Question 1

Which of the following best describes the main difference between oxygenic and anoxygenic photosynthesis?

Accepted Answer

Oxygenic photosynthesis produces $\mathrm{O_2}$ as a byproduct, while anoxygenic photosynthesis does not.

Question 2

A microbiologist is studying two bacteria: one is a photoautotroph, the other is a chemoheterotroph. Which statement correctly compares their energy and carbon sources?

Accepted Answer

The photoautotroph uses light for energy and $\mathrm{CO_2}$ for carbon; the chemoheterotroph uses chemicals for energy and organic compounds for carbon.

Question 3

Which of the following is NOT a phase of the standard bacterial growth curve?

Accepted Answer

Apoptotic phase

Question 4

A hospital-acquired infection is traced to a biofilm on a catheter. Which property of biofilms most contributes to their persistence in clinical settings?

Accepted Answer

Biofilms protect bacteria from antibiotics and immune responses.

Question 5

Which of the following best describes a defined (synthetic) medium?

Accepted Answer

A medium in which all chemical components and their concentrations are known.

Question 6

A microbiologist wants to isolate a bacterium that can tolerate high osmotic pressure. Which growth requirement is most relevant?

Accepted Answer

Osmolarity

Question 7

Which of the following is a correct example of a chemolithoautotroph?

Accepted Answer

A bacterium that oxidizes $\mathrm{NH_3}$ for energy and uses $\mathrm{CO_2}$ as a carbon source.

Question 8

Which of the following best explains why selective media are used in microbiology?

Accepted Answer

They inhibit the growth of some organisms while allowing others to grow.

Question 9

A culture medium contains peptone, beef extract, and agar. Which type of medium is this most likely to be?

Accepted Answer

Complex medium

Question 10

Which of the following is NOT one of the four toxic forms of oxygen produced in cells?

Accepted Answer

Hydroxylamine ($\mathrm{NH_2OH}$)

Question 11

A bacterium is found to grow only at the bottom of a thioglycollate broth tube. Which term best describes its oxygen requirement?

Accepted Answer

Obligate anaerobe

Question 12

Which enzyme is primarily responsible for neutralizing hydrogen peroxide ($\mathrm{H_2O_2}$) in aerobic bacteria?

Accepted Answer

Catalase

Question 13

A bacterial culture is exposed to a sudden increase in temperature. Which phase of the growth curve is most likely to be affected first?

Accepted Answer

Lag phase

Question 14

Which of the following best explains why differential media are useful in clinical microbiology?

Accepted Answer

They allow identification of bacteria based on metabolic differences.

Question 15

A bacterium is classified as a facultative anaerobe. Which of the following best describes its growth in the presence and absence of oxygen?

Accepted Answer

It grows better with oxygen but can grow without it.

Question 16

Which of the following best describes the role of superoxide dismutase in bacteria?

Accepted Answer

It converts superoxide anion ($\mathrm{O_2^-}$) to hydrogen peroxide ($\mathrm{H_2O_2}$).

Question 17

A patient with a wound infection is found to have bacteria growing in thick, slimy layers. Which structure is most likely responsible for this growth pattern?

Accepted Answer

Biofilm

Question 18

Which of the following best explains why enriched media are used in clinical laboratories?

Accepted Answer

They support the growth of fastidious organisms that require additional nutrients.

Question 19

A bacterium is able to grow at pH 2 and at 70°C. Which term best describes its growth requirements?

Accepted Answer

Acidophilic thermophile

Question 20

Which of the following best describes the relationship between metabolic capabilities and oxygen requirements in microbes?

Accepted Answer

Microbes with enzymes like catalase and superoxide dismutase can tolerate oxygen, while those lacking these enzymes are sensitive to oxygen.

Microbial Metabolism, Growth, and Oxygen Requirements: Study Guide

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