Viability of yeast

Jarosch E, Rodel G, Schweyen RJ (1997) A soluble 12-kDa protein of the mitochondrial intermembrane space, Mrs lip, is essential for mitochondrial biogenesis and viability of yeast cells. Mol Gen Genet 255 157-165... 

It is important not to mix up vitality and viability of yeast cells. The vitality is the condition of the physiological capabilities of the cell, while viability describes if a cell is alive or dead. The viability is reported as a percentage of live cells (so live and dead cells are counted), whereas the vitality gives the status of the metabolic function (Report of Subcommittee, 2003 Van Zandycke, Simal, Gualdoni, Smart, 2003). 

So far GPI biosynthesis raises many questions as its correct regulation is crucial for viability in yeast and for embryonic development in mammals. Many steps remain unclear, also due to the fact that most of the proteins involved still have to be characterized. The same is true for the biological function of the GPI anchor apart from membrane insertion. Several suggestions have been made according to which GPI anchors are targeting lipid rafts, specific intracellular compartments, or the apical membrane of polarized epithelial cells. 

RspSp- Ubiquitination of several yeast membrane proteins, including Fur4p (Hein et al. 1995 Galan et al. 1996), have been found to be dependent on the HECT domain E3 ubiquitin-Iigase RspSp. Both Nedd-4 and Itch of nummalian cells resemble the domain structure of Rsp5p. The protein is essential for cell viability in yeast, but mutations in RspSp are suppressed by... 

As illustrated by the [PS / ] phenomenon the relative abundance of the eRFl/eRF3 complexes is an important determinant for the efficiency of translation termination. Similar effects have been obtained in depletion studies and with eRF3 and eRFl mutants that decrease their cellular concentration (Stansfield et al. 1996 Moskalenko et al. 2003 Chabelskaya et al. 2004 Salas-Marco and Bedwell 2004). Wild type yeast contains approximately 10- to 20-fold fewer termination factors compared to ribosomes (Didichenko et al. 1991 Stansfield et al. 1992). The threshold level of eRFl/eRF3 required to maintain viability is even lower. A 10-fold decrease reduces viability by only about 10% (Valouev et al. 2002) and a decrease in eRF3 of 99% does not affect viability of the cells significantly (Chabelskaya et al. 2004). As eRF3 is associated with polysomes or ribosomes, the mechanism of translation termination depends on efficient recycling (Didichenko et al. 1991 and compare below). 

TaI la, E., de Mendonca, R.L., Degand, I., Coffeau, A. and Chislain, M. (1998) Schistosoma mansoni Ca2+-ATPase SMA2 restores viability to yeast Ca2+-ATPase-deficient strains and functions in calcineurin-mediated Ca2+ tolerance. Journal of Biological Chemistry 273, 27831-27840. 

Korogodin, V.I. Malumina, T.S. (1959). Recovery of viability of irradiated yeast cells. Priroda 48, 82-85 (in Russian). 

Influence of Cryoprotectants on Viability and Heterologous Activity of Lyophilized Yeasts in Simulated Gastrointestinal Conditions To evaluate the influence of cryoprotectants on both the survival rate and CA4H activity of WRP45073A1 in simulated gastrointestinal conditions, 1010 viable freeze-dried yeasts and 200 pmol of franx-cinnamic acid were simultaneously introduced into the TIM. Yeast cells were lyophilized in the presence of the milk protein-trehalose mix, trehalose, lactose, or maltose, as previously explained (see above). The freeze-dried samples were introduced into the artificial stomach suspended in 300 mL of yeast culture medium without any storage period. The number of viable cells introduced into the TIM was determined from previously obtained survival rates (cf. Section 5.5.3.1). 

Berny, J. F., and Hennebert, G. L. (1991), Viability and stability of yeast cells and filamentous fungus spores during freeze-drying Effects of protectants and cooling rates, Mycologia, 83, 805-815. 

Abadias,M.,Benabarre,A.,Teixido,N.,Usall, J.,and Vias I. (2001), Effect of freeze-drying and protectants on viability of the biocontrol yeast Candida sake, Int. J. Food Microbiol., 65,173-182. 

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