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Why the primary stain and the secondary stain is not needed for the negative stain?
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What is the secondary stain in gram stain procedure?
It is crystal violet & stains all cells purple.
What type of dye is used to stain the specimen when the acid-fast stain and the gram stain are used?
Both processes use 2 stains. The Gram staining process uses crystal violet as the primary stain and safranin as the secondary stain. Acid-fast staining uses carbol fuchsin as the primary and methylene blue as the secondary.
Why does the counterstain not change the color of all of the cells is it because the primary stain repels or masks the secondary stain?
In a gram stain the primary stain is crystal violet. Iodine then sets that dye into the gram positive cells while alcohol washes out the crystal violet from the gram negative cells. Then safranin, which is the counterstain in a gram stain, is used to dye the rest of the bacteria. This is the example I can give you of why a counterstain does not change the look in all the cells. Though safranin stains all the cells, the gram positive cells that were dyed purple from crystal violet don't look pink - only the gram negative do.
Can Gram-positive organism appear as Gram-negative?
Staphylococcus are Gram positive because, in Gram's test, the decolorizing agent (ETOH) cannot penetrate the thick cell walls, and the stain remains behind: hence Gram positive. I am not aware of a gram negative staph species and, considering the degree of mutation that would be needed to form such a strain, I do not believe that it's possible. I should add that a not-so-brief scan of the net showed me no Gram negative staph mentioned anywhere. So -- for now -- no. That said, let's see what the future holds.
What is secondary and counter stain?
counterstains are selected to be contrasting color so that the target of the primary stain can easily be differentiated on a contrasting background. This makes life easier, when, for example you need to count the number of nuclei in a smear, or number of gram positive bacteria in a mixed population.
What is the gram stain for cholera?
Gram Negative
Is B subtilis a gram positive or gram negative bacterium?
gram positive Exactly. When doing a gram stain on B. subtilis, this bacterium resists decolorization (keping the first stain and NOT taking on the color of the secondary stain). Therefore, this bacterium is gram (+).
What is secondary stain?
A secondary stain is Methylene blue. This type of stain is used in a acid fast staining. This type of staining test can determine medical conditions such as tuberculosis.
Why is it essential that the primary stain and the counterstain be of contrasting colors?
It is essential that primary stain and the counterstain be of contrasting colors so that the target of the primary stain can easily be differentiated on a contrasting background.
Why do gram positive bacteria retain the primary stain methylene blue while gram negative bacteria are decolorized by rinsing with ethanol?
capsule
Why is counterstaining necessary when using a differential staning technique such as the gram stain?
The counter-stain allows you to see all the structures that were not stained with the primary stain. Without the counter-stain, all you would see is the purple-stained structures (nucleus, some cytoplasmic proteins), but you would have a difficult time observing the cell membrane and many cytoplasmic structures.
Is uranyl acetate a negative stain?
Yes, uranyl acetate is used as a negative stain in electron microscopy.
