Mycobacterium tuberculosis, the causal agent of Tuberculosis, is an ancient and unique pathogen that has been living amongst us for many years. Despite this, the first contact between the pathogen and the host, which occurs in the alveolar lining fluid (ALF), is still poorly understood. Our laboratory is studying how this first host-pathogen interaction shapes the initial stages of infection and ultimately leads to different outcomes depending on the ALF status and composition. By studying how the different components of the ALF are able to interact and change M. tuberculosis, we will be able to generate better strategies for the prevention, treatment and diagnostic of Tuberculosis. We are currently studying M. tuberculosis metabolic changes that occur upon contact with the human ALF and how those changes shape the infection progression in vivo.