1,720,953 research outputs found
A molecular-based analysis of the antibiotic biosynthetic potential of selected marine Micromonosporaceae Species
No full textThesis (MSc (Biomedical Technology))--Cape Peninsula University of Technology, 2019Introduction:
The discovery of the first antibiotic, penicillin, paved way for many other discoveries and developments much to the benefit of antibiotic treatment against bacterial infections. As years went by, the irresponsible use of antibiotic compounds in the medical, agricultural and veterinary fields, as well as lack of robust infection control protocols in clinical spaces, led to the emergence of antibiotic tolerant and resistant microorganisms. In an attempt to arrest the crisis, the discovery of new bioactive compounds that can be developed into potent novel antibiotics has been of importance. Amongst the many sources of bioactive compounds that have been researched for decades, microorganisms of the genus Micromonospora have been well documented as producers of potent bioactive metabolites, many of which have been successfully developed into novel commercial antibiotics. There is, however, a dearth of research information concerning the possibility of novel bioactive metabolites isolated from Micromonospora species from South Africa. Therefore, this study aimed to investigate the antibiotic biosynthetic potential of selected marine Micromonospora species isolated from the Algoa Bay region in Port Elizabeth, South Africa.
Method:
A total of 30 Micromonospora strains isolated from Algoa Bay region, Port Elizabeth in South Africa were provided as frozen stock cultures at the Cape Peninsula University of Technology’s Biocatalysis and Technical Biology (BTB) research unit. The strains were first cultured on SGG and 172 F solid and liquid media, with and without artificial sea water (ASW). The Gram stain was performed to ensure purity of strains and to evaluate microscopic morphology before extracting DNA. Multi-Locus Sequence Analysis (MLSA) of the rpoB and gyrB housekeeping genes was performed as well as 16S rRNA gene analysis. Phylogenetic analysis was performed using MEGA X and phylogenetic trees were constructed to this effect. Eight antibiotic biosynthetic gene clusters (BGCs) were screened for via PCR. Gaps in the current primer sets available for BGC screening were analysed. Genomic data for 44 Micromonospora strains was retrieved from EzBiocloud and antiSMASH and these assisted with primer designing after assessing primer-knowledge gaps. The designed primers were designed to target BGCs encoding for bacteriocins and lanthipeptides and were tested on five selected Micromonosporaceae strains. The antibacterial activity of the top five strains was also investigated using overlay studies on solid media cultures and bioautography studies in liquid media cultures. In addition, the efficacy of antibiotic extraction was tested through the use of five different antibiotic extraction techniques.
Results:
Our results demonstrated that all the strains under study were viable Micromonospora species. Phylogenetic analysis of the five strains chosen for further analysis identified their closest related validly published type strain as Micromonospora aurantiaca ATCC 27029. Furthermore, one of the eight BGCs that were screened for, the Type II PKS BGC, was positive in 28 out of the 30 strains. Genomic information of the genus Micromonospora was retrieved from antiSMASH which assisted in assessing gaps in current primer knowledge. Ultimately this led to the design of new primers to target bacteriocin and lanthipeptide BGCs. Four of the five strains tested gave a positive PCR result, albeit with multiple bands. The multiple bands on the agarose gel signified non-specificity in the binding capacity of the designed bacteriocin BGC primers hence there was no exclusive and convincing evidence of existence of this gene cluster. Negative PCR results were observed for the Lanthipeptide primer set. Antibacterial activity analysis on solid and in liquid culture media proved that the five selected strains produced bioactive compounds that were active against Gram-positive (Bacillus cereus ATCC 10876) and Gram-negative (Escherichia coli ATCC 25922) pathogens as well as yeast (Candida albicans ATCC 24433).
Conclusion:
The Micromonosporaceae species that were under investigation in this study show great potential as sources of bioactive metabolites with broad spectrum antibacterial activity as well as antifungal activity. These should be considered as suitable candidates for whole genome sequencing as well as comparative genome sequence analysis for greater insights into the M. aurantiaca group
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
No full text“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
No full textWe 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
No full textWe 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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
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