Comparative sequence analyses were performed on 14 genes encoding bacterial elongation factors EF-Tu and 7 genes encoding the beta-subunit of bacterial F1F0 type ATP-synthases. The corresponding predicted amino acid sequences were compared with published primary structures of homologous molecules. Phylogenetic trees were reconstructed from both data sets of aligned protein sequences and from an equivalent selection of 16S rRNA sequences by applying distance matrix and maximum parsimony methods. The EF-Tu data were in very good agreement with the rRNA data, although the resolution within the EF-Tu tree was reduced at certain phylogenetic levels. The resolution power of the ATPase beta-subunit sequence data were more reduced than those of the EF-Tu data. In comparison with the 16S rRNA tree there are minor differences in the order of adjacent branchings within the ATPase beta-subunit tree.

Amino Acid Sequence↗

PubMedDate not supplied

What are mycoplasmas: the relationship of tempo and mode in bacterial evolution.

In phenotype the mycoplasmas are very different from ordinary bacteria. However, genotypically (i.e., phylogenetically) they are not. On the basis of ribosomal RNA homologies the mycoplasmas belong with the clostridia, and indeed have specific clostridial relatives. Mycoplasmas are, however, unlike almost all other bacteria in the evolutionary characteristics of their ribosomal RNAs. These RNAs contain relatively few of the highly conserved oligonucleotide sequences characteristic of normal eubacterial ribosomal RNAs. This is interpreted to be a reflection of an elevated mutation rate in mycoplasma lines of descent. A general consequence of this would be that the variation associated with a mycoplasma population is augmented both in number and kind, which in turn would lead to an unusual evolutionary course, one unique in all respects. Mycoplasmas, then, are actually tachytelic bacteria. The unusual evolutionary characteristics of their ribosomal RNAs are the imprints of their rapid evolution.

Base Composition↗

PubMedDate not supplied

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.

Bacteria↗