Mineralogical composition and biomass studies of the microbial mats sediments from the Ebro Delta, Spain

The mineral composition of the microbial mats at La Banya spit was studied. The spit is formed by a narrow sand bar and a peninsula and is located south of the main body of the Ebro Delta (Tarragona, Spain). Although quartz was the predominant mineral component in all sampling sites, clay, feldspars, calcite, aragonite, halite, dolomite and gypsum were also found. An increase in both the fine material (clay) and the halite content was observed in the sites influenced by nearby salterns. The amount of each mineral did not differ significantly along a 55 cm deep profile, except for halite and aragonite, which reached a maximum in the surface and decreased with depth. Dolomite, which ranged from 0.5 to 5% (w/w), is a possible indicator of sulfate-reducing bacteria activity in the past. Organic carbon and total nitrogen were quantified for biomass assessment. Total nitrogen ranged from 0.1 to 0.56% in the uppermost layer, where the microbial mat is active, but was undetectable at deeper layers. Organic carbon ranged from 1 to 5.5% in the active microbial mat layers and decreased to 0.3% at deeper layers. During the summer, both organic carbon and total nitrogen contents (biomass) of the microbial mat samples from some sites increase, whereas other sites show constant concentrations throughout the year, and others have a fluctuant biomass content

Characterization of Attachment and Growth of Thiobacillus denitrificans on Pyrite Surfaces

Anaerobic growth and attachment of the autotrophic denitrifying bacterium Thiobacillus denitrificans on pyrite surfaces were studied. Polished pyrite slabs were exposed to T. denitrificans for 1 to 9 weeks. The reacted pyrite surfaces were imaged with scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). Cells were observed as isolated attached cells, cells in division and cells forming microcolonies embedded in organic films. Bacteria began to colonize pyrite surfaces after 1 week, forming microcolonies after 3 weeks. The rate of colonization of the pyrite surface was around 35 cells mm−2 h−1 for the 3-week period. After 9 weeks, larger areas of the pyrite surface were covered by organic films. Bacterial enumeration on the pyrite surface and in solution showed that most of the cells were not attached to the mineral surface. Nevertheless, both attached and free-living bacteria probably contributed to pyrite-driven denitrification. The results may be applied to the natural environment to better understand pyrite-driven denitrification in aquifers and to improve the long-term performance of bioremediation processes using pyrite

Release of trace elements during bioreductive dissolution of magnetite from metal mine tailings: Potential impact on marine environments

Adverse impacts of mine tailings on water and sediments quality are major worldwide environmental problems. Due to the environmental issues associated with the deposition of mine tailings on land, a controversial discussed alternative is submarine tailings disposal (STD). However, Fe(III) bioreduction of iron oxides (e.g., magnetite) in the tailings disposed might cause toxic effects on coastal environments due to the release of different trace elements (TEs) contained in the oxides. To study the extent and kinetics of magnetite bioreduction under marine conditions and the potential release of TEs, a number of batch experiments with artificial seawater (pH 8.2) and a marine microbial strain (Shewanella loihica) were performed using several magnetite ore samples from different mines and a mine tailings sample. The elemental composition of the magnetite determined in the tailings showed relatively high amounts of TEs (e.g., Mn, Zn, Co) compared with those of the magnetite ore samples (LA-ICP-MS and EMPA analyses). The experiments were conducted at 10 °C in the dark for up to 113 days. Based on the consumption of lactate and production of acetate and aqueous Fe(II) over time, the magnitude of Fe(III) bioreduction was calculated using a geochemical model including Monod kinetics. Model simulations reproduced the release of iron and TEs observed throughout the experiments, e.g., Mn (up to 203 μg L−1), V (up to 79 μg L−1), As (up to 17 μg L−1) and Cu (up to 328 μg L−1), suggesting a potential contamination of pore water by STD. Therefore, the results of this study can help to better evaluate the potential impacts of STD

Denitrification of groundwater with pyrite and Thiobacillus denitrificans

Anaerobic batch and flow-through experiments were performed to confirm the role of pyrite as electron donor in bacterial denitrification and to look into the feasibility of pyrite-driven denitrification of nitrate- contaminated groundwater. Nitrate reduction was satisfactorily accomplished in experiments with pyrite as the sole electron donor, in presence of the autotrophic denitrifying bacterium Thiobacillus denitrificans and at nitrate concentrations comparable to those observed in contaminated groundwater. The experimental results corroborated field studies in which the reaction occurred in aquifers. Nitrate reduction rates and nitrate removal efficiencies were dependent on pyrite grain size, initial nitrate concentration, nitrate-loading rate and pH. The N and O isotopic enrichment factors (εN and εO) obtained experimentally for pyrite-driven nitrate reduction by T. denitrificans ranged from − 13.5¿ to − 15.0¿ and from − 19.0¿ to − 22.9¿, respectively. These values indicated the magnitude of the isotope fractionation that occurs in nitrate- contaminated aquifers dominated by autotrophic denitrification

Enhanced denitrification in groundwater and sediments from a nitrate-contaminated aquifer after addition of pyrite

Using chemical, isotopic and microbiologic techniques we tested in laboratory experiments the extent to which the addition of pyrite to groundwater and sediments from a nitrate-contaminated aquifer could stimulate denitrification by indigenous bacteria. In addition to this biostimulated approach, a combined biostimulated and bioaugmented treatment was also evaluated by inoculating the well-known autotrophic denitrifying bacterium Thiobacillus denitrificans. Results showed that the addition of pyrite enhanced nitrate removal and that denitrifying bacteria existing in the aquifer material were able to reduce nitrate using pyrite as the electron donor, obviating the need for the inoculation of T. denitrificans. The results of the 16S rRNA and nosZ gene-based DGGE and the quantitative PCR (qPCR) showed that the addition of pyrite led to an increase in the proportion of denitrifying bacteria and that bacterial populations closely related to the Xanthomonadaceae might probably be the autotrophic denitrifiers that used pyrite as the electron donor. Not only autotrophic but also heterotrophic denitrifying bacteria were stimulated through pyrite addition and both populations probably contributed to nitrate removal. Isotopic analyses (δ15N and δ18ONO3) were used to monitor enhanced denitrification and the N and O isotopic enrichment factors (−26.3±1.8¿ and −20.4± 1.3¿, respectively) allowed to calculate the degree of natural nitrate attenuation in the aquifer. Furthermore, flow-through experiments amended with pyrite confirmed the long-term efficiency of the process under the study conditions. Further research under field conditions is needed to determine whether stimulation of denitrification by pyrite addition constitutes a feasible bioremediation strategy for nitrate-contaminated aquifers

Peer text revision using models as feedback

This paper analyses peer interaction during a task of text revision that used models as a means of written corrective feedback. The data was gathered from a state secondary school in the surrounding area of Barcelona. Learners wrote texts which they then revised in small groups or pairs by contrasting them with a written model. The analysis carried out tries to determine what learners do during interaction in order to elucidate if this particular type of feedback produces linguistic improvementEl present treball analitza la interacció entre iguals durant una tasca de revisió de texts que va usar models com a eina de feedback correctiu sobre un text escrit. Les dades es van recollir en un institut públic dels voltants de Barcelona. Els aprenents van escriure textos que després van revisar en grups reduïts o parelles, contrastant-los amb un model escrit. L'anàlisi dut a terme intenta determinar que fan els alumnes durant la interacció per aclarir si aquest particular tipus de feedback produeix millores lingüístiquesEl presente trabajo analiza la interacción entre iguales durante una tarea de revisión de textos que utilizó modelos como herramienta de feedback correctivo sobre un texto escrito. Los datos se recogieron de un instituto público de los alrededores de Barcelona. Los aprendices escribieron textos que después revisaron en grupos pequeños o parejas contrastándolos con un modelo escrito. El análisis llevado a cabo intenta determinar que hacen los alumnos durante la interacción para esclarecer si este particular tipo de feedback produce mejoras lingüística

Caracterizació ecofisiològica d'un mutant de Rhodobacter sphaeroides deficient en la síntesi de carotenoides

A mutant strain of Rhodobacter sphaeroides, altered in carotenoid biosynthesis. was compared to the wild type in relation to the physiological response of both strains to different light intensities (230-925 lux). Absorption spectra analysis showed that spheroidene, the main carotenoid present in this species, was substituted by chloroxanthin (hydroxyneurosporene) in the mutant strain. The mutation does not affect significantly the growh of the mutant under neither photoorganoheterotrophic nor chemoorganoheterotrophic metabolisms. Mutant cells growing anaerobically at light intensities below 800 lux, surprisingly showed higher growth rates than wild type cells. At light intensities above 800 lux, growth rates of both strains were very similar. Growth rates in chemoorganotrophic metabolism were much higher than in photoorganotrophic growth for both strains. Although pigments do not intervene in nonphotosynthetic metabolism, the wild type strain showed a higher growth rate than the mutant strain. In addition to growth rate measurement, pigment content was studied in order to characterize the physiological behaviour of the mutant. In the wild type strain, specific pigment content decreased as light intensity increased. Bacteriochlorophyll and carotenoids showed the same response. On the contrary, for the mutant cells, bacteriochlorophyll specific content was much higher at high light intensities than at the lower ones. Carotenoids had very low specific content. which was independent of light intensity. Both the physiological implications and the possible ecological meaning of that behaviour are discussed

Impact of treated sewage effluent on the bacterial community composition in an intermittent mediterranean stream

Water quality monitoring is essential to safeguard human and environmental health. The advent of next-generation sequencing techniques in recent years, which allow a more in-depth study of environmental microbial communities in the environment, could broaden the perspective of water quality monitoring to include impact of faecal pollution bacteria on ecosystem. In this study, 16 S rRNA amplicon sequencing was used to evaluate the impact of wastewater treatment plant (WWTP) effluent on autochthonous microbial communities of a temporary Mediterranean stream characterized by high flow seasonality (from 0.02 m(3)/s in winter to 0.006 m(3)/s in summer). Seven sampling campaigns were performed under different temperatures and streamflow conditions (winter and summer). Water samples were collected upstream (Upper) of the WWTP, the secondary effluent (EF) discharge and 75 m (P75) and 1000 m (P1000) downstream of the WWTP. A total of 5,593,724 sequences were obtained, giving rise to 20,650 amplicon sequence variants (ASV), which were further analysed and classified into phylum, class, family and genus. Each sample presented different distribution and abundance of taxa. Although taxon distribution and abundance differed in each sample, the microbial community structure of P75 resembled that of EF samples, and Upper and P1000 samples mostly clustered together. Alpha diversity showed the highest values for Upper and P1000 samples and presented seasonal differences, being higher in winter conditions of high streamflow and low temperature. Our results suggest the microbial ecology re-establishment, since autochthonous bacterial communities were able to recover from the impact of the WWTP effluent in 1 km. Alpha diversity results indicates a possible influence of environmental factors on the bacterial community structure. This study shows the potential of next-generation sequencing techniques as useful tools in water quality monitoring and management within the climate change scenari

AICLE - CLIL - EMILE : educació plurilingüe. Experiencias, research & polítiques

Aquest volum és resultat del projecte R+D+i EDU2010-15783 Discurso Académico en lengua extranjera: Aprendizaje y evaluación de contenidos científicos en el aula multilingüe, finançat pel MICINN.El present volum és el resultat de la selecció de les millors comunicacions presentades en la primera Taula Rodona Internacional TRI-CLIL sobre Aprenentatge Integrat de Continguts i Llengües (AICLE). El congrés va aconseguir reunir professionals de la docència i de la recerca, tant de matèries escolars, llengües estrangeres i llengües considerades oficials o co-oficials a diferents territoris, que esdevenen llengües addicionals per a la població escolar migrada

Explaining Life: Microorganisms in Science Museums

5 pages, 3 figuresMicroorganisms were first described by van Leeuwenhoek in the 17th century. Later, Pasteur and Koch related them to diseases. Since then, the scientific community has striven to extend awareness of the many junctions of microorganisms. Science museums provide an excellent setting in which to disseminate such knowledge, but the presentation of living microorganisms is a challenge. We describe an approach to the exhibition of living microorganisms pursued in a science museum in Barcelona (CosmoCaixa Barcelona). In two exhibits, the museum shows photosynthesis in cyanobacteria and Winogradsky columns, which provide an example of living microbial ecosystemsPeer reviewe