Bound Water Structure on the Surfaces of Usnea antarctica as Observed by NMR and Sorption Isotherm

Abstract

Antarctic lichens are extremophilic organisms very resistant on desiccation stress and cold [1–3]. They perform active photosynthesis below 0◦C [4, 5] and below ice nucleation of their cellular fluids [6]. An important mechanism of freezing resistance is the ice crystallite growth in extracellular spaces accompanied by simultaneous drastic decrease in hydration of intracellular spaces, thus the explanation of the molecular mechanisms of drought resistance and the mechanisms of cold resistance may be common. During acute desiccation stress lichen thallus is covered by single or less than monolayer of water [7], may hydrate from gaseous phase to the level allowing the initiation of photosynthesis [7, 8], and reversibly dehydrates below the two-dimensional percolation threshold of water [7]. Therefore, the knowledge on bound water structure (organization) may help in understanding of molecular mechanisms of the metabolic activity recovery during rehydration. ∗corresponding author; e-mail: hubert.haranczyk@uj.edu.pl