Responses ofSaccharomyces cerevisiae to thermal stress

Abstract

We studied the mechanisms involved in heat gradient-induced thermotolerance of Saccharomyces cerevisiae. Yeasts were slowly heated in a nutrient medium from 25 to 50 degrees C at 0.5 degrees C/min or immediately heat shocked at 50 degrees C, and both sets of cultures were maintained at this temperature for 1 h. Cells that had been slowly heated showed a 50-fold higher survival rate than the rapidly heated cells. Such thermotolerance was found not to be related to protein synthesis. Indeed Hsp104 a known protein involved in yeast thermal resistance induced by a preconditioning mild heat treatment, was not synthesized and cycloheximide addition, a protein synthesis inhibitor, did not affect the thermoprotective effect. Moreover, a rapid cooling from 50 to 25 degrees C applied immediately after the heat slope treatment inhibited the mechanisms involved in thermotolerance. Such observations lead us to conclude that heat gradient-induced thermal resistance is not directly linked to mechanisms involving intracellular molecules synthesis or activity such as proteins (Hsps, enzymes) or osmolytes (trehalose). Other factors such as plasma membrane phospholipid denaturation could be involved in this phenomenon.

Assessing yeast viability from cell size measurements?

“…Different authors have already showed the relevance of cell size measurements to study the response of yeast cells submitted to different stress: osmotic stress (Marechal and Gervais, 1994;Camisard et al, 2002;Pratt and Bryce, 2003), heat stress (Guyot et al, 2005), oxidative stress (Belo et al, 2005), hyperbaric stress (Coelho et al, 2004) and ethanol stress (Pratt and Bryce, 2003;Canetta et al, 2006). The present results showed that whatever the studied stress, cell death (as detected by PI staining) went along with an immediate cell shrinking.…”

“…Several authors have studied the response of a yeast population exposed to a physicochemical stress with a morphological approach (De Maranon et al, 1996;Adya et al, 2005;Belo et al, 2005;Guyot et al, 2005). Different methods have been proposed using more or less automated image processing, either off-line (Pons et al, 1993) or at-line (Berner and Gervais, 1994) and online (Bittner et al, 1998;Camisard et al, 2002;Joeris et al, 2002).…”

Osmo-, thermo- and ethanol- tolerances of Saccharomyces cerevisiae S1

“…At the beginning of fermentation, cells are subjected to high substrate concentration and as the ethanol level increases, both the substrate and product causes stress to the organism (14). During fermentation, heat is liberated due to exothermic reactions and if the environmental temperature is already high, the fermenter temperature tends to increase (1).…”

Use of response surface methodology to optimise environmental stress conditions on Penicillium glabrum, a food spoilage mould

“…It is known that elevated temperature can affect: (i) the structure of proteins, possibly modifying their biological activity and overall cellular functioning; (ii) the biosynthesis of a large number of ubiquitous proteins which decrease or are completely stopped (Plesofsky-Vig & Brambl 1987;Curle & Kapoor 1988); and (iii) plasma membrane fluidity (Beney & Gervais 2001). As described in S. cerevisiae, an increase of plasma membrane permeability can affect cellular integrity and metabolism (Guyot et al 2005).…”