Expert: Walter Hintz - 7/16/2007

Question
If I omit the alcohol step in a gram stain for a gram negative bacteria, would I end up wih a purple or red color?
Why? Also, Gram positive bacteria will remain purple because the iodine has crystallized the crystal violet in the cell, right?

Answer
Hi Em
The alcohol is used to decolorize the bacteria.Therefore it would stay purple. If you do not decolorize the bacteria how would you know it is gram - And If you know you have a gram negative to start with why would you gram stain it in the first place?
Gram positives retain the crystal violet because ofthe presence of peptidoglycan that traps the stain in the cell wall. I am not sure if it involves crystal formation