TRANSFORMATION OF SELENATE AND SELENITE TO ELEMENTAL SELENIUM BY DESULFOVIBRIO-DESULFURICANS

Desulfovibrio desulfuricans (DSM 1924) can be adapted to grow in the presence of 10 mM selenate or 0.1 mM selenite. This growth occurred in media containing formate as the electron donor and either fumarate or sulfate as the electron acceptor. As determined by electron microscopy with energy-dispersive X-ray analysis, selenate and selenite were reduced to elemental selenium which accumulated inside the cells. Selenium granules resulting from selenite metabolism were cytoplasmic while granules of selenium resulting from selenate reduction appeared to be in the periplasmic region. The accumulation of red elemental selenium in the media following stationary phase resulted from cell lysis with the liberation of selenium granules. Growth did not occur with either selenate or selenite as the electron acceptor and C-13 nuclear magnetic resonance indicated that neither selenium oxyanion interfered with fumarate respiration. At 1 mu M selenate and 100 mu M selenite, reduction by D. desulfuricans was 95% and 97%, respectively. The high level of total selenate and selenite reduced indicated the suitability of D. desulfuricans for selenium detoxification.