Phylogenetic analysis treatment

It was the analysis of the 16S rRNAs that first revealed the unique evolutionary position of the archaebacteria, and defined the primary evolutionary divisions of life on this planet (4,6). Figure 1 shows an unrooted phylogenetic tree based upon complete 16S rRNA sequences of representatives of the three primary lines of evolutionary descent the archaebacteria, the eubacteria and the eukaryotes. Within these primary lines of descent other major lines of descent have been delineated. Within the eubacteria, for example, some ten major divisions are now recognized. It has been suggested that these be given a systematic rank equivalent to phylum (12). However, this chapter will not elaborate upon the emerging phylogenetic description of life on this planet. The reader is referred to a recent review for a dedicated treatment of this subject (4,12). 

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