Genomic and cDNA Sequence Tags of the Hyperthermophilic Archaeon Pyrobaculum Aerophilum

The hyperthermophilic archaeum, Pyrobaculum aerophilum, grows optimally at 100°C with a doubling time of 180 min. It is a member of the phylogenetically ancient Thermoproteales order, but differs significantly from all other members by its facultatively aerobic metabolism. Due to its simple cultivation requirements and its nearly 100% plating efficiency, it was chosen as a model organism for studying the genome organization of hyperthermophilic ancient archaea. By a G+C content of the DNA of 52 mol%, sequence analysis was easily possible. At least 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 primed cDNA library and 55 sequence tags from a 1–2 kb Sau3AI-fragment containing genomic library were analyzed and the corresponding amino acid sequences compared with protein sequences from databases. Fourteen percent of the cDNA and>9% of genomic DNA sequence tags revealed significant similarities to proteins in the databases. Matches were obtained to proteins from archaeal, bacterial and eukaryal sources. Some sequences showed greatest similarity to eukaryal rather than to bacterial versions of proteins, other matches were found to proteins which had previously only been found in eukaryotes.