Competition of As and other Group 15 elements for surface binding sites of an extremophilic Acidomyces acidophilus isolated from a historical tin mining site

An arsenic-resistant fungal strain, designated WKC-1, was isolated from a waste roaster pile in a historical tin mine in Cornwall, UK and successfully identified to be Acidomyces acidophilus using matrix-assisted laser desorption/ionization time-of-flight/time-of-flight tandem mass spectrometry (MALDI-TOF/TOF MS) proteomic-based biotyping approach. WKC-1 showed considerable resistance to As⁵⁺ and Sb⁵⁺ where the minimal inhibitory concentration (MIC) were 22500 and 100 mg L⁻¹, respectively, on Czapex-Dox Agar (CDA) medium; it was substantially more resistant to As⁵⁺ than the reference strains CBS 335.97 and CCF 4251. In a modified CDA medium containing 0.02 mg L⁻¹ phosphate, WKC-1 was able to remove 70.30% of As⁵⁺ (100 mg L⁻¹). Sorption experiment showed that the maximum capacity of As⁵⁺ uptake was 170.82 mg g⁻¹ dry biomass as predicted by the Langmuir model. The presence of Sb⁵⁺ reduced the As⁵⁺ uptake by nearly 40%. Based on the Fourier-transform infrared spectroscopy (FT-IR) analysis, we propose that Sb is competing with As for these sorption sites: OH, NH, CH, SO₃ and PO₄ on the fungal cell surface. To our knowledge, this is the first report on the impact of other Group 15 elements on the biosorption of As⁵⁺ in Acidomyces acidophilus.