Letters in Applied Microbiology 1997, 25, 43–47 Barotolerance is dependent on both trehalose and heat shock protein 104 but is essentially different from thermotolerance in Saccharomyces cerevisiae H. Iwahashi, K. Obuchi, S. Fujii and Y. Komatsu National Institute of Bioscience and Human Technology, Agency of Industrial Science and Technology, Tsukuba, Ibaraki, Japan 1347/96: received 15 November 1996 and accepted 2 December 1996 H. IWAHASHI, K. OBUCHI, S. FUJII AND Y. KOMATSU. 1997. The contribution of trehalose and hsp104 to barotolerance in Saccharomyces cerevisiae has been investigated. Mutant strains, which lacked the ability to accumulate trehalose and/or hsp104, were examined for barotolerance and thermotolerance. All the mutants showed lower barotolerance and thermotolerance than their control strains. Trehalose had a greater protective effect towards high pressure than high temperature. Thus, trehalose and hsp104 are important factors for barotolerance and thermotolerance, but trehalose is more important for barotolerance than for thermotolerance. INTRODUCTION acquire the ability to survive at much higher than optimum temperature (Piper 1993 ; Craig et al. 1993). Hsps are highly Hydrostatic pressure affects almost all physiological activities conserved from bacteria to mammalian cells and are directly in living cells. Bett and Cappi (1965) studied the viscosity of involved in the biogenesis of proteins (Craig et al. 1993). In water as a function of pressure up to 10 000 kg cm -2 . They the yeast Saccharomyces cerevisiae, targeted hsp gene dis- found that relative and absolute viscosities decrease with ruption studies have shown the importance of hsp104 to pressure increases from zero to 2000 kg cm -2 at ambient thermotolerance, with other hsps only making minor con- temperature (Bett and Cappi 1965). Decreased viscosity due tributions (Sanchez and Lindquist 1990 ; Piper 1993). Tre- to high pressure results in the destruction of hydrogen bond- halose can also be a protectant when yeast cells are exposed ing, as does an increase in temperature (Bett and Cappi 1965). to temperature extremes, and a strong correlation between Thus, the effects of high temperature and high hydrostatic cellular trehalose content and thermotolerance is observed pressure may have analogous effects on living organisms. On (Hottiger et al. 1987). It was also observed that trehalose the basis of this theory, a new technology for inactivating prevents protein denaturation (Hottiger et al. 1987) and that micro-organisms which uses hydrostatic pressure instead of trehalose stabilizes membrane fluidity (Obuchi et al. 1992 ; high temperature has been developed in the food industry Iwahashi et al. 1995a). Thus, the primary function of trehalose (Hayashi 1989). However, from the biological aspect, basic in yeast is proposed not as an energy source but as a protectant research on the effect of hydrostatic pressure on living cells of the macromolecular structures (Piper 1993 ; Hottiger et or on the analogy between hydrostatic pressure and high al. 1994). Although thermotolerance is complicated and is temperature has not been carried out (Hayashi 1993). Such comprised of many factors, hsp104 and trehalose are the basic research is strongly recommended for the developing factors that have been genetically confirmed to contribute to hydrostatic pressure food industry (Hayashi 1993). thermotolerance in yeast (Sanchez and Lindquist 1990 ; De Much is known about the response and damage to living Virgilio et al. 1994). cells by high temperature. When yeast cells are exposed to a Using S. cerevisiae, we have been studying the analogy temperature slightly greater than that optimal for growth, or between hydrostatic pressure and temperature. We showed when they enter the stationary phase, the synthesis of heat that heat-shock treatment confers tolerance towards the dam- shock proteins (hsps) and trehalose is enhanced, and the cells age caused by hydrostatic pressure (barotolerance) (Komatsu et al. 1991 ; Iwahashi et al. 1991), and that the changes in Correspondence to : Dr H. Iwahashi, National Institute of Bioscience and thermotolerance and barotolerance due to the state of the Human Technology, Higashi 1-1, Tsukuba, Ibaraki 305, Japan (e-mail: iwahashi@nibh.go.jp). cells are very similar (Iwahashi et al. 1993). However, we © 1997 The Society for Applied Bacteriology