Molecular genetic evidence for early evolutionary origin of budding peptidoglycan-less eubacteria

Recent studies on the cell wall composition of budding, non-prosthecate bacteria have shown that representatives of the genera Planctomyces and Pasteuria (sensu Staley, 1973) lack the peptidoglycan moiety, which is the characteristic feature of eubacterial cell walls, but possess an as yet unidentified protein sheet instead; in this respect Planctomyces and Pasteuria strains resemble certain archaebacteria more than eubacteria. To determine their phylogenetic positions, the 16S ribosomal RNAs of three budding, peptidoglycan-less strains with and without stalks were subjected to partial sequence analyses. As we report here, the comparison of data with those obtained from about 320 eubacterial and 40 archaebacterial strains revealed that the strains investigated are not members of the archaebacterial kingdom but represent an ancient line of descent of the eubacterial kingdom. Furthermore the diphtheria toxin reaction of Planctomyces and Pasteuria shows that they behave like eubacteria.