SLSs in B. anthracis , E. coli , and M. tuberculosis. In the six panels, bars represent SLSs found in B. anthracis, E. coli, and M. tuberculosis genomes and in randomized genomes produced from them. Bars 1 to 13 refer to randomly shuffled genomes preserving the frequency of 1 to 13 nucleotide words, respectively. Bar U (Unshuffled) refers to the natural genome, while bar DS (Double Shuffle) refers to the genome shuffled preserving information about coding regions (see Results and Methods). In each column, stacked bars are used to separate SLSs of different dG (top panels) or loop size (bottom panels), as indicated. Only SLSs with dG < -5 KCal/mole were selected. Pre-filtering of SLSs was not performed. Standard deviations are always lower than 1% and are not reported in the figure.