FIG 1 .

Presence of CcoA homologues encoded in alphaproteobacterial genomes. (A) Evolutionary relationships between the CcoA homologues identified in sequenced alphaproteobacterial genomes. Branch lengths were ignored, and branch points with Shimodaira-Hasegawa scores of <0.5 were deleted. Branches and nodes are colored by order as shown at the bottom of panel A. The presence of ccoN (inner circle) or cox1 (outer circle) in each genome is represented by black or gray shading, respectively. Corresponding protein IDs are listed in Table S1. (B) Schematic representation of the cbb₃-Cox structural (ccoNOQP) and assembly (ccoGHIS) gene clusters together with the ccoA homologue in the Rhizobiales genomes indicated. (C) Co-occurrence plot with circles indicating the presence or absence of ccoA (red or white, respectively), the cbb₃-Cox structural and assembly gene clusters (black or white, respectively), and the aa₃-Cox-related genes (gray or white, respectively). Not all species are shown because of space limitations, but for a complete profile and a summary, see Tables S1 and S2, respectively.