FIG. 1.—

(A) Plot of mean π_A/π_S versus mean π_S for 12 bacterial taxa (r_S = −0.699; P = 0.011). Abbreviations for taxa: Burk (Burkholderia), Camp (Campylobacter), Chlam (Chlamydophila), Ehr (Ehrlichia), Helic (Helicobacter), Neis (Neisseria), Pseud (Pseudomonas), Shig (Shigella), Staph (Staphylococcus), Streppn (Streptococcus pneumoniae), Streppy (Streptococcus pyogenes), and Yers (Yersinia pestis). (B) Numbers of genes with NI < 1 and NI ≥ 1. There was a significant difference among taxa with respect to the portion of genes with NI ≥ 1 (χ² = 1158.5; 11 df; P < 0.001).