Masters Degrees (Microbial, Biochemical and Food Biotechnology)

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Browsing Masters Degrees (Microbial, Biochemical and Food Biotechnology) by Subject "3-hydroxy oxylipins"

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    Ascospore release and oxylipin production in the yeast Dipodascopsis
    (University of the Free State, 2007-11) Goldblatt, Monique E.; Kock, J. L. F.; Van Wyk, P. W. J.; Pohl, C. H.
    The genus Dipodascopsis was extensively studied with regards to reproductive cycles as well as the presence, distribution and function of 3-OH oxylipins. Most of this research was carried out on D. uninucleata var. uninucleata (Canadian strain) as well as D. tóthii. However, little is known concerning D. uninucleata var. uninucleata isolated from South African soil, as well as D. uninucleata var. wickerhamii. Consequently, using gas chromatography-mass spectrometry, electron microscopy and confocal laser scanning microscopy, the two varieties were compared regarding their morphologies, oxylipin production, mitochondrial activity as well as life cycles and ascospore release. According to literature, the two varieties differ only in their ability to assimilate certain carbon sources. During this study, differences in ascospore size as well as differences in ascospore clustering, after release, was observed. Furthermore, differences in the type of 3-OH oxylipin produced by the two varieties, also existed. 3-OH oxylipin production was found to be associated mainly with the sexual stage and concentrated in the ascus surrounding the ascospores, in both varieties. Furthermore, increased mitochondrial activity was also observed during the sexual stage and found to be concentrated in close vicinity of the ascospores. Since mitochondria produce 3-OH oxylipins, it is suggested that the increased activity during sexual development would be to aid in the production and release of the ascospores, as well as the accumulation of these 3-OH oxylipins. In addition, acetylsalicylic acid was found to inhibit the production of 3-OH oxylipins by probably decreasing mitochondrial activity resulting in the inhibition of ascospore release.
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    Oxylipins in automictic yeast life cycles
    (University of the Free State, 2007-11) Swart, Chantel Wendy; Kock, J. L. F.; Van Wyk, P. W. J.; Pohl, C. H.
    English: 3-OH oxylipins are saturated and unsaturated oxidized fatty acids which are produced in mitochondria via incomplete b-oxidation or fatty acid synthesis type II. These compounds possibly play an important role in the sexual cycle of yeasts by assisting with ascospore liberation. Literature suggests that 3-OH oxylipins act as a lubricant during ascospore liberation, thereby ensuring efficient release of ascospores. Since the discovery of oxylipins i.e. 3-hydroxy (OH) oxylipins in the early 1990’s, these compounds were found to be distributed in various species of the fungal domain. Studies performed thus far, however, focused mainly on non-fermenting yeast species such as Ascoidea, Dipodascopsis and Eremothecium. According to various studies performed so far, 3-OH oxylipins were found to accumulate specifically in the sexual structures (asci and surrounding ascospores) of various nonfermenting yeasts. These studies also revealed that the sexual stages of nonfermenting yeasts are most susceptible to acetylsalicylic acid (ASA), a known mitochondrial (respiration and 3-OH oxylipin production) inhibitor. No information regarding oxylipin accumulation in asci or ASA-sensitivity of fermentative yeasts, however, has so far been reported. Using confocal laser scanning microscopy in combination with an oxylipin probe for 3-OH oxylipins and coupled to a fluorescing secondary antibody, the accumulation of these oxylipins was discovered in the asci of the following fermentative yeasts i.e. Pichia anomala, Pichia farinosa and Schizosaccharomyces octosporus. Interestingly, no 3-OH oxylipin accumulation was observed in the asci of the fermenting yeast Zygosaccharomyces bailii. This could be ascribed to the fact that this yeast depends more on a fermentative pathway for growth and sexual reproduction, than on mitochondrial respiration. Since 3-OH oxylipins are produced in the mitochondria, it is expected that there should be an increase in mitochondrial activity associated with these sexual structures. Using confocal laser scanning microscopy and a mitochondrial fluorescing probe (Rhodamine 123), an increase in mitochondrial activity was also observed in the asci of the fermenting yeasts tested, again with the exception of Z. bailii. Furthermore, during this study links between yeast sexual reproduction, 3-OH oxylipin accumulation/production, mitochondrial activity and oxygen requirement were established. This study revealed that fermenting yeasts are more resistant to ASA than non-fermenting yeasts when grown in liquid media. This is probably due to the fact that these yeasts can use either aerobic respiration or a fermentative pathway for growth and reproduction. This research prompted the development of a bio-assay that may find application in screening for effective antimitochondrial antifungals.
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    Oxylipins in the yeast genus Ascoidea
    (University of the Free State, 2007-05) Ncango, Desmond Mbulelo; Kock, J. L. F.; Van Wyk, P. W. J.; Pohl, C. H.; Joseph, M.
    English: Acetylsalicylic acid (ASA)-sensitive 3-hydroxy (3-OH) oxylipins were uncovered in 1991 in the yeast Dipodascopsis uninucleata. Since then, various similar oxylipins were found to be widely distributed in fungi. Interestingly, 3-OH oxylipins were reported to play a role in ascospore release from enclosed asci, where they are involved in assisting nano-scale gear-like (D. uninucleata); sliding (Dipodascus); drilling (Eremothecium sinecaudum) and piercing movements (E. ashbyi and E. coryli). In Ascoidea africana, a 3- OH 10:1 oxylipin was found to be associated with hat-shaped ascospores carried inside ellipsoidal asci. However, in this study no function was proposed for this oxylipin. Since only one species representing the genus Ascoidea was studied, it became the aim to further expand this study to also include A. corymbosa and A. rubescens. Using confocal laser scanning microscopy (CLSM) on cells stained with fluorescein-coupled 3-OH oxylipin specific antibodies, this study suggests that oxylipins are specifically associated with ascospores and not vegetative cells of A. corymbosa and A. rubescens. Using gas chromatography - mass spectrometry (GC-MS) the oxylipin, 3-OH 17:0, was identified in A. corymbosa. Here, oxylipin-coated razor sharp ascospore brims may play a role in rupturing the ascus to affect forced release of hat-shaped ascospores. Literature suggests that 3-OH oxylipins are produced by β-oxidation or fatty acid synthesis in mitochondria of yeasts. Since these oxylipins accumulate in sexual cells (asci), increased mitochondrial activity is therefore expected in these structures. Strikingly, this assumption is supported in this study. Using selective fluorescence mitochondrial staining and CLSM, evidence is provided that mitochondrial function is much higher in asci containing increased amounts of 3-OH oxylipins compared to the corresponding asexual vegetative cells. Furthermore, when ASA, a mitochondrial inhibitor, was added in increased concentrations to cultures of Ascoidea, the sexual stage was found to be more sensitive. Ascospore liberation from asci was first inhibited followed by asci formation while some vegetative growth could still be observed.