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Graeme M Walker

Publications and source records attributed to Graeme M Walker.

5 recordsLinked to original sources
PubMed2006

Correlating yeast cell stress physiology to changes in the cell surface morphology: atomic force microscopic studies.

Atomic Force Microscopy (AFM) has emerged as a powerful biophysical tool in biotechnology and medicine to investigate the morphological, physical, and mechanical properties of yeasts and other biological systems. However, properties such as, yeasts' response to environmental stresses, metabolic activities of pathogenic yeasts, cell-cell/cell-substrate adhesion, and cell-flocculation have rarely been investigated so far by using biophysical tools. Our recent results obtained by AFM on one strain each of Saccharomyces cerevisiae and Schizosaccharomyces pombe show a clear correlation between the physiology of environmentally stressed yeasts and the changes in their surface morphology. The future directions of the AFM related techniques in relation to yeasts are also discussed.

Ethanol↗
PubMed2006

Atomic force microscopic study of the influence of physical stresses on Saccharomyces cerevisiae and Schizosaccharomyces pombe.

Morphological changes in the cell surfaces of the budding yeast Saccharomyces cerevisiae (strain NCYC 1681), and the fission yeast Schizosaccharomyces pombe (strain DVPB 1354), in response to thermal and osmotic stresses, were investigated using an atomic force microscope. With this microscope imaging, together with measurements of culture viability and cell size, it was possible to relate topological changes of the cell surface at nanoscale with cellular stress physiology. As expected, when the yeasts were exposed to thermostress or osmostress, their viability together with the mean cell volume decreased in conjunction with the increase in thermal or osmotic shock. Nevertheless, the viability of cells stressed for up to 1 h remained relatively high. For example, viabilities were >50% and >90% for the thermostressed, and >60% and >70% for the osmostressed S. cerevisiae and Schiz. pombe, respectively. Mean cell volume measurements, and bearing and roughness analyses of atomic force microscope images of stressed yeasts indicate that Schiz. pombe may be more resistant to physical stresses than S. cerevisiae. Overall, this study has highlighted the usefulness of atomic force microscope in studies of yeast stress physiology.

Heat-Shock Response↗
PubMed2006

Atomic force microscopic study of the effects of ethanol on yeast cell surface morphology.

The detrimental effects of ethanol toxicity on the cell surface morphology of Saccharomyces cerevisiae (strain NCYC 1681) and Schizosaccharomyces pombe (strain DVPB 1354) were investigated using an atomic force microscope (AFM). In combination with culture viability and mean cell volume measurements AFM studies allowed us to relate the cell surface morphological changes, observed on nanometer lateral resolution, with the cellular stress physiology. Exposing yeasts to increasing stressful concentrations of ethanol led to decreased cell viabilities and mean cell volumes. Together with the roughness and bearing volume analyses of the AFM images, the results provided novel insight into the relative ethanol tolerance of S. cerevisiae and Sc. pombe.

Cell Membrane↗
PubMed1995

Anti-Candida activity of a novel killer toxin from the yeast Williopsis mrakii.

A screening of putative killer yeast strains showed that spore-forming ascomycetous yeasts of the genera Pichia and Williopsis displayed the broadest range of activity against sensitive strains of Candida spp. and Saccharomyces cerevisiae. Williopsis mrakii (NCYC 500) showed extensive anti-Candida activity against strains isolated from clinical specimens. W. mrakii killer factor was produced in minimal media as a function of growth and its activity reached constant levels as cells entered stationary phase. The proteinaceous killer toxin was found to be unstable without a specific range of temperature and pH (above 30 degrees C and pH 4.0), and further analysis showed that the active toxin molecule was an acidic polypeptide with a relative molecular mass between 1.8-5.0 kDa. At critical concentrations the killer factor exerted a greater effect on stationary phase cells of Candida than cells from an exponential phase of growth. At low concentrations, the killer toxin produced a fungistatic effect on sensitive yeasts but at higher concentrations there was evidence to suggest that membrane damage accounted for the zymocidal effects of the killer factor. the cidal nature of the toxin was reflected in a rapid decrease in sensitive cell viability. Findings presented suggest that W. mrakii killer toxin has potential as a novel antimycotic agent in combatting medically important strains of Candida.

Antifungal Agents↗