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

Abstract

We isolated the human pathogen <em>Wallemia mellicola</em> 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 <em>Wallemia</em>, as confirmed by molecular methods (i.e., ITS1-5.8S-ITS2 nrDNA sequencing). We compared the halotolerance and chaotolerance of <em>W. mellicola</em> to other those of halotolerant fungi (<em>Talaromyces diversus</em> and <em>Aureobasidium pullulans</em>) isolated from an anchialine cave. The <em>W. mellicola</em> 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 <em>W. mellicola</em> decreased slightly. Dose–response curves for the two reference fungi <em>T. diversus</em> and <em>A. pullulans</em> revealed much lower tolerance of these fungi to increasing concentrations of NaCl. Our results indicated that <em>W. mellicola</em> is an advanced kosmotrope that is distinctly adapted to saline environments.