VUMIE Online - Section 2

Worksheet – Amino acid utilization


1. Complete the blanks in the following table:

Sterile medium inoculated Day 1 Incubated culture observed on Day 2 Incubated culture observed on Day 3 Test result




Section 1

Indicate whether these statements are true or false.

2. Glucose is always used in metabolism before amino acids are used.

3. In an arginine dihydrolase test, the broth turning from purple to yellow after a day of incubation indicates a positive test.

4. The LDC test will not work unless the microbe can use glucose.

5. If you do not observe the result of the ornithine decarboxylase test after one day of incubation, you cannot know whether a purple tube after two days indicates a positive result.

6. Brom cresol purple is added to the medium to acidify the culture and activate ADH, LDC, and ODC.

7. The same basic medium can be used for the ADH, LDC, and ODC tests, with the only change being which amino acid has been added.

8. Phenylalanine metabolism is indicated when the pH indicator in the medium turns green.

9. The test for PDA must be incubated for 48 hours before evaluating the results.

10. A pattern of purple tube, then yellow tube after incubation 1, and finally purple tube after incubation 2 represents a positive test result for either ADH, LDC, or ODC tests.

11. Hydrochloric acid and Ferric Chloride are added to phenylalanine agar before it is autoclaved to help determine whether a microbe can metabolize phenylalanine.

12. The indicator brom cresol purple is not involved in detection of phenylalanine deaminase activity.

13. The pH changes observed during the ODC test is acid to alkaline, and then back to acid.

14. In order to test for phenylalanine deaminase, glucose must first be used to acidify the medium.

15. To determine the changes in a positive test, LDC test uses an indicator and ADH uses a reagent.

16. Brom thymol blue is not used in any of these four tests.

17. Ornithine is an amino acid used in protein synthesis only by birds.

18. It takes two days for the decarboxylase tests to turn acidic to allow interpretation of results.

19. PDA, ADH, LDC, and ODC test all use broth media found in tubes.

20. PDA is interpreted by adding brom thymol blue after incubation and looking for a green color change.

21. Sugar hydrolysis generates acids, but amino acid hydrolysis generates alkaline chemicals.

Section 2

Based on the following image, indicate whether the statements are true or false.

22. The test shown above could be ADH or PDA.

23.  The test shown above could be LDC or ODC.

24. The test shown above shows a positive test result.

25. The indicator present is brom thymol blue.

26. The yellow tube has had FeCl3 and 0.1N HCl added.

27. The pH of the tube in the middle is alkaline (basic).

28. The microbe has used an amino acid for growth.

29. The result went from positive on Day 2 to negative on Day 3.

30. The main event between Days 1 and 2 was amino acid digestion.

31. The main event between Days 2 ad 3 was a rise in pH.