BIOL 2100 Lecture Notes - Lecture 3: Gram Staining, Methylene Blue, Crystal Violet
Document Summary
Chapter 3 observing microorganisms through a microscope. Prokaryote cell wall: bacteria cell wall = slightly negative; basic dye (positive charge) would be better to use to stain. Cell wall of gram-positive bacteria: composition and characteristics: thick, rigid (many layers) peptidoglycan, teichoic acids: consist primarily of an alcohol and a phosphate, no outer membrane, turns blue/purple. Smear preparation: add specimen to microscope slide: 2. Heat fix smear: adhere bacteria to slide: 3. Crystal violet (primary stain; purple) applied to a heat fixed smear: a basic stain, leave for one minute, then wash with water, 4. Iodine solution (the mordant: leave for one minute, then wash with water, 5. Decolorizer (alcohol or alcohol-acetone: very critical step because it determines what color you will have at the end of the procedure, 15 seconds, 6. Safranin (the counterstain; secondary stain: a basic stain, set for one minute, then wash, 7. Water (wash off excess stain after each step)
