Mycobacterium tuberculosis is a slow-growing obligate aerobic bacillus that causes most cases of tuberculosis (TB). It is a small, rod-like microbe that can withstand weak disinfectants and survive in a dry state for weeks, but can only grow within a host organism. M. tuberculosis has a thick waxy cell wall that is responsible for the typical caseous granuloma formation in tuberculosis. ESAT6 is a protein secreted by M. tuberculosis that induces a strong immune response in infected organisms, making it a strong candidate for the development of a vaccine against tuberculosis. ESAT6 may also be useful in the detection of the disease. Deletion of the ESAT6 gene leads to the loss of virulence of M. tuberculosis.