Fungi are ubiquitous microorganisms known for their ability to grow even in environments where living conditions are extreme. Such environments also include those with elevated salt concentrations. In this master’s thesis, we determined the presence of the same fungal genera and species in seven geographically distinct hypersaline environments. We found that representatives of four fungal genera, Alternaria, Aspergillus, Cladosporium, and Penicillium, were common to all environments and were usually represented by at least three species. In terms of geographical distribution, C. sphaerospermum stood out, as it was present in four different selected hypersaline environments. Selected genera and species were then examined for growth at different concentrations of MgCl₂ and MgSO₄ in media with reduced and standard nutrient concentrations. Fungal growth was significantly better at high MgSO₄ concentrations compared to MgCl₂. At a concentration of 2.0 M MgCl₂, only four out of a total of 76 tested isolates grew, indicating a strong inhibitory effect of this salt. In contrast, at 2.5 M MgSO₄, as many as 65 out of 76 isolates grew, with growth assessed as very good in 27 isolates. The results confirm that MgCl₂ represents a considerably more stressful environment for fungi than MgSO₄, which is consistent with the concept of chaotropicity, as MgCl₂ more strongly destabilizes cellular structures. We also found that low nutrient availability further enhances the inhibitory effect of salt, highlighting an important interaction between ionic stress and nutrient availability, due to energy requiremenstfor growth at elevated salt concentrations. Favorable nutrient conditions play a key role in the sporulation of the studied fungi, as sporulation was most dense on standard and moderately nutrient depleted media and at moderate MgSO₄ concentrations. Among all isolates, we defined four potentially polyextremophilic species (A. terreus, C. halotolerans, C. sphaerospermum ter P. chrysogenum). Due to the described growth characteristics, such isolates are potentially suitable and interesting for biotechnological processes carried out under elevated salinity or in the bioremediation of saline wastewater. For better understanding and applicability, further molecular analyses and studies investigating the combined effects of multiple environmental factors would be required.
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