Alsopresent in Parachlamydia ancanthamoebae but not in "Ca. Protochlamydia amoebophila," even though both are currently classified as genera belonging to the family Parachlamydiaceae. (ii) Except for the Chlamydiaceae, all of the other Chlamydiales families possess an unusual LysC aspartokinase having a catalytic domain but no allosteric domain. A common ancestor of the Chlamydiaceae may have acqu