Dynamic, mitotic-like behavior of a bacterial protein required for accurate chromosome partitioning.

The Bacillus subtilis spo0J gene is required for accurate chromosome partitioning during growth and sporulation. We have characterized the subcellular localization of Spo0J protein by immunofluorescence and, in living cells, by use of a spo0J-gfp fusion. We show that the Spo0J protein forms discrete stable foci usually located close to the cell poles. The foci replicate in concert with the initiation of new rounds of DNA replication, after which the daughter foci migrate apart inside the cell. This migration is independent of cell length extension, and presumably serves to direct the daughter chromosomes toward opposite poles of the cell, ready for division. During sporulation, the foci move to the extreme poles of the cell, where they function to position the oriC region of the chromosome ready for polar septation. These observations provide strong evidence for the existence of a dynamic, mitotic-like apparatus responsible for chromosome partitioning in bacteria.