Lateral Gene Transfers and Organismal Phylogeny in Bacteria: Implications for Ancestral Genome Reconstruction

Thursday, October 23, 2003 - 3:00pm - 3:50pm
Keller 3-180
Emmanuelle Lerat (Université Claude-Bernard (Lyon I))
Genome reconstruction is of particular interest from a biological perspective. This knowledge can illuminate the history of events that led to the present contents and organization of genomes. The principle of reconstruction methods is the inference of rearrangements that occurred during the history of the genome. This makes the strong assumption that genes are faithfully transmitted with their genome through generations. However in bacteria, lateral (or horizontal) gene transfers (LGT) are known to be very numerous. LGT might be an obstacle in the attempt to establish genome history, because some homologous genes may be transmitted between different species. It has even been argued that LGT may prevent the establishment of organismal relationships based on individual gene phylogenies. Thus to reconstruct ancestral genomes in bacteria seems to be particularly hazardous unless LGT is taken into account. It is therefore very important to test the hypothesis of vertical transmission of the genes used in genome reconstruction. In order to determine the impact of LGT on the potential organismal phylogeny, an approach to multigene phylogeny using complete genomes is necessary to identify the genes that have been, without ambiguity, vertically transmitted and that are thus good candidates to be used in genome reconstruction. This will allow a real biological interpretation of the genome reconstruction but also facilitate the reconstruction itself.