Genomic DNA shuffling in archaebacteria - Comparison of the genomes of twoPyrococcus species

The complete genomic DNA sequence of a hyperthermophilic archaebacterium, P yrococcus sp. OT3, of the length of 1,738,505 bp (Kawarabayasi et al., 1998 , DNA Res. 5, 55-57) has been compared with the nearly complete genomic DNA sequence of a related species, Pyrococcus furiosus, of the length of 1,744 ,644 bp (deposited in the Utah genome center database, http://www.genome.ut ah.edu). Approximately 60 segments of the lengths close to 20 kbp on averag e are identified to be shared by the two genomes but in different orders. A pproximately half of the segments are oriented in the opposite directions i n the two genomes. Approximately two thirds of the segments are found relat ively shifted in the two genomes only by 200 kbp or shorter. It is likely t hat translocation of DNA segments has been one of the important mechanisms to drive the evolution of archaebacterial genomes.