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Early Evolution and Phylogeny

Bastien Boussau 1 
Abstract : During this thesis, I studied the early evolution of life, from the Last Universal Common Ancestor (LUCA) to the ancestors of the three kingdoms, Archaea, Bacteria and Eukarya. Notably, I have attempted to place a few organisms in the tree of life, namely the bacteria Aquifex aeolicus and the archaea Cenarchaeum symbiosum, and I also studied the evolution of optimal growth temperatures over the last four billion years. To this end, I developed algorithms to reconstruct ancestral gene sequences, and used these sequences to predict the optimal growth temperatures of now-extinct organisms. My colleagues and I estimate that LUCA did not live in a very hot environment, but that its descendants the ancestors of Bacteria and of the group containing Archaea and Eukarya both lived at higher temperatures. This implies that the two lineages descending from LUCA underwent the same kind of evolution in parallel, perhaps caused by the same unique selection pressure. This pressure may have resulted from an intense meteoritic bombardment 3.8 billion years ago, and have been accompanied by the transition from an RNA genome in LUCA to DNA genomes in its descendants. Subsequently in the bacterial lineage, optimal growth temperature dropped, which may correspond to the evolution of oceanic temperatures in the last 3.5 billion years.
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Contributor : Bastien Boussau Connect in order to contact the contributor
Submitted on : Tuesday, December 9, 2008 - 5:43:24 PM
Last modification on : Tuesday, July 20, 2021 - 5:20:05 PM
Long-term archiving on: : Thursday, October 11, 2012 - 1:10:20 PM


  • HAL Id : tel-00345743, version 1



Bastien Boussau. Early Evolution and Phylogeny. Symbiosis. Université Claude Bernard - Lyon I, 2008. English. ⟨tel-00345743⟩



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