Mycobacterium tuberculosis (M. tuberculosis) is a bacterium that causes tuberculosis (TB) in humans. TB is a disease that primarily affects the lungs, although it can attack other parts of the body. It spreads much like a cold or the flu — through the expelled airborne droplets from a person with infectious TB Mycobacterium tuberculosis is a species of pathogenic bacteria in the family Mycobacteriaceae and the causative agent of tuberculosis. First discovered in 1882 by Robert Koch, M. tuberculosis has an unusual, waxy coating on its cell surface primarily due to the presence of mycolic acid. Mycobacterium tuberculosis (M. tuberculosis) is a bacterium that causes tuberculosis (TB) in humans. TB is a disease that primarily affects the lungs, although it can attack other parts of the body. It spreads much like a cold or the flu — through the expelled airborne droplets from a person with infectious TB