Halotolerance (ionic NaCl) and chaotolerance (ionic MgCl2) of the human pathogen Wallemia mellicola isolated, for the first time, from indoor air in Poland

We isolated the human pathogen Wallemia mellicola from the class Wallemiomycetes for the first time in Poland. The fungus was isolated from indoor dust in Cracow. The strain belonged to the genus Wallemia, as confirmed by molecular methods (i.e., ITS1-5.8S-ITS2 nrDNA sequencing). We compared the halotolerance and chaotolerance of W. mellicola to other those of halotolerant fungi (Talaromyces diversus and Aureobasidium pullulans) isolated from an anchialine cave. The W. mellicola strain tolerated up to 20% NaCl and up to 15% MgCl2. As the concentration of NaCl in the culture medium increased, the colony diameter of W. mellicola decreased slightly. Dose–response curves for the two reference fungi T. diversus and A. pullulans revealed much lower tolerance of these fungi to increasing concentrations of NaCl. Our results indicated that W. mellicola is an advanced kosmotrope that is distinctly adapted to saline environments.