Biochemical Test Questions

1-3. Phenol Red is used as a pH indicator for the phenol red carbohydrate broth fermentation test. At what pH (acidic or basic) is the pH indicator: yellow _______, or red ________?

4-6. All bacteria ferment glucose in order to produce ATP, but some bacteria can ferment sugars that contain more than just glucose. What two sugars or other chemical components are found in each of the following?

            Sucrose ___________________

            Lactose ___________________

            Mannitol __________________

7-10. Urease is an enzyme produced by some bacteria in order to break down urea.

What is the chemical formula of urea? __________________________

What are the two endproducts of urea utilization?

_________________              __________________

            What might the endproducts of urea break down be used for by the bacterium?

                        ______________________________________________

11-12. H₂S is produced as an endproduct of utilization of what amino acid by a bacterium?                   _____________________________

           H₂S is a clear gas that is not easily observed. What is added to the SIM media so the black precipitate will form indicating H₂S production?        _______________________

13-14. Indole is an endproduct of the utilization of which amino acid?

________________________________

           What reagent must be added to the indole tube to confirm the presence of indole?              _________________________

15-18. All bacteria have the ability to utilize glucose, but they can use two different metabolic pathways to accomplish it. (Note: the bacterium use one pathway or the other, not both.)

What pathway does the methyl red indicator test for? ______________________

The Voges Proskauer test, tests for the utilization of the Butylene Glycol Pathway. In order to read the test, Barrett’s A & Barrett’s B reagents must be added after incubation.

What chemical is Barritt’s A?   _________________________

What chemical is Barritt’s B? _________________________

How are the endproducts of the Butylene Glycol Pathway different from the endproducts that are tested for by the addition of Methyl Red?

            __________________________________________________________

19. If the Citrate tube remains green after inoculation and incubation, what does this negative reaction mean?            ____________________________________________

20. Why is it important to place sterile oil over the decarboxylase media after inoculation?            ______________________________________________

Referencing of where information was obtained, to answer these questions, is required!