Maximum likelihood tree of archaeal and bacterial biotin carboxylase (BC) domain sequences. This tree is based on 196 representative sequences and 322 conserved sites and was arbitrarily rooted on the PYC-related sequences. Numbers at nodes indicate bootstrap robustness values higher than 50. 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.