Investigation and Partial Purification of Tellurite Reducing Enzyme from a Moderately Halophilic Bacterium Salinicoccus iranensis

Introduction: Excessive use of tellurite nowadays, has suffered the environment from the toxic effects of the oxyanion. Hence, biological treatment of polluted areas is considered as an environmentally friendly and inexpensive method. Although the toxic effects of tellurite for most microorganisms have been reported, but several species of the bacteria including the halophilic bacteria used in this project can overcome the toxicity of the oxyanion by its reduction to the elemental form. The aim of this study was to identify the mechanism (s) involved in tellurite detoxification. Materials and methods: In order to enhance and maintain enzymatic activity during purification, the test conditions and enzyme production by the strain were optimized. The optimization was done by One Factor at A Time (OFAT) method. Several factors, including: time, various percentages of inoculum, range of pH, concentration of tellurite and various salts effects were optimized. For assurance tellurite removal was examined during the experiment. The enzyme was purified by various methods, including ammonium sulphate precipitation and hydrophobic interaction column chromatography in which the Concentration of 1.4 M saturated ammonium sulphate was applied. The purity of the enzyme was assessed by SDS-PAGE during each phase. Results: The optimum conditions obtained showed that at 30 hours, 3% inoculum, pH 7.5, without tellurite and with 5% NaCl the highest enzyme activity and tellurite removal are observed. Purification of the enzyme greatly reduced the concentration of unrelated proteins and caused a concentrated band which could be one subunit of the enzyme targeted. The partially purified enzyme’s fraction was shown to have nitrate and selenite reductase activity other than tellurite reductase activity. Discussion and conclusion: This study is an approach to the identification of the halophilic microorganisms Physiology and enzymes involved in restoring tellurite. The production of the enzyme responsible for this phenomenon has been optimized and partially purified.