Question 1

Which enzyme is responsible for breaking down hydrogen peroxide into oxygen and water in aerobic bacteria?

Accepted Answer

Catalase

Question 2

A urine sample is streaked on an agar plate using 0.01 ml. After incubation, you count 150 colonies. What is the original bacterial count per ml in the urine sample? Use the formula $$	ext{CFU/ml} = 	ext{Number of colonies} 	imes 100.$$

Accepted Answer

$$15,000$$ CFU/ml

Question 3

Which group of bacteria can grow in both the presence and absence of oxygen, but prefers oxygen for growth?

Accepted Answer

Facultative anaerobes

Question 4

In the GasPak anaerobic jar, what is the role of hydrogen gas released by the envelope?

Accepted Answer

It reacts with oxygen to form water, removing oxygen from the jar.

Question 5

Which of the following bacteria is an example of an obligate anaerobe?

Accepted Answer

Clostridium

Question 6

Why do obligate anaerobes die in the presence of oxygen?

Accepted Answer

They lack enzymes to detoxify reactive oxygen species.

Question 7

A thioglycollate broth tube appears pink at the top and colorless at the bottom. What does this indicate about the oxygen concentration?

Accepted Answer

Oxygen concentration is highest at the top and lowest at the bottom.

Question 8

Which of the following is a common cause of urinary tract infections according to the study materials?

Accepted Answer

Escherichia coli

Question 9

Microaerophiles require which of the following conditions for optimal growth?

Accepted Answer

Low oxygen concentration (5-10%)

Question 10

Which enzyme converts superoxide radicals into oxygen and hydrogen peroxide?

Accepted Answer

Superoxide dismutase

Question 11

A facultative anaerobe is inoculated into a thioglycollate tube. Where would you expect the most growth?

Accepted Answer

Throughout the tube, but more at the top

Question 12

Which of the following is NOT a typical sign of urinary tract infection when analyzing a urine sample?

Accepted Answer

Neutral pH

Question 13

Why is resazurin dye used in thioglycollate medium?

Accepted Answer

To indicate the presence of oxygen by turning pink

Question 14

Which of the following statements about Streptococcus species is correct?

Accepted Answer

They are aerotolerant organisms that can grow in the presence of oxygen but do not use it.

Question 15

In a candle jar, which type of bacteria would most likely thrive?

Accepted Answer

Microaerophiles

Question 16

Which of the following is a byproduct of aerobic respiration that can be toxic to cells?

Accepted Answer

Hydrogen peroxide

Question 17

What is the main function of agar in thioglycollate medium?

Accepted Answer

To localize anaerobes by slowing oxygen diffusion

Question 18

Which of the following best describes the growth pattern of obligate aerobes in a thioglycollate tube?

Accepted Answer

Growth only at the top

Question 19

If the indicator strip in a GasPak jar remains blue after sealing, what does this indicate?

Accepted Answer

Oxygen is still present in the jar.

Question 20

Which of the following is a correct multi-step procedure for determining the original bacterial count in a urine sample?

Accepted Answer

Streak 0.01 ml of urine, count colonies, multiply by 100.

Cultivating Anaerobes and Urine Sample Analysis: Oxygen Requirements and Laboratory Methods

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