FIG. 2.

(a) Schematic diagram of homologous genome region in strains H37Rv and CDC1551 encoding several membrane lipoproteins. The region in strain H37Rv contains two genes in tandem (Rv2543 and Rv2544) that are 87% identical to each other at the protein level. The homologous region in strain CDC1551 contains three genes (MT2618, MT2619, and MT2620), with the middle gene, MT2619, being unique to strain CDC1551 and 88 and 84% identical to MT2619 and MT2620, respectively. Homology between strain CDC1551 and M. bovis and equivalent evolutionary distances between paralogs suggest that the three paralogs arose in a common ancestor of the M. tuberculosis complex and subsequent loss of MT2619 occurred in the H37Rv lineage. (b) Schematic diagram of the tandem adenylate cyclase region. Two paralogous cyclases flank the region (MT1359/Rv1318c and MT1362/Rv1320c). Analysis revealed two cyclases (MT1360 and MT1361) between the two flanking genes in strain CDC1551 and only one cyclase (Rv1319c) in strain H37Rv. Rv1319c appears to be a chimera of the 5′ half of MT1361 and the 3′ half of MT1360. The 3′ halves of all orthologs share >80% nucleotide identity, while the 5′ halves appear diverse. Phylogenetic analysis indicates that the duplication events share a similar evolutionary distance. Inspection of the M. bovis sequence data reveals that this region is organized in an identical way to the H37Rv genome.