Extreme resistance to thermally induced DNA backbone breaks in the hyperthermophilic archaeon Pyrococcus furiosus

Pyrococcus furiosus is a hyperthermophilic archaeon that grows optimally at 100 degrees C. It is not conceivable that these organisms could survive with genomic DNA that was subject to thermal destruction, yet the mechanisms protecting the genomes of this and other hyperthermophiles against such destruction are obscure. We have determined the effect of elevated temperatures up to 110 degrees C on the molecular weight of DNA in intact P. furiosus cells, compared with the effect of elevated temperatures on DNA in the mesothermophilic bacterium Escherichia coli. At 100 degrees C, DNA in P. furiosus cells is about 20 times more resistant to thermal breakage than that in E. coli cells, and six times fewer breaks were found in P. furiosus DNA after exposure to 110 degrees C for 30 min than in E. coli DNA at 95 degrees C. Our hypothesis for this remarkable stability of DNA in a hyperthermophile is that this hyperthermophile possesses DNA-binding proteins that protect against hydrolytic damage, as well as other endogenous protective mechanisms and DNA repair enzyme systems.