The evolutionary conservation of promoters is limited to Gammaproteobacteria and to sigma70 promoters. In general an promoter is conserved if, i) the position of the promoter from the gene start is conserved, or ii) the promoter sequence recognized by the sigma70 factor is conserved (p < 0.0001). To avoid redundancy, the orthologous regions were purged using the program Purge-Sequence from RSAtools. Orthologs consisted of BLAST reciprocal best hits using soft masking and Smith-Waterman alignments.
