An Antioxidant Defense System in Radiation-Resistant Bacterium Deinococcus geothermalis against Oxidative Stress

A radiation-resistant bacterium, Deinococcus geothermalis has various stress response mechanisms, including antioxidation. Features that maintain vitality at high radiation doses include the following: enzymatic scavengers of ROS such as catalase, SOD, and peroxidase; strain-specific DNA repair systems such as Deinococcal unique proteins; non-enzymatic responses such as manganese complexes, carotenoids, and DNA-binding proteins. This chapter summarizes the primary response mechanism by redox balance centered on the cystine transporter. It also reviews action characteristics of DNA-binding protein Dps and a putative LysR family protein, and effects on loss of function of the carotenoid biosynthesis genes by transposition of insertion sequences. Environmental adaptation and molecular evolution of radiation-resistant bacterium are also considered to explain the potentials of molecular behavior induced by oxidative stress.