(Science: microbiology) bacteria with unusual cell walls that are resistant to digestion, being waxy, very hydrophobic and rich in lipid, especially esterified mycolic acids. Staining properties differ from those of gram-negative and gram-positive organisms, being acid-fast. Many are intracellular parasites, causing serious diseases such as leprosy and tuberculosis. Cell wall has strong immunostimulating (adjuvant) properties due to muramyl dipeptide (MDP). Mycobacterium bovis causes tuberculosis in cattle, attenuated strain is bacille Calmette-Guerin (bCG), used for immunisation. Mycobacterium leprae is the causative agent of leprosy. Mycobacterium microti is a mycobacterium that causes tuberculosis like disease in small rodents (Microtus microtus is the vole), will infect mice but not humans and is therefore much used as a laboratory model. Releases large amounts of cAMP which may inhibit lysosome phagosome fusion. Mycobacterium tuberculosis Is an obligate anaerobic nonmotile bacterium, causative agent of tuberculosis in humans. Lives intracellularly in macrophages.