Toxicity Comparison Of Dimethyl Selenone And Oxyanions Selenate And Selenite Using A Selenium Resistant Strain P. Fluorescens K27 In A Minimal Medium

Rui Yu, Verena Van Fleet-Stalder and Thomas G. Chasteen

Department of Chemistry, Sam Houston State, University, Huntsville, TX 77341-2117

The mechanism of biomethylation of selenate and selenite by microorganisms has not been clearly interpreted. Proposed mechanisms suggest that dimethyl selenone [(CH3)2SeO2] is an intermediate of this biomethylation pathway and that both selenate and selenite have the same reduction pathway. Toxicity tests of (CH3)2SeO2, Na2SeO3 and Na2SeO4 were performed in minimal medium by using growth inhibition, growth rate and colony count methods with a facultative anaerobe, P. fluorescens K27. Atomic absorption and UV/VIS spectrometry were used to quantitatively analyze the selenium species in the medium supernatant and the elemental selenium precipitate produced by K27. The results suggest that selenite and selenate may have different reduction pathways.