EFFECT OF ORGANIC CARBON SOURCE AND CONCENTRATION ON RADIAL GROWTH OF FILAMENTOUS FUNGI IN THE PRESENCE AND ABSENCE OF SELENITE

Selenium (Se) is an “essential toxin”— it is required by most organisms for growth, but at high concentrations, Se can become toxic. Elevated environmental Se concentrations are caused by waste produced by a variety of anthropogenic activities such as mining, agricultural, and industrial manufacturing operations. Selenate (Se(VI)) and selenite (Se(IV)) are toxic, so it is preferential to find a way to reduce them to solid Se(0) or volatile Se(-II) forms which are far less bioavailable. In previous research, it has been proven that environmental microorganisms such as fungi are capable of transforming Se species through a range of processes including reduction. Therefore, Se-transforming fungi have potential to transform soluble Se oxyanions to insoluble and less biologically available forms in contaminated water and could be a useful method for remediation of Se contaminated environments. Previous experiments in the Santelli Lab utilized liquid media containing yeast extract as a carbon source. The problem with using yeast extract as a carbon source is that the chemical composition cannot be specifically verified, and the conditions of an experiment cannot be recreated consistently. The purpose of this study was to determine how the source and concentration of organic carbon affect radial growth of metal-tolerant fungi, both in the presence and absence of selenite. Specifically, this research examined how two organic carbon sources, acetate and glucose, provided at four different concentrations influenced the radial growth of six metal-tolerant species of fungi. This same experiment was repeated, but with the added presence of selenite as a contaminant of concern. We find that glucose allowed more growth than acetate in the presence of Se and the highest organic carbon concentrations allowed the most growth in the presence of Se. This research will ultimately help enhance Se bioremediation strategies and improve water and soil health of environments impacted by Se.