Smear Prep/ Stain Types/Negative Staining Flashcards
What is most important in obtaining a smear?
Inoculating loop with bunsen burner and test tubes to keep aseptic technique
Why must smears be heat fixed?
To kill the bacteria, and also preserve microbes w/ minimal shrinkage or distortion while stained, AND to prevent smears being washed away from slide
What is simple staining?
Technique that uses SINGLE dye to stain
A chromophore is
Dyes that consist of charged colored ions
Basic Dyes carry what charge and do what to cells?
Basic dyes carry a positive charge, and are attracted to negatively charged cellular components. Basic dyes STAIN CELLS
Basic Dye Examples include
Methylene Blue, Crystal Violet, Safranin, Malachite Green
What is negative staining?
A technique that uses acidic dye to stain background against where colorless cells can be seem
Acidic dyes carry what charge and do what to cells?
Acidic dyes carry a negative charge that is repelled by cells, stains background so colorless cells stand out against it.
Acidic Stain examples
India Ink, Nigrosin
What is differential staining?
Techniques used to distinguish groups of bacteria
Examples of differential staining
Gram Staining, Acid Fast Staining
What charge does a cell wall membrane have?
Negatively charged
Why does negative staining color background and not cells?
Negative staining use acidic dye, which carries negative charge. This is repelled by bacteria’s cell wall which is also negative.
Negative staining is useful when
other staining techniques don’t clearly indicate morphology or size
Negative Stain Technique
Nigrosin (India Ink) at one end of slide, Add drop of water, Add bacteria, take another slide and create smear across the entire slide. Let smear air dry
