Question

Discuss the structural differences and similarities between Gram positive and Gram negative cells using as much detail as possible and explain how the Gram stain works related to the structure of Gram positive and Gram negative cells. Use your own words.

Answer 1

Gram staining procedure:
i. Cell fixation
ii. Crystal violet addition
iii. Iodine treatment
iv. Decolorization
v. Counterstain with Saffranin

Gram +ve bacteria appear in purple color after staining.
Gram-ve bacteria appear in red color after staining.

Gram +ve bacteria contain thick cell wall which retains the crystal violent even after decolorization. So, they do not further take up the safranin dye. Hence they appear in purple color.
Gram +ve bacteria contain thin cell wall which loses the crystal violent after decolorization. So, they take up the safranin dye. Hence they appear in red color.