Bacteria such as mycobacterium have cell walls that contain a high lipid content. One of the cell wall lipids is a waxy material called mycolic acid. Mycolic acid is a complex lipid that is made of fatty acids and fatty alcohols and have carbon chains up to 80 carbons in length. Mycolic acid significantly affects the staining properties of these bacteria and prevents them from being stained by many of the stains routinely used in microbiology. The acid fast stain is an important tool in the identification of Mycobacterium tuberculosis, the organism that causes tuberculosis and Mycobacterium leprae, the bacterium that causes leprosy in humans. Mycolic acid makes the cell wall impermeable to many stains. In order to stain bacteria with high lipid content one must use a technique that makes them more permeable to stains. The Ziehl-Neelsen method and the Kinyoun acid-fast method will be discussed in next week’s post.
Paul’s Favorite Posts