Figure 3.

Model for chromosome segregation and Spo0J localization during the cell cycle. (1) Immediately after cell division, there is no FtsZ ring and a partly replicated chromosome with two discrete sites of Spo0J staining oriented toward the cell poles. (2) As replication and cell growth continue, the FtsZ ring forms and the chromosomes continue to separate. Spo0J localization becomes markedly polar, with one site on each nucleoid oriented toward the cell pole and away from the FtsZ ring at midcell. (3) DNA replication reinitiates, most of the time on both chromosomes, and progresses far enough so that the Spo0J binding region is replicated. This is visualized as two discrete sites of Spo0J staining on each of the two nucleoids. One site on each nucleoid is toward a cell pole while the other site is closer to the FtsZ ring at midcell. (4) The FtsZ ring contracts and disassembles during septation and division, generating two cells with partly replicated chromosomes and two distinct sites of Spo0J staining.