A recent paper suggests that the Mycobacterial genome has been shaped by a biphasic process involving gene acquisition (including lateral gene transfer) and duplications followed by gene loss [79] . Other studies report numerous genes, including a large number involved in lipid metabolism, that have been acquired by horizontal gene transfer at different phylogenetic strata and have led to the emergence of pathogenesis in Mtb [80, 81] . Previous studies indicate a possible more ancient lateral gene transfer of fatty acid biosynthesis genes from α-proteobacteria to actinobacteria [84] . However, genetic studies show that the Mtb complex and pathogenic Mycobacteria do not exchange genetic material frequently [85, 86] , so there is limited lateral gene transfer within the Mtb complex.