fungal biogeochemistry
It has been estimated that 1.5 million species of fungi exist in the environment, yet less than 8% of theses species have been described. Fungi greatly impact the fate and transport of metals through both passive (e.g., acidification, metabolites) and active (e.g., redox, assimilation) processes. Furthermore, it has been widely observed that fungi may serve as reactive templates for mineral nucleation and precipitation. Fungi can mediate the reduction (e.g., Se, Te, Hg) and oxidation (e.g., Fe, Mn) of metals, inducing biomineralization in some cases. Although fungal mediated processes are universally observed and their impact on geological processes indisputable, little is known about the fungal species involved in the biogeochemical cycles of metals, the mechanisms that are employed, and their impact on the mineralogical framework and reactivity of soils and sediments. Our research seeks to define the importance of fungi in the oxidation of metals within surface environments, including those impacted by acidic mine waters.
We have recently found that oxidation and subsequent immobilization of Mn in acid mine drainage (AMD) environments is mediated by an abundant fungal community that completely and rapidly oxidizes Mn(II) to Mn(III/IV) oxides. The objectives of our current research are to define (1) the phylogenetic and ecological diversity of Mn(II)-oxidizing fungi in AMD systems, (2) the fungal mediated (a)biotic Mn(II) oxidative pathways, (3) the role of biological clocks on Mn(II) oxidation, and (4) the Mn(II) oxidation rates and solid-phase. This research involves a multidisciplinary approach coupling molecular biology, enzymatic and chemical assays, microscopy and sophisticated micro-spectroscopic techniques to probe microbe-metal-mineral interactions at the molecular and bulk scale. This research will fill major gaps in our knowledge of the biological and geochemical controls of the Mn cycle – information that is of crucial importance for improving in situ bioremediation (e.g. AMD treatment), stimulating primary productivity, and predicting the fate and transport of contaminants in the environment.