Archaea lack a membrane-bounded nucleus and, in most species, the genome is organized into a single circular chromosome. Thus, the cellular and genomic organization is similar to that of bacteria, while most archaeal information processing genes are homologous to those of eukaryotes. This brings up questions regarding the extent with which the regulatory and molecular features of the cell cycle may be determined by intracellular organization (bacterial-like), by gene and protein properties (eukaryotic-like), and by the evolutionary history of the archaeal lineage (unique). These questions will be discussed in light of our work on the cell cycle of different archaea, with the main focus on the genus Sulfolobus.
