Tuberculosis is a Mycobacterium which is a genus classified in the phylum Actinobacteria. This genus is known to cause diseases in mammals. Tuberculosis' scientific name is Mycobacterium tuberculosis. Robert Koch discovered pathogenic bacterial species discovered in 1882 by. M. tuberculosis has a waxy coating on the cell's surface which makes it unable to be Gram stained.(Brennan, 2003). Gram staining is a method to differentiate bacterial species into two groups. This bacterium is Gram-negative because the waxy coating will not absorb the stain. When M. tuberculosis is in the lungs it is engulfed by macrophages trying to eradicate the disease, but the cell wall is coated in mycolic acid which blocks the fusion of the phagosome and lysosome so the M. tuberculosis bacterium survives being “eaten” by the macrophage. M. tuberculosis is can also withstand weak disinfectants. The M. tuberculosis bacterium divides every 15 – 20 hours which is very slow compared to Escherichia coli which divides every 20 minutes (Havlir, 1991).
Vega, Adrian and Heath, Brennan, "A Look Into Tuberculosis" (2015). Infectious Diseases Project 2015. 15.