Melanized halophilic fungi are eukaryotic members of microbial communities in hypersaline waters of solar salterns

Until recently, it was believed that microbial communities at high salinities are dominated exclusively by Archaea and Bacteria and one eukaryotic species, the alga Dunaliella salina. Recently, it became evident that melanized fungi, so far described only in the crystallization pond of Adriatic salterns within the season of salt production, can be considered as a new group of eukaryotic halophiles. They were represented by black, yeast-like hyphomycetes: Hortaea wemeckii, Phaeotheca triangularis, Trimmatostroma safinum, Aureobasidium pullulans, together with phylogenetically closely related Cladosporium species. In the present study, the distribution of the melanized fungal population in five different evaporating ponds in the Adriatic salterns [covering the entire salinity range (3-30% NaCl)] was followed throughout the year. It appeared in three peaks, at 5-8%, 10-20% and 18-25% NaCl, which correlated primarily with high nitrogen values. At the highest environmental salinities, melanized fungi represented 85-100% of the total isolated mycobiota, but with lowering salinities they were partially replaced by non-melanized fungi and, at the end of the season, with NaCl concentrations below 5%, they were detected only occasionally. Melanized fungi have been isolated from hypersaline waters on three continents, indicating that they are present globally in hypersaline waters of man-made salterns.