Microcalorimetric monitoring of growth of Saccharomyces cerevisiae: osmotolerance in relation to physiological state

Abstract

The importance of the physiological state of a culture of Saccharomyces cerevisiae for tolerance to sudden osmotic dehydration was studied, and it was investigated whether specific osmotolerance factors were demonstrable. The microcalorimeter was used to monitor growth, and different physiological states of the culture were selected and their osmotolerance was tested. In addition to cells in the stationary phase, cells from the transition phase between respirofermentative and respiratory catabolism were osmotolerant. S. cerevisiae exhibited ever-changing metabolism during batch growth on either glucose or ethanol as the carbon source. Instantaneous heat production per biomass formation (dQ/dX) and specific activity of sn-glycerol 3-phosphate dehydrogenase (GPDH) (EC 1.1.1.8) were shown to differ for different physiological states. Neither high respiratory activity nor low total cellular activity, nor factors involved in osmoregulation, i.e., intracellular glycerol or activity of GPDH, correlated with the osmotolerant phenotype.

Global changes in protein synthesis during adaptation of the yeast Saccharomyces cerevisiae to 0.7 M NaCl

“…Growth was slightly retarded in the saline medium, and the generation time for fully adapted cells during saline growth was estimated as 3.3 h. The proportion of budded cells in the exponentially growing culture was around 75% at the time of transfer from basal medium, and no significant change in the size of the budding fraction was observed during the initial hour of osmotic adaptation (data not shown). Exponentially growing cells in basal medium exhibited a fermentative capacity of 27 Ϯ 2 (SD) mol of CO 2 per mg (dry weight) per h, a rate consistent with earlier obtained results for cells with a high level of fermentative activity (8). A slight drop in the activity level to 20 Ϯ 1 (SD) mol of CO 2 per mg (dry weight) per h was recorded during the first 20 min, indicating a minor impact on fermentation during the initial period of adaptation.…”

“…Warburg measurements to record CO 2 production were performed essentially as described earlier (8). The fraction of budding cells was estimated by snapfreezing samples in liquid nitrogen at intervals during the adaptation period, for later microscopic observation.…”

“…In addition, blockage of protein synthesis inhibits the acquisition of the tolerant state, indicating a protein-mediated phenotype. Furthermore, increased activity of the glycerol-producing enzyme GPD has been shown not to be the single tolerance determinant (8). Thus, the aim of this study was twofold: (i) to study the cellular response in terms of quantitative and temporal changes in the rate of synthesis of proteins during adaptation to osmotic stress and (ii) to identify proteins potentially responsible for the cellular state of tolerance to a sudden osmotic shock.…”

The Osmotic Hypersensitivity of the Yeast Saccharomyces cerevisiae is Strain and Growth Media Dependent: Quantitative Aspects of the Phenomenon

“…Strain Y41, however, displayed a somewhat less striking response, and growth on galactose or ethanol only slightly affected the hypersensitivity ( Figure 5B). This result is consistent with data obtained in an earlier study on this strain, where post-diauxic growth on ethanol only marginally influenced osmotic hypersensitivity (Blomberg et al, 1988). Glycerol was the carbon source that exhibited the greatest impact on osmotic hypersensitivity in strain Y41; the LD 10 value increased by 400 m.…”

“…Analysis of glycerol was carried out by enzymatic methods, as described previously (Blomberg et al, 1988).…”