Both crystal violet and safranin are basic stains and may be used to do simple s

Question

Both crystal violet and safranin are basic stains and may be used to do simple stains on Gram-positive and Gram-negative cells. This being the case, explain how they end up staining Gram-positive and Gram-negative cells differently in the Gram stain. If you saw large, eukaryotic cells in the preparation made from your gumline, they were most likely your own lial cells. Are you Gram-positive or Gram-negativet (You can make a good guess about this even if you didn't see your cells.) 4 One of your lab partners has followed the recommended procedure of running Gram-postive and Gram-negative control organisms on her Gram stain of an unknown species. Her choices of controls were Escherichia coli and Bacillus subtilis. She tries several times and each time concludes she is decolorizing too long because both controls have pink cells (one more than the other). What might you suggest she try and why?

Explanation / Answer

2. GRAM STAINING:-
-Heat fixed smear is stain with crystal violet.
Crystal violet stain both Gram- and Gram+ so it is called primay stain.
- Add Gram's iodine. It will adhere only gram+ because of peptidoglycan in their cell wall.
- wash with acetone for about 30 second.
- Gram- purple dye washed away.
- Gram+:- purple dye remain adherent. - lastly add safranin which will stain cells pink.

Interpretation:-
(a) Gram positive will appear purple- colour of crystal violet.
(b) Gram negative will appear pink- color of safranin.
Examples:-
- Staphylococcus-gram-positive
- Enterobacterisceae:- gram negative

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