Snapshot of a Bacterial Microbiome Shift during the Early Symptoms of a Massive Sponge Die-Off in the Western Mediterranean

30 páginas, 7 figuras, 1 tabla.Ocean warming is affecting marine benthic ecosystems through mass mortality events that involve marine invertebrates, in particular bivalves, corals, and sponges. Among these events, extensive die-offs of Ircinia fasciculata sponges have been recurrently reported in western Mediterranean. The goal of our study was to test whether the temperature-related mass sponge die-offs were associated with or preceded by an early unbalanced bacterial microbiome in the sponge tissues. We took advantage of the early detection of disease and compared the microbiomes of healthy vs. early diseased I. fasciculata tissues. Our results showed a microbiome shift in early diseased tissues. The abundance of Gammaproteobacteria and Acidobacteria increased and that of Deltaproteobacteria decreased in diseased vs. healthy tissues. The change in community composition was also noticeable at the operational taxonomic unit (OTU) level. Diseased tissues contained more bacterial sequences previously identified in injured or stressed sponges and corals than healthy tissues. Bacterial diversity increased significantly in diseased tissues, which contained a higher number of low abundance OTUs. Our results do not support the hypothesis of one particular pathogen, whether a Vibrio or any other bacteria, triggering the Northwestern Mediterranean mass mortalities of I. fasciculata. Our data rather suggest an early disruption of the bacterial microbiome balance in healthy sponges through a shift in OTU abundances, and the purported consequent decline of the sponge fitness and resistance to infections. Opportunistic bacteria could colonize the sponge tissues, taking benefit of the sponge weakness, before one or more virulent pathogens might proliferate ending in the mass sponge die-off.AcknowledgmentsThis study has partially been funded by projects MarSymbiOmics (MINECO, I+D+I ofExcellence, CTM2013-43287-P), the Benthic Ecology Consolidate Team 2014-SGR-120(Generalitat de Catalunya), and BluePharm Train FP7 People-INT, to MU The work of PGwas supported by the Agence Nationale de la Recherche (ANR) through the projectsEUREKA (ANR-14-CE02-0004-01).Peer reviewe

Structure de buts, relations enseignants-élèves et adaptation scolaire des élèves : une analyse multi-niveaux

Cet article cherche à identifier les facteurs qui peuvent influencer la motivation des élèves et plus généralement leur adaptation scolaire. Les recherches passées en revue indiquent que la perception qu’ont les élèves des structures de buts et de la qualité des relations enseignants-élèves sont des éléments importants pour leur engagement scolaire. Une série d’analyses multi-niveaux visant à évaluer si ces perceptions des élèves peuvent refléter des différences de pratiques d’enseignement entre les classes ou si elles reflètent uniquement des interprétations individuelles et/ou des effets de composition sont présentées. Les seuls effets de composition observés de manière récurrente concernent le genre et l’année de scolarité des élèves. Confirmant les résultats antérieurs, les analyses montrent qu’une structure centrée sur la maîtrise a un effet positif sur la motivation des élèves. Mais ces analyses montrent en outre qu’une structure centrée sur la performance a un effet négatif sur la motivation des élèves et augmente le risque de victimation. Enfin, ces analyses indiquent que des relations enseignants-élèves de qualité ont un effet pacificateur sur l’agressivité des élèves.This article tries to identify the elements that can influence students’ motivation and more generally their adaptation to school. Research work that had been looked through showed that the way the students see the goal structures and the quality of student-teacher relationships is an important element in their involvement in school. The article presents a series of multilevel tests. They aim at gauging whether those perceptions from the students can be linked to different teaching practices or if they reflect only personal interpretations and/or composition effects. The only composition effects observed several times are the gender and grade of the students. Confirming past results, the tests show that mastery-centred structures have positive effects on the students’ motivation. But those tests show moreover that performance-centred structures increase the risks of victimisation. Finally, those tests indicate that high-quality student-teacher relationships have a pacifying effect on students’ aggressiveness.Este artículo intenta identificar los factores que pueden influir en la motivación de los alumnos y más generalmente en su adaptación escolar. Las investigaciones examinadas indican que la percepción que tienen los alumnos de las estructuras de objetivos y de la calidad de las relaciones docentes-alumnos son elementos importantes para su implicación escolar. Se presentan una serie de análisis a varios niveles que intentan evaluar si estas percepciones de los alumnos podían reflejar diferencias de prácticas de enseñanza entre las clases o si reflejaban únicamente interpretaciones individuales y/o efectos de composición. Los únicos efectos de composición observados de manera recurrente conciernen el género y el año de escolaridad de los alumnos. Confirmando los resultados anteriores, los análisis muestran que una estructura centrada en el dominio tiene un efecto positivo sobre la motivación de los alumnos. Pero estos análisis muestran además que una estructura centrada en la performancia tiene un efecto negativo sobre la motivación de los alumnos y aumenta el riesgo de victimación. En fin, estos análisis indican que relaciones docentes- alumnos de calidad tienen un efecto pacificador sobre la agresividad de los alumnos.Dieser Artikel versucht es, die Faktoren zu identifizieren, die die Motivation der Schüler und ferner ihre Schulanpassung beeinflussen. Die bearbeiteten Forschungsarbeiten deuten darauf hin, dass die Art und Weise, wie die Schüler die Zielstrukturen und die Qualität der Lehrer-Schüler Beziehungen wahrnehmen, wichtige Faktoren für ihren Einsatz in der Schule sind. Eine Reihe vielschichtiger Analysen wird vorgelegt, die sich vornimmt zu analysieren, ob diese Wahrnehmungen der Schüler etwa Unterschiede der Lehrpraktiken oder ausschließlich individuelle Interpretationen und/oder Zusammensetzungseffekte widerspiegeln. Die einzigen wiederkehrenden beobachteten Zusammensetzungseffekte betreffen das Taxon und das Schuljahr der Schüler. Die Analysen bestätigen die vorherigen Ergebnisse und zeigen, dass eine auf Beherrschung zentrierte Struktur eine positive Auswirkung auf die Motivation der Schüler aufweist. Dagegen zeigen diese Analysen darüber hinaus, dass eine auf Leistung zentrierte Struktur eine negative Auswirkung auf die Motivation der Schüler hat und das Risiko des Opferdenkens steigert. Zum Schluss deuten diese Analysen darauf hin, dass hochwertige Lehrer-Schüler Beziehungen eine befriedende Auswirkung auf die Aggressivität der Schüler aufweisen

Stable carbon isotope fractionation during methanogenesis in three boreal peatland ecosystems

The degradation of organic matter to CH4 and CO2 was investigated in three different boreal peatland sys- tems in Finland, a mesotrophic fen (MES), an oligotrophic fen (OLI), and an ombrotrophic peat (OMB). MES had sim- ilar production rates of CO2 and CH4, but the two nutrient- poor peatlands (OLI and OMB) produced in general more CO2 than CH4. δ 13C analysis of CH4 and CO2 in the pres- ence and absence methyl fluoride (CH3F), an inhibitor of acetoclastic methanogenesis, showed that CH4 was predom- inantly produced by hydrogenotrophic methanogenesis and that acetoclastic methanogenesis only played an important role in MES. These results, together with our observations concerning the collective inhibition of CH4 and CO2 pro- duction rates by CH3F, indicate that organic matter was de- graded through different paths in the mesotrophic and the nutrient-poor peatlands. In the mesotrophic fen, the ma- jor process is canonical fermentation followed by aceto- clastic and hydrogenotrophic methanogenesis, while in the nutrient-poor peat, organic matter was apparently degraded to a large extent by a different path which finally involved hydrogenotrophic methanogenesis. Our data suggest that degradation of organic substances in the oligotrophic envi- ronments was incomplete and involved the use of organic compounds as oxidants.Peer reviewe

High bicarbonate assimilation in the dark by Arctic bacteria

10 páginas, 4 figuras, 1 tabla.Although both autotrophic and heterotrophic microorganisms incorporate CO2 in the dark through different metabolic pathways, this process has usually been disregarded in oxic marine environments. We studied the significance and mediators of dark bicarbonate assimilation in dilution cultures inoculated with winter Arctic seawater. At stationary phase, bicarbonate incorporation rates were high (0.5–2.5 μg C L−1 d−1) and correlated with rates of bacterial heterotrophic production, suggesting that most of the incorporation was due to heterotrophs. Accordingly, very few typically chemoautotrophic bacteria were detected by 16S rRNA gene cloning. The genetic analysis of the biotin carboxylase gene accC putatively involved in archaeal CO2 fixation did not yield any archaeal sequence, but amplified a variety of bacterial carboxylases involved in fatty acids biosynthesis, anaplerotic pathways and leucine catabolism. Gammaproteobacteria dominated the seawater cultures (40–70% of cell counts), followed by Betaproteobacteria and Flavobacteria as shown by catalyzed reporter deposition fluorescence in situ hybridization (CARDFISH). Both Beta- and Gammaproteobacteria were active in leucine and bicarbonate uptake, while Flavobacteria did not take up bicarbonate, as measured by microautoradiography combined with CARDFISH. Within Gammaproteobacteria, Pseudoalteromonas-Colwellia and Oleispira were very active in bicarbonate uptake (ca. 30 and 70% of active cells, respectively), while the group Arctic96B-16 did not take up bicarbonate. Our results suggest that, potentially, the incorporation of CO2 can be relevant for the metabolism of specific Arctic heterotrophic phylotypes, promoting the maintenance of their cell activity and/or longer survival under resource depleted conditions.This work is a contribution to the International Polar Year – Circumpolar Flaw Lead system study (IPY-CFL 2007/2008) lead by D. Barber (University of Manitoba) supported through grants from the Canadian IPY Federal Program Office, the National Sciences and Engineering Research Council, grant BOREAL (CLG2007-28872-E/ANT) from the Spanish Ministry of Science and Innovation to C.P.-A., and grants from the Swedish Research Council to S.B and L.A.S. L.A.S. was supported by a Marie Curie Intraeuropean Fellowship (CHEMOARC PIEF-GA-2008- 221121), E.O.C by the Spanish grant CGL2009-13318- BOS, and P. E. G by a Marie Curie grant (CRENARC MEIF-CT-2007-040247).Peer reviewe

Spontaneous recovery in phacolytic glaucoma

We report a case of phacolytic glaucoma in which spontaneous absorption of the hypermature lens allowed a patient who refused surgery to recover a normal pressure and satisfactory visual acuity

Redbook: 1995

Advice compiled by Boston University School of Medicine students for incoming first year students and third or fourth year students preparing for clinical rotations

The environment drives microbial trait variability in aquatic habitats

A prerequisite to improve the predictability of microbial community dynamics is to understand the mechanisms of microbial assembly. To study factors that contribute to microbial community assembly, we examined the temporal dynamics of genes in five aquatic metagenome time-series, originating from marine offshore or coastal sites and one lake. With this trait-based approach we expected to find gene-specific patterns of temporal allele variability that depended on the seasonal metacommunity size of carrier-taxa and the variability of the milieu and the substrates to which the resulting proteins were exposed. In more detail, we hypothesized that a larger seasonal metacommunity size would result in increased temporal variability of functional units (i.e., gene alleles), as shown previously for taxonomic units. We further hypothesized that multicopy genes would feature higher temporal variability than single-copy genes, as gene multiplication can result from high variability in substrate quality and quantity. Finally, we hypothesized that direct exposure of proteins to the extracellular environment would result in increased temporal variability of the respective gene compared to intracellular proteins that are less exposed to environmental fluctuations. The first two hypotheses were confirmed in all data sets, while significant effects of the subcellular location of gene products was only seen in three of the five time-series. The gene with the highest allele variability throughout all data sets was an iron transporter, also representing a target for phage infection. Previous work has emphasized the role of phage-prokaryote interactions as a major driver of microbial diversity. Our finding therefore points to a potentially important role of iron transporter-mediated phage infections for the assembly and maintenance of diversity in aquatic prokaryotes

Temporal Dynamics of Active Prokaryotic Nitrifiers and Archaeal Communities from River to Sea

International audienceTo test if different niches for potential nitrifiers exist in estuarine systems, we assessed by pyrosequencing the diversity of archaeal gene transcript markers for taxonomy (16S ribosomal RNA (rRNA)) during an entire year along a salinity gradient in surface waters of the Charente estuary (Atlantic coast, France). We further investigated the potential for estuarine prokaryotes to oxidize ammonia and hydrolyze urea by quantifying thaumarchaeal amoA and ureC and bacterial amoA transcripts. Our results showed a succession of different nitrifiers from river to sea with bacterial amoA transcripts dominating in the freshwater station while archaeal transcripts were predominant in the marine station. The 16S rRNA sequence analysis revealed that Thaumarchaeota marine group I (MGI) were the most abundant overall but other archaeal groups like Methanosaeta were also potentially active in winter (December–March) and Euryarchaeota marine group II (MGII) were dominant in seawater in summer (April–August). Each station also contained different Thaumarchaeota MGI phylogenetic clusters, and the clusters' microdiversity was associated to specific environmental conditions suggesting the presence of ecotypes adapted to distinct ecological niches. The amoA and ureC transcript dynamics further indicated that some of the Thaumarchaeota MGI sub-clusters were involved in ammonia oxidation through the hy-drolysis of urea. Our findings show that ammonia-oxidizing Archaea and Bacteria were adapted to contrasted conditions and that the Thaumarchaeota MGI diversity probably corresponds to distinct metabolisms or life strategies

The Effect of Captivity on the Dynamics of Active Bacterial Communities Differs Between Two Deep-Sea Coral Species

Microbes play a crucial role in sustaining the coral holobiont’s functions and in particular under the pressure of environmental stressors. The effect of a changing environment on coral health is now a major branch of research that relies heavily on aquarium experiments. However, the effect of captivity on the coral microbiome remains poorly known. Here we show that different cold-water corals species have different microbiome responses to captivity. For both the DNA and the RNA fraction, Madrepora oculata bacterial communities were maintained for at least 6 months of aquarium rearing, while Lophelia pertusa bacteria changed within a day. Interestingly, bacteria from the genus Endozoicomonas, a ubiquitous symbiont of numerous marine hosts, were resilient and remained active in M. oculata for several months. Our results demonstrate that a good knowledge of the coral microbiome and an understanding of the ecological strategy of the holobiont is needed before designing aquarium experiments