Acidophilic phytoplankton in Argentina: the case study of Lake Caviahue (Patagonia)

This article presents a review of the studies carried out over a 10-year period in Lake Caviahue, a natural acidic lake located in Patagonia. The main patterns of the phytoplankton populations are described. Five extremophiles phytoplanktonic species were studied in relation to the zooplankton and nutrients bioavailability under the environmental conditions registered in Lake Caviahue: very low pH (~3), high concentrations of iron (18.4 mg L-1) and sulphur (130 mg L-1). During the 10-years studies, the biomass (0.2 and 1.4 mg fw L-1) and the biodiversity were very low being Keratococcus rhaphidioides the dominant species (60 to 100% of the total biomass). Philodina sp. (Bdelloidea) was the only zooplankter responsible of the zooplankton biomass. From the lack of relationship between phytozooplankton biomass, as well as from the results obtained in the feeding experiments, we conclude that no control of algal abundance by the zooplankton occurs. The microalgae were nitrogen limited in the lake and according to the results from experiments with nutrient addition, the phytoplankton showed nitrogen limitation on growth rate and yield. The species have also the capacity to use mixotrophically alternative sources of organic and inorganic carbon and organic nitrogen. The importance of the uptake and the expression of CO2 concentrating mechanisms (CCMs) were demonstrated in Euglena and in the ellipsoidal form of Watanabea but not in the spherical form of Watanabea and in Palmellopsis. The two forms of Watanabea differed in their possession of a CCM.Fil: Diaz, Monica Mabel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación en Biodiversidad y Medioambiente; ArgentinaFil: Beamud, Sara Guadalupe. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación en Biodiversidad y Medioambiente; Argentin

Content and language integrated learning:A duoethnographic study about CLIL pre-service teacher education in Argentina and Spain

Content and language integrated learning (CLIL) is a dual-focussed approach that promotes the learning of curricular content in tandem with an additional language, usually English. Since its inception in the 1990s in Europe, CLIL provision has increased considerably not only in Europe but also in other contexts, such as Latin America, given its purported benefits in terms of motivation, cognitive skills development, and language awareness. However, little is known about how future teachers, i.e. pre-service teachers, are trained to teach through CLIL. This article aims to address this gap by describing how we – two CLIL teacher educators based in Argentina and Spain – offer CLIL courses. Through duoethnography, we show how we plan and implement CLIL input and what lessons we have learnt drawing on reflective practice in interaction. Analysis of our interaction illustrates how CLIL is conceived and operationalized and what CLIL competences are prioritized in our practices. Pedagogical implications are included

Summer phytoplankton composition and nitrogen limitation of the deep, naturally-acidic (pH∼2.2) Lake Caviahue, Patagonia, Argentina

AbstractDuring the warm seasons of 1998–2004, the naturally-acidic (pH∼2.2) Lake Caviahue was sampled for conductivity, temperature, oxygen, light, nutrients, and phytoplankton (density, biomass and chlorophyll a) with a view to studying the summer phytoplankton population changes with relation to environmental factors, as well as the significance of nitrogen limitation on the phytoplankton yield. Lake Caviahue is characterized by its low transparency, CO2, and N concentration; significant P values; a distinctive vertical distribution of phytoplankton biomass with high values along the water column; and sometimes maximum meta-hypolimnion values. Biodiversity is very low as a result of extreme environmental conditions, Chlorophyceae being the prevailing algae group. Two types of bioassays were carried out to assess nitrogen limitation. For the first bioassay, a solution of ammonium–nitrogen chloride and/or wastewater (rich in ammonium and phosphorus) was used, while one of the lake's sediments was the source of nutrients for the second bioassay. Contrary to the case of acidic mining lakes, N-ammonium proved to be a significant supportive capacity limiting factor as to phytoplankton yield. The present paper provides for the first time information on phytoplankton nitrogen limitation in a naturally-acidic lake

The effect of the genetic background on phage infectivity in an encapsulated host

Los bacteriófagos desempeñan un papel clave en la ecología y evolución bacterianas y son potenciales antimicrobianos. Sin embargo, los factores determinantes de la especificidad fago-hospedador siguen siendo poco conocidos. Debido a la prevalencia de bacterias encapsuladas, la cápsula es la primera barrera que encuentran muchos fagos. Esta capa, normalmente de polisacáridos, puede bloquear el acceso de los fagos a los receptores de su pared celular. Para superarla, algunos fagos codifican dominios depolimerasa (Dpos) específicos en sus proteínas de unión a receptores. En este trabajo, hemos cuantificado la predictibilidad de las interacciones fago-bacteria basándonos en el tipo de locus capsular del hospedador (CLT) y Dpos. Para ello, utilizamos Klebsiella pneumoniae como modelo debido a su alta diversidad capsular y a su importancia en salud pública. En primer lugar, establecimos una colección de 138 cepas clínicas de K. pneumoniae representativas de la diversidad genómica de la especie. Estas cepas se testaron con 46 fagos ambientales diferentes que comprendían 13 grupos filogenéticos. Las pruebas de spot revelaron que la mayoría de los fagos (42 de los 46) mostraban especificidad capsular, con un patrón de infección predicho con precisión (92%) por el CLT del hospedador. En consecuencia, las Dpos codificadas por los fagos, que a menudo han sufrido transferencia horizontal a largas escalas taxonómicas, eran determinantes clave del tropismo del hospedador. La tolerancia a la identidad de los Dpos de los fagos era alta, como mostró el tropismo capsular predicho con profagos de RefSeq para 13 CLT importantes epidemiológicamente. Aunque las cápsulas y el Dpos predijeron los primeros pasos del reconocimiento del virión y la adsorción, su precisión disminuyó para las infecciones productivas (53%). Aparte de los fagos especializados en cápsulas, encontramos que los fagos de los grupos S8/S9 tenían un rango de hospedador más amplio como resultado de un tropismo dependiente e independiente de la cápsula. El tropismo capsular de los fagos S8/S9 no estaba mediado por depolimerasas, sino que estos fagos codificaban proteínas de cola larga con múltiples dominios de unión a carbohidratos. Es importante destacar que >90% de las cepas bacterianas presentaban heterogeneidad fenotípica capsular, con la coexistencia de clones encapsulados y no encapsulados. Esta heterogeneidad afectó al tropismo de los fagos, ya que los fagos de amplio espectro infectaron preferentemente bacterias con un mayor número de bacterias acapsulares, al contrario que los fagos especialistas en cápsulas. Se observó que los mutantes acapsulares adquirían resistencia en 286 de las 406 combinaciones analizadas (70%). Ni la especificidad capsular de los fagos ni la infección de bacterias acapsulares se correlacionaron con la clasificación filogenética de los fagos. Sorprendentemente, el 43% de los fagos mostraron un comportamiento de unión capsular obligado o facultativo en función de la cepa bacteriana y su mecanismo de inactivación capsular, lo que a su vez dio lugar a diferentes tasas de emergencia de resistencia. Estos resultados amplían nuestro conocimiento de las complejas interacciones entre bacterias y sus virus y señalan la viabilidad de predecir los primeros pasos de la infección fágica utilizando secuencias genómicas de bacterias y fagos.Bacteriophages play key roles in bacterial ecology and evolution and are potential antimicrobials. However, the determinants of phage-host specificity remain elusive. Due to the prevalence of encapsulated bacteria, the capsule is the first barrier encountered by many phages. This layer, usually made of polysaccharides, can block phage access to their cell wall receptors. To overcome this, some phages encode specific depolymerase (Dpos) domains in their receptor-binding proteins. Here, we have quantified the predictability of phage-bacteria interactions based on the capsular locus type of host (CLT) and Dpos. For this, we used Klebsiella pneumoniae as a model due to its high capsular diversity and importance in global health. First, we established a collection of 138 clinical strains of K.pneumoniae representative of the genomic diversity of the species. These were challenged with 46 different environmental phages comprising 13 phylogenetic groups. Spot tests revealed that most of the phages (42 out of the 46) showed capsular specificity, with their infection pattern accurately predicted (92%) by the host CLT. Consequently, phage-encoded Dpos, which have often undergone horizontal gene transfer across large taxonomic scales, were key determinants of host tropism. The identity tolerance of phage Dpos was high, as shown by the predicted capsular tropism of RefSeq prophages for 13 important CLTs. Even though capsules and Dpos predicted the first steps of virion recognition and adsorption, their accuracy dropped for productive infections (53%). Apart from capsule-specialist phages, we found that the phages of groups S8/S9 had a broader host-range resulting from both capsule-dependent and independent tropism. Capsular tropism of S8/S9 phages was not mediated by depolymerases, instead these phages encoded long tail proteins with multiple carbohydrate-binding domains. Importantly, >90% of bacterial strains presented capsular phenotypic heterogeneity, with the co-existence of both encapsulated and non-encapsulated clones. This heterogeneity affected phage tropism, as broad-range phages preferentially infected bacteria with a higher number of acapsular bacteria, contrary to capsular-specialist phages. We found that acapsular mutants gained resistance in 286 of the 406 combinations tested (70%). Neither phage capsular specificity nor infection of acapsular bacteria was correlated with the phylogenetic classification of phages. Remarkably, 43% of the phages showed an obligate or facultative capsule attachment behavior depending on the bacterial strain and its mechanism of capsule inactivation, which in turn led to different trade-offs in resistance. These findings expand our knowledge of the complex interactions between bacteria and their viruses and point out the feasibility of predicting the first steps of phage infection using bacterial and phage genome sequences

Distinguishing the effect of diapir growth on magnetic fabrics of syn-diapiric overburden rocks: Basque-Cantabrian basin, Northern Spain

An analysis of Anisotropy of Magnetic Susceptibility was done on Aptian–Albian sediments from the Basque–Cantabrian basin. Samples were collected from 39 sites in the halokinetic sequences of the Bakio, Bermeo, Guernica and Mungia diapirs; 28 sites were sampled close to diapirs, and 11 sites were far from the diapir edges. The magnetic foliation is parallel to bedding, suggesting it reflects depositional and compaction processes, whereas the orientation of magnetic lineation varies. Far from the diapir edges, the magnetic lineation is interpreted as being related to the regional Pyrenean compression. Close to diapir edges, the observed behaviour shows that diapirs, predominantly formed by rigid ophites, have acted as buttresses, with shadow areas at their northern faces being protected from the Pyrenean compression. The high sensitivity of AMS makes it a very useful tool to distinguish deformation in halokinetic sequences related to diapir growth from that related to subsequent compression.Funding came from projects CGL2014-54118-C2-1-R and CGL2014-54118-C2-2-R (Spanish Ministry).Peer reviewe

Early-Middle Miocene subtle compressional deformation in the Ebro foreland basin (northern Spain); insights from magnetic fabrics

The results of anisotropy of magnetic susceptibility analyses of 19 sites carried out on magnetostrigraphically-dated, Lower to Middle Miocene (20.4 to 13.7 Ma) 'non-deformed' mudstones from the central part of the Ebro basin reveal the presence of a subtle tectonic overprint lasting at least until the Langhian (Middle Miocene) in the southern Pyrenean foreland. Magnetic ellipsoids show a sedimentary fabric in 42% of sites and a weak and well-defined magnetic lineation in 47% and 11% of sites. The magnetic lineation is roughly oriented around the east-west direction, compatible with a very weak deformation occurring there and related to the north-south compression linked to the convergence between Europe, Iberia and Africa during the Early-Middle Miocene. A slight variation of the magnetic parameters Km, Pj, and T exists through time, probably due to changes in the sedimentary conditions in the basin

Primera detección del alga invasiva Didymosphenia geminata en el lago Nahuel Huapi: Argentina, Patagonia

The benthic diatom Didymosphenia geminata (L yngbye) M. Schmidt is a ver y aggressive invasive species found in riversand streams in different parts of the world. It has become a major concern for its tendency to form conspicuous blooms in oligotrophic aquatic systems with potential for detrimental impacts on recreational fi shing. Given its explosive development and the notable appearance in Lake Nahuel Huapi during the austral summer of 2013, our aim was to document the fi rst record for a large (557 km 2 ) lentic waterbody in the Andean Patagonia region.Fil: Beamud, Sara Guadalupe. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación en Biodiversidad y Medioambiente; ArgentinaFil: Baffico, Gustavo Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación en Biodiversidad y Medioambiente; ArgentinaFil: Pedrozo, Fernando Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación en Biodiversidad y Medioambiente; ArgentinaFil: Diaz, Monica Mabel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación en Biodiversidad y Medioambiente; Argentin

Datos paleomagnéticos en materiales sin-diapíricos Aptienses-Albienses (cuenca Vasco-Cantábrica, N Iberia)

In order to obtain a kinematic model linking the diapir formation and the geometry of the syn-diapir sediments, a paleomagnetic study has been conducted in selected syn-diapiric sequences of the Basque-Cantabrian Basin. The studied diapirs (Bakio, Bermeo, Guernika and Mungia) developed during the Early Cretaceous in relation to the North Iberian extensional margin which was subsequently reactivated during the Pyrenean contractional deformation (Late Cretaceous-Miocene). They are cored by Triassic red clays and evaporites and they are flanked by synkinematic Albian shelf and slope carbonates and Upper Albian to Cenomanian siliciclastics. The paleomagnetic study has focused on the synkinematic overburden to detect and quantify vertical axis rotations related to the growth of the diapirs. 29 paleomagnetic sites have been analyzed. After obtaining the site mean directions it can be concluded that most of the sites are remagnetized, hindering the kinematics of the diapirs growth to be deduced. The age of this remagnetization is difficult to assess, it could be either an earlier Albian-Maastrichtian remagnetization or a remagnetization linked to the Pyrenean compression.Trabajo financiado gracias a los proyectos coordinados CGL2014-54118-C2-1-R y CGL2014-54118-C2-2-R y al GGAC 2014SGR467Peer Reviewe