Microbiology - Identification of Bacteria - Discussion

Discussion :: Identification of Bacteria - Section 1 (Q.No.11)


What is the colour of gram -postive bacteria on a gram staining?

[A]. Purple
[B]. Pink
[C]. Colourless
[D]. Green

Answer: Option A


No answer description available for this question.

Md.Shofiqul Islam said: (Mar 1, 2018)  
Gram positive bacteria have a thicker peptidoglycan cell wall than gram negetive bacteria. When crystal violet and Iodine complex enter into gram positive cell and combine to form CV-I. This molecule is larger than crystal violet molecule that entered the cell and it can not washed away after alcohol wash. So it don't change its purple color on the other hand this CV-I Complex can easyly washed away after alcohol wash for the thin peptidoglycan cell wall and then gram negetive bacteria become colorless. After using counter stain sufranin it retain its pink color. Thats why the gram negetive bacteria become pink after gram staining. Thank you.

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