The Rates of Synonymous (Ka) and Nonsynonymous (Ks) Nucleotide Substitutions for Essential Versus Nonessential Bacterial Genes
| Ks (±se)[i] | Ka (±se)[ii] | r[iii] | Ka/Ks | |
| Escherichia coli—all[iv] | 26.99 × 10−3 | 1.11 × 10−3 | 0.35 | 4.50 × 10−2 |
| Essential (n = 205) | (±2.1 × 10−3) | (±0.1 × 10−3) | (±0.7 × 10−2) | |
| Nonessential (n = 1794) | 51.0 × 10−3 | 3.60 × 10−3 | 0.44 | 8.40 × 10−2 |
| (±1.0 × 10−3) | (±0.2 × 10−3) | (±0.2 × 10−2) | ||
| Undetermined (n = 1107) | 48.6 × 10−3 | 5.00 × 10−3 | 0.47 | 11.67 × 10−2 |
| (±1.3 × 10−3) | (±0.3 × 10−3) | (±0.5 × 10−2) | ||
| Significance of the difference[vi] | P = 0 | P = 5.6 × 10−16 | na | P = 6.4 × 10−6 |
| E. coli—experimental[v] | 35.33 × 10−3 | 1.36 × 10−3 | 0.33 | 4.73 × 10−6 |
| Essential (n = 150) | (±2.5 × 10−3) | (±0.2 × 10−3) | (±0.7 × 10−2) | |
| Nonessential (n = 1736) | 51.29 × 10−3 | 3.60 × 10−3 | 0.44 | 8.27 × 10−2 |
| (±1.0 × 10−3) | (±0.2 × 10−3) | (±0.4 × 10−2) | ||
| Significance of the difference[vi] | P = 1.2 × 10−7 | P = 1.2 × 10−8 | na | P = 5.6 × 10−4 |
| Helicobacter pylori | 111.33 × 10−3 | 12.89 × 10−3 | 0.43 | 11.32 × 10−2 |
| Essential (n = 98) | (±4.1 × 10−3) | (±1.1 × 10−3) | (±0.9 × 10−2) | |
| Nonessential (n = 130) | 135.24 × 10−3 | 21.64 × 10−3 | 0.30 | 16.14 × 10−2 |
| (±3.1 × 10−2) | (±1.4 × 10−3) | (±0.8 × 10−2) | ||
| Significance of the difference[vi] | P = 3.5 × 10−6 | P = 6.1 × 10−7 | na | P = 6.1 × 10−4 |
| Neisseria meningitidis | 65.37 × 10−3 | 4.76 × 10−3 | 0.68 | 7.32 × 10−2 |
| Essential (n = 98) | (±6.9 × 10−3) | (±0.7 × 10−3) | (±1.0 × 10−2) | |
| Nonessentials (n = 130) | 91.56 × 10−3 | 9.60 × 10−3 | 0.49 | 17.65 × 10−2 |
| (±5.9 × 10−3) | (±0.9 × 10−3 | (±1.9 × 10−2) | ||
| Significance of the difference[vi] | P = 1.6 × 10−4 | P = 1.0 × 10−7 | na | P = 4.2 × 10−5 |
[i] The average synonymous substitution (nucleotide substitutions that do not change the encoded amino acid sequence) rate (Ks) for all orthologous genes within a given fitness class and species is shown with the standard error (in parentheses).
[ii] The average nonsynonymous substitution (nucleotide substitutions that change the encoded amino acid sequence) rate (Ka) for all orthologous genes within a given fitness class and species is shown with the standard error (in parentheses).
[iii] Correlation coefficient between the Ks and Ka values.
[iv] This set includes all of the E. coli genes characterized as essential or nonessential (on the basis of experimental and functional information).
[v] This set includes only the E. coli genes characterized as essential or nonessential on the basis of experimental evidence.
[vi] Statistical significance of the difference between the essential and nonessential classes for a given measurement as determined using the Mann-Whitney U test.