronics for the MAJORANA DEMONSTRATOR

The MAJORANA DEMONSTRATOR is a planned 40 kg array of Germanium detectors intended to demonstrate the feasibility of constructing a tonne-scale experiment that will seek neutrinoless double beta decay ($0\nu\beta\beta$) in $^{76}\mathrm{Ge}$. Such an experiment would require backgrounds of less than 1 count/tonne-year in the 4 keV region of interest around the 2039 keV Q-value of the $\beta\beta$ decay. Designing low-noise electronics, which must be placed in close proximity to the detectors, presents a challenge to reaching this background target. This paper will discuss the MAJORANA collaboration's solutions to some of these challenges

Search for Pauli Exclusion Principle Violating Atomic Transitions and Electron Decay with a P-type Point Contact Germanium Detector

A search for Pauli-exclusion-principle-violating K-alpha electron transitions was performed using 89.5 kg-d of data collected with a p-type point contact high-purity germanium detector operated at the Kimballton Underground Research Facility. A lower limit on the transition lifetime of 5.8x10^30 seconds at 90% C.L. was set by looking for a peak at 10.6 keV resulting from the x-ray and Auger electrons present following the transition. A similar analysis was done to look for the decay of atomic K-shell electrons into neutrinos, resulting in a lower limit of 6.8x10^30 seconds at 90 C.L. It is estimated that the MAJORANA DEMONSTRATOR, a 44 kg array of p-type point contact detectors that will search for the neutrinoless double-beta decay of 76-Ge, could improve upon these exclusion limits by an order of magnitude after three years of operation