Mycosporines in Extremophilic Fungi—Novel Complementary Osmolytes?

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Abstract
Environmental Context.The occurrence of fungi in extreme environments, particularly in hypersaline water and in subglacial ice, is much higher than was previously assumed. When glacial ice melts as a result of calving or surface ablations, these organisms are released in the Arctic soil or sea and have a yet uninvestigated impact on the environment. Knowledge of the metabolites of these extremophilic fungi is important because they could provide signature molecules in the environment, but they can also contribute nutrients to the otherwise oligotrophic polar conditions. In the present work, we examine the osmotic behaviour of fungi grown under hypersaline conditions. Fungi isolated from hypersaline waters and polar glacial ice were screened for the presence of mycosporines and mycosporine-like amino acids under non-saline and saline growth conditions. Two different mycosporines and three unidentified UV-absorbing compounds were detected by high performance liquid chromatography in fungal isolates from hypersaline waters and polar glacial ice. It was shown for the first time that the mycosporine–glutaminol–glucoside in halophilic and halotolerant black yeasts from salterns was higher on saline growth medium. This substance might act as a supplementary compatible solute in some extremophilic black yeasts exposed to saline growth conditions.