Distribution of the genomic distance between the downstream genes and the sequence elements that are most similar to the Sigma-54 promoter motif. The distance distribution (in bins of 100 nucleotides) was summed for A) all genomes that lack Sigma-54 and its activator (A; EBP = 0), and for those genomes that have Sigma-54 and one (B; EBP = 1) or multiple EBP54s (C; EBP = 2-5, D; EBP = 10-19). The distance distribution for genomes with EBP = 6-9 and EBP ≥ 20 are similar to the latter and therefore not shown. For every identified element two distances were included as indicated in the figure inset. As a result the distribution actually represents the sum of two distributions. The distance was taken from the -11 position of the promoter to the predicted translation start of the gene (situation i). In case the element was located within a gene (situation ii) the distance to the first gene was taken as negative. In blue the distance distribution is given for the cases that the gene downstream is oriented in line with the predicted promoter and in red for the cases that it opposes the promoter. The sum of the distributions was normalized.