Resistance to Ionizing Radiation and Oxidative Stress in Halobacterium salinarum NRC-1

Abstract

Oxidative stress results from environmental challenges that cause unchecked production of reactive oxygen species (ROS). We analyzed the cellular damage and stress response of the extremophile <italic>Halobacterium salinarum</italic> NRC-1 exposed to chemical oxidants and to ionizing radiation (IR). In contrast to IR, cellular damage from H₂O₂ and superoxide suggested that cell death resulted from interference with major metabolic pathways rather than generalized oxidative lesions. We found that essential ROS scavenging enzymes were not necessary for <italic>H. salinarum</italic> NRC-1 survival to IR. Protection assays using enzyme-free cellular extracts from <italic>H. salinarum</italic> NRC-1 demonstrated high level of protection for protein activity but not for DNA integrity against IR. Biochemical analysis of the extracts underlined an essential role in ROS scavenging for specific nucleosides and MnPO₄ complexes. These studies contributed novel findings on the critical role played by non-enzymatic systems in IR resistance in <italic>H. salinarum</italic> NRC-1.