Gram Staining: Purple + Red = Blue???

[Gauss44]

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Is this accurate, and if so, why?...

Gram positive bacteria previously stained with crystal violet retain the violet color after being rinsed with alcohol. (Okay, so they're purple or violet.) Then, a red-colored counter-stain called, safranin is added. "The purple colored gram-positive bacteria pick up the red stain and now appear blue."

This seems odd to me: purple+red=blue? If I were to mix purple and red paint, I don't think I would get blue.

Please explain.

 

[SuperSneaky24]

Wait where you getting this from? From what I remember about gram staining and what I googled, safranin is a pretty strong counterstain so the bacteria would look red/pink, not blue. Did a color blind person write this?

 

[Czarcasm]

Is this accurate, and if so, why?...

Gram positive bacteria previously stained with crystal violet retain the violet color after being rinsed with alcohol. (Okay, so they're purple or violet.) Then, a red-colored counter-stain called, safranin is added. "The purple colored gram-positive bacteria pick up the red stain and now appear blue."

This seems odd to me: purple+red=blue? If I were to mix purple and red paint, I don't think I would get blue.

Please explain.

Well the key thing to realize is that both Gram + and - pick up the safranin stain. Initially we do 1. Crystal Violet 2. Alcohol wash - For gram negative, the alcohol removes the stain from Gram - bacteria, but because of the thick layer in Gram +, it is retained. 3. Safranin - both pick up the stain (red), however, because Gram + also have the violet stain, it appears violet. The violet stain masks the red safranin stain.

Also, the red is almost pinkish in color. It's not a strong red like you're thinking, hence why the purple stain masks it.

 

[pepocho]

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