1,720,999 research outputs found
Identification of Bifidobacteria by the Phosphoketolase Assay
No full textBifidobacteria are commensal bacteria, which naturally colonize the gastrointestinal tract of a large number of animals, including humans, contributing to their health and well-being. An important taxonomic marker for the identification of members of the bifidobacterial group is the presence of the fructose-6-phosphate phosphoketolase (F6PPK) activity. The F6PPK enzyme is involved in the bifidus shunt based on the ability of F6PPK to split fructose-6-phosphate into erythrose-4-phosphate and acetyl phosphate. Here, we describe the two main methods utilized to detect the presence of F6PPK activity, that is, the enzymatic assay and the presence of the D-xylulose-5-phosphate/fructose-6-phosphate phosphoketolase bifidobacterial gene
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
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
Multidisciplinary approaches for studying rhizobium–legume symbioses
No full textThe rhizobium–legume symbiosis is a major source of fixed nitrogen (ammonia) in the biosphere. The potential for this process to increase agricultural yield while reducing the reliance on nitrogen-based fertilizers has generated interest in understanding and manipulating this process. For decades, rhizobium research has benefited from the use of leading techniques from a very broad set of fields, including population genetics, molecular genetics, genomics, and systems biology. In this review, we summarize many of the research strategies that have been employed in the study of rhizobia and the unique knowledge gained from these diverse tools, with a focus on genome- and systems-level approaches. We then describe ongoing synthetic biology approaches aimed at improving existing symbioses or engineering completely new symbiotic interactions. The review concludes with our perspective of the future directions and challenges of the field, with an emphasis on how the application of a multidisciplinary approach and the development of new methods will be necessary to ensure successful biotechnological manipulation of the symbiosis
On-site microbiome study of silica structures in a subterranean Mars analog environment
Full text linkAmorphous silica deposits found in orthoquartzite caves offer valuable analogues for understanding early life on Earth and potential biosignatures on Mars. This study presents the fully on-site microbial community analysis of silica stromatolite-like structures in the ancient and remote orthoquartzite cave Imawar & iacute; Yeut & aacute; (Auyan Tepui, Venezuela). Using a portable laboratory setup, we performed ATP-based microbial activity assessments and the full DNA-based analysis workflow directly in the cave, without internet access or high computational resources. The data obtained in the cave were then validated in the laboratory using a standard bioinformatics pipeline, qPCR and Biolog EcoPlate assays. The sequencing results revealed that the microbial communities in the stromatolite differ from other biofilms on the cave floor for the higher abundance of Actinobacteriota (particularly the genus Crossiella) and members of Subgroup 13 (Acidobacteriota) suggesting a possible role in the stromatolite formation/development. The ATP-based and Biolog results indicated that the most metabolically active microorganisms are localized in the white layer/colonies at basis of the stromatolite suggesting that the stromatolite development occurs at the interface of this structure with the quartz rock. These findings validate the feasibility of real-time microbial analyses in remote caves with astrobiological interest and provide novel understanding on the microbiological aspects involved in the formation of the silica stromatolites in non-thermal and aphotic environments
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe 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
Genomic Diversity and Evolution of Rhizobia
No full textThe rhizosphere is colonized by a large variety of bacterial community and, thanks to the attractive chemical composition of the root exudates, some of them can penetrate inside the tissues and colonize the plant. The rhizobia are bacteria able to establish a mutualistic nitrogen-fixing endosymbiosis with specific legumes forming root nodules on the host plant. They are spread throughout the α- and β-subdivision (classes) of Proteobacteria, which often are united by the multipartite genome structure, consisting in a chromosome and additional plasmid, acquired later, and enriched in dispensable genes that play a key role in the determination of bacterium fitness in different ecological niches. Presently, Sinorhizobium meliloti is the main representative of α-proteobacteria for studies on multipartite genome evolution and environmental adaptation, but Burkholderia and Cupriavirus may represent a new frontier for the β-rhizobia knowledge
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