12. Microbial Metabolism

Define and explain the importance of each of the following:

a. Catalase

b. Hydrogen peroxide

c. Peroxidase

d. Superoxide radical

e. Superoxide dismutase

Which of the following does not affect the function of enzymes?

a. Ubiquinone

b. Substrate concentration

c. Temperature

d. Competitive inhibitors

The _______________________ test detects if an organism can convert hydrogen peroxide to water and oxygen. The test result is usually _______________________ in anaerobic microbes and usually _______________________ in aerobic microbes. You know the test is positive by _______________________.

Use the key in the Clinical Focus box to identify the gram-negative, oxidase-positive rod causing pneumonia in a sea otter. It is H₂S-positive, indole-negative, and urease-positive.

An organism that has peroxidase and superoxide dismutase but lacks catalase is most likely an

a. aerobe.

b. aerotolerant anaerobe.

c. obligate anaerobe.

Why are vitamins essential metabolic factors for microbial metabolism?

Suppose you inoculate three flasks of minimal salts broth with E. coli. Flask A contains glucose. Flask B contains glucose and lactose. Flask C contains lactose. After a few hours of incubation, you test the flasks for the presence of ß-galactosidase. Which flask(s) do you predict will have this enzyme?

a. A

b. B

c. C

d. A and B

e. B and C

A laboratory scientist notices that a certain bacterium does not utilize lactose when glucose is available in its environment. Describe a cellular regulatory mechanism that would explain this observation.

Which of the following are examples of the functions of enzymes?

a) A lactase enzyme breaking down lactose sugar in the small intestine.

b) A DNA polymerase enzyme synthesizing new strands of DNA.

c) A lipase enzyme breaking down fats (lipids) in the small intestine.

d) A helicase enzyme unraveling DNA so it can be replicated.

e) All of the above.

Which characteristics are likely associated with an enzyme isolated from a human stomach where conditions are strongly acidic.

a) An enzyme that functions properly at 70 degrees Fahrenheit and at a neutral pH.

b) An enzyme that functions properly at 98 degrees Fahrenheit and at an acidic pH.

c) An enzyme that functions properly at 98 degrees Fahrenheit and at a neutral pH.

d) An enzyme that functions properly at 70 degrees Fahrenheit and at an acidic pH.

Which of the following statements best describes ribozymes?

a. Ribozymes are proteins that aid in the production of ribosomes.

b. Ribozymes are nucleic acids that produce ribose sugars.

c. Ribozymes store enzymes in ribosomes.

d. Ribozymes process RNA molecules in eukaryotes.

Why are enzymes necessary for anabolic reactions to occur in living organisms?

How does amination differ from transamination?

Bacteria use the enzyme urease to obtain nitrogen in a form they can use from urea in the following reaction:

What purpose does the enzyme serve in this reaction? What type of reaction is this?