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

An evolutionary tree, reconstructed from 1232 bacterial small ribosoma l subunit RNA sequences by a distance method, reflects the existence o f 11 divisions and a number of subdivisions originally recognized by W oese and collaborators. However, the order of divergence that gave ris e to these taxa remains indeterminate and the division of Gram positiv es and relatives does not behave as a monophyletic taxon. Analysis of the data by a novel approach led to a preferred order of divergence fo r 10 out of 16 tree nodes, but the Gram positives still behaved as bip hyletic.