Ex. 4: Gram Stain. Chromophores Basic vs. acidic dyes. Primary stain (stains all cells on slide) Decolorizing step (removes stain from certain types of cells) Counterstain (stains the decolorized cells). Differential Stain. Strongly advised:.
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Decolorizing step (removes stain from certain types of cells)
Counterstain (stains the decolorized cells)Differential Stain
When doing any of the microbiology labs, make sure to carefully follow the procedure outlined in the Materials and Methods section . . . And any advice given by your instructor!
From now on: read the labs before coming to class!
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From Liquid Medium
Transfer one loopful of H2O into circle area of slide.
Using loop, suspend very small quantity of colony of interest in that drop of water and spread the suspension evenly. It should only appear slightly milky. Do NOT use too many bacteria
Air-dry and heat-fix
…the most important bacterial stain!
Memorize steps as soon as possible
ASM Microbe Library
MacGraw Hill Animation
Precipitated crystal violet stain may resemble cocci. Clues: dense clumping, small size of the gram-positive dots. Paucity of organisms elsewhere in the field.