1,720,979 research outputs found
Development and validation of an oligonucleotide microarray to characterise ectomycorrhizal fungal communities
Get PDFBackground: In forest ecosystems, communities of ectomycorrhizal fungi (ECM) are influenced by several biotic and abiotic factors. To understand their underlying dynamics, ECM communities have been surveyed with ribosomal DNA-based sequencing methods. However, most identification methods are both time-consuming and limited by the number of samples that can be treated in a realistic time frame. As a result of ongoing implementation, the array technique has gained throughput capacity in terms of the number of samples and the capacity for parallel identification of several species. Thus far, although phylochips (microarrays that are used to detect species) have been mostly developed to trace bacterial communities or groups of specific fungi, no phylochip has been developed to carry oligonucleotides for several ectomycorrhizal species that belong to different genera. Results: We have constructed a custom ribosomal DNA phylochip to identify ECM fungi. Specific oligonucleotide probes were targeted to the nuclear internal transcribed spacer (ITS) regions from 95 fungal species belonging to 21 ECM fungal genera. The phylochip was first validated using PCR amplicons of reference species. Ninety-nine percent of the tested oligonucleotides generated positive hybridisation signals with their corresponding amplicons. Cross-hybridisation was mainly restricted at the genus level, particularly for Cortinarius and Lactarius species. The phylochip was subsequently tested with environmental samples that were composed of ECM fungal DNA from spruce and beech plantation fungal communities. The results were in concordance with the ITS sequencing of morphotypes and the ITS clone library sequencing results that were obtained using the same PCR products. Conclusion: For the first time, we developed a custom phylochip that is specific for several ectomycorrhizal fungi. To overcome cross-hybridisation problems, specific filter and evaluation strategies that used spot signal intensity were applied. Evaluation of the phylochip by hybridising environmental samples confirmed the possible application of this technology for detecting and monitoring ectomycorrhizal fungi at specific sites in a routine and reproducible manner
Spatial resolution of aquatic fungal communities driven by the interplay of environmental factors and ecological processes
No full textAquatische Pilze sind eine weit verbreitete Organismengruppe und sie nehmen Schlüsselrollen in wichtigen ökologischen Prozessen wie zum Beispiel dem Nährstoffkreislauf ein. Aufgrund ihrer evolutiven Entwicklung im aquatischen Bereich sowie sekundäre Besiedlungsschritte mariner Systeme verfügen sie über diverse ökologisch interessante Eigenschaften. Allerdings ist nur wenig über das Zusammenspiel von Diversität und Struktur aquatischer Pilzgemeinschaften und den beeinflussenden Faktoren bekannt. Vor allem ist die räumliche Auflösung aquatischer Pilzgemeinschaften kaum erforscht. Als Konsequenz wurden bisher Pilze kaum beachtet, wodurch die Entwicklung eines holistischen Bildes aquatischer ökologischer Prozesse gehemmt ist. Ziel meiner Dissertation war es daher, zu verstehen, wie aquatische Pilzgemeinschaften in (i) Flüssen und angrenzender Küstenzone und (ii) benthischen Systemen durch die Interaktion ökologischer Prozesse oder einzelner bis mehrerer Umweltfaktoren räumlich aufgelöst werden.
In meiner Doktorarbeit habe ich die mykopelagischen und mykobenthischen Gesellschaftsstrukturen mit tag-Sequenzierung aufgelöst (18S rDNA Gensequenz oder Internal Transcribed Spacer 2 (ITS2)). Dadurch konnte ich in meinem ersten Projekt zeigen, dass die Assemblierungs-Prozesse mykopelagischer Flussgemeinschaften sich bereits über kürzeste Entfernungen drastisch unterscheiden und es zu einem Zusammenspiel von Umweltfaktoren sowie ökologischen Prozessen von Selektion und Verteilung kommt. In meinem zweiten Projekt habe ich neben der tag-Sequenzierung eine umfassende Literatur- und Datenbankrecherche zwecks einer globaler biogeographischer Auflösung mariner benthischer Pilze durchgeführt. Die erlaubte mir, erstmals ein konzeptionelles Bild von Verbreitungsmustern benthischer Pilze zu entwerfen. Überraschenderweise war die 100 km-Marke eine Distanz, ab der die pilzliche Verbreitung stark limitiert war. Durch eine Merkmals-Analyse konnte ich weiterhin zeigen, dass die pilzliche Verbreitung durch individuelle Merkmale wie Morphologie oder trophischer Modus signifikant beeinflusst wird. In meinem dritten Projekt habe ich erstmals den Einfluss von Anoxie auf mykobenthischen Gemeinschaften aus Küstenregionen in Inkubationsexperimenten durchgeführt. Die erhobenen Daten habe ich zusätzlich mit Meta-Gesellschaftsdaten aus publizierten Datensätzen unterfüttert. Somit konnte ich die Anpassungsfähigkeit und diverse Strategien des Mykobenthos mit anoxischen Bedingungen umzugehen, untersuchen und einzelne Keyplayer für die unterschiedlichen oxischen Bedingungen im Allgemeinen detektieren.
Insgesamt unterstreicht diese Arbeit, wie wichtig das Verständnis des Zusammenwirkens räumlicher Verteilungsmuster, ökologischer Prozesse sowie diverser Umweltfaktoren ist, um die Assemblierung einzelner Pilzgemeinschaften vorherzusagen und zu modellieren. Nur dies erlaubt, verläßliche Voraussagen von sich änderenden Stoffflüssen zu machen unter der Einbeziehung aller relevanter Organismengruppen. Meine Arbeit ist ein wichtiger Bestandteil davon, denn sie eröffnen neue Sichtweisen auf pilzliche Assemblierungsprozesse, auf denen weiterführende Forschungsarbeiten aufbauen können
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Mycoplankton diversity in the Elbe River
No full textRivers are important transport systems for nutrients and organic material and thus influence biogeochemical cycles and food web structures. Microorganismal biodiversity is an important parameter for the ecological balance of river ecosystems. Despite the knowledge that freshwater fungi perform important ecological functions, there is scarcely any fungal data available for river systems. In this study, we address the fundamental question of how mycoplankton communities are structured and assembled over a longer river section with strong environmental gradients and anthropogenic pressure and what variables control on it. The mycoplankton communities from the shallow freshwater to the coastal-oceanic transition zone were analyzed based on 18S rRNA gene tag-sequencing and the observed patterns were related to environmental and spatial factors by multivariate statistics. Finally, the underlying assembly processes were revealed by Quantitative Process Estimates (QPE) method. The partitioning of mycoplankton communities deviated from the previously described patterns of fluvial microbial communities, triggered by a strong influence of local environmental conditions, which were partly under spatial control. The deepening of the Elbe River for improved navigation purpose seemed to have a strong secondary effect. The salinity gradient was the most explaining variable and zoosporic fungi showed higher sensitivity to high salinity levels. Consequently, none of the zoosporic taxon groups occurred solely in the marine environment. Significant differences were found in the assemblage processes with a dominance of environmental selection in the upstream region compared to undominated processes in downstream and coastal transition regions. The results suggest that fungi play various ecological roles along the diverse river sections and that their biotic interactions become more complex in the estuary. These results provide an important framework to help predict the functional consequences of changes in mycoplankton community structure and to help conserve microbial biodiversity in river ecosystems
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe 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
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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