Figure 1

Amino acid usage is correlated with optimal growth temperature across prokaryotes. Correlation between a measure of amino acid usage bias that is related to protein stability, ERK = E + R + K - D - N - Q - T - S - H - A, and optimal growth temperature in 204 prokaryotes (Pearson's R = 0.72, p = 10^-15; Spearman's ρ = 0.46, p = 10^-12). See Additional file 1: Supplemental Figure S1 for a correlated alternative measure of amino acid usage bias.