Distribution of major and trace elements in the bolete mushroom Suillus luteus and the bioavailability of rare earth elements

Abstract

Fungi are eukaryotic organisms within the kingdom Fungi. They are classified as macrofungi when they produce, usually above-ground, fruit bodies which are often simply referred to as “mushrooms”. Since many species are edible, numerous studies discuss major elements and the accumulation of toxic and radioactive elements. Rare earth elements are economically important metals which are increasingly used for high-technology applications like renewable energies and state-of-the-art electronic devices. Although the significantly increasing anthropogenic input into the environment may affect living organisms, available data on the concentration, distribution and uptake of rare earth elements and yttrium (REY) by fungi are limited and often ambiguous.Here, we present trace element and REY concentrations for the fungus species Suillus luteus and the distribution of major and trace elements between the different compartments of individual fruit bodies separated into cuticle, flesh of cap, tubes & pores, and stipe. Our results show that P, K, Zn, Rb and Cs are the only elements enriched in fruit bodies relative to soil. All elements are unevenly distributed within the fruit bodies and the parts comprising the cap generally contain higher concentrations of trace elements than the stipes. The total REY concentrations in the individual mushroom parts range from 13.1 μg kg−1 in dry matter (DM) to 72.6 μg kg−1 DM, whereas concentrations in the whole mushrooms are 13.4 to 74.2 μg kg−1 DM. The highest of the generally rather low REY concentrations are shown by the cuticles. All mushroom parts have the same rather flat shale-normalized REY patterns very similar to those of ambient soil, but show positive Y anomalies in all and positive La anomalies in most samples. The cuticles and the whole fruit bodies show a slight depletion of light relative to heavy REY (LREY and HREY, resp.), while flesh, tubes & pores and the stipe exhibit no or a small enrichment of LREY relative to HREY. The fractionation between LREY and MREY is only small, whereas the fractionation between MREY and HREY is more pronounced. Soil leaching experiments with the siderophore desferrioxamine B suggest that although Suillus luteus produces siderophores which are important ligands for REY complexation, such hydroxamate siderophores do not significantly affect REY mobilization and transport to the mushrooms. The close similarity of the REY distribution in the fruit bodies of Suillus luteus and ambient soil and the lack of significant fractionation suggest that fungi may have the potential to be developed into bioarchives for tracers used in geochemical exploration.