 "Rickettsiaceae", "Anaplasmataceae", "Rhodospirillaceae", "Acetobacteraceae", "Bradyrhiozobiaceae", "Brucellaceae" and "Bartonellaceae").These molecular signatures provide novel means for the circumscription of these taxonomic groups and for identification/assignment of new species into these groups.Phylogenetic analyses and conserved indels in large numbers of other proteins provide evidence that "Alphaproteobacteria" have branched off later than most other phyla and Classes of Bacteria except "Betaproteobacteria" and "Gammaproteobacteria".