The absence of Mn<sup>2+</sup> from the sporulation medium delays asymmetric Z-ring formation.

<p>Pie-chart representation of sporulating <i>B</i>. <i>subtilis</i> cells in the presence (+) and absence (-) of Mn<sup>2+</sup>. Four different types of cell (representative images in the legend) were scored: cells without any Z-ring in the cell (no ring), cells with a Z-ring in the middle of the rod (mid-cell ring), cells with two rings assembled at the cell poles (two polar rings) and cells with only one polar ring (polar ring). Non-sporulating cells are marked in blue shades, while sporulating cells are marked in orange shades. Each pie chart is the result of two independent classification experiments in which at least 290 cells were classified per condition. Actual percentages and standard deviations are included in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0174713#pone.0174713.s001" target="_blank">S1 Table</a>.</p>