SD sequences for RP, PHX, and PMX gene classes. (A) The y axis, OAS%, is the fraction of SD sequences present at the three OAS (given in Table 1) for each gene class. * indicates genomes where the OAS% for RP is significantly higher than for PMX genes (P < 0.05 for a χ2 test using the Yates correction). ** indicates that the OAS% for both the RP and PHX genes are significantly higher than for the PMX genes. (B) The y axis shows mean ΔGSD, the mean free energy of binding of the SD sequences in a gene group. * indicates genomes where the mean ΔGSD for the RP genes is significantly less than that for the PMX genes (the difference is at least 20% of the bacterial mean ΔGSD, or 1.3 kcal/mol); ** indicates that the mean ΔGSD for both the RP and PHX genes is significantly less than for the PMX genes. Abbreviations: ESCCO, Escherichia coli; HAEIN, Haemophilus influenzae; VIBCH, Vibrio cholerae; PSEAE, Pseudomonas aeruginosa; CAMJE, Campylobacter jejuni; HELPY, Helicobacter pylori; RICPR, Rickettsia prowazekii; NEIME, Neisseria meningitidis; CHLPN, Chlamydophila pneumoniae; CHLTR, Chlamydia trachomatis; BORBU, Borrelia burgdorferi; TREPA, Treponema pallidum; BACSU, Bacillus subtilis; MYCGE, Mycobacterium genitalium; MYCPN, Mycobacterium pneumoniae; UREUR, Ureaplasma urealyticum; MYCTU, Mycobacterium tuberculosis; SYNSQ, Synechocystis sp. strain PCC6803; DEIRA, Deinococcus radiodurans; AQUAE, Aquifex aeolicus; THEMA, Thermotoga maritima; METJA, Methanococcus jannaschii; METTH, Methanobacterium thermoautotrophicum; ARCFU, Archaeoglobus fulgidus; PYRAB, Pyrococcus abyssi; PYRHO, Pyrococcus horikoshii; THEAC, Thermoplasma acidophilum; HALSP, Halobacterium sp. strain NRC-1; SULSO, Sulfolobus solfataricus; PYRAE, Pyrococcus aerophilum.