2420-Lab 3- Bacterial Staining Techniques-II-(Differential)

Directions:

Answer following questions after reading the information and watching the video from the link below. Use color RED or BLUE for your answers. Submit the completed document on eCampus for grading. Refer to

· the textbook chapter 3 (3.2) (Nester- McGraw Hill)

· Link: Bacterial Staining Techniques-II, Virtual Edge Experiment-4

Differential Staining

1. What is differential staining?

Gram Staining (4A on Virtual Edge)

Watch the video of Gram Staining from the textbook chapter 3- review 3.2 (pages 53-54), 3.5 (pages 65-67– cell wall of prokaryotic cells) and answer the following questions.

2. What is the purpose of Gram staining?

3. Who invented the Gram staining procedure?

4. What is the first stain used in Gram staining procedure?

5. Do all cells pick up this stain?

6. What is the function of a mordant?

7. Which mordant is used in the Gram staining procedure?

8. What would be the result if the mordant is forgotten from the procedure?

9. What is alcohol used for?

10. Why is decolorization necessary?

11. What is a counterstain?

12. Which counterstain is used in Gram staining?

13. What are cells called that retain the primary stain?

14. What are cells called that lose the primary stain?

15. What are cells called that take up the counterstain?

16. What type of cells do not take up the counterstain?

17. After the Gram staining procedure, Gram positive bacterial cells appear ______________ colored.

18. After the Gram staining procedure, Gram negative bacterial cells appear ______________ colored.

19. Which component of the cell wall in Gram positive bacteria is responsible for the retention of the primary stain?

20. Which component of the cell wall in Gram negative bacteria is responsible for the retention of the counterstain?

21. What would be the color of Gram negative bacterial cells if the decolorization step is forgotten? Explain.

22. Which bacteria were used in this experiment and what were their shapes? (From the textbook, review 3.3- Morphology of prokaryotic cells)

23. From what you have learned from the textbook, if a patient has E. coli infection which are Gram negative bacteria, would you advise them to take a course of Penicillin? Why or Why not?- Explain

24. Following picture shows the Gram staining result. Point out (or describe) Gram positive and Gram negative cells from the picture. Be sure to specify morphology:

Acid-fast Staining- (4B on Virtual Edge):

Read the text from the following to help answering the following questions.

· link Acid-fast Staining,

· textbook chapter 3- section 3.2

25. List two genera of bacteria that are stained for identification by using Acid-fast staining method.

26. Which fatty acid is found in the cell walls of acid-fast bacteria?

27. Which primary stain is used in the acid-fast staining procedure?

28. Why is steaming necessary at this step?

29. Which counterstain is used in the acid-fast staining procedure?

30. Why is acid-alcohol used to decolorize in the acid-fast staining process instead of regular ethanol?

31. Which two types of bacteria were used in this experiment?

32. Which of the above two types of bacteria were acid-fast? (or retained the primary stain?)

33. From the picture below, point out the acid-fast cells:

34. If you are working in a clinical diagnostic laboratory, which of the above staining methods would you use to predict the cause of infection under following conditions?

a. Tuberculosis

b. Strep throat

 

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