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

A Cudowski,A Pietryczuk

doi:10.1038/s41598-019-56088-5

Abstract

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.

Highlights

The occurrence of microfungi has been so far recorded in all types of aquatic ecosystems in the world
The objective of the paper was to determine the effect of iron(III) ions on the growth and metabolism of potentially pathogenic fungi commonly occurring in waters: the yeast R. mucilaginosa and filamentous fungus C. herbarum
The filamentous fungus C. herbarum was much more sensitive to the effect of high concentrations of iron(III) ions than the yeast R. mucilaginosa. It seems that iron is not a microelement necessary for the growth and functioning of C. herbarum because no significant biomass growth of the fungus was observed under the influence of ions of the metal in contrast to yeast

Summary

Introduction

The occurrence of microfungi has been so far recorded in all types of aquatic ecosystems in the world. Species of pathogenic or potentially pathogenic fungi that are most frequently isolated from aquatic ecosystems belong to the following genera: Candida sp., Cryptococcus sp., Rhodotorula sp., Aspergillus sp., Trichophyton sp., and Cladosporium sp.[2] An important role of fungi involves their capacity for the biotransformation of xenobiotics[3] and heavy metals[4] supplied to the aquatic environment. They can contribute to reducing the effects of anthropogenic stress and improving water quality. Insight into such correlations will permit finding the answer to the following question: do iron(III) ions activate or limit the development of these pathogens in surface waters, or perhaps are the studied fungal species able to remove iron(III) ions from the environment? Answering these questions will constitute an important step towards including the species in the group of bioindicators for determining the sanitary state of waters

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