Microarray analysis of the hyperthermophilic archaeon Pyrococcus furiosus exposed to gamma irradiation

The remarkable survival of the hyperthermophilic archaeon Pyrococcus furiosus to ionizing radiation was previously demonstrated. Using a time course study and whole-genome microarray analyses of mRNA transcript levels, the genes and regulatory pathways involved in the repair of lesions produced by ionizing irradiation (oxidative damage and DNA strand breaks) in P. furiosus were investigated. Data analyses showed that radA, encoding the archaeal homolog of the RecA/Rad51 recombinase, was moderately up regulated by irradiation and that a putative DNA-repair gene cluster was specifically induced by exposure to ionizing radiation. This novel repair system appears to be unique to thermophilic archaea and bacteria and is suspected to be involved in translesion synthesis. Genes that encode for a putative Dps-like iron-chelating protein and two membrane-bound oxidoreductases were differentially expressed following gamma irradiation, potentially in response to oxidative stress. Surprisingly, the many systems involved in oxygen detoxification and redox homeostasis appeared to be constitutively expressed. Finally, we identified several transcriptional regulators and protein kinases highly regulated in response to gamma irradiation. Keywords: time course P. furiosus cultures grown to approximately 5 · 10^6 cells/ml were chilled to 4 C and exposed to 2,500 Gy of gamma radiation using a 26,000- curie (9.6 · 1014 Bq) 60Co gamma source at the University of Maryland College Park Gamma Test Facility, at a dose rate of 73 Gy/min. Cultures were further incubated at 90 C and samples for RNA extraction were taken at 0, 20, 40, 60, 120 and 240 min after the temperature of the cultures reached 90 C.