Question 1

Which of the following best describes the growth pattern of a facultative anaerobe in a fluid thioglycolate medium, as shown in the first image?

Accepted Answer

Growth throughout the tube, but heaviest at the top where oxygen is present.

Question 2

What is the primary function of sodium thioglycolate in fluid thioglycolate medium?

Accepted Answer

To reduce molecular oxygen and create an oxygen gradient.

Question 3

Which bacterial category would show growth only at the bottom of a fluid thioglycolate tube, as seen in tube (e) of the fourth image?

Accepted Answer

Obligate anaerobe

Question 4

A student shakes a fluid thioglycolate tube before inoculation. What is the most likely outcome for an obligate anaerobe inoculated into this tube?

Accepted Answer

It will not grow or will be killed due to oxygen exposure throughout the tube.

Question 5

Which of the following best explains why obligate anaerobes cannot survive in the presence of oxygen?

Accepted Answer

They lack the enzymes necessary to detoxify reactive oxygen species.

Question 6

In the anaerobic jar shown in the second image, what is the role of the gas generator envelope?

Accepted Answer

To chemically remove oxygen and generate carbon dioxide.

Question 7

Which organism would you expect to show the best growth in a candle jar, as depicted in the third image?

Accepted Answer

Neisseria subflava (microaerophile)

Question 8

Which of the following equations correctly represents the detoxification of hydrogen peroxide by catalase?

Accepted Answer

$$2 \mathrm{H}_2\mathrm{O}_2 \rightarrow 2 \mathrm{H}_2\mathrm{O} + \mathrm{O}_2$$

Question 9

A tube of fluid thioglycolate medium shows a thin band of growth just below the surface. Which oxygen category does this pattern indicate?

Accepted Answer

Microaerophile

Question 10

Which metabolic pathway is used by facultative anaerobes when oxygen is absent?

Accepted Answer

Anaerobic respiration or fermentation

Question 11

Which enzyme is commonly present in both obligate aerobes and facultative anaerobes, but absent in strict anaerobes, allowing them to survive in oxygen?

Accepted Answer

Superoxide dismutase (SOD)

Question 12

A Petri plate inoculated with Pseudomonas aeruginosa is incubated in an anaerobic jar. What is the expected result?

Accepted Answer

No growth.

Question 13

Which of the following best describes the growth of an aerotolerant anaerobe in fluid thioglycolate medium?

Accepted Answer

Even growth throughout the tube.

Question 14

Why is it important not to shake a fluid thioglycolate tube before inoculation?

Accepted Answer

Shaking will mix oxygen throughout the tube, disrupting the oxygen gradient.

Question 15

Which of the following organisms is most likely to grow best in the presence of increased carbon dioxide and reduced oxygen, such as in a candle jar?

Accepted Answer

Microaerophile

Question 16

Which of the following statements about the anaerobic jar is correct?

Accepted Answer

It removes oxygen and increases carbon dioxide to create anaerobic conditions.

Question 17

Which of the following best explains why microaerophiles grow poorly at atmospheric oxygen levels?

Accepted Answer

Their enzymes are inhibited or damaged by high oxygen concentrations.

Question 18

Which of the following is a correct prediction for Escherichia coli growth in the three incubation conditions: incubator (air), candle jar, and anaerobic jar?

Accepted Answer

Growth in all conditions, but best in air.

Question 19

Which of the following best describes the metabolic flexibility of facultative anaerobes?

Accepted Answer

They can switch between aerobic respiration and fermentation depending on oxygen availability.

Question 20

Which of the following is the correct order of oxygen tolerance from highest to lowest among the following categories: obligate aerobe, facultative anaerobe, microaerophile, obligate anaerobe?

Accepted Answer

Obligate aerobe \u003e facultative anaerobe \u003e microaerophile \u003e obligate anaerobe

lab 11 - Oxygen Requirements for Bacterial Growth: Categories, Metabolic Basis, and Culturing Techniques

Guida di studio - Domande di pratica

Study guide - Flashcard