Index >>Prokaryotes Microbes >> Structure of Mycobacteria/Serpentine Cords

The walls contain a peptidoglycan with diaminopimelate, and the cells can be  converted to spheroplasts by lysozyme. The walls have a remarkably high lipid content (up to 60% of its dry weight), much of which is attached to polysaccharide. The Polysaccharides which include glucan, mannan, arabinogalactan and arabinonmannan, are also found in culture filtrate. The glycolipids and protein are ocated in a firmly attached outer layer of the wall and the externallocation of the lipid accounts for the hydrophobic character of the cells.

The virulent strains of tubercle bacilli differ from a virulent strains in the nature of their growth. On the surface of liquid or solid media, virulent strains grow as inter wining serpentine cords, in which the bacilli aggregate with their long axes parallel. Most a virulent strains grow in a more disordered manner. The factor, which may be essential for both virulence and serpentine growth is known as cord factor, which was extracted by Bloch from virulent cells by petroleum ether. The cord factor has been identified as a mycoside, 6-mycolyl trehalose. It is toxic, inhibiting migration of normal polymorphonuclear leukocytes in vitro . It is more abundant in virulent strains. The toxicity of this factor has been related to much disturbances in microsomal enzymes, mitochondria. and lipid metabolism in mice liver