Determination of synteny and deletion events between three extant symbionts (BAp, BBp, Bfl) and their reconstructed free-living ancestor (LCA1), through "alignment" of orthologous genes ordered in each genome. Shaded arrows represent genes from the chosen fragment of LCA1 and still present in symbionts (open symbols for genes in symbionts represent genes from LCA1 present in another fragment) while genes of this fragment that were lost are represented by dotted arrows. The numbers below genes in symbionts show their rank in these genomes. The figure illustrates our approach in three steps: alignment between BAp and LCA1 suggest a non syntenic deletion of 8 genes. Alignment between BBp and LCA1 suggest a non syntenic deletion of 7 genes. Alignment between Bfl and LCA1 finally suggest a syntenic deletion of only 1 gene.