Biomedical Engineering Reference
In-Depth Information
to using a microorganism to identify potential human drug targets, use of the well-
characterized
Saccharomyces cerevisiae
yeast showed striking advantages in several
applications.
14.1.2
Saccharomyces cerevisiae
as a Model
14.1.2.1 S. cerevisiae Biology
Saccharomyces cerevisiae
is the world's most pop-
ular yeast, being instrumental in baking and brewing since ancient times. During at
least the past 9000 years, humans have taken advantage of the properties of
S. cere-
visiae
for wine, bread, and beer production. The first wine fermentation observed
dates back 9000 years, based on the discovery of residues of ancient
S. cere-
visiae
DNA in Chinese pots [11] and in jars at the King Scorpion tomb in Abydos
(3150 B.C.) [12]. After a thousand years of appreciation of the products of its fer-
mentations,
S. cerevisiae
has gained increasing interest among scientists. Thanks
to several features that make it an easy-to-handle organism, this budding yeast has
made possible the discovery and deepening of fundamental biological processes often
shared with higher eukaryotic cells.
The
S. cerevisiae
cell has a mean diameter of 8 to 10
m and it is covered by a
cell wall composed by a small fraction of chitin, a polymer of the glucose derivative
N
-acetyl glucosamine. In addition to chitin, the wall is composed of other molecules
that constitute a cementing matrix: polysaccharides (80 to 90%), proteins, lipids,
polyphosphates, and inorganic ions.
S. cerevisiae
cells exist in two forms: haploid
(a single copy of each one of the 16 chromosomes) or diploid (two copies of each
chromosome). Haploid cells in turn exist in two forms, called
mating types
:aor
. The
budding yeast can multiply by both sexual and asexual reproduction (Figure 14.1).
The mating of two haploid cells generates a diploid cell, which in adverse conditions
can sporulate. Sporulation, driven by meiosis, is a process through which the yeast
FIGURE 14.1
Cell cycle of
Saccharomyces cerevisiae.
