Tellurite removal by a tellurium-tolerant halophilic bacterial strain, Thermoactinomyces sp QS-2006

Among the 25 strains of moderately halophilic bacteria isolated from the hypersaline environments of Iran, a Gram-positive and moderately halophilic bacterial strain isolated from a saline soil was identified as Thermoactinomyces sp. strain QS-2006. This strain was found to tolerate high concentrations of tellurite with growth occurring up to a concentration of 500 mM Te. When the strain was cultured aerobically in medium containing 0.1-3.0 mM potassium tellurite, tellurium was removed from the soluble toxic oxyanion form under a wide range of conditions including pH (7-10), temperature (30-45A degrees C), agitation (0-220 rpm), and various concentrations of salts including NaCl , KCl , NaNO3 and NaCH3COOH (0.5-1.5 M). Maximum tellurite removal (95.5%) occurred in a medium containing 1-3% NaCl with a pH of 7.5 incubated at 35A degrees C. Transmission Electron Microscope (TEM) coupled with Energy Dispersive X-ray (EDX) showed that tellurium compounds were adsorbed to the bacterium wall and inside the cytoplasm.