Polyol and water in the salt-tolerant yeastDebaryomyces hanseniias studied by1H nuclear magnetic resonance

Abstract

When cultured in media containing high concentrations of solutes, xerotolerant yeasts respond by increased accumulation of polyhydroxy alcohols (polyols) [1-4]. During growth in saline media the predominant intracellular solute is glycerol [1,2]. At high salinities the intracellular glycerol concentration may attain molar levels. Any solute that is accumulated intraceUularly to such high concentrations must be compatible with metabolic functioning and the innocuous nature of glycerol is well documented [1,4-6]. Schobert [7] proposed that polyols by means of their hydroxyl groups may participate in the intracellular structure thereby preserving the hydration of the cellular biopolymers at the reduced cellular water activities prevailing in concentrated environments. The properties of water in biological systems have frequently been investigated by NMR techniques and the general observations are linewidth broadening of the water spectrum and reduced relaxation times for the water protons. Most investigators have interpreted these data as indicating that a significant fraction of the intracellular water exhibits a reduced mobility due to interaction with cellular macromolecules [8-10]. Similarly, interactions between macromolecular surfaces and polyols may sufficiently alter the physical state of the polyols to be visualized by NMR spectroscopy. The present work is a first step in a study of the NMR properties of cell water and polyol in a xerotolerant yeast grown under salt stress. A substantial increase of linewidth and reduction in spin-lattice relaxation times (T I) were observed for intracellular water and polyol. The intensity of the polyol signal corresponded, however, only to a minor fraction of the total polyol content.