Iron inactivation by Sporobolomyces ruberrimus in a plant-endophyte consortium in light of plant intoxication

The endophytic Basidiomycete Sporobolomyces ruberrimus protected its host Arabidopsis arenosa against metal toxicity. Plants inoculated with the fungus yielded more biomass and exhibited significantly less stress symptoms in medium mimicking mine dump conditions (medium supplemented with excess of Fe, Zn and Cd). Aside from fine-tunning plant metal homeostasis, the fungus was capable of precipitating Fe in the medium limiting host exposition to metal toxicity. The precipitated residue was identified by AAS, FTIR, SEM-EDX, XPS, XRF and XRD techniques. The performed analyses revealed that the fungus transforms iron into amorphous (oxy)hydroxides and immobilizes them in the form of a precipitate changing Fe behavior in the substrate. Moreover, the complexation of free Fe ions by fungus could be obtained by biomolecules such as lipids, proteins, or biosynthesized redox-active molecules.