Introduction to Fungi, Third Edition

264 HEMIASCOMYCETES
organelles and cellular processes (Baba & Osumi,
1987), although many issues of yeast cytology
have remained controversial. A vegetative yeast
cell (Fig. 10.1) is densely packed with organelles,
including one nucleus, a large central
vacuole, and mitochondria. Mitochondria are
very dynamic in shape, showing a pronounced
tendency to fuse into one or a few large reticulate
organelles when the energy demand is
high, or to fragment into numerous small
promitochondria during anaerobic fermentation
or metabolic inactivity (Jensen et al., 2000;
Okamoto & Shaw, 2005).
An immense amount of literature exists on
S. cerevisiae, covering aspects of genetics and
molecular biology (Pringle et al., 1997), physiology
(see Jennings, 1995), cytology (Baba & Osumi,
1987) and biotechnology (Spencer & Spencer,
1990; Walker, 1998). We can only broach a few
selected topics here to give an impression of
Fig10.1 Saccharomyces cerevisiae. Sketch of a budding yeast cell as seen by transmission electron microscopy using material fixed by
freeze-substitution.The presence of a morphologically recognizable Golgi stack is unusual among Eumycota. Modified and redrawn
from Baba and Osumi (1987).