Question 1

Which ingredient in the O/F Glucose test medium is responsible for indicating a change in pH due to acid production?

Accepted Answer

Brom-thymol blue

Question 2

During the O/F Glucose test, what does a color change from green to yellow at the top of the tube under aerobic conditions indicate?

Accepted Answer

The organism is oxidative and produces acid via respiration

Question 3

Why is mineral oil added to one tube in the O/F Glucose test procedure?

Accepted Answer

To create anaerobic conditions by preventing oxygen diffusion

Question 4

Which control organism is used in the O/F Glucose test to represent a facultative anaerobe?

Accepted Answer

Escherichia coli

Question 5

In a specific sugar fermentation test using phenol red, what does the appearance of a yellow color indicate?

Accepted Answer

Acid production due to fermentation

Question 6

Which of the following is a neutral end product of glucose fermentation detected in the MR-VP test?

Accepted Answer

2,3-butanediol

Question 7

What is the role of methyl red in the MR-VP test?

Accepted Answer

To detect the presence of mixed acids from glucose fermentation

Question 8

Which enzyme is responsible for breaking down hydrogen peroxide into water and oxygen in the catalase test?

Accepted Answer

Catalase

Question 9

What is the expected result when Enterobacter aerogenes is inoculated into Simmons citrate agar?

Accepted Answer

Color change from green to Prussian blue

Question 10

Which artificial electron acceptor is used to detect cytochrome oxidase activity?

Accepted Answer

N,N,N,N-tetramethyl-p-phenylenediamine

Question 11

A bacterium produces gas in a Durham tube and a deep red color after addition of Nitrate reagents A and B. What does this indicate about its metabolism?

Accepted Answer

It reduces nitrate to nitrite and possibly further to nitrogen gas

Question 12

Which metabolic pathway is indicated by a positive mixed acid fermentation test?

Accepted Answer

Production of lactic, succinic, acetic, and formic acids

Question 13

If a bacterium is positive for mixed acid fermentation, what is the expected result for 2,3-butanediol fermentation?

Accepted Answer

Negative for 2,3-butanediol fermentation

Question 14

Which of the following reactions is catalyzed by cytochrome oxidase in aerobic bacteria?

Accepted Answer

Transfer of electrons from reduced cytochrome c to molecular oxygen

Question 15

What is the chemical reaction for the breakdown of hydrogen peroxide by catalase?

Accepted Answer

$$2H_2O_2 \rightarrow 2H_2O + O_2$

Question 16

Which of the following best describes the function of a Durham tube in fermentation tests?

Accepted Answer

Detects gas production during fermentation

Question 17

What is the main nitrogen source in Simmons citrate agar?

Accepted Answer

Ammonium salts

Question 18

Which of the following bacteria is known for reducing nitrate to nitrogen gas ($$N_2) as a $$final end product?

Accepted Answer

Bacillus species

Question 19

A student observes a Prussian blue color in Simmons citrate agar after incubation. What does this result indicate about the organism?

Accepted Answer

It can utilize citrate and produces alkaline end products

Question 20

Which of the following is a correct interpretation of the O/F Glucose test result: yellow in both aerobic and anaerobic tubes?

Accepted Answer

The organism is a facultative anaerobe

Physiological Characteristics: Oxidative and Fermentation Tests

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