1)Please list the purpose of each of the following reagents in the Gram Stain: Crystal Violet,...

1)Please list the purpose of each of the following reagents in the Gram Stain: Crystal Violet, Iodine, 95% alcohol, Safranin.

2)What color would a Gram negative cell be if we skipped the alcohol step? What color would a Gram positive cell be if we skipped the same step? Why?

Expert Solution

Gram Staining

This is a method of staining of bacteria depending on their cell wall composition and differentiates them into Gram positive or Gram negative .The four components of Gram’s staining procedure along with their roles are mentioned below

a)Crystal violet : Acts as the primary stain which is basic in nature stains both positive and negative bacteria.

b)Iodine : It is used as mordant where when treated with iodine it forms a complex with the primary stain so that the stain may not move out of the cell.The complex restricts such movement .

c)95% alcohol : Alcohol is used as a decolorizing agent .It causes the effect by eliciting dehydration of the lipids which are present in the bacterial cell by causing their shrinkage .

d)Safranin : It acts as the secondary stain or the counter stain.

In bacteria when more amount of peptidoglycan is present ,initially crystal violet is taken up and then complex is formed using iodine and when alcohol is added this peptidoglycan shrinks and almost immobilizes the complex and when secondary stain is added they do not get stained by it and appears purple .This group of bacteria is called Gram positive .

On the other hand in bacteria where the amount of peptidoglycan is less there during the addition of alcohol the primary stain is washed as in turn it takes up the secondary stain and such bacteria are termed Gram negative and they give red color as they are stained by safranin.

b)If the alcohol step is skipped then Gram negative bacteria will not lose the primary stain and will appear purple.

Gram positive bacteria will also appear purple for the same reason.

gladiator answered 2 years ago

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