 The basal group is "Magnetococcidae", which is composed by a large diversity of magnetotactic bacteria, but only one is described, "Magnetococcus marinus".The "Rickettsidae" is composed of the intracellular "Rickettsiales" and the free-living "Pelagibacterales".The "Caulobacteridae" is composed of the "Holosporales", "Rhodospirillales", "Sphingomonadales", " Rhodobacterales", "Caulobacterales", "Kiloniellales", "Kordiimonadales", "Parvularculales" and "Sneathiellales".