He gained broad experience in mycobacterial research in the tuberculosis (TB) research field, where he had important impact on groundbreaking genome projects of Mycobacterium tuberculosis, the etiological agent of TB, the BCG vaccine, and the ancestral gene pool of TB-causing mycobacteria (Mycobacterium canettii). He was also involved in pioneering work on the evolution of the M. tuberculosis complex and the discovery and functional characterization of the ESX / type VII secretion system of M. tuberculosis. He continues to be very interested in these topics, which remain key issues for the identification of new virulence mechanisms of M. tuberculosis, for elucidating the extraordinary evolutionary success of M. tuberculosis, and for gaining new insights and perspectives into host-pathogen interaction, new vaccine concepts and therapeutic interventions.