Switching may be triggered by cell-volume changes.

<p>(A) Snapshots from time-lapse fluorescence microscopy: (left) lacY-gfp of <i>E. coli</i> in yellow [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0121681#pone.0121681.ref043" target="_blank">43</a>], (middle) PcomK-cfp of <i>B. subtilis</i> in purple, and (right) PcomG-cfp of <i>B. subtilis</i> in red [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0121681#pone.0121681.ref002" target="_blank">2</a>] with time in units of cell-cycle time <i>T</i>_<i>c</i>. (B) Total fluorescence intensities inside cell contours normalized to the maximal observed total intensity of a cell (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0121681#sec010" target="_blank">Materials and Methods</a> for details) with color-coding same as in panel (A). Two yellow daughter cells are shown by solid and dashed lines. Note also the appearance of multiple red and purple daughter cells right after cell division in competence. (Inset) Normalized cell lengths over time in units of maximal cell length <i>L</i>_max. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0121681#pone.0121681.s007" target="_blank">S6 Fig</a> shows same for intensity density, <i>i.e.</i> total intensity divided by cell area.