VUMIE Online - Section 2

Worksheet – Use of indicators and reagents

Section 1

For the following questions, choose whether the description applies to indicators, reagents, both, or neither.

1. Results from growth are not obvious until this is added

2. Added to the medium before autoclaving

3. Added to the medium after autoclaving and before incubation

4. Typically looks for production of acidic or alkaline growth products

5. Not an ingredient of the medium when made 

6. Present in the powdered medium used to make tubes and plates

7. Added to the medium after incubation

8. Typically show results by means of a color change

9. Typically looks for pH change

10. Results shown when mature culture is removed from incubator

11. Typically looks for production of specific chemicals produced by metabolism

Section 2

Indicate whether each of the following tests is determined using an Indicator, Reagent, or Neither.

Note: you will not be responsible for what indicator and reagents are used in these. But knowing when indicators are used instead of reagents, and the fact that there are some tests that do not use indicators at all, is helpful in understanding media and tests.

12. Urease test

13. Malonate test

14. Indole test

15. Nitrate reductase test

16. Potassium cyanide test

17. Glucose fermentation test

18. Lysine decarboxylase test

19. Citrate utilization test

20. Esculin hydrolysis test

21. Oxidase test

22. Catalase test


23. Complete the blanks in the following table:

Chemical Indicator or reagent? Color of uninoculated medium Color of acidic medium pH where this change occurs

Methyl red

Phenol red

Brom Thymol Blue