RomR acts upstream of MglA and MglB and downstream of FrzZ.

<p>(A) Motility phenotypes of strains of the indicated genotypes. The WT and Δ<i>romR</i> images from <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1002951#pgen-1002951-g001" target="_blank">Figure 1</a> are included for comparison. Note that hyper- or hypo-reversing mutants expand less than WT colonies due to the abnormal reversal frequency and not due to defects in A- and S-motility <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1002951#pgen.1002951-Leonardy2" target="_blank">[26]</a>, <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1002951#pgen.1002951-Zhang2" target="_blank">[28]</a>. The indicated strains were incubated at 32°C for 24 h on 0.5% agar/0.5% CTT medium and 1.5% agar/0.5% CTT medium to score S- and A-motility, respectively. Motility is evaluated as described in <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1002951#pgen-1002951-g001" target="_blank">Figure 1A</a>. Scale bars, 1 mm, 200 µm, 1 mm, and 5 µm from top to bottom row. (B) Box plot of reversal frequencies measured in the strains of the indicated genotypes. The boxes below indicate alleles present: Colored, WT; white, in-frame deletion; QA, DN and DE: MglA^Q82A, RomR^D53N and RomR^D53E. n>50. Cells were transferred from a liquid culture to a thin agar pad, covered with a coverslip and followed by time-lapse microscopy in which cells were imaged at 30-s intervals for 15 min. For each strain, 50 cells were followed. In the box plot, the Y-axis is number of reversals per 15 min, boxes enclose the 25^th and 75^th percentile with the dark grey line represents the mean, whiskers represent the 10^th and 90^th percentile, and diamonds outliers.