The core Frz-apparatus can promote S-motility-dependent behaviors.

<p><b>(A)</b> Single cell Tfp-dependent reversals are observed in carboxymethylcellulose-coated glass microfluidic chambers. FrzS-YFP and MglA-YFP dynamic localization are observed during single cell Tfp-dependent reversals. Fluorescence micrographs (left) and quantification of the corresponding fluorescence intensities (arbitrary units, au) of FrzS-YFP and MglA-YFP at both poles over time are shown (time resolution: 15s). Red line: initial leading pole, blue line: initial lagging pole (Frame 1). R: reversals. <b>(B)</b> Reversal frequency of WT and selected mutants on carboxymethylcellulose. The assays are run in the presence of 0.15% of Isoamyl alcohol (IAA) to allow reversal counts (see <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1005460#sec016" target="_blank">Methods</a>). Shown are boxplots of the measured reversal frequency of isolated cells (n, tracked for at least 10 min) for each strain. The lower and upper boundaries of the boxes correspond to the 25% and 75% percentiles, respectively. The median is shown as a thick black line and the whiskers represent the 10% and 90% percentiles. Statistics: Wilcox test (n<40) for Δ3 (<i>frzB frzZ aglZ</i>) and student test (t-test, n>40) for all the other strains. ** p value<0.01, *** p value<0.0001. <b>(C)</b> RomR but not FrzZ is essential for S-motility-dependent reversals. FrzS-YFP pole-to-pole oscillations were counted in the presence of 0.10% of IAA to score reversals (the exact procedure is described in Methods and <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1005460#pgen.1005460.s009" target="_blank">S9A and S9B Fig</a>). Briefly, for each pole, fluorescence intensity was measured at any given time point as described in Methods and <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1005460#pgen.1005460.s009" target="_blank">S9A and S9B Fig</a>. The boxplots read as in (B). Statistics: Wilcox test (n<40) for WT, <i>frzE</i>, <i>romR</i>, <i>frzE frzZ</i> or student test (t-test, n>40) for <i>frzZ</i>, <i>frzE romR</i> and <i>frzZ romR</i>. ** p value<0.01, *** p value<0.0001. <b>(D)</b> Multicellular development is restored in a triple mutant <i>frzB frzZ aglZ</i> (Δ3) on soft (0.5%) CF starvation medium agar in a Frz-dependent manner (compare with the Δ3 <i>frzE</i> mutant). On the contrary the <i>frzB frzZ aglZ</i> cannot aggregate on a hard (1.5%) CF agar, where A-motility is also required.