Operon and genomic maps of Buchnera. The small circle portrays a simplified E. coli map (only genes having an orthologue in the Buchnera genome were used in drawing the map), each gene is specifically colored (consecutive genes have proximal colors). The inner circle depicts the Buchnera genome; the same colors are used for the genes as for their orthologues in E. coli. The middle circle is the operon map of Buchnera, in which only the polycistronic TUs are shown. The outer circle shows the consecutive blocks of adjacent genes in Buchnera of which the orthologues in E. coli are also adjacent and belong to a single TU. The blocks are colored alternately in grey and green in order to make it possible to distinguish between two adjacent blocks. The synteny map of Buchnera (versus E. coli) is not shown here; nevertheless the gene color gives some insight into the multiple genomic rearrangements that have occurred since the lineages diverged.