81-1 Divalent Metals Drive Changes in Fungal Manganese Oxide Formation and Metal Speciation

Abstract:

Manganese (Mn) oxides are widespread in terrestrial and aquatic environments and strongly influence trace metal mobility and speciation. In nature, Mn oxide formation is largely driven by microbial Mn(II) oxidation, producing highly reactive phyllomanganates structurally similar to birnessite. Although many environments contain multiple coexisting metals, their effects on fungal Mn oxide formation, structure, and reactivity remain poorly understood. This study examined the influence of divalent metals on Mn oxidation by two fungal strains with distinct Mn(II) oxidation responses: Curvularia lunata TC1, isolated from wastewater at the Tar Creek Superfund site (Oklahoma), and Paraconiothyrium sporulosum AP3s5JAC2a, isolated from Mn-oxide-rich pebbles in Ashumet Pond (Massachusetts). Fungal Mn oxidation experiments were conducted in AY medium containing 200 µM MnCl₂ and varying concentrations of Zn, Pb, Co, and Cd. Dissolved metal concentrations were measured by ICP-OES to quantify Mn and other trace metal removal. Synchrotron-based micro-X-ray fluorescence (µXRF) mapping and X-ray absorption spectroscopy (Mn, Zn, and Co K-edge XANES/EXAFS) were used to characterize metal distributions, oxidation states, and Mn oxide phases. Our results show, at low Zn concentration, both strains removed Zn concurrently with Mn oxidation. However, high Zn concentration strongly inhibited Mn oxide formation by C. lunata without affecting fungal growth, whereas P. sporulosum exhibited only partial inhibition. µXRF mapping showed Zn co-localized with fungal Mn oxides in C. lunata, indicating that Zn removal was primarily associated with Mn oxide formation rather than fungal uptake. XANES/EXAFS analyses will further reveal that how divalent metals will affect average Mn oxidation state and Mn oxide phase composition. These findings demonstrate that coexisting metals can regulate fungal Mn oxidation and modify Mn oxide properties, with important implications for trace metal speciation and mobility in contaminated environments.

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