1,721,532 research outputs found
Glycopeptide Antibiotic Biosynthesis and Resistance in Streptomyces toyocaensis NRRL 15009
No full textGenetic and biochemical studies were conducted on S. toyocaensis NRRL 15009, a gram-positive sporulating filamentous bacterium, and producer of the glycopeptide antibiotic A47934. This compound is structurally similar to the clinically important antibiotic vancomycin, and the recent spread of vancomycin-resistant enterococci (VRE) in North American hospitals has driven the need for new glycopeptides with enhanced activities. Studies were aimed at developing an understanding of the mechanism of A47934 biosynthesis in S. toyocaensis NRRL 15009, as well as the mechanism of resistance employed by this organism. Two cosmid clones, containing a partial A47934 biosynthesis gene cluster on a total of 65 kilobases of S. toyocaensis NRRL 15009 chromosomal DNA, were isolated for study. Preliminary sequencing indicates the presence of several genes predicted in glycopeptide assembly, such as peptide synthetases and glycosyltransferases. Furthermore, using a oligonucleotide probe designed to identify D-alanine-D-alanine ligases, an 8.1 kilobase chromosomal fragment was isolated from S. toyocaensis NRRL 15009 and found to contain genes very similar to VRE vanH, vanA and vanX. Phylogenetic analysis of the predicted products of these genes showed them to be more similar to the VRE enzymes than any other in each enzyme class. These genes were also found in the vancomycin producer A. orientalis C329.2 and several other glycopeptide antibiotic producing organisms. Not only does this imply that these organisms employ a mechanism of resistance similar to clinical VRE, it also suggests that these organisms may have been the source of the VRE genes. The enzymes VanHst and DdlN were studied in some detail and found to have biochemical properties similar to their corresponding VRE enzymes VanH and VanA, respectively. Given that the latter group of enzymes has physical properties that have impeded detailed analysis of enzyme mechanism, these new enzymes could find use as model systems in drug development programs.Doctor of Philosophy (PhD
MAPPING OF 3 PLASMIDS FROM LACTOBACILLUS-HELVETICUS ATCC-15009
No full textThree plasmids isolated from Lactobacillus helveticus ATCC 15009 were analysed by restriction digestion. A restriction map of the 22.0, 6.0 and 3.5 kb plasmids is presented. The existence of genetic markers such as carbohydrate fermentation, lactose metabolism, antibiotics and heavy metal ions resistance was also investigated but the plasmids remain cryptic
Genome Sequence of Streptomyces toyocaensis NRRL 15009, Producer of the Glycopeptide Antibiotic A47934.
Full text linkHere we report the draft genome sequence of Streptomyces toyocaensis strain NRRL 15009 which is the producer of the glycopeptide antibiotic A47934. The genome sequence is predicted to harbor a total of 26 secondary metabolite biosynthetic gene clusters including the A47934 cluster
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
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
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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