Mycobacterium tuberculosis is a rod-shaped, immobile bacteria, says Kenneth Todar of Todar's Online Textbook of Bacteriology. It thrives only in the presence of oxygen and is an intracellular parasite.
Mycobacterium tuberculosis, the causative agent of tuberculosis, is an oblong, bacillus-type bacterium that grows and multiplies within cells, according to Todar. It is acid-fast and neither Gram-positive or Gram-negative, meaning that it is impermeable to many common staining methods used in visualizing bacteria. Mycobacterium tuberculosis is slow-growing and typically requires up to six weeks to form visible colonies in laboratory cultures. Over half of the cell wall of Mycobacterium tuberculosis is lipid, creating a protective water-resistant shell around the bacteria.
Mycobacterium tuberculosis enters hosts via inhalation from the air, says About.com. After inhalation the bacteria enter a type of white blood cell known as a macrophage. Macrophages normally locate and destroy pathogens in the body, but Mycobacterium tuberculosis is able to live and multiply inside the cells without being destroyed.
In healthy individuals tuberculosis lies dormant and causes no symptoms, reports the World Health Organization. In many individuals, uninfected white blood cells enclose the bacteria to prevent its spread. These individuals are not contagious. Symptomatic individuals typically present with a cough, bloody sputum, fever and weakness. Treatment for tuberculosis requires a lengthy course of antibiotics.