Isolation and initial characterization of the tellurite reducing moderately halophilic bacterium, Salinicoccus sp. strain QW6

Among the 49 strains of moderately halophilic bacteria isolated from the salty environments of Iran, a Gram-positive coccus designated as strain QW6 showed high capacity in the removal of toxic oxyanions of tellurium in a wide range of culture medium factors including pH (5.5-10.5), temperature (25-45 degrees C), various salts including NaCl, KCl, and Na(2)SO(4) (0.5-4M), selenooxyanions (2-10mM), and at different concentrations of potassium tellurite (0.5-1mM) under aerobic condition. Phenotypic characterization and phylogenetic analyses based on 16S rDNA sequence comparisons indicated that this strain was a member of the genus Salinicoccus. The maximum tellurite removal was exhibited in 1.5M NaCl at 35 degrees C, while the activity reduced by 53% and 47% at 25 and 45 degrees C, respectively. The optimum pH for removal activity was shown to be 7.5, with 90% and 83% reduced removal capacities at the two extreme values of 5.5 and 10, respectively. The impact of different concentrations of selenooxyanions (2-10mM) on tellurite removal by strain QW6 was evaluated. The ability of strain QW6 in the removal of tellurite in the presence of 6mM selenite increased by 25%. The concentration of toxic potassium tellurite in the supernatant of the bacterial culture medium decreased by 99% (from 0.5 to 0.005mM) after 6 days and the color of the medium changed to black due to the formation of less toxic elemental tellurium.