title: Protein-based phylogenies support a chimeric origin for the eukaryotic genome.
abstract: The phylogenetic position of the archaebacteria and the place of eukaryotes in the history of life remain a question of debate. Recent studies based on some protein-sequence data have obtained unusual phylogenies for these organisms. We therefore collected the protein sequences that were available with representatives from each of the major forms of life: the gram-negative bacteria, gram-positive bacteria, archaebacteria, and eukaryotes. Monophyletic, unrooted phylogenies based on these sequence data show that seven of 24 proteins yield a significant gram-positive-archaebacteria clade/gram-negative-eukaryotic clade. The phylogenies for these seven proteins cannot be explained by the traditional three-way split of the eukaryotes, archaebacteria, and eubacteria. Nine of the 24 proteins yield the traditional gram-positive-gram-negative clade/archaebacteria-eukaryotic clade. The remaining eight proteins give phylogenies that cannot be statistically distinguished. These results support the hypothesis of a chimeric origin for the eukaryotic cell nucleus formed from the fusion of an archaebacteria and a gram-negative bacteria.
authors.affiliation: Department of Biology, McMaster University, Hamilton, Ontario, Canada.
authors.forename: G B
authors.initials: GB
authors.lastname: Golding
authors.forename: R S
authors.initials: RS
authors.lastname: Gupta
mesh_terms: D001105:Archaea / Q000145:classification / Q000235:genetics; D001419:Bacteria / Q000145:classification / Q000235:genetics*; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics*; D002678:Chimera; D010802:Phylogeny; D011336:Probability
chemical_list: D001426:Bacterial Proteins