Physiological Responses of the Hyperthermophilic Archaeon “ Pyrococcus abyssi ” to DNA Damage Caused by Ionizing Radiation

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Abstract
The mechanisms by which hyperthermophilic Archaea , such as “ Pyrococcus abyssi ” and Pyrococcus furiosus , survive high doses of ionizing gamma irradiation are not thoroughly elucidated. Following gamma-ray irradiation at 2,500 Gy, the restoration of “ P. abyssi ” chromosomes took place within chromosome fragmentation. DNA synthesis in irradiated “ P. abyssi ” cells during the DNA repair phase was inhibited in comparison to nonirradiated control cultures, suggesting that DNA damage causes a replication block in this organism. We also found evidence for transient export of damaged DNA out of irradiated “ P. abyssi ” cells prior to a restart of chromosomal DNA synthesis. Our cell fractionation assays further suggest that “ P. abyssi ” contains a highly efficient DNA repair system which is continuously ready to repair the DNA damage caused by high temperature and/or ionizing radiation.