Maximum likelihood tree of the biotin carboxylase (BC) domain. This tree is based on 284 representative sequences and 384 conserved sites and was arbitrarily rooted on the bacterial ACC-related sequences. Numbers at nodes indicate bootstrap values higher than 50. Triangles correspond to collapsed groups of eukaryotes and Proteobacteria. Colors on leaves represent the affiliation of the sequences to their respective domain of life: archaea (red), bacteria (blue) and eukaryotes (green). Bars on the right report the functional assignment of the sequences; sequences that are not in front of any bar are assumed to bear an acyl-CoA carboxylase activity.