SIMPLE STAINING EXP 1 Flashcards
Used to increase the contrast between the specimen and the background.
Colour compound stain
A type of stain or technique where a single stain is used and all cells stain the same colour
Simple Staining procedure
How would you describe a cell’s morphology? How about the type of dyes?
Cocci, rods, spirals and vibrios
Dyes: Methylene blue, basic fuchsin, and crystal violet
What are the two types of staining procedures? What are they used for, the morphology of the stains.
Positive and negative
- Positive staining procedure: basic stain, for light microscopy, positively charged chromophore, and blue methylene is used for staining.
- Negative staining procedure: acidic stain, negatively charged chromophore to differentiate the background instead of the cell wall
Pure cultures used for simple staining experiment?
Escherichia coli, Bacillus brevis, Staphylococcus epidermidis
How to aseptically transfer bacteria?
Hold it like a pencil 45 angle, flame from up (yellow) to the cone of the flame (blue)
What is the purpose of heating the test tube when transferring from a broth culture?
Flaming the mouth of the test tube sterilizes the air in and around the mouth of the tube and prevents cool air which may contain contaminants, from entering the pure culture
Why is the smear air dried before heat fixing?
if drying process is sped up, the cell’s shapes will be distorted. It is always best to wait until the slide is dry before heat fixing.
What are the limitations of simple staining?
it only provides information of the cell’s morphology (size, shape and arrangement)
What can be determined about a cell through simple staining?
the cell’s charged chromophore, to determine bacterial cell morphology
What is the purpose of heat fixing the smear?
it coagulates the bacterial proteins and fixes them on the slide
Can dyes other than methylene blue be used for direct staining?
Yes, as long as it is positively charged, since bacterial cell wall is negative charged
