GENOMIC AND CDNA SEQUENCE TAGS OF THE HYPERTHERMOPHILIC ARCHAEON PYROBACULUM-AEROPHILUM

The hyperthermophilic archaeum, Pyrobaculum aerophilum, grows optimall y at 100 degrees C with a doubling time of 180 min, It is a member of the phylogenetically ancient Thermoproteales order, but differs signif icantly from all other members by its facultatively aerobic metabolism , Due to its simple cultivation requirements and its nearly 100% plati ng efficiency, it was chosen as a model organism for studying the geno me organization of hyperthermophilic ancient archaea. By a G+C content of the DNA of 52 mol%, sequence analysis was easily possible. At leas t some of the mRNA of P. aerophilum carried poly-A tails facilitating the construction of a cDNA library, 245 sequence tags of a poly-A prim ed cDNA library and 55 sequence tags from a 1-2 kb Sau3Al-fragment con taining genomic library were analyzed and the corresponding amino acid sequences compared with protein sequences from databases. Fourteen pe rcent of the cDNA and > 9% of genomic DNA sequence tags revealed signi ficant similarities to proteins in the databases. Matches were obtaine d to proteins from archaeal, bacterial and eukaryal sources. Some sequ ences showed greatest similarity to eukaryal rather than to bacterial versions of proteins, other matches were found to proteins which had p reviously only been found in eukaryotes.