BI 420L Medical Microbiolo Fixing a Slide and the Gram Stain 10 points In the fo
ID: 149061 • Letter: B
Question
BI 420L Medical Microbiolo Fixing a Slide and the Gram Stain 10 points In the following vid and the Gram stain: eo you can view the procedure for fixing a slide https://youtu.be/sxa46xKIOY Answer the following questions: 1. What color would Gram negative bacteria be after the first step, i.e. staining with crystal violet? 2. Why did Hans Christian Gram develop the stain, i.e. what was his original purpose for the stain? 3. How does Streptococcus pyogenes appear after negative? What color are they after the stain? 4. How does Salmonella typhi appear after staining the Gram stain, i.e. Gram positive or Gram with the Gram stain? What color are they after the stain? 5. Explain why we think bacteria stain differently with the Gram stain. In other words, how do Gram positive and Gram negative bacteria differ?Explanation / Answer
1) After the first step i.e. after the applying crystal violet stain, both Gram positive and Gram Negative bacteria will look purple unitl the washing and decolorization step.
2) Gram develoed the stain for identification of bacteria. Christian gram's intial work was concerned with the study of human RBCs. But, later on, he started examining the lung tissues of patients who died of pneumonia. When Gram studied the tissues, he found out that there are certain stains which were preferentially taken up and retained by the bacterial cells present in those affected tissues. During this study he found out that certain bacteria (pneumococci) retained the color of Gentian Crystal Violet solution (Gram Positive ) while other species became bleached or de-colorized by the alcohol wash, so he termed them Gram Negative.
3) Streptococcus pyogens are gram positive bacteria, so they will appear viotel in color after Grams staining.
4) Salmonella typhi are Gram negative bacteria, so they will take the counterstain and will appear pink after staining.
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