Studies on the yeasts Saccharomyces cerevisiae and Saccharomycopsis lipolytica
Skipton, Michael D.
The elucidation of the biochemistry of oxidative phosphorylation is a problem capable of no easy solution. Combined genetic and biochemical investigation is a more recent approach in this direction.\ud \ud Mutants of the yeast Saccharomyces cerevisiae resistant to inhibitors or to uncouplers of oxidative phosphorylation have been isolated in this Laboratory. In part, this Thesis is an investigation into their further properties. Growth characteristics of selected strains are described together with differences in their cytochrome profiles. The phosphorylation capabilities of isolated mitochondria have also been assayed. The effects of the various agents on cellular and mitochondrial respiration are measured.\ud \ud Resistance to uncouplers may be manifest at the mitochondrial level; but in any case this does not lead to a more efficient energy conservation process.\ud \ud The metabolism of hydrocarbons by microorganisms is now becoming of greater importance. Saccharomycopsis lipolytica is a yeast which is able to grow on n-alkanes of medium chain length. Growth curves and cytochrome contents of S. lipolytica cultured on various substrates, Including n-alkanes, are compared. Isolated mitochondria are also examined.\ud \ud Biological membranes contain characteristic fatty acids. The fatty acid profiles of cells and mitochondria of S. cerevisiae and of S. lipolytica after growth on various substrates are illustrated. The kinetics of membrane bound respiratory enzymes are affected by these lipid constitutents as evidenced by Arrhenius plots.