Figure 3From: Massive comparative genomic analysis reveals convergent evolution of specialized bacteriaPlot of the first Principal Coordinate Analysis (PCO) axis of COGs content distances. Multivariate analysis graphics of the COGs content of all studied bacteria using R ade4 package. Each bacterium is represented by a symbol linked by a line to the gravity center of the group it belongs to (M, obligate intracellular mutualists, red triangles; P, obligate intracellular parasites, purple triangles; FHA, facultative host- associated, green asterisks; and FL, free-living, blue squares). An ellipse was also drawn for each class, which size increases with the coordinates' dispersion in the class. It is computed such that it would contain 68% of the individuals in the studied class if the distribution were Gaussian. Otherwise, it is just a way to compare dispersion between classes. 1 represents Treponema pallidum; 2 represents Mycobacterium leprae; 3 represents Candidatus Protochlamydia amoebophila UWE25; 4 represents Coxiella burnetii. These species with larger genome sizes and gene contents than the other obligate intracellular bacteria undergo reductive evolution [28, 30]. Some of these bacteria have high number of pseudogenes [27, 29, 31]. The presence of pseudogenes displays an ongoing process of gene degradation.Back to article page