BIO 315 Lecture Notes - Lecture 6: Gram Staining, Crystal Violet, Negative Stain
23 Jan 2020
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Document Summary
Staining bacteria: preparing smears for staining, live and/or unstained specimens have little contrast with the surrounding medium. In a basic dye, the chromophere is a cation. In an acidic dye, the chromophere is an anion: staining the background instead of the cell is called negative staining, simple and differential stains, simple stain: use of a single basic dye. Highlights the entire microorganism to visualize cell shapes and structures. A mordant may be used to hold the stain or coat the specimen to enlarge it: differential stains: used to distinguish between bacteria. Gram positive cell wall: alcohol dehydrated peptidoglycan cv-i crystals do not leave. Cell wall integrity and permeability may change in cultures older than 24 hr: cell density of the smear. Improper heat fixing of the smear: duration and thoroughness of washing at each step particularly after crystal violet, clinical importance of gram staining, very useful in differentiation and identification of bacteria, procedure is simple and quick.
