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The development of the intestine and early establishment of commensal bacteria is important for rapid growth and enteric disease resistance of the modern broiler. Three studies measured the impact of yeast derivatives in diets of broilers. The objective of the first study was to determine if yeast products alone or in combination effected performance or gut morphology of broilers during a mild coccidia challenge. Day-old Cobb 500 chicks were placed in floor pens on litter seeded with coccidia and fed diets with or without yeast products. The objectives of the second and third studies were to 1) evaluate the effect of feeding cecal droppings collected from heavy (HW) or low weight (LW) broilers on performance and 2) to determine if dietary supplementation with yeast derivatives would effect growth and gut morphology in broilers fed the cecal droppings from HW or LW populations. Cobb 500 chicks were divided into two groups (HW or LW microflora; n=1400/group) and given access to the cecal droppings for a period of 48 hours then given 1 of 4 diets. The results from the studies showed that in a challenge setting, yeast products were not detrimental to growth. Inclusion of single yeast derivative or nucleotides was more beneficial than combination of these products for intestinal morphology. Cecal droppings from HW vs. LW birds did not have an effect on performance of birds. However, interactions of cecal dropping source and diet did affect intestinal morphology. / Master of Science

Yes / Integrating a desired DNA sequence into the yeast genomes is a widely-used genetic manipulation in the budding yeast Saccharomyces cerevisiae. The conventional integration method is to use an integrative plasmid such as pRS or YIplac series as the target DNA carrier. The nature of this method risks multiple integrations of the target DNA and the potential loss of integrated DNA during cell proliferation. In this study, we developed a novel yeast integration strategy based on the widely used CRISPR-Cas9 system and created a set of plasmids for this purpose. In this system, a plasmid bearing Cas9 and gRNA expression cassettes will induce a double-strand break (DSB) inside a biosynthesis gene such as Met15 or Lys2. Repair of the DSB will be mediated by another plasmid bearing upstream and downstream sequences of the DSB and an integration sequence in between. As a result of this repair the sequence is integrated into genome by replacing the biosynthesis gene, the disruption of which leads to a new auxotrophic genotype. The newly-generated auxotroph can serve as a traceable marker for the integration. In this study, we demonstrated that a DNA fragment up to 6.3 kb can be efficiently integrated into the Met15 or Lys2 locus using this system. This novel integration strategy can be applied to various yeasts, including natural yeast isolated from wild environments or different yeast species such as Candida albicans. / This work was supported by the Wellcome Trust [202062 to B.H. and 207127 to A.M.] This work was also supported by a SURE studentship from the University of Sheffield [325537] awarded to P.W.D

Two yeast/E.coli shuttle vector plasmids were studied in 1994, termed pIBIDB and pBP33. According to this study, each plasmid should contain at least one ADH2UAS (upstream activation sequence in the alcohol dehydrogenase 2 gene) insert. In the present study, the constructed plasmids were analysed and transformed into laboratory strain yeast. The aim of this project was to identify the orientation, quantity and quality of the insert in the selected plasmids. Methods such as restriction analysis, polymerase chained reaction (PCR), sequencing, plate assays and enzyme assays were used to identify and evaluate the novel inserts. The data presented in this thesis suggest the inserted ADH2UAS fragment did enhance the production of maltose permease and maltase when the transformants were cultivated in maltose and ethanol-glycerol medium. The results suggested that transformants containing two inserts of ADH2UAS had a greater influence on the transformants than a single insert. But the inserts within the vectors and in transformed laboratory stain yeast appeared unstable. This could be due to the method used for plasmid construction and the storage condition of the transformants / Master of Science (Hons)

Thesis (PhD)--University of Stellenbosch, 2008. / Bibliography. Also available via the Internet.

Infrared spectra of microbial cells are highly specific, fingerprint-like signatures which can be used to differentiate microbial species and strains from each other. In this study, the potential applicability of Fourier transform infrared (FTIR) spectroscopy for the classification of yeast strains in terms of their biological taxonomy, their use in the production of wine, beer, and bread, and their sensitivity to killer yeast strains was investigated. Sample preparation, spectral data preprocessing methods and spectral classification techniques were also investigated. All yeast strains were grown on a single growth medium. The FTIR spectra were baseline corrected and the second derivative spectra were computed and employed in spectral analysis. The classification accuracy was improved when the principal component spectra (calculated from the second derivative spectra) were employed rather than the second derivative spectra or raw spectra alone. Artificial neural network (ANN) with 10 units in the input layer and 12 units in the hidden layer produced a robust prediction model for the identification of yeasts. Cluster analysis was employed for the classification of yeast strains in terms of their use in the production of wine, beer, and bread and in terms of their sensitivity to killer yeast strains. The optimum region for the classification in the former case was found to be between 1300 and 800 cm-1 in the infrared spectrum whereas the optimum region for the classification of yeast strains in terms of their sensitivity was between 900 and 800 cm-1 . The results of this work demonstrated that FTIR spectroscopy could be successfully employed for the classification and identification of yeast strains with minimal sample preparation.

Thesis (Ph. D.)--Victoria University (Melbourne, Vic.), 2007. / Includes bibliographical references.

Thesis (MSc)--University of Stellenbosch, 2005. / Bibliography. Also available via the Internet.

Thesis (MSc)--University of Stellenbosch, 2006. / Bibliography. Also available via the Internet.

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