Archaeal and Bacterial Sulfur Oxygenase-Reductases: Genetic Diversity and Physiological Function

Many chemolithotrophs oxidize elemental sulfur for energy transformation under acidothermophilic conditions. Research has revealed that some of these acidothermophilic sulfur oxidizers adopt sulfur oxygenase-reductase (SOR) for catalysis of the initial reactions involved in such elemental sulfur oxidation. Archaeal SORs were firstly purified from Acidianus brierleryi and Acidianus ambivalens, and were subsequently characterized at molecular levels. Acidianus tenchongensis represents an example of an acidothermophilic archaeon from hot springs in China. Oxidation of elemental sulfur by this archaeon is initiated by SOR, and this SOR gene was cloned, expressed in Escherichia coli. Furthermore, archaeal SOR gene from Sulfolobus tokodaii was identified from genome data, and when it was cloned in E. coli, functional SOR was synthesized. More recently, bacterial SORs have been identified from a microbial community in a bioleaching reactor by a metagenomic method. Bacterial SORs have been identified also from Acidithiobacillus species and Aquifex aeolicus.