GL03

1:Institut Pasteur

In the tree of life, the genus Mycobacterium is part of the phylum Actinobacteria and represents a single entity comprising almost 200 bacterial species, most of them representing environmental saprophytes, and some that can cause infections of different severity in humans and/or animals. Among the latter group, Mycobacterium tuberculosis is the causative agent of tuberculosis (TB), one of the deadliest infectious diseases in human history, which remains a huge public health concern in many countries even today. M. tuberculosis is part of a group of closely related mycobacteria belonging to the M. tuberculosis complex (MTBC), which can be subdivided into several lineages of human- and animal-adapted strains, thought to have shared a last common ancestor emerged by clonal expansion from a pool of recombinogenic Mycobacterium canettii-like mycobacteria. A better understanding of how MTBC populations evolved from less virulent mycobacteria may allow for discovering improved TB control strategies and future epidemiologic trends. Here, I will highlight latest insights into the evolution of mycobacteria at the genus level, describing selected milestones in their evolution, with focus on the genomic events that have likely enabled the emergence and dominance of the MTBC. I will also review the various MTBC lineages and highlight their particularities and differences with focus on host preferences and geographic distribution. Finally, I will focus on putative mechanisms driving the evolution of tubercle bacilli and mycobacteria in general, by taking the mycobacteria-specific distributive conjugal transfer as an example.