MCB2010L Study Guide - Midterm Guide: Mycelium, Nocardia, Cryptococcus
11 Nov 2020
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Dyes: carbol fuchsin, acid alcohol, methylene blue. Non-acid fast is blue: g (+) & g. Used to find pathogenic mycobacterial species (e. g. mycobacterium tuberculosis; mycobacterium and some nocardia) Mycolic acid and allow movement of the dye through the cell wall. If ethyl alcohol is used instead of acid alcohol, only g (-) changes, g (+) will stay magenta throughout. Uses both basic and acidic dyes: cvsm basic; pen acidic. Cells capable of producing an extracellular capsule includes: strep. The capsules make the bacteria sticky, allowing it to stick and enhance the bacterium"s ability to evade phagocytosis and hide from the body"s immune system. With both basic and acidic dyes staining the background and cells, the capsules (white) can be easily visualized. Water is used to decolorize the vegetative cells. Peptidoglycan is responsible for cell wall composition and rigidity. G (+) can become pink if washed with too much alcohol and if its over 24 hours old.
