Using fluorine-induced chemiluminescence to detect organo-metalloids the headspace of phototrophic bacterial cultures amended with selenium and tellurium

Abstract

Purple nonsulfur bacteria are resistant to metalloid oxyanions. The key to this resistance seems to lie in their ability to reduce and, in some cases, methylate these toxic chemical species. Six strains of purple nonsulfur bacteria have been grown under photo-heterotrophic conditions and exposed to varied concentrations of inorganic forms of selenium, tellurium and dimethyl selenone, a proposed biological intermediate of the selenium reduction/methylation process. Selenium and tellurium metallic powders have also been added to live cultures. All of the phototrophic bacteria studied here reduce and methylate one or the other oxyanion of Se used, and three strains reduce and methylate Te° and Se°. All strains respond to the addition of dimethyl selenone by producing dimethyl selenide and/or dimethyl diselenide. In all six cases the highest amounts of volatile selenium compounds are found in cultures amended with dimethyl selenone and the lowest amounts in cultures doped with selenate. Some of the phototrophic bacteria studied here, when amended with oxyanions of both Se and Te, increase their release of dimethyl telluride (produced by their bioreduction and methylation of tellurate) in the presence of selenate. Control experiments show that this synergism is biological and not merely caused by the presence of other organo-sulfides or -selenides in culture.