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چکیده
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Tellurite is a rare-earth oxyanions that can be found in high concentrations in land and water near sites of waste discharge of industrial manufacturing processes. There has been growing concern about tellurite toxicity in the natural environment (1). Tellurite is highly toxic to mammalian cells and microorganisms at concentrations as low as 1 µgml-1. Removal and bioreduction of tellurite (TeO3-2) by bacteria has been studied in previous works, but little is known about uptake of this oxyanion in halophilic microorganisms (2). In the current study, high-level tellurite resistant moderately halophilic coccus was isolated and tellurite removal from the growth medium and effect of salinity on this removal was determined. This is the first report describing uptake of tellurite by moderately halophilc bacteria. According to Bergeys Manual of Systematic bacteriology and the physiological and biochemical tests formed, it was tentatively named as Salinicoccus sp. strain QW6. The quantitative determination of tellurite was done using the reagent diethyldithiocarbamate (DDTC) as described by Turner et al. (3). The influence of various concentration of NaCl, KCl and Na2SeO4 (0.5, 1, 1.5, 2, 2.5, 3 and 3.5 M) on tellurite removal was determined. The maximum removal of tellurite was showed in the presence of 1.5 M NaCl. The isolate was capable of removal tellurite in the presence of Na2SO4 and KCl. By highering the NaCl concentration from 0.5 M to 1.5 M, tellurite concentration in the supernatant of culture decreased to below 0.1 mM within 3 days when 0.5 mM of tellurite was added to the growth medium. At the same conditions, enhancing the KCl concentrations from 0.5 to 1 M, tellurite concentration decreased to below 0.2 mM in the supernatant of medium, while increasing the Na2SO4 concentration from 0.5 to 2 M decreased tellurite removal by this strain and maximum removal tellurite was shown in 0.5 M Na2SO4 (0.14 mM). The color of the cell suspension turned black, due to the for
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