High level, intrinsic resistance of Natronococcus occultus to potassium tellurite

Natronococcus occultus, a haloalkaliphilic archaeon, was examined for its resistance to potassium tellurite. Cells grown in the presence of 1 mM potassium tellurite reduced it to metallic tellurium resulting in the deposition of intracellular crystals in the cytoplasm. The minimal inhibitory concentration for potassium tellurite was 10 mM. N. occultus had an inducible tellurite reductase activity. Cell-free extracts catalyzed the enzymatic reduction of potassium tellurite in a reaction which was dependent on NADH oxidation and a reduced environment. (C) 1999 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.