Fig. 1.

Pairwise comparison of the GC contents between closely related prokaryotes with different growth temperature ranges. Both bacteria (A) and archaea (B) were classified into four ranks according to their growth temperature, from low to high: psychrophiles/psychrotrophiles, mesophiles, thermophiles, and hyperthermophiles. The diagonal line represents cases in which prokaryotes with different ranks have the same GC contents. Points above the line (153 pairs of bacteria and 17 pairs of archaea) represent cases in which prokaryotes with higher ranks have higher GC contents than their paired relatives, while points below the line (119 pairs of bacteria and 24 pairs of archaea) indicate the reverse. The p values were calculated using two-tailed Wilcoxon signed-rank tests. The exact values of the GC contents are present in Additional file 1: Table S18