Biochemical response of Rhodotorula mucilaginosa and Cladosporium herbarum isolated from aquatic environment on iron(III) ions.

The objective of the paper was to determine the influence of iron(III) ions on the growth and metabolism of fungi commonly occurring in waters: the yeast Rhodotorula mucilaginosa and filamentous fungus Cladosporium herbarum. Cells of R. mucilaginosa were shown to absorb the most iron(III) ions at a concentration of 1 mg/L iron(III) ions. Yeast cells showed a considerable increase in the content of proteins and monosaccharides, as well as biomass growth. At higher concentrations of iron(III) ions, the yeast limited the intake of iron(III) ions, and a decrease in the basic metabolites in cells was observed, as well as an increase in the secretion of such metabolites into the medium. Moreover, the activity of antioxidant enzymes increased in the fungal cells, suggesting that iron(III) ions have a toxic effect. Simultaneously, even at high concentrations of iron(III) ions in the medium, no decrease in the yeast biomass was recorded. It seems therefore that the potentially pathogenic R. mucilaginosa will likely be present in waters moderately contaminated with iron(III) ions. It can be useful as a water quality bioindicator. A considerably higher capacity for the biosorption of iron(III) ions was recorded for the filamentous fungus C. herbarum. Defensive mechanisms were observed for C. herbarum, which were manifested in a substantial increase in the content of proteins and monosaccharides, as well as an increase in the activity of antioxidant enzymes, particularly under the influence of high concentrations of iron(III) ions. Moreover, it was evidenced that in the filamentous fungus, iron(III) ions limited the extracellular secretion of metabolites. These results suggest that the fungus can actively accumulate iron(III) ions and therefore eliminate them from the aquatic environment. It can be useful in water treatment processes, which has a significant impact on water ecology.

Abundance and Species Diversity of Fungi in Rivers with Various Contaminations.

The main objective of this work was to determine the abundance and species diversity of fungi in the waters of selected rivers of Central Europe, NE Poland (Augustów Lakeland), differing in size, physical and chemical properties, and streamflow rate. The minimum abundance of fungi in the analysed rivers was recorded for a river with low concentration of organic matter (8200 CFU/mL, Czarna Hancza River), and maximum for a strongly anthropogenically polluted river (24,800 CFU/mL, Kamienny Bród River). A total of 49 fungal species were identified based on PCR ITS-RFLP and DNA sequencing methods. However, RFLP-PCR method has proved to be sufficient to determine the species of 34 fungi. The highest taxonomic diversity was determined for the waters abundant in organic matter (Piecówka and Rospuda Rivers), and the lowest for rivers poor in organic matter (Netta and Czarna Hancza Rivers). From the 49 identified species, 47% were aquatic hyphomycetes, and 18% were potentially pathogenic fungi mainly occurring in the waters of polluted rivers with increased organic matter concentrations. Moreover, a higher number of fungal taxa were recorded in fluvial waters distinguished by higher streamflow rate, and therefore, stronger water turbulence. The study results suggest that the most important factors influencing the structure of mycoplankton in rivers include pH of water, content of organic matter, degree of anthropogenic pollution, and streamflow rate.

Effect of trophic status in lakes on fungal species diversity and abundance.

The objective of this study was to determine the species diversity and abundance of fungi in relation to the hydrochemical conditions, with special emphasis on the trophic status and degree of pollution of lakes. The study was conducted in 14 lakes of the Augustów Lakeland (central Europe, NE Poland) with different hydrological conditions, type of stratification and trophic status. The analyses were performed in the hydrological year 2013. In the waters of the studied lakes, the mean abundance of fungi was 5600±3600 CFU/mL. The minimum value (800 CFU/mL) was recorded for the mesotrophic Plaskie Lake, and the maximum value (14,000 CFU/mL) was recorded for the eutrophic Pobojno Lake. A total of 38 species of fungi were identified, including 11 belonging to the aquatic hyphomycetes; up to 14 species were potentially pathogenic fungi. The potentially pathogenic fungi, particularly Candida albicans and Scopulariopsis fusca, were found in lakes with increased concentrations of chloride and sulphate(VI) ions and may thus serve as indicators of the degree of water pollution. This paper illustrates that the species diversity and abundance of fungi in limnic waters depend on the concentration of organic matter, chlorophyll a concentration, and the degree of water pollution. The results suggest that aquatic fungi can be a valuable indicator of the degree of pollution and the sanitary quality of the water.