Logo of the information matrix obtained from the alignment of ArcA sequences for S . Typhimurium. Sequences were obtained by searching the S. Typhimurium LT2 genome [Accession #: AE006468 (chromosome) and AE606471 (plasmid)] with known ArcA sequences derived from the corresponding ArcA-regulated genes in E. coli. A total of 20 E. coli sequences were used to obtain the logo shown. The total height of each column of characters represents the amount of information [measured in bits, which is the maximum entropy for the given sequence type (ex. Log2 4 = 2 bits for DNA/RNA and log2 20 = 4.3 bits for proteins)] for that specific position and the height of each individual character represents the frequency of each nucleotide.