ABOUT THE ORDER OF DIVERGENCE OF THE MAJOR BACTERIAL TAXA DURING EVOLUTION

An evolutionary tree, reconstructed from 1232 bacterial small ribosomal subunit RNA sequences by a distance method, reflects the existence of 11 divisions and a number of subdivisions originally recognized by Woese and collaborators. However, the order of divergence that gave rise to these taxa remains indeterminate and the division of Gram positives and relatives does not behave as a monophyletic taxon. Analysis of the data by a novel approach led to a preferred order of divergence for 10 out of 16 tree nodes, but the Gram positives still behaved as biphyletic.