Figure 3

Mauve alignment of the chromosomes of R. litoralis (upper line) and R. denitrificans (lower line). Colored boxes represent syntenic regions and white/grey areas the unique regions of the two organisms. The two Roseobacter species share a high amount of genetic material but the chromosomes have been subject to frequent rearrangements and events of lateral gene transfer. Marked are two HVRs and the adjacent GEIs of R. litoralis that have corresponding regions on similar positions of the chromosome of R. denitrificans. An X-like structure is formed when the HVRs are connected by lines. The areas display a mosaic-like structure of syntenic regions interspersed with unique regions in the respective organism. HVR I of R. litoralis contains a variety of genes that are connected to the association with the algal host of the bacterium, whereas HVR V contains genes for formaldehyde degradation and sugar metabolism. Both areas have little synteny with other Roseobacter clade members and are therefore important for the identification of genus-unique genes.