Shuffling of Sulfolobus genomes by autonomous and non-autonomous mobile elements

Each of the sequenced Sulfolobus genomes contains large numbers of putatively mobile elements, both IS elements (insertion sequence elements) and MITEs (miniature inverted-repeat transposable elements). There are 344 in the 3.0 Mb genome of Sulfolobus solfataricus P2 and 95 in the 2.7 Mb genome of Sulfolobus tokodaii. In the former they constitute more than 10% of the genome. Experimental data suggest that transposition of IS elements occurs frequently. Moreover, the gene order between the two organisms differs greatly, indicating that multiple rearrangements have occurred. This has also led to considerable speculation as to how the cells are viable. Recently, a third Sulfolobus genome was completed which contains no IS elements or MITEs. This enabled us to compare the gene orders of the three genomes and provide evidence for mobile element-induced rearrangements of sections of the genomes.