Specific jarosite biomineralization by P urpureocillium lilacinum , an acidophilic fungi isolated from R ío T into

R ío T into ( H uelva, southwestern S pain) is an extreme environment with a remarkably constant acidic pH and a high concentration of heavy metals, conditions generated by the metabolic activity of chemolithotrophic microorganisms thriving in the rich complex sulfides of the I berian P yrite B elt ( IPB ). Fungal strains isolated from the T into basin were characterized morphologically and phylogenetically. The strain identified as P urpureocillium lilacinum specifically induced the formation of a yellow‐ocher precipitate, identified as hydronium‐jarosite, an iron sulfate mineral which appears in abundance on the banks of Río Tinto. The biomineral was characterized by X ‐ray diffraction ( XRD ) and its formation was observed with high‐resolution transmission electron microscopy ( TEM ) and scanning electron microscopy ( SEM ) coupled to energy‐dispersive X ‐ray spectroscopy ( EDX ) microanalysis. Jarosite began to nucleate on the fungal cell wall, associated to the EPS , due to a local increase in the Fe 3+ / Fe 2+ ratio which generated supersaturation. Its formation has been also observed in non‐viable cells, although with much less efficiency. The occurrence of P . lilacinum in an ecosystem with high concentrations of ferric iron and sulfates such as R ío T into suggests that it could participate in the process of jarosite precipitation, helping to shape and control the geochemical properties of this environment.