Phylogenetic Trees Derived from Mitochondrial, Nuclear, Eubacterial and Archaebacterial rRNA Sequences: Implications on the Origin of Eukaryotes

A phylogenetic tree analysis of small ribosomal subunit RNA (S-rRNA) gene sequences from Aspergillus nidulans, yeast, human and mouse mitochondria, E. coli, maize chloroplasts and nuclei from yeast and animals supports the endosymbiotic eubacterial origin of mitochondria and further raises the possibility, that fungal and animal mitochondria derive from different bacterial species.

Two archaebacterial 5 S rRNA sequences (from Halobacterium cutirubrum and Thermoplasma acidophilum) were incorporated into a recently described 5S tree: the two sequences exhibit a common root and diverge early from the nuclear branch.

The present sequence data are compatible with the idea that unicellular precursors to the eukaroytic kingdoms have been formed by divergence of archaebacteria-like cells prior to the invasion of endosymbiotic eubacteria.