It is known that yeast cells survive enviromental stress such as desiccation and high temperature when they accumulate trehalose. On the other hand, according to our previous studies, trehalose is an excellent promoter of water structure. Here, we investigate the relationship between trehalose content in yeast cells and their survival in response to heat shock. We prepare a mutant of yeast cell (Δnthl) which lacks trehalase called NTH1. This mutant accumulates trehalose about three times more than does the parent wild type cell (WT) in both logarithmic and stationary phases. ^1H NMR, thermogravimetry and differential scanning calorimetry are used to investigate the properties of the intracellular water in the Δnthl and WT cells. In additon, we measure the survival rate of these cells in resonse to heat shock (50℃, 10min). As a result, the trehalose content is not necessarily correlated with the viability of the cells. It is, however, found that there is a good correlation between the survival rate and the T_1 relaxation time of the intracellular water proton in both types of cells. This finding suggests that structuring of intracellular water, induced by trehalose and/or heat shock proteins, is essential for high resistance to water stress in yeast cells.
