The complete genome of the crenarchaeon Sulfolobus solfataricus P2

The genome of the crenarchaeon Sulfolobus solfataricus P2 contains 2,992,24 5 bp on a single chromosome and encodes 2.977 proteins and many RNAs. One-t hird of the encoded proteins have no detectable homologs in other sequenced genomes. Moreover, 40% appear to be archaeal-specific, and only 12% and 2. 3% are shared exclusively with bacteria and eukarya, respectively. The geno me shows a high level of plasticity with 200 diverse insertion sequence ele ments, many putative nonautonomous mobile elements, acid evidence of integr ase-mediated insertion events. There a re also ion g clusters of regularly spaced tandem repeats. Different transfer systems are used for the uptake o f inorganic and organic solutes, and a wealth of intracellular and extracel lular proteases, sugar, and sulfur metabolizing enzymes are encoded, as wel l as enzymes of the central metabolic pathways and motility proteins. The m ajor metabolic electron carrier is not NADH as in bacteria and eukarya but probably ferredoxin. The essential components required for DNA replication, DNA repair and recombination, the cell cycle, transcriptional initiation a nd translation, but not DNA folding, show a strong eukaryal character with many archaeal-specific features. The results illustrate major differences b etween crenarchaea and euryarchaea, especially for their DNA replication me chanism and cell cycle processes and their translational apparatus.