Fig. 1.

CLEOA is the closet relative of Coxiella burnetii. Maximum likelihood and Bayesian trees built using 117 single-copy protein-coding genes were combined to generate the shown phylogenomic tree. Bootstrap support and posterior probabilities agreed at all branchpoints and are depicted as a single confidence value. The Dot/Icm Type IVB secretion system (T4BSS), which is critical to pathogenesis, is found in all members of the order Legionellales, but has been pseudogenized in CLEs. Nodes N1–N5 mark major branching points in the evolution of C. burnetii.