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Intraspecies diversity of Cryptococcus laurentii (Kufferath) C.E. Skinner and Cryptococcus podzolicus (Bab’eva & Reshetova) originating from a single soil sampleRhode, Owen H. J. 12 1900 (has links)
Thesis (MSc (Microbiology))--University of Stellenbosch, 2005. / Intraspecific diversity among yeasts, including basidiomycetous yeasts has mostly
been studied from a taxonomic point of view. The heterobasidiomycetous genus Cryptococcus
is no exception and it was found to contain species that display heterogeneity both
on a genetic and physiological level, i.e. diversity among strains originating from different
geographical areas. It was stated that this diversity within yeast species is possibly caused
by intrinsic attributes of the different habitats the strains of a particular species originate
from. However, little is known about the diversity of a species within a specific habitat.
Thus, in this study intraspecific diversity among selected cryptoccoci isolated from a
single soil sample originating from pristine Fynbos vegetation , was investigated.
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Native Fusarium species from indigenous fynbos soils of the Western CapeBushula, Vuyiswa Sylvia 12 1900 (has links)
Thesis (MSc (Microbiology))--Stellenbosch University, 2008. / The genus Fusarium contains members that are phytopathogens of a number of
agricultural commodities causing severe diseases such as wilts and rots. Fusarium
species also secrete mycotoxins that have devastating effects on humans and animals.
The ability of Fusarium species to change their genetic makeup in response to their
immediate environment allows these fungi to exist in diverse habitats. Due to the
ubiquitous nature of Fusarium, it forms part of the fungal communities in both
agricultural and native soils. Fynbos is the major vegetation type of the Cape Floristic
Region (CFR), which is a region that is renowned for its high plant species diversity and
endemism. In this study, the occurrence and distribution of Fusarium species in
indigenous fynbos soils and associated plant debris is investigated. In addition, the
phylogenetic relationships between Fusarium species occurring in this particular habitat
are evaluated.
Fusarium isolates were recovered from soils and associated plant debris, and
identified based on morphological characteristics. The morphological identification of
isolates was confirmed using Polymerase Chain Reaction (PCR) based restriction
fragment length polymorphism (RFLP) analyses of the translation elongation factor 1
alpha (TEF-1α) and internal transcribed spacer (ITS) regions. Furthermore, phylogenetic
relationships between Fusarium species were based on the TEF-1α, ITS and β-tubulin
gene regions.
One-hundred-and-twenty-two (122) Fusarium strains were isolated from the
fynbos soils in the Cape Peninsula area (Western Cape). Based on both morphological
and molecular identification, the most prevalent Fusarium species in the fynbos soils were F. oxysporum Schlecht. emend. Snyd. and Hans., F. solani (Martius) Appel and
Wollenw. emend. Snyd. and Hans., F. equiseti (Corda) Sacc. and an undescribed
Fusarium species. Fusarium oxysporum was the dominant species in fynbos soils and
strains of this species displayed significant genetic variability. Some strains of both
F. oxysporum and F. solani showed close phylogenetic affinities to formae speciales
(strains pathogenic to specific plant hosts) in the phylogenetic analyses. However, no
diseased plants were observed in and within the vicinity of our sampling sites.
In the third chapter, the undescribed Fusarium strains are described as Fusarium
peninsulae prov. nom. Morphologically these strains are characterized by falcate
macroconidia produced from brown sporodochia. The macroconidia are pedicellate,
falcate to curved with hooked apical cells. Also, this fungus produces apedicellate
mesoconidia on polyphialides in the aerial mycelium and forms microconidia sparsely.
Chlamydospores are formed abundantly on aerial mycelium and submerged hyphae. All
these morphological characteristics closely relate this fungus to F. camptoceras species
complex in Fusarium section Arthrosporiella. However, phylogenetic analysis based on
the ITS sequences differentiate these strains from F. camptoceras and other related
species in section Arthrosporiella.
Considering the fact that both as phytopathogens and saprophytic fungi, Fusarium
species secrete a variety of cell wall degrading enzymes such as cellulases and xylanases.
These enzymes allow the fungi to degrade the plant cell wall components to obtain
nutrients. In Fusarium, notably endoxylanases play a role in phytopathogenesis of these
fungi. Endoxylanase enzymes from F. oxysporum f. sp. lycopersici, F. verticillioides and
F. graminearum have been characterized. In this final chapter, the use of the endoxylanase encoding gene, as a molecular marker in phylogenetic analysis was
evaluated using F. graminearum (Fg) clade species as model. Degenerated primers were
designed and the endoxylanase region amplified by PCR, cloned and sequenced. PAUPgenerated
neighbour-joining analysis of the endoxylanase (XYL) region enabled all
species to be distinguished and was as informative as the analysis generated with UTPammonia
ligase (URA), phosphate permase (PHO), reductase (RED) and trichothecene 3-
О-acetyltransferase (TRI101). Furthermore, the results of the phylogenetic analysis of
XYL showed better species resolution in comparison to the analysis of the structural
genes (TEF-1α and histone H3). Overall, the results demonstrated that phylogenetic
analysis of XYL combined with other functional genes (URA, PHO, RED and TRI101)
clearly distinguished between the Fg clade species far better than the analysis of
structural genes (TEF-1α and histone H3).
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Molecular studies on the TOL plasmid of Pseudomonas putida (arvilla) mt-2Meulien, Pierre January 1981 (has links)
No description available.
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Initiation and control of yeast sporulationCalvert, Geoffrey R. January 1983 (has links)
No description available.
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Investigation of cell cycle genes in Escherichia coliHatfull, Graham F. January 1981 (has links)
No description available.
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Aspects of the ecology of salmonellas in poultry litterMorgan-Jones, Susan C. January 1984 (has links)
No description available.
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Dysregulated T-B Lymphocyte Collaboration in Autoimmunity Poses a Barrier to Transplant ToleranceStocks, Blair Taylor 24 July 2016 (has links)
Achieving transplant tolerance in the autoimmune environment will require targeting multiple immunologic dysregulations in T-B lymphocyte collaboration that drive the aggressive anti-graft response. At a biologic level, my findings reveal the necessity of overcoming B lymphocyte mediated restriction of CD4 Treg function, failed HSC mobilization, and enhanced T cell metabolism in achieving transplant tolerance in murine models of Type 1 Diabetes (T1D) and Systemic Lupus Erythematosus (SLE). At a cellular level, my dissertation demonstrates that specific failures in CD4 and CD8 Treg mediated suppression of the effector cell response in autoimmune T1D and SLE contributes to a generalized resistance to transplant tolerance observed in these strains. Overall, identification of and surmounting the key dysregulations in T-B cell collaboration that permit loss of tolerance in autoimmunity will advance the clinical potential of transplantation as a cure for autoimmune disease.
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Analysis of a vaccine-elicited anti-H5N1 antibody and its unmutated common ancestorWinarski, Katie Lynn 29 July 2016 (has links)
Seasonal influenza remains a worldwide health concern and recently, the novel avian influenza virus, H5N1, has infected and caused disease in humans, though the virus is not currently capable of human-to-human transmission. Since 2003, 850 human cases of the novel influenza virus H5N1 have been reported with a 50% mortality rate. Recently two labs have shown, very few mutations may be necessary for efficient transmission between humans. In order to examine the immune response to H5N1, a panel of antibodies from subjects in a phase I clinical trial of an experimental H5N1 vaccine were isolated and characterized. We choose a potent and specific anti-H5N1 antibody, H5.3, for further studies in order to determine the molecular mechanism of neutralization used by H5.3 and how the antibody developed. The structure of the H5.3 Fab in complex with the H5 head domain showed H5.3 interacts with the highly conserved receptor binding site and polymorphic residues on the edges of the interface, indicating breadth and potency of the antibody conflict due to variability outside the receptor-binding site. As evidenced by the structures of the H5.3 Fab in complex with H5 respiratory droplet transmissible variants, the receptor preference of the virus may not be critically important for recognition by a receptor binding site directed antibody. The H5N1 vaccine elicited a primarily naïve antibody response, as the H5-specific antibodies had a lower number of somatic mutations than the broadly neutralizing influenza antibodies. The H5.3 somatic mutations do not stabilize the protein conformation, as it remains flexibility after affinity maturation, and do not have a large effect on increasing the affinity of H5.3 for H5. Overall, this research will contribute to influenza vaccine design.
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Investigations of bacteria on building stone and their role in stone decayLewis, F. J. January 1987 (has links)
The role of bacteria in the decay of building stone from ancient monuments was examined using the framework of Koch's postulates. This involved a stepwise approach to investigate the occurrence, nature and decay potential of bacteria on stone. Prior to investigating the occurrence of bacteria on stonework it was necessary to develop a standardised procedure of high precision for the recovery and enumeration of these bacteria. A number of different methods to remove bacteria from stone were studied including physical agitation, chemical desorption and surfactant treatment. Finally a method was adopted in which stone samples were powdered, homogenised in a dilute solution of surfactant (Tween 80) and counted on an automatic plating system. A range of growth media were used to examine three different bacterial types, namely, sulphur-oxidising, nitrifying and heterotrophic. To investigate the occurrence and distri but10n of bacteria on both sound and decayed stone extensive bacteriological surveys were conducted on stonework at two monuments, Portchester Castle and Tintern Abbey. All types of bacteria were widely distributed on both sandstone and limestone at the monuments. At each monument, significantly more sulphur-oxidising and heterotrophic bacteria were associated with severely decayed stone than undecayed stone. Electron microscopy confirmed that large populations of bacteria could be found predominantly 5-10mm below the surface of decayed stone. Approximately 200 bacteria were isolated into pure culture during the field surveys of the two monuments. All isolates were screened for decay potential using a liquid culture system involving static growth of bacteria in the presence of 1cm stone discs. From the 200 isolates, about 30 were capable of causing substantial weight loss in sandstone discs under heterotrophic conditions. Five isolates were able to cause a large weight loss using only mineral nutrients. Some isolates caused a significant weight gain in the stone discs under these conditions. Statistical analysis of the data from this decay screen indicated that weight loss of stone could be directly correlated to a decrease in pH of the medium and a release of calcium and silicate from the stone. Futher decay studies carried out on selected isolates suggested that under heterotrophic conditions the bacteria secreted quantities of organic acids in to the medium which could attack the stone. However, in the presence of an inorganic nutrient source, the generation of mineral acids may be involved. Under both conditions different stones had varying resistance to bacterial decay and this appeared to be dependent upon the level of calcite in the stone. Specific antibody techniques such as BLISA and FAT were examined and proved very useful in demonstrating the presence of certain principal decay species on samples of decayed stone.
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Isolation and survival of Campylobacter jejuni in foodsTimm, Elizabeth M. 24 November 1981 (has links)
The objective of this project was to evaluate various culturing
and isolation techniques of Campylobacter jejuni and to develop methods
to detect the organism in foods. The morphological, cultural and biochemical
characteristics of C. jejuni were studied using developed
microbiological methods. A variety of media, broths, microaerophilic
atmospheres and diluents, now available, were tested for their
applicability to detect low numbers of the organism in food samples.
Direct plating, filtration, double incubation enrichment, milk
separation enrichment and swabbing methods were used to recover C. jejuni
from seeded milk and fowl samples. As few as 16 organisms per ml of
milk could be recovered using the double incubation enrichment. Raw
milk samples from retail supermarkets and the Oregon State University
Dairy Herd were tested for the presence of C. jejuni with the double
incubation enrichment. No positive confirmation of the organism was made,
although suspect microorganisms were observed microscopically.
The survival of C. jejuni in foods and effect of sanitizers was
studied. Raw and underprocessed foods pose the greatest risks as vehicles
of Campylobacter infections. If contaminated foods are held at refrigeration
temperatures C. jejuni could survive. Properly sanitized dairy
equipment poses no apparent health problem and water should have a
residual chlorine level of greater than 5 ppm to be safe. / Graduation date: 1982
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