Independent replication of the plasmids pRN1 and pRN2 in the archaeon Sulfolobus islandicus.

The 5.4-kb and 6.9-kb plasmids pRN1 and pRN2 from the crenarchaeon Sulfolobus islandicus are name-giving for a small family of archaeal plasmids. Both plasmids have hitherto been supposed to be dependent on each other because they are always found together in their natural host. Here we demonstrate that each of the plasmids can stably propagate and replicate on its own independent of the other plasmid. Moreover, we could show that in vivo the plasmids bear tightly bound proteins.