You are in microbiology lab and are approached by another member of the class wh

Question

You are in microbiology lab and are approached by another member of the class who asks you to help him with a Gram stain. He tells you that he has performed the first 4 steps of the procedure (as shown in Fig 2.22 of the Slonczweski textbook) but just remembered he needs to make an important phone call and asks if you will complete the procedure as he is running out the door. You complete the procedure for him but after he returns and reviews his notes, he realizes that he omitted the step in which the cells are stained with crystal violet. The specimen that your friend was staining contained the Gram-positive organism B. subtilis.

A) When the Gram stain procedure is done properly, what color should these cells be when viewed in the microscope?

B) What color will the cells that you stained be?

Explanation / Answer

A). When gram staining is done properly, the cells should be violet colored as Gram positive cells retain the color even after treatment with alcohol.

B). The cells that we stained should be pink colored because we skipped the first step in which cells are first stained with crystal violet. The pink color comes from counter stain (usually Safranin or fuschin) that's that is added in last step of gram staining.

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