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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
491

Impact of Environmental and Cellular Factors on the Bioactivity of a Novel Antifungal, Occidiofungin

Robinson, Chase Alexander 14 August 2015 (has links)
Occidiofungin is a novel glycolipopeptide, synthesized and secreted by Burkholderia contaminans MS14, demonstrating broad-spectrum antifungal activity and potential for successful clinical applications. Its mechanism of action has not yet been determined but is known to exhibit fungicidal activity via the induction of apoptosis in a manner unique from that of currently approved antifungals. As an early investigation into occidiofungin’s mechanism of action, we aimed to identify environmental and cellular factors that significantly alter the susceptibility of the model organism, Saccharomyces cerevisiae. To that end, we have demonstrated that occidiofungin’s bioactivity requires active cellular growth, that new protein synthesis is necessary to adequately respond to occidiofungin exposure, and that alterations in transcriptional regulation in response to glucose and phosphate deprivation have synergistic and antagonist consequences, respectively, on occidiofungin’s effectiveness. Together, this data provides a foundation on which occidiofungin’s mechanism of action can be illuminated.
492

Ethanolic fermentation of bio-oil hydrolysate

Livingston, Darrell Rex, Jr 06 August 2011 (has links)
As production of ethanol climbs, nonood feedstocks need to be utilized such as lignocellulosic biomass. The sugars present in bio-oil produced by fast pyrolysis can potentially be fermented by microbial organisms to produce cellulosic ethanol. This study shows the potential for microbial digestion of the aqueous fraction of bio-oil in an enrichment medium to consume glucose and produce ethanol. In addition to glucose, inhibitors such as furans and phenols are present in the bio-oil. A pure glucose enrichment medium of 20 g/L was used as a standard to compare with glucose and aqueous fraction mixtures for digestion. 30% by volume of aqueous fraction in media was the most that could be consumed and yielded 0.4 g of ethanol per g of glucose. Inhibitor removal tests by extraction, activated carbon, air stripping, and microbial means were also mildly successful. Ethanol could potentially be produced for $14 per gallon using these methods.
493

Protein glycosylation studies in mammalian cells and yeast

Huang, Kristen Marie January 1994 (has links)
No description available.
494

Functional splicing domains within the fourth intron of the cytochrome B gene of yeast mitochondria : DNA sequence of splicing defective mutants /

Anziano, Paul Quentin January 1984 (has links)
No description available.
495

The Role of Carbohydrate in the Germination of Yeast Ascospores

Banerjee, Maya January 1971 (has links)
<p>The content and utilization of carbohydrate during the yeast life cycle were studied with special reference to spore germination. The experiments were designed to investigate the nutritional requirements, the changes in the carbohydrate content and dry weight, the respiratory activities, the possible substitution of exogenous glucose by other carbon sources, the effect of temperature treatments, the uptake and distribution of exogenous glucose and the effect of inhibitors of carbohydrate metabolism on germination.</p> <p>The experiments showed the relative importance of endogenous and exogenous carbohydrates, the kind of respiratory activity and the fate of exogenous glucose carbon during germination. The pathway of carbon metabolism essential for germination was also indicated.</p> <p>The present work is the first attempt to compare qualitatively and quantitatively the carbohydrate content of yeast during the three major· phases of life cycle, viz., growth, sporulation and germination. Quantitative data on uptake and distribution of exogenous glucose during germination of yeast ascospores are provided. From an analysis of the results an attempt is made to assess the role, of carbohydrate in the germination of yeast ascospores.</p> / Doctor of Philosophy (PhD)
496

Analysis of SSS1P: An Essential Tail-Anchor Protein of the ER Translocon in the Yeast Saccharomyces cerevisiae / Analysis of SSS1P: An Essential Tail-Anchor Protein in Yeast

Nieuwland, Hendrik 05 1900 (has links)
Sss1p is an essential component, along with Sec61p, of the protein conducting channel (PCC) in the ER of the yeast Saccharomyces cerevisiae. It belongs to a family of proteins termed tail-anchor (TA) proteins. The TA consists of a single hydrophobic sequence at the carboxyl-terminus which anchors the protein to the membrane in a Type II (N_cytoplasm-C_lumen) orientation. TA proteins are targeted to their membranes of function through an uncharacterized SRP-independent, post-translational mechanism. The targeting mechanism and function of Sss1p are not known. In this thesis, results will be presented from targeting and functional studies of Sss1p. Sss1p is predicted to contain an ER targeting signal similar to mammalian VAMP-1A. Disruption of this putative signal caused incomplete mislocalization of Sss1p to the mitochondria which did not affect yeast growth. Mutations in the TA of Sss1p had numerous effects. Yeast expressing these mutants showed diminished growth, a defect in co-and post-translational translocation, inefficient ribosome binding to Sec61 p and the mislocalization of translocon components from light membranes (predominantly ER) to heavy membranes (predominantly mitochondria). It is argued that mutations in the TA of Sss1p disrupt the function of the protein, subsequently leading to the general defects listed above. Two possible functions for Sss1p are proposed: Sss1p is involved in forming the signal sequence binding pocket of the translocon and/or is essential for the integrity of the PCC. / Thesis / Master of Science (MS)
497

Upstream Sequences Involved in Regulating the Candida tropicalis Gene Encoding Peroxisomal Trifunctional Enzyme / Regulation of Hydratase-Dehydrogenase-Epimerase

Sloots, James 03 1900 (has links)
We have inestigated the expression of the genes hydratase-dehydrogenase-epimerase (HDE), acyl-CoA oxidase (AOX) and catalase (CATL) of the diploid yeast Candida tropicalis. These genes encode enzymes which are localized to the peroxisome. Expression of each gene was monitored by immunoblot analysis of yeast lysates using antibodies directed against each protein. We demonstrate that carbon sources influence expression of these genes, and do so in a coordinate fashion. We expressed C. tropicalis HDE in Saccharomyces cerevisiae and demonstrate that this trifunctional enzyme can be regulated by S. cerevisiae in a fashion that closely resembles that of C. tropicalis. Expression of constructs containing deletions in the upstream region of the HDE gene allowed us to localize regions responsible for regulating the expression of this gene. Regions were identified that are responsible for both repression by glucose and induction by oleic acid. A glucoseresponsive region lies between nucleotides -466 and -334. An oleic acid-responsive region lies between nucleotides -333 and -281. An additional region controlling derepression by nonfermentable carbon sources is located downstream of nucleotide -281. Comparison of the upstream nucleotide sequences of HDE, AOX and CATL both to each other, and to upstream regions of other oleic acid-responsive genes of C. tropicalis has identified possible consensus nucleotide sequences for glucose-and oleic acid-responsive upstream elements. Since the regulation of the HDE gene in S. cerevisiae closely resembles that of C. tropicalis, this implies that similar mechanisms of transcriptional control operate in both yeasts. / Thesis / Master of Science (MS)
498

The effects of different processing parameters (cold soak and percent alcohol (v/v) at dejuicing) on the concentrations of grape glycosides and glycoside fractions and glycosidase activities in selected yeast and lactic acid bacteria

McMahon, Heather 16 December 1998 (has links)
Grape-derived aroma and flavor precursors exist partially as non-volatile, sugar-bound glycosides. Hydrolysis of these compounds may modify sensory attributes and potentially enhance wine quality. Cold soak (prefermentation skin contact) at two temperatures and alcohol content (%, v/v) at dejuicing were monitored to determine effects on Cabernet Sauvignon glycoside concentration. Total, phenolic-free, and red-free glycoside concentrations were estimated by the quantification of glycosyl-glucose. Cold soak (5 days at 10° C) increased total glycosides by 77%, red-free glycosides by 80%, and phenolic-free glycosides by 96%. Ambient soak (3 days at 20° C) enhanced color extraction, and increased total glycosides by 177%, red-free glycosides by 144%, and phenolic-free glycosides by 106%. Wines produced by early pressing (10% sugar) had 25% more total and red-free glycosides than late press (0.25% sugar). After post-fermentation malolactic fermentation, total glycosides were 14% lower and phenolic-free glycosides were 35% lower. In a second study, the activities of a-L-arabinofuranosidase, b-glucosidase, and a-L-rhamnoyranosidase were determined in model systems for thirty-two strains of yeasts belonging to the following genera: Aureobasidium, Candida, Cryptococcus, Hanseniaspora, Hansenula, Kloeckera, Metschnikowia, Pichia, Saccharomyces, Torulaspora, and Brettanomyces (10 strains); and seven bacteria (Leuconostoc oenos strains). Only one Saccharomyces strain exhibited -glucosidase activity, but several non-Saccharomyces yeast species had substantial production. Aureobasidium pullulans hydrolyzed a-L-arabinofuranoside, b-glucoside, and a-L-rhamnoyranoside. Eight Brettanomyces strains had -glucosidase activity. Location of enzyme activity was determined for those species with enzymatic activity. The majority of -glucosidase was located in the whole cell fraction (66%), followed by the permeabilized fraction (35%), and extracellular production (2%). Aureobasidium pullulans was also capable of hydrolyzing grape glycosides. / Master of Science
499

Mathematical modeling of macronutrient signaling in Saccharomyces cerevisiae

Jalihal, Amogh Prabhav 08 July 2020 (has links)
In eukaryotes, distinct nutrient signals are integrated in order to produce robust cellular responses to fluctuations in the environment. This process of signal integration is attributed to the crosstalk between nutrient specific signaling pathways, as well as the large degree of overlap between their regulatory targets. In the budding yeast Saccharomyces cerevisiae, these distinct pathways have been well characterized. However, the significant overlap between these pathways confounds the interpretation of the overall regulatory logic in terms of nutrient-dependent cell state determination. Here, we propose a literature-curated molecular mechanism of the integrated nutrient signaling pathway in budding yeast, focussing on carbon and nitrogen signaling. We build a computational model of this pathway to reconcile the available experimental data with our proposed molecular mechanism. We evaluate the robustness of the model fit to data with respect to the variations in the values of kinetic parameters used to calibrate the model. Finally, we use the model to make novel, experimentally testable predictions of transcription factor activities in mutant strains undergoing complex nutrient shifts. We also propose a novel framework, called BoolODE for utilizing published Boolean models to generate synthetic datasets used to benchmark the performance of algorithms performing gene regulatory network inference from single cell RNA sequencing data. / Doctor of Philosophy / An important problem in biology is how organisms sense and adapt to ever changing environments. A good example of an environmental cue that affects animal behavior is the availability of food; scarcity of food forces animals to search for food-rich habitats, or go into hibernation. At the level of single cells, a range of behaviors are observed depending on the amount of food, or nutrients present in the environment. Moreover, different types of nutrients are important for different biological functions in single cells, and each different nutrient type will have to be available in the right quantities to support cellular growth. At the subcellular level, intricate molecular machineries exist which sense the amounts of each nutrient type, and interpret this information in order to make a decision on how best to respond. This interpretation and integration of nutrient information is a complex, poorly understood process even in a simple unicellular organism like the budding yeast. In order to understand this process, termed nutrient signaling, we propose a mathematical model of how yeasts respond to nutrient availability in the environment. Our model advances the state of knowledge by presenting the first comprehensive mathematical model of the nutrient signaling machinery, accounting for a variety of experimental observations from the last three decades of yeast nutrient signaling. We use our model to make predictions on how yeasts might behave when supplied with different combinations of nutrients, which can be verified by experiments. Finally, the cellular machinery that helps yeasts respond to nutrient availability in the environment is very similar to the machinery in cancer cells that causes them to grow rapidly. Our proposed model can serve as a stepping stone towards the construction of a model of cancer's responses to its nutritional environment.
500

The relative importance of carbon dioxide, pH, anaerobiosis, and composition of medium on filamentation in Candida albicans

Makooi, Mina January 1967 (has links)
Thesis (M.A.)--Boston University / PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you. / Gandida albicans strain 105 from a normal human and strain 582 (from the American type Culture Collection) were used for studying the effect in vitro of pH, various amounts of carbon dioxide, nitrogen, and composition of media on filamentation in this yeast-like organism. The yeast phase of the organism was maintained on a glucose, glycine, yeast extract (GGY) medium (1%; 1%; 0.5%) at 37°C. The experiments were conducted on both solid and liquid media. All cultures were incubated at 37°C. for 48 hours. The two strains of c. albicans, although similar to one another in their yeast forms, behaved differently toward the environmental conditions used; strain 582 responded more readily to the factors inducing filament formation than did strain 105. Increasing the pH above 6.5 to 7.0, 7.5 and 8.0 induced maximum filamentation in strain 582, whereas no filaments were produced by strain 105. All the aerobic cultures on solid GGY medium showed alkalinity and were positive for ammonia at the end of the incubation period. In liquid media, no alkalinity was observed at any pH values. Presence of 75% carbon dioxide in the atmosphere increased filamentation in strain 582 to a maximum degree, and induced mycelial formation in strain 105. With 94% or 95% carbon dioxide, growth and filamentation decreased in both strains. None of the CO2 cultures showed alkalinity at the end of the incubation period. Moreover, all the CO2 cultures were negative for ammonia. Growth under nitrogen (9J%) was less than that of the aerobic cultures. However, colonies appeared larger in size. Nitrogen stimulated filamentation in strain 105 only at a pH of 8.0, whereas strain 582 formed a maximum amount of filaments at pH values of 7.0 to 8.0. All the solid cultures under nitrogen showed alkalinity, while the liquid cultures were acid at all pH values. The occurrence of deamination in a medium without glucose in both strains of C. albicans showed that this organism was able to use glycine its source of both nitrogen and carbon. However, only a sparse growth was obtained in a medium lacking glucose. Strain 105 did not form filaments in such a medium, while strain 582 did so. Since more filaments were produced by the latter strain when a fresh subculture on a GGY medium was transferred to a medium without glucose, it was concluded that possibly glucose is required for both growth and filamentation. Comparative studies of the effect of a medium containing mannose with a glucose medium showed the two sugars behaved similarly with regard to fermentation and filament induction in both strains or c. albicans. Under conditions where glucose induced filamentation (e.g., with C02 or N2), mannose also induced filamentation. The decreased growth in the presence of oleic or stearic acid in a concentration of 40 micrograms per liter was attributed to the toxic effect of the fatty acids. Moreover, it was noted that the two acids had different effects on filamentation in the two strains. Oleic acid in a solid GGY medium induced hyphal formation in strain 105 only under nitrogen; without glucose, oleic acid did not bring about filamentation under any of the atmospheric conditions tested. In liquid media, oleic acid induced filamentation for strain 105 only when glucose was omitted. With strain 562, oleic acid promoted filamentation in both liquid and solid media with or without glucose, except for solid cultures incubated under nitrogen in the absence or glucose. Stearic acid did not stimulate filamentation in strain 105 under any conditions, but did increase hypha! formation in strain 582. In the presence of stearic acid, maximum filamentation occurred in aerobic cultures wnen glucose was absent. Although maximum filamentation occurred with an increase in the pH of the medium under aerobic conditions, in the presence of 75% C02, under nitrogen or in the presence of stearic acid in a medium without glucose, yeast cells were also present, indicating that this Y to f transformation was not complete. / 2999-01-01

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