Distribution of genome size (A), the number of EBP54-activators (B), and motility (C), for species with (blue) and without (red-brown) Sigma-54. A) the analyzed species were binned according to genome size in bins of one Mbase, and divided in two groups that related to the presence or absence of Sigma-54. B) for every size-bin the fraction of genomes with a particular number of EBP-activators was determined and a height-plot was created. The grey dots indicate the data points. The contour was generated with Microsoft Office Excel 2007. C) Within every bin the fraction of motile species was determined for the genomes with Sigma-54 and without. The corresponding data can be found in additional file 1.