Yeast Mitochondria and the Petite Mutation

Abstract

The structure and function of yeast mitochondria and a plethora of eukaryotes have been the subject of intensive investigations for many decades. The predominant concept is that mitochondria are the “energy powerhouses of the cell”. These studies, combined with the evolutionary origin of mitochondria, have focussed on this organelle as an essential, independent, functional cell component. A mitochondrion (plural mitochondria) is a membrane-enclosed organelle found in most eukaryotic cells including yeast. Mitochondria are readily recognizable in electron micrographs of aerobically grown yeast cells as spherical or rod-shaped structures surrounded by a double membrane. They contain cristae, which are formed by the folding of the inner membrane. A number of spontaneous mutations can occur in brewing and distilling strains. The most frequently identified spontaneous mutation is the respiratory-deficient (RD) or cytoplasmic “petite” mutation. In brewing yeast strains, the RD mutation normally occurs at frequencies between 0.5 and 5.0%. The RD mutation has the following influence on brewer’s and distiller’s strains: effects on the uptake of wort sugars, effects of RD mutants on yeast flocculation and sedimentation characteristics and influence of stress conditions (e.g. centrifugation and heat) on the formation of RD mutants. Damage and subsequent dysfunction of mitochondria is an important factor in a range of human diseases because of their influence on cellular metabolism. Fundamental research on the mitochondrion structure and function of brewer’s (and baker’s) yeast strains has been extrapolated to an understanding of mammalian mitochondrial disorders.