Question

- Which of the following pairs is mismatched? d. iodine mordant e. none of the above a. alcohol-decolorizer b. crystal violet-basic dye c. safranin-acid dye 2, Suppose you Gram stained a sample from one colony and observed a field of red and blue cocci. Adjacent cells were not always the same color. You could conclude that you have d. old cells e. made a mistake a. a mixed culture b. young cells c. dividing cells 3. Which of the following components is found only in gram-positive cell walls? b. N-acetylmuramic acid a. Lipopolysaccharide d. lipoprotein e. Techoic acid c peptidoglycan for questions through not at all. Place the letter corresponding to the correct color in the answer blank Choices may be used once, more than once, or a. purple c, colorless d. brown e. none of the above The appearance of gram positive bacteria after addition of the first dye in the Gram stain. S. The appearance of the gram negative bacteria after addition of the mordant in the Gram stain. .The appearance of the gram negative bacteria after addition of the decolorizing agent in the Gram stain 7- The appearance of the gram positive bacteria after adding the counterstain - The appearance of the gram negative bacteria after completing the Gram What is the total magnification of an E. coli cell viewed with a 10x ocular in the Gram stain. stain. lens and a 45x objective lens? a. 10x b. 45x c. 100x d. 450x e. none of the above

Answer 1

Due to high thickness of peptidoglycan present in the cell wall of bacteria and less thickness of peptidoglycan in gram negative bacteria, both type of bacteria retain different color on gram staining. Applying, gram stain method, we can answer these questions

1. The safranin is used as a counterstain in gram staining specifically for the gram negative bacteria. Safranin and crystal violet are both basic dye. Hence, incorrect match is option c.

2. Adjacent cell will be of different color because it could be mixed culture having both gram positive and gram negative bacteria. Hence, option a is correct

3. Gram positive bacteria have techoic acid in their cell wall. This is the unique characteristic of group positive bacteria. Hence, e is correct option.

4. Purple

5. Purple

6. Colorless

7. Purple

8. Red or pink