1,721,272 research outputs found
Morphology-driven downscaling of Streptomyces lividans to micro-cultivation
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Environmental and metabolomic study of antibiotic production by actinomycetes
Get PDFThis thesis may be regarded as a concept work, to see how feasible drug discovery approaches still are. For this, a strain collection was built up consisting of actinomycetes from soil in the Qinling and Himalaya mountains, which were subsequently tested for antibiotic production against multi-drug resistant clinical isolates. This resulted in close to 100 strains that showed strong antimicrobial activity, which were then analyzed in more detail. Two of the strains were subjected to extensive NMR-based metabolomics assisted by mass spectrometry, and several known and also novel antimicrobial compounds were elucidated. Finally, we also focused on the antibiotic activity of volatile organic compounds (VOCs)UBL - phd migration 201
Function and control of the ssg genes in streptomyces
Get PDFStreptomycetes are Gram-positive soil-dwelling bacteria, in appearance similar to filamentous fungi. The SsgA-like proteins or SALPs, of which streptomycetes typically have at least five paralogues, control specific steps of sporulation-specific cell division in streptomycetes. The expression level of SsgA, the best studied SALP, has a rather dramatic effect on septation and on hyphal morphology, which is not only of relevance for our understanding of (developmental) cell division but has also been succesfully applied in industrial fermentation, to improve growth and production of filamentous actinomycetes. The different regulation of ssgA transcription in different Streptomyces species, is at least one of the reasons why some strains are able to produce spores in liquid-grown mycelium, while others cannot. By far the most conserved SALP is SsgB, which is most likely is the archetypal SALP, with only SsgB orthologues occurring in all morphologically complex actinomycetes. SsgB is essential for sporulation of Streptomyces, and orthologues have a universally conserved function in actinomycete morphogenesis.UBL - phd migration 201
Molecular characterization of copper-dependent enzymes involved in Streptomyces morphology
Get PDFThe filamentous soil bacteria of the genus Streptomyces are commercially exploited for the production of a wide range of natural products such as antibiotics, anticancer agents and immunosuppressants. Additionally, there is a strong interest in the use of these bacteria for the production of industrial proteins. Optimal production of these secondary metabolites and enzymes is tightly coupled to morphology. However, relatively little is known about the genetic determinants influencing the morphology of streptomycetes in liquid-grown cultures. The work presented in this thesis focuses on the formation of extracellular macromolecules and their influence on morphogenesis, with a special emphasis on the role of the cellulose synthase-like protein CslA and the radical copper oxidase GlxA in the production of a tip-localized glycan. This research is of fundamental importance for understanding the determinants of growth and development of this multicellular model organism, and at the same time may help us to further optimize their exploitation for the industrial production of secondary metabolites and enzymes.UBL - phd migration 201
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
Control of sporulation-specific cell division in Streptomyces coelicolor
Get PDFDuring developmental cell division in sporulation-committed aerial hyphae of streptomycetes, up to a hundred septa are simultaneously produced, in close harmony with synchromous chromosome condensation and segregation. Several unique protein families are involved in the control of this process, including that of the SsgA-like proteins (SALPs). While SsgA and SsgB are essential for sporulation-specific cell division in S. coelicolor, SsgC-G are responsible for correct DNA segregation/condensation, spore wall synthesis, autolytic spore separation, or exact septum localisation. The SALPs are a novel protein family that acts through timing and localisation of the activity of penicillin-binding proteins and autolysins, thus controlling important steps during the initiation and the completion of sporulation. The formation of septa is initiated by the formation of a ring of the tubulin-like protein FtsZ (the Z-ring), functioning as a scaffold for the construction of septa. Subsequently, other cell division proteins are recruited to the Z-ring, forming the divisome. In S. coelicolor, the cell division proteins FtsE and FtsX participate during autolytic spore separation, and most likely function by re-importing peptidoglycan subunits for recycling. The cytoskeletal protein MreB is involved in cell shape determination and chromosome segregation in many rod-shaped bacteria. In S. coelicolor, the actin-like proteins MreB and Mbl are not essential for vegetative growth but exert their function in the formation of environmentally stable spores, thereby primarily influencing the assembly of the spore wall.UBL - phd migration 201
Wetenschapper in wonderland : onderzoek in geuren en kleuren
Get PDFCoördinatie bio-anorganische chemi
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
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
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