SMALL FUNGI, BIG (SELENIUM) PROBLEM: TRACKING THE REMOVAL OF ELEVATED SELENATE CONCENTRATIONS BY ALTERNARIA ALTERNATA

Selenium (Se) is considered an “essential toxin”: small quantities are needed for proper function in most organisms, but large quantities can be fatal. Some species of filamentous fungi are capable of transforming aqueous selenium in the form of selenate, Se(VI), or selenite, Se(IV) into solid elemental [Se(0)] or volatile [Se(-II)] forms. Bioavailable forms of selenium include selenate and selenite, which, if accumulated, can be fatal. At present, most work in the Santelli lab has focused on Se(IV) transformations by fungi,, and little is known about how these fungi perform in extremely high selenate concentrations. To determine the amount of selenate removed from solution and rate of reduction, one metal-tolerant Ascomycete fungus, Alternaria alternata, was cultured in a defined, liquid medium. After 14 days of growth, these cultures were spiked with 10 mM selenate and the reduction of selenate to solid Se(0) or potentially volatilized Se(-II) will be tracked through time. The amount of selenium left in solution will be analyzed with an ion chromatograph, and the amount of selenium transformed into the solid phase will be determined with a solid-phase digestion followed by quantification with inductively coupled plasma - optical emission spectroscopy. By subtracting the original selenate concentration added from the aqueous and solid phase measurements, the remaining mass will be determined to infer the percent of Se volatilized by Alternaria. As the experiments are still in progress, the results will be presented in May. After this work is completed, we hope to gain a better understanding of the genetic mechanisms of fungal selenate reduction through additional ‘-omics type approaches coupled to the geochemistry results in this study. In turn, the use of these and other Ascomycete fungi may be used in the design of an effective bioremediation strategy for the treatment of Se-contaminated wastewater.