D.Tech. (Biomedical technology) / The majority of the South African rural black population remain is exposed to HIV/ AIDS and other chronic diseases, tuberculosis, malaria and cancer. The effect of single and combined mycotoxins on their health and particularly their immune system is unknown and remain of concern as these populations are on daily basis exposed more than one mycotoxin at once. The aim of this study was to evaluate the exposure of South African rural black populations to mycotoxins via animal products in comparison to urban populations and to assess the effect of the major mycotoxins (fumonisin B1 (FB1), aflatoxin B1 (AFB1) and ochratoxin A (OTA)) mostly present in their food on human and animals (pigs) mononuclear cells and by extrapolation, evaluate possibilities of these mycotoxins on the immune system. To achieve this, animal feed and animal products (milk, serum, and tissues) obtained from selected rural and commercial farms in selected areas of South Africa were analysed for fungal and mycotoxins contamination. It was found in this study that almost all of the samples from both areas were contaminated with the major mycotoxin producing fungal strains (Fusarium, Aspergillus and Penicillium spp.) with the most prominent among them being Aspergillus flavus (87%), A. parasiticus (43%), A. niger (69%), A. ochraceus (42%), A. candidus (23%), F. verticillioides (98%) F. graminearum (67%) and P. Verrucosum (48.9%) and in commercial samples A. flavus (98%), A. parasiticus (51%), A. ochraceus (65%), A. niger (31%), A. candidus (21%), F. verticillioides (F. moniliforme) (68%), F. graminearum (43%) and P. verrucosum (7%). While, the three main mycotoxins were also present and contaminated most samples with fumonisins (FBs) 0in rural and commercial samples at 90.6% and 93.3% respectively with respective means values of 10136.4 ppb and 1045.4 ppb. Aflatoxins (AFs) contamination was of 92.0% in rural samples and 96.2% in commercial samples with means concentrations of 168.8 ppb and 294.1 ppb respectively. While 85.4% and 83.7% of rural and commercial samples respectively were contaminated with ochratoxin A (OTA), with mean concentrations of 67.6 ppb and 89.4 ppb respectively. Zearalenone (ZEA) concentrations were of 43.6 ppb in rural samples and 62.7 ppb in commercial samples with respective contamination of 50.6% and 55.3%. In addition, a co-occurrence of fungi and mycotoxins contaminations was found in both rural and commercial samples. It was found that, 50.5% of rural and 53% of commercial samples were contaminated with all four analyzed mycotoxins. (FBs, AFs, OTA and ZEA), whereas, 81.2% and 79.5% of samples respectively from rural and commercial farms were contaminated with FBs, AFs and OTA mycotoxins simultaneously. The above-obtained results are of significance in this study as they confirm the hypothesis of fungal contamination and mycotoxin co-occurrence in South African feed and their possible combined effects on consumers.

M.Sc. / A phytotoxic protein-lipopolysaccharide complex (PLPC) was isolated from 7 day old culture filtrates of Verticillium dahliae. The complex was purified to electrophoretic homogeneily by means of acetone precipitation, gel, chromatography and preparative agarose electrophoresis with a yield of 4.5 mg PLPC per litre culture filtrate ...

Senescence, the progressive loss of growth potential culminating in death, is common among Kauaian strains of Neurospora intermedia. Senescence is initiated by the insertion of kalilo DNA into the mitochondrial DNA. Mitochondrial DNA molecules carrying the insert accumulate and death occurs when the insert is equimolar with the mitochondrial DNA. The inserted form of kalilo DNA is referred to as mtlS-kalDNA. Studies on the somatic transmission of mtlS-kalDNA in ascospore series have revealed that kalilo DNA is capable of assuming new locations within the mitochondrial DNA. It is proposed that these novel insertions originate from intramitochondrial movement and an autonomous form of kalilo DNA, mtFF-kalDNA, is predicted to be an intermediate in movement. Novel insertion of kalilo DNA appears to depend on the form of mtlS-kalDNA transmitted sexually. If a mutagenic insert is transmitted, senescence is initiated at the onset of vegetative growth of the ascospores and no novel insertions are detected. The lifespans of these ascospores are quite short, death occurring in 10 subcultures or less. Transmission of a nonmutagenic insert delays the onset of senescence until either a novel insertion or a rearrangement of the transmitted insert occurs. The lifespans of these ascospores usually exceed 10 subcultures and are variable. Information obtained from tetrad analysis has revealed that novel insertion of kalilo DNA may also be under the influence of the host genome. A senescent Kauaian strain was identified which shows some but not all characteristics of kalilo senescence. In this strain and its derivatives, the behaviour of mtlS-kalDNA is erratic and in, some cultures the characteristic mitochondrial biochemical deficiencies, normally accompanying kalilo senescence, are not observed. It is suspected that kalDNA is not responsible for senescence in this strain and its derivatives but rather some other unknown factor is affecting the normal growth patterns of these cultures. Kauaian strains were surveyed for the presence of dsRNA to determine whether kalDNA has a viral origin. Only one senescent strain contains detectable amounts of dsRNA which was not homologous with a kalDNA probe. The survey identified six nonKauaian strains which contain dsRNA and seven dsRNA species were delineated. Although the presence of dsRNA is not relevant to kalilo senescence, analysis of dsRNA in a genetically-well defined organism like Neurospora may give insight into the significance of dsRNA in fungi in general. / Medicine, Faculty of / Medical Genetics, Department of / Graduate

The present study was undertaken to examine the litter decay fungi of red cedar (Thuja piicata Donn). The fungi involved in conifer litter decay have not been examined intensively and there has been no study of red cedar litter decay. Since Thuja is often found in wet, poorly drained areas, it provided an opportunity to observe occurrence of litter decay fungi relative to slight differences in distance from a stream margin. This was determined by observing changes in the frequency of the fungi at various distances from the margin of a stream and also by observing seasonal changes in fungal populations. An ordination of the data was performed to determine if there were species associations which would characterize the relatively minor horizontal and vertical spatial changes in the sites. The sites were divided into subsites (high, middle and low with respect to the stream) and samples were taken at each subsite. Red cedar branchlets from the L and F litter layers were washed and plated on a selective medium or placed in moist chambers; all observed species were isolated and identified. Most of these were members of the Fungi Imperfecti. The frequency of occurrence of the more commonly isolated species was utilized in a Principal Components Analysis (PCA) to determine associations of subsites, layers or species. There was little distinction between the three subsites, but there was a general separation of the high subsite from the low subsite, the middle subsite showing affinities to both. The L and F layers represented a division of the litter layer which formed more distinct clusters in the ordination, especially in the Site B data. Seasonal distinction among the samples seemed to reflect the extremes of the seasons. The spring and summer samples generally grouped together, as did the fall and winter samples. Species associations reflected various combinations of the above groupings, depending on the species groups involved. Again the most distinct groups represented extremes, e.g., species prominent in dry samples, especially in the high subsite, or species prominent in moist conditions, especially in the low subsite. No single variable provided clear distinction among the various subsites, layers, seasons or species. However, the combination of all of these gave general indications as to probable fungal associations. / Science, Faculty of / Botany, Department of / Graduate

No description available.

No description available.

The work described in this thesis was undertaken to study the reasons why Azotobacter vinelandii ATCC 12837 after incubation in Burk's nitrogen-free liquid will not form as many colonies when plated on Difco Tryptic Soy Agar as when planted on Burk's nitrogen-free agar. The difference in growth of A. vinelandii on the two agars was established by performing viable cell-plate counts. The difference in growth was most apparent at 24-hours incubation of the Burk's liquid-media cultures. Phase contrast microscopic observations of Tryptic Soy media cultures of A. vinelandii disclosed the regular formation of fungoid cells at early stages of growth of the bacteria, 18 to 24 hours.

This thesis describes the isolation and structure elucidation of secondary metabolites formed in static culture from a number of endophytic Xylariaceous fungi. Four Xylaria endophytes isolated from a palm tree in Thailand were surface cultured on an aqueous malt extract-glucose medium. They all produced cytochalasin D, coriloxin, (S)-mellein and (3R,4R)-4-hydroxymellein as the main secondary metabolites suggesting that the four endophytes could be the same species. The endophytic fungus A116 produced cytochalasin D as the main secondary metabolite. Another non-endophytic fungus B315, produced cytochalasin D, (R)-mellein, a mixture of two isomers of 4-hydroxymellein and phloroglucinol. X.62, an endophytic fungus, produced 19,20-epoxycytochalasin C from the mycelium as the main secondary metabolite. The fungus Engleromyces sinensis produced engleromycin acetate as the main secondary metabolite. Fungus X. polymorpha produced (3E)-4-(3¿-acetyl-2¿,6¿-dihydroxy-5¿-methylphenyl)-2-methoxybut-3-enoic acid. / Ministry of Higher Education; Kingdom of Saudi Arabia.

A preliminary survey of caves located in the limestone belt of the Appalachian Valley of Virginia, has revealed the presence of numerous soil and water inhabiting species of aquatic Phycomycetes. A review of the literature indicates a paucity of information dealing with these organisms. The caves sampled and the methods used in this investigation are briefly described. From nineteen caves 162 soil and water samples were collected from which 33 isolates have been obtained. In addition a number of monocentric chytrids were observed, but have not been further identified. Each species isolated has been studied and described under unifungal cultural conditions. The occurrence and distribution of each species is cited and any variations in morphology or development are discussed. Questions dealing with the taxonomy and nomenclature are considered in each case. The cavernicolous environment may be regarded as a new station for each species reported herein. Three species of Pythium, P. afertile, P. irregulare, and P. nagaii, are reported for the first time as saprophytic inhabitants of the soil. / Master of Science

Studies of breeding relationships are integrated with the nomenclature of Agrocybe praecox. Type studies of potential synonyms are presented. Nomenclatorial and type studies indicate that Agrocybe molesta has been confused with A. praecox sensu lato. New field and microscopic characteristics are introduced which differentiate between A. molesta and the A. praecox group. A. molesta is redescribed to reduce confusion and a neotype is designated for this taxon. Four sibling species of Agrocybe praecox are identified and neotypes designated for A. praecox and A. gibberosa. A new species, Agrocybe montanus is described. / M.S.