Quantitative Detection of Syntrophic Fatty Acid-degrading Bacterial Communities in Methanogenic Environments

In methanogenic habitats, volatile fatty acids (VFA), such as propionate and butyrate, are major intermediates in organic matter degradation. VFA are further metabolized to H2, acetate and CO2 by syntrophic fatty acid-degrading bacteria (SFAB) in association with methanogenic archaea. Despite their indispensable role in VFA degradation, little is known about SFAB abundance and their environmental distribution. To facilitate ecological studies, we developed four novel genus-specific quantitative PCR (qPCR) assays, with primer sets targeting known SFAB: Syntrophobacter, Smithella, Pelotomaculum and Syntrophomonas. Primer set specificity was confirmed using in silico and experimental (target controls, clone libraries and melt-curve analysis) approaches. These qPCR assays were applied to quantify SFAB in a variety of mesophilic methanogenic habitats, including a laboratory propionate enrichment culture, pilotand full-scale anaerobic reactors, cow rumen, horse faeces, an experimental rice paddy soil, a bog stream and swamp sediments. The highest SFAB 16S rRNA gene copy numbers were found in the propionate enrichment culture and anaerobic reactors, followed by the bog stream and swamp sediment samples. In addition, it was observed that SFAB and methanogen abundance varied with reactor configuration and substrate identity. To our knowledge, this research represents the first comprehensive study to quantify SFAB in methanogenic habitats using qPCR-based methods. These molecular tools will help investigators better understand syntrophic microbial communities in engineered and natural environments

The Contribution of Syntrophic Fatty-Acid Degrading Microbial Communities to Anaerobic Digester Function and Stability

Anaerobic digestion (AD), the conversion of complex organic matter to methane, occurs through a series of reactions mediated by different guilds of microorganisms. AD process imbalances, such as organic overload or high organic loading rates (OLR), can result in the accumulation of volatile fatty acids (VFA) e.g., propionate, which must be degraded to maintain stable reactor function. VFAs are metabolized by syntrophic fatty-acid degrading bacteria (SFAB) in association with methanogenic archaea (collectively, syntrophic microbial communities, SMC). Despite their indispensable role in AD, little is known about the ecology of SFAB, especially under stressed conditions. To facilitate ecological studies, four quantitative PCR assays, targeting propionate- and butyrate-degraders were developed, and applied to a variety of methanogenic environments. The highest SFAB abundance was observed in propionate enrichment cultures and anaerobic reactors. In addition, SFAB and methanogen abundance varied with reactor configuration and substrate identity. The contribution of SMC to AD function and stability was investigated in lab-scale reactors exposed to two forms of disturbance: shock overload (pulse disturbance) and increased OLR (press disturbance). SMC dynamics were linked to AD function using physicochemical and molecular techniques. The first experiment examined the effect of shock overloads on SMC structure and function. Results showed that functional resilience to the pulse disturbance in reactors was linked to the abundance of propionate-degraders and Methanosarcinaceae. Reactors with reduced numbers of these microorganisms displayed increased VFA buildup, however, there was a subsequent increase in the abundance of propionate-degraders and Methanosarcinaceae which improved the functional resilience in these reactors to the next perturbation. The second experiment examined the effect of increased OLRs on SMC structure and function. SMC decreased in abundance with increasing OLR. Prior to system collapse, a decrease in acetoclastic methanogens corresponded with an increase in syntrophic acetate oxidizers and hydrogenotrophic methanogens. In summary, this work demonstrates that an increased abundance of syntrophic fatty acid degrading microbial communities are essential in AD during stressed conditions, such as organic overload and high OLRs. These results could change how digesters are monitored and aid in the design of better anaerobic treatment processes

Le centre d'apprentissage de langues: Représentations, motivations et réalités.

Au delà de son aspect matériel, la réalité d'un centre de langues est composée d'un 'espace' cognitif destiné à favoriser l'apprentissage. Les apprenants évoluent dans cet espace de manière plus ou moins autonome, le personnel du centre étant là pour les guider le cas échéant. Afin de trouver une organisation optimale, le personnel tente de prendre en compte les représentations et les motivations des étudiants, pour qui l'apprentissage dans un centre de langues est souvent une expérience nouvelle. Une évaluation du centre est nécessaire pour savoir comment ses ressources sont perçues et utilisées. Le dispositif mis en place peut ensuite être modifié pour favoriser l'émergence de stratégies propices à l'apprentissage. Nous présentons ici un exemple de cette réalité « interne » d'un centre de langues, où l'espace créé résulte de la rencontre entre réflexion didactique, supports matériels et comportements d'apprenants

Le centre d'apprentissage de langues: Représentations, motivations et réalités.

Au delà de son aspect matériel, la réalité d'un centre de langues est composée d'un 'espace' cognitif destiné à favoriser l'apprentissage. Les apprenants évoluent dans cet espace de manière plus ou moins autonome, le personnel du centre étant là pour les guider le cas échéant. Afin de trouver une organisation optimale, le personnel tente de prendre en compte les représentations et les motivations des étudiants, pour qui l'apprentissage dans un centre de langues est souvent une expérience nouvelle. Une évaluation du centre est nécessaire pour savoir comment ses ressources sont perçues et utilisées. Le dispositif mis en place peut ensuite être modifié pour favoriser l'émergence de stratégies propices à l'apprentissage. Nous présentons ici un exemple de cette réalité « interne » d'un centre de langues, où l'espace créé résulte de la rencontre entre réflexion didactique, supports matériels et comportements d'apprenants

Étude expérimentale de la perception de la modalité à travers l'intonation en anglais

18 pagesInternational audienceIn English, as in French, a question can be formed without changing the syntax of a sentence but simply by giving it an interrogative intonation. This study examines the perception of two intonation modalities, interrogative and declarative, in spoken sentences which included three levels of syntactic or lexical difficulty. The participants' task was to discern the modality of each sentence, interrogative or declarative, and to react by means of a device which recorded their response times. There were three groups of participants: native English speakers, French students of English who had lived in an English-speaking country for a year and French students studying a subject other than English. Results reveal a significant group factor with native speakers responding quicker than specialist students of English who responded quicker than the non-specialists. There was also an interaction between group and modality, whereby French speakers identified declaratives more quickly than interrogatives, but the opposite held for the native speakers. Regarding the type of sentence, response times were significantly slower for syntactically incomplete sentences.En anglais comme en français, on peut formuler une question sans changer la syntaxe d'un énoncé, simplement en lui associant une intonation interrogative. Cette étude porte sur la perception de deux modalités d'intonation - interrogative et déclarative - dans des énoncés comportant trois niveaux de difficulté syntaxique ou lexicale. Les participants avaient pour tâche de discerner quelle était la modalité de chaque énoncé, interrogative ou déclarative, et de réagir à l'aide d'un dispositif enregistrant leur temps de réponse. Il y avait trois groupes de participants : des anglophones, des étudiants français anglicistes ayant séjourné une année en pays de langue anglaise et des étudiants français non anglicistes. Les résultats permettent de dégager des tendances par groupe : les anglophones répondent plus rapidement que les anglicistes qui sont eux-mêmes plus rapides que les non anglicistes. Il y a également une interaction entre groupes et modalité, car les étudiants francophones identifient les énoncés déclaratifs plus rapidement que les interrogatifs, alors que pour les anglophones c'est l'inverse. En ce qui concerne les types d'énoncés, les temps de réponse sont significativement plus lents pour les phrases syntaxiquement incomplètes

GLOBAL CURRENT TRENDS IN NATURAL PRODUCTS FOR DIABETES MANAGEMENT: A REVIEW

Diabetes mellitus is a major health problem in the world. There is no cure for diabetes. It is, therefore, essential to practice effective methods of the diagnosis, treatment, and management of diabetes. With the increase in a number of newer drugs for diabetes, there is the possibility of a wide range of side effects that vary from one drug to another. Hence, the need to explore oral antidiabetic drugs of natural origin with minimal side effects is highly essential. This review provides a scientific perspective on the usage and research of natural and Indian traditional remedies in the management of diabetes while also providing insight into the advances in our understanding of diabetic pathology.Keywords: Diabetes, Hyperglycemia, Diabetic complications, Medicinal plant

Trapping ultracold atoms at 100 nm from a chip surface in a 0.7-micrometer-period magnetic lattice

We report the trapping of ultracold 87Rb atoms in a 0.7 micron-period 2D triangular magnetic lattice on an atom chip. The magnetic lattice is created by a lithographically patterned magnetic Co/Pd multilayer film plus bias fields. Rubidium atoms in the F=1, mF=-1 low-field seeking state are trapped at estimated distances down to about 100 nm from the chip surface and with calculated mean trapping frequencies as high as 800 kHz. The measured lifetimes of the atoms trapped in the magnetic lattice are in the range 0.4 - 1.7 ms, depending on distance from the chip surface. Model calculations suggest the trap lifetimes are currently limited mainly by losses due to surface-induced thermal evaporation following loading of the atoms from the Z-wire trap into the very tight magnetic lattice traps, rather than by fundamental loss processes such as surface interactions, three-body recombination or spin flips due to Johnson magnetic noise. The trapping of atoms in a 0.7 micrometer-period magnetic lattice represents a significant step towards using magnetic lattices for quantum tunneling experiments and to simulate condensed matter and many-body phenomena in nontrivial lattice geometries.Comment: 11 pages, 7 figure

L’apprentissage lexical en deuxième langue : des réseaux évolutifs

En partant de la prise en compte de la dimension physiologique de l’apprentissage, le présent article explore la notion de réseau telle qu’elle s’applique à l’apprentissage lexical en deuxième langue. Conformément à la plupart des théories psycholinguistiques, y compris le connexionnisme, on supposera que les représentations mentales s’établissent et deviennent accessibles grâce à la diffusion d’une activation à travers des populations de neurones. En gardant cette idée en tête lors de l’établissement d’un modèle fonctionnel des phénomènes cognitifs, on peut tenter de caractériser le développement du lexique mental en deuxième langue. Certains aspects de ce développement sont automatiques, variant selon le degré et la nature des contacts avec la langue cible. D’autres peuvent être infléchis par une pédagogie appropriée, c’est-à-dire qui prend en compte non seulement les objectifs à atteindre, mais aussi les contraintes imposées par le fonctionnement cognitif des apprenants.Beginning with a consideration of the physiological dimension of learning, this article explores the notion of network as it applies to second language vocabulary learning. In common with most psycholinguistic theories, notably connectionism, it is assumed that mental representations are established and become accessible thanks to the spread of activation through populations of neurones. Bearing in mind this idea when drawing up a functional model of cognitive processing, a description of the way a second language mental lexicon develops may be attempted. Certain aspects of this development are automatic, varying according to the degree and nature of exposure to the target language. Others may be influenced by appropriate teaching methods, namely those that take into account not only the goals to be achieved but also the constraints imposed by learners’ cognitive functioning