The Phylogenetic Tree of Life: a Two Domain System?
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The document discusses the two-domain tree of life, focusing on the relationship between Archaea and Eukarya, with insights from DNA analysis of Asgard archaea. It presents findings from microbial sediment sampling that suggest a significant link of eukaryotic signature proteins to Asgard genomes, supporting the existence of a last archaeo-eukaryotic common ancestor. The analysis includes references to key literature that contributes to the understanding of the evolution of cellular complexity.
The Phylogenetic Tree of Life: a Two Domain System?
- 1. A Two-Domain Tree of Life Jack Dazley
- 3. Overview Three domains – Archaea, Bacteria, Eukarya Proposed branching of Eukarya from Archaea Four groups in Archaea – Euryarchaeota, Crenarchaeota, Nanoarchaeota and Korarchaeota Lokiarchaeota – proposed group within Crenarchaeota Two domain system?
- 4. Methodology DNA from Asgard archaea (including Lokiarchaeota) analysed – sampling of marine sediments from seven sites Reconstruction of ‘genome bins’ for representative species Analysis of 16s rRNA sequences Identification of eukaryotic signal proteins (ESPs) and eukaryotic TRAPP complexes Comparison of protein complexes to identify classification in relation to eukaryotic cells
- 8. Conclusions 16s rRNA analysis – indication of community in marine sediments ESP and TRAPP complex analysis – Asgard genomes encode for many eukaryotic signature proteins Some are similar to bacterial proteins – explanation of bacterial genes present in eukaryotic genomes Last archaeo-eukaryotic common ancestor (LAECA) – may have been able to bend membranes and form vesicles similar to modern eukaryotes
- 9. References Forterre, P., 2015. The universal tree of life: an update. Frontiers in Microbiology, 6 (717), 1-18. Spang, A., Saw, J., Jørgensen, S., et al., 2015. Complex archaea that bridge the gap between prokaryotes and eukaryotes. Nature, 521 (7551), 173-179. Zaremba-Niedwiedzka, K., Caceres, E., Saw, J., et al., 2017. Asgard archaea illuminate the origin of eukaryotic cellular complexity. Nature, 541 (7637), 353-358. Woese, C. R., Kandler, O and Wheelis, M. L., 1990. Towards a natural system of organisms: proposal for the domains Archaea, Bacteria and Eucarya. PNAS, 87 (12), 4576-7579.
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Editor's Notes
- #3: Last Universally Common Ancestor – represented at root of tree
- #4: Lokiarcheota – based on DNA samples collected from seven locations across the world – see Zaremba et al. 2017
- #5: TRAPP complex – multi-subunit vesicle tethering factors involved in endoplasmic reticulum and trans-golgi transport Comparison with eukaryotic TRAPP complexes using DNA sequencing
- #7: Lokiarchaeota – closest archaeal branch to Eukarya