Coordination of chromosome segregation and cell division in the archaeon Sulfolobus acidocaldarius

Despite its fundamental importance for the propagation of all cellular life, very little is known about the molecular basis of chromosome segregation in archaea. This is a particularly intriguing issue in members of the genus Sulfolobus which encode homologs of a "bacterial-like" candidate segregation machinery, termed SegAB, related to the bacterial ParA-based systems, yet rely on a "eukaryotic-like" ESCRT machinery for cell division. While investigating the temporal dynamics of Sulfolobus chromosome architecture, we uncovered conformational changes at the candidate segregation locus. Loss of the Seg system results in altered nucleoid morphology and induction of a DNA damage response. Significantly, loss of the Seg system also leads to precocious assembly of the key cell division protein CdvA. Finally, we observe interactions between SegA and CdvA, indicating dual roles for the Seg system in effecting chromosome segregation and defining the positioning of the cell division apparatus.