Groups of coevolving sites correlate in their entropies forming independent protein sectors. We measured entropy and correlation entropies for each pair of groups belonging to different bacteria using the equations 1 to 4 from the text. Compared groups were taken from the same protein domain (Apical, Intermediate or Equatorial). Bacteria groups compared included Actinobacteria (a) Bacteroidetes (b) Cyanobacteria (c) Spirochaetes (d) Firmicutes (e) and Proteobacteria (f). Two groups of coevolution (g1 and g2) were considered independent when the joined correlation entropy for the groups (IS(g1,g2)) was approximately equal to the sum of correlation entropies (IS(g1)) and (IS(g2)). The significance of the difference between these two parameters [Θ = IS(g1,g2) – (IS(g1) + IS(g2))] was tested against a null distribution of Θ drawn from a 1000 groups built by randomly sampling sites from the same protein domain. Significant Θ values under a normal test (P < 0.05) are indicated with *.
Ruiz-González and Fares BMC Evolutionary Biology 2013 13:156 doi:10.1186/1471-2148-13-156