DNA protection mechanisms are not involved in the radioresistance of the hyper thermophilic archaea Pyrococcus abyssi and P-furiosus

Hyperthermophilic archaea of the genus Pyrococcus are resistant to gamma ra diation, suggesting that efficient mechanisms for DNA repair exist in these organisms. To determine whether protective mechanisms might also be implic ated in this radioresistance, we have estimated the linear density of DNA d ouble-stranded breaks caused by gamma irradiation in the genomic DNA of two Pyrococcus species, using Escherichia coli and the radioresistant bacteriu m Deinococcus radiodurans as controls. The linear density of double-strande d breaks was essentially the same in all four microorganisms when irradiati on was carried under similar anaerobic conditions, indicating that no speci fic DNA protection mechanisms exist in Pyrococcus species. Using one- and t wo-dimensional gel electrophoresis we compared the protein patterns from Py rococcus abyssi and P. furiosus cells that had or had not been exposed to g amma rays. We did not detect any significant protein induction following DN A damage in either species.