FtsZ overproduction reduces the delay in Z ring assembly at midcell in the <i>noc minCD</i> double mutant.

<p>Spores of double-mutant (SU685) and the wild-type (SU558) strains, containing P<i>_spachy-ftsZ</i> integrated at <i>amyE</i>, were outgrown at 34°C in PAB with 0.05 mM IPTG or without IPTG and collected at 120 min for visualization of FtsZ using immunofluorescence microscopy. (A to D) FtsZ localization in wild-type cells germinated with IPTG at 120 min (A), in the double-mutant without IPTG at 120 min (B), and in the double-mutant with IPTG at 120 min (C and D). Images are phase-contrast (left), and FtsZ immunofluorescence (right). Open triangles point to constricting Z rings and closed triangles point to examples of Z rings. Stars denote spore coats. Scale bars are 2 µm. (E) Frequency of outgrown spores that contain Z rings for the wild-type and double-mutant strains. Z ring frequencies are shown in the presence (++FtsZ) or absence (FtsZ) of IPTG (n>400). The height of the bar shows the total frequency of cells with Z rings. Each bar is divided into percentages of cells with a single midcell Z ring (midcell only, black bar), cells with more than one Z ring (midcell+polar, dark grey bar), a single Z ring located at a future (potential) division site (PDS, light grey bar) and a single polar Z ring (polar, white bar). Average cell lengths of the whole population in the wild-type background were 2.8±0.05 (µm ± SEM) with IPTG (++FtsZ) and 2.6±0.06 without IPTG (FtsZ); and in the double-mutant background were 3.1±0.07 with IPTG (++FtsZ) and 3.3±0.07 without IPTG (FtsZ). (F and G) Z ring positioning at the first (medial) division site in the wild-type (F) and double-mutant (G) outgrown spores overproducing FtsZ. Top left-hand corner denotes the average cell length of the cells plotted (µm ± SEM).