The genus includes many other types of yeast important to food production. The taxonomic structure of Saccharomyces cerevisiae is as follows:
S. cerevisiae (Baker's yeast) is subjected to various environmental stresses during its propagation and industrial application. Yeast being prepared for the baker's facilities is subjected to many such stresses as freezing, frozen storage and thawing of bread dough. Besides this there are the usual stresses of fluctuations in nutrient supply, acidity levels, osmolarity and temperature and exposure to toxic substances like heavy metals and radiation (Schade et al, 2004). This often reduces the yeast's dough-leavening capabilities as well as other viable factors (Rodriguez-Vargas et al, 2002). The same is true when the yeast is applied to other food production techniques as wine-and beer-making. Thus, the negative effects of environmental stress on this species of yeast have great technological and economic impact (Rodriguez-Vargas et al, 2002). ...
Thus, the negative effects of environmental stress on this species of yeast have great technological and economic impact (Rodriguez-Vargas et al, 2002). The organisms, through special stress response factors that act at the transcriptional levels, either induce or repress a set of genes known as the general or environmental or common stress response (ESR) (Schade et al, 2004). Genome wide transcriptional profiling has revealed that 10% of the entire genome is induced or repressed in this stress response (Schade et al, 2004). The induced genes usually are involved in cellular functions such as protein folding and degradation, transport and carbohydrate metabolism while the repressed genes are associated with cell growth-related processes that are suppressed till more convenient circumstances evolve. Such related processes may be RNA metabolism, nucleotide biosynthesis, secretion and ribosomal performance (Schade et al, 2004).
Stress Regulation in S. cerevisiae
Cells of Saccharomyces cerevisiae handle a diverse range of stresses by mediation via a penta-nucleotide element called stress response element (STRE). This is quite in line with the 5-nucleotide heat shock regulatory element discussed later in the paper. STRE mediates in conjunction mainly with two transcriptional proteins Msn2p and Msn4p (Treger et al, 1998). Several genes, the induced ones that are also the ones that are instrumental in inactivating the ones that are repressed in the environmental stress response, responding to stress like heat shock, osmotic shock, post-diauxic shift growth and nitrogen starvation are induced to transcriptional activity by sequences containing STRE, especially the Msn2p/Msn4p/STRE pathway (Treger et al, 1998). There are also a few