1,720,989 research outputs found
Sediment Features and Human Activities Structure the Surface Microbial Communities of the Venice Lagoon
Full text linkSediment microbial communities play essential roles in marine ecosystem functioning. Their study is crucial to understand how environmental conditions affect microbial diversity and biogeochemical cycles. The Venice Lagoon, one of the largest Adriatic transitional systems, is subjected to different natural and anthropogenic stressors. In this study, surface sediments microbial communities were finely characterized using 16S rRNA gene amplicon sequencing and metagenomics. Samples were collected seasonally in 2019 and 2020 at different sites within Lagoon sub-basins. Our results indicated a stable spatial distribution of the sediment microbiome: salinity, grain size, and total organic carbon were found to be important drivers in shaping prokaryotic communities, while temperature had a minor role. We detected high microbial diversity at all stations, mainly due to low abundant taxa: bacteria represented the vast majority of the reads (∼96.1%), with Woeseia the most abundant genus (∼4.4%). The metagenomic analysis highlighted significant differences among sites in terms of biogeochemical processes (e.g., C, N, Fe, and S metabolism), and cell-cell interaction strategies (e.g., mobilome, regulations and cell signaling). Chioggia, a sandy site subjected to marine influence, presented the highest abundance of ammonia-oxidizing archaeon Candidatus Nitrosopumilus, in accordance with the highest amount of ammonia monooxygenase subunit genes. At the same site, sulfate-reducing bacteria (Desulfobacteria and Desulfobacterales) and sulfur-related genes were found in lower abundance. Marghera and Tresse, the most polluted sites, showed higher abundance of sewage-related bacteria and antibiotic and toxic compound resistance genes. Furthermore, these sites showed higher amount of genes related to cell-cell interaction, such as pathogenicity islands, transposable-elements, and biofilm formation. Our findings highlighted that sediment features and human-related activities have profound and long-term impacts on the surface sediment microbial communities of the Venice Lagoon
Approccio metodologico allo studio dipopolamenti picocianobatterici del Golfo di Trieste (Alto Adriatico).
No full textPolysaccharide degradation and utilisation during a spring phytoplankton bloom in the northwestern Adriatic Sea
No full textThe northern Adriatic Sea is among the most productive areas within the Mediterranean Sea, mainly because of the important river discharges that characterise the area. During an oceanographic cruise in April 2011, 12 stations located in the western sector of the basin were sampled in order to deepen the current knowledge on polysaccharide utilisation within phytoplankton blooms. The bloom detected in the proximity of the Po river delta was mainly supported by Skeletonema marinoi and several species of Chaetoceros and determined the spatial distribution of total carbohydrates in surface and subsurface waters. The kinetics of four glycolytic exoenzymes were tested (alpha- and beta-glucosidase together with alpha- and beta-galactosidase), and cellulose-degrading and cellobiose-utilising microbes were enumerated. The fastest enzymatic cleavage was performed by α-galactosidase in low-chlorophyll areas. The highest abundance of cellulose-degrading microorganisms corresponded to the lowest degradation rates. Relatively slow hydrolysis was compensated by a pronounced affinity of the enzymes for their substrates. This metabolic strategy would minimise energy consumption, by producing few, high-performance enzymes. No evident relationship between phytoplankton assemblages and polysaccharide degradation dynamics was found
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Ecological advantages from light adaptation and heterotrophic-like behavior in Synechococcus harvested from the Gulf of Trieste (Northern Adriatic Sea).
No full textUptake-release dynamics of the inorganic and organic carbon pool mediated by planktonic prokaryotes in the deep Mediterranean Sea
No full textUnderstanding the ecosystem functioning in the dark portion of the ocean is a challenge that microbial ecologists are still facing. Due to the large volume, the global deep Ocean plays a central role in the regulation of climate, possibly buffering the rise of atmospheric carbon dioxide if processes of CO2 fixation compensate for respiration. We investigated the rates of several prokaryotic activities (dissolved and particulate primary production, heterotrophic carbon production and respiration) in meso- and bathypelagic waters of the Mediterranean Sea, covering all sub-basins. Chemosynthesis was the main process for C uptake. The rates of organic C (OC) excretion (or viral-induced cell lysis) inferred from the dissolved primary production measurements were noteworthy, being comparable to particulate primary production, and possibly contributing to the formation of non-sinking particulate organic matter. Inorganic C fixation rates were significantly higher than those reported for other deep-sea systems, probably as a consequence of the persistently higher temperature of dark Mediterranean waters or to phylogenetically diverse communities involved in the process. Primary production was negatively correlated with dissolved organic carbon concentration and showed an inverse pattern to heterotrophic carbon production, indicating a niche partitioning between heterotrophs and autotrophs. In sum, the deep Mediterranean Sea harbors active autotrophic communities able to fix inorganic carbon faster than the heterotrophic carbon production rates
Water masses bacterial community structure and microbial activities in the Ross Sea (Antarctica).
No full textDuring the summer 2005/06, an oceanographic cruise was carried out in the Ross Sea, from Cape
Adare, through the Terra Nova Bay polynya to the eastern edge of the Ross Ice Shelf. We analysed microbial
activities (prokaryotic carbon production, protease, phosphatase, beta-glucosidase and lipase activity) and
bacterial community structure (using Denaturing Gradient Gel Electrophoresis - DGGE) in order to establish if
differences in bacterioplankton assemblages and their metabolic requirements occur within the five Ross Sea
water masses: Antarctic Surface Waters (AASW), High Salinity Shelf Water (HSSW), Ice Shelf Water (ISW),
Antarctic Bottom Water (AABW), Circumpolar Deep Water (CDW). Differences in activities were found
between the highly active AASW and all the other water bodies. A Principal Component Analysis highlighted
two main gradients: in the Cape Adare area (AASWn, CDW and AABW) higher phosphatase, lipase and
glycolytic activities, increasing towards the surface, were identified, whereas in the southern sector of the basin
[AASWs and (m)HSSW] higher leucine uptake and polypeptide degradation characterized the second gradient.
DGGE fingerprinting showed for the first time that different water masses harboured diverse bacterial
communities, highlighting the high specificity of deep water assemblages. Alpha- and Gammaproteobacteria
represented the main phylogenetic groupings in all samples and no substantial difference in the phylogenetic
composition of assemblages was found between different water masses
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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