Our analysis also reveals differences in evolutionary profiles between genes predicted to be involved in catabolism and anabolism of lipids. Both sets of genes are expanded in soil-dwelling and pathogenic Mycobacteria, but lipid synthesis genes are additionally expanded in pathogens relative to soil dwellers. General lipid synthesis genes are expanded across the Mycobacteria, but certain groups of lipid synthesis genes, including those related to cell wall synthesis, are further expanded in the Mtb complex (see Supplementary Information) . In pathogenic Mycobacteria, the waxy mycolic acid coat helps evade the host immune system [34] . Consistent with this, we see categories related to mycolic acid synthesis showing up among the most non-uniform categories, highly expanded in the Mtb complex (see Supplementary Information) .