Affiliation:
1. Environmental Sciences and Biotechnology, Savannah River National Laboratory, Aiken, South Carolina
2. Electron Microscopy Center, University of South Carolina, Columbia, South Carolina
Abstract
ABSTRACT
The actinobacterium
Kineococcus radiotolerans
is highly resistant to ionizing radiation, desiccation, and oxidative stress, though the underlying biochemical mechanisms are unknown. The purpose of this study was to explore a possible linkage between the uptake of transition metals and extreme resistance to ionizing radiation and oxidative stress. The effects of six different divalent cationic metals on growth were examined in the absence of ionizing radiation. None of the metals tested were stimulatory, though cobalt was inhibitory to growth. In contrast, copper supplementation dramatically increased colony formation during chronic irradiation.
K. radiotolerans
exhibited specific uptake and intracellular accumulation of copper, compared to only a weak response to both iron and manganese supplementation. Copper accumulation sensitized cells to hydrogen peroxide. Acute-irradiation-induced DNA damage levels were similar in the copper-loaded culture and the age-synchronized no-copper control culture, though low-molecular-weight DNA was more persistent during postirradiation recovery in the Cu-loaded culture. Still, the estimated times for genome restoration differed by only 2 h between treatments. While we cannot discount the possibility that copper fulfills an unexpectedly important biochemical role in a low-radioactivity environment,
K. radiotolerans
has a high capacity for intracellular copper sequestration and presumably efficiently coordinated oxidative stress defenses and detoxification systems, which confers cross-protection from the damaging effects of ionizing radiation.
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology
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