Oteobacteria). The evolutionary history deduced here based on signature sequences in some of the most highly conserved protein sequences in the biota is in contrast to the rather confusing picture that seems to be emerging from other analyses of the completed bacterial genomes (21, 50, 68, 130, 143, 144, 182, 191, 255). However, as has been pointed out (50, 143, 144, 182), of the large number of s