Section: New Results

Bacterial syntenies

The automatic identification of syntenies across multiple species is a key step in comparative genomics that helps biologists shed light both on evolutionary and functional problems. We developed a versatile algorithm to extract all syntenies from multiple bacterial species based on a clear-cut and very flexible definition of the synteny blocks that allows for gene quorum, partial gene correspondence, gaps, and a partial or total conservation of the gene order [8] . We then applied this algorithm to two different kinds of studies. The first one is a search for functional gene associations. In this context, we compared our algorithm to a widely used heuristic - I-ADHORE - and showed that at least up to ten genomes, the problem remains tractable with our exact definition and algorithm. The second application was linked to evolutionary studies: we verified in a multiple alignment setting that pairs of orthologs in synteny are more conserved than pairs outside, thus extending a previous pairwise study. We then showed that this observation is in fact a function of the size of the synteny: the larger the block of synteny is, the more conserved the genes are. This work was done in collaboration with F. Boyer.