Biology/Question about Gram stains?
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Question
I am trying to figure out the effect of a gram stain if you reversed the crystal violet and the safranin stains.
Hi Elizabeth: The purpose of the Gram stain is to differentiate various kinds of bacteria for identification. It is usually the first step in classification of unknown bacteria.
After the first stain (crystal violet) ALL the cells are blue. That's why we destain the Gram neg bacteria with alcohol/acetone. The then (colorless) gram negative bacteria are stained with safranin (red) so we can see them.
There would be no point in doing the safranin stain first, since it would be covered up by the crystal violet.
Hope this helps, write back if you have more questions.
FM Rollwagen, PhD
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Answers by Expert:
Florence M Rollwagen
Expertise
I can answer questions in biology, microbiology and immunology on the undergraduate or graduate level. I can also address medical and health concerns regarding alternative medicine, autoimmune diseases (lupus, MS) liver disease and intestinal problems.
Experience
I have over 20 years experience in research and teaching at the medical/graduate level, and 5 years teaching college biology and microbiology. My expertise is in microbiology and immunology, specifically the biology of cytokines and soluble immune response modifiers. I also carried out original research in blood substitutes and shock/trauma.
Organizations
American Association of Immunologists (AAI)
American Association for the Advancement of Science (AAAS)
Publications
Journal of Experimental Medicine, Journal of Immunology, Cytokine, Shock, Experimental Hematology
Education/Credentials
BS biology 1966
MS biology 1968
PhD immunology 1979
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