Figure 1.
The pattern of synonymous SNPs.
The figure shows the correlation between Z, the proportion of GC↔AT SNPs that are GC→AT, and GC4, across 149 bacterial species.
Table 1.
The mean value of Z across bacterial phyla and classes.
Figure 2.
The infinite sites assumption.
The figure shows the predicted value of Z, allowing for a violation of the infinite sites assumption, assuming that base composition is due to mutation bias alone and base composition is stationary, plotted against GC4 under the (A) constant rate and (B) exponential rate models, along with the effect of removing this bias from the observed value (Z-Zpred) for the (C) constant and (D) exponential models.
Figure 3.
The equilibrium GC content under the mutation bias model.
The figure shows the relationship between GC4pred, the GC4 to which each species is predicted to evolve under mutation pressure, and the current GC4.
Figure 4.
The figure shows the relationship between GC4 for putatively highly expressed genes and GC4 for all other annotated genes. The line is for GC4high = GC4other.
Figure 5.
The figure shows the effect of selection in favour of GC on Z. The relationship between Zpred and S (2Nes) for three values of f, the equilibrium GC-content when there is no selection (i.e. the mutation bias); from top to bottom f is 0.7, 0.5 and 0.3. In these examples 2Neμ = 0.1 and n = 10; qualitatively similar patterns are observed for other values of these two parameters.