Title: Evolution of tubercle bacilli, from recombinogenic to clonal populations

Author: Roland Brosch¹

Affiliation: ¹Institut Pasteur, Université Paris Cité, Unit for integrated mycobacterial pathogenomics, Paris, France

Abstract: Mycobacterium tuberculosis, the causative agent of human tuberculosis is one of the most widely spread and deadliest human pathogens. These bacteria have achieved to infect a quarter of the global human population by employing most sophisticated pathways to circumvent innate and adaptive immune defences. This specialized, major human pathogen has emerged from a pool of ancestral environmental mycobacteria, whose extant representatives are known under the name of Mycobacterium canettii. Recent whole genome analyses in combination with different phenotypic screens have provided new insights into some key genetic changes, gene acquisitions and gene losses that have likely contributed to the emergence of M. tuberculosis and closely related members regrouped in the M. tuberculosis complex (MTBC) as top pathogens in various mammalian species. These evolutionary events also included horizontal gene transfer episodes that might have also played an important role in the early phase of evolution, as well as lateral gene transfer and clonal expansion. In summary, we here present the most recent evolutionary models of the MTBC and various factors that have contributed to the outstanding evolutionary success of the tuberculosis agent.