Figure 2.

Analysis of Spo0J localization. Shaded blobs represent the nucleoids and black balls indicate Spo0J on the nucleoid. (A) Localization of Spo0J during vegetative growth (as in Fig. 1 A–J). In several different experiments, 75–90% of the cells had discrete sites of Spo0J staining and ≈60% of all cells had visible, well-defined FtsZ rings. The proportion of cells with discrete sites of Spo0J staining was similar in cells with and without FtsZ rings, indicating that the appearance of sites of Spo0J staining does not correlate with the presence or absence of FtsZ rings. (Classes 1 and 2) Cells with no FtsZ ring and a single nucleoid body with either a single site (class 1) or two sites (class 2) of Spo0J staining. (Classes 3 and 4) Cells with an FtsZ ring (indicated by the oval at midcell) and two nucleoid bodies, one on each side of the FtsZ ring and a single site (class 3) or two sites (class 4) of Spo0J staining per nucleoid. Of the 117 cells with an FtsZ ring and two sites of Spo0J per nucleoid, 7 cells actually had two sites on one nucleoid and only one site on the other nucleoid. We infer that in a small fraction of cells, reinitiation of replication or subsequent elongation did not occur synchronously on each chromosome. Alternatively, there were two Spo0J sites, but we could not resolve them. If these cells divide before the appearance of the second site of Spo0J staining, they would produce a few cells with a single nucleoid with a single site of Spo0J staining (class 1). For simplicity, cells in all four classes are drawn the same length. In fact, there is a rough correlation with the indicated class and cell length, with class 4 cells the longest and class 1 and 2 cells the shortest (see Fig. 1). (B) Localization of Spo0J during stage I of sporulation. (C) Localization of Spo0J during stage II of sporulation.