Question 1

Which of the following statements best describes the main ecological role of Pelagibacter in marine environments?

Accepted Answer

It is an extremely small, abundant microorganism that plays a significant role in the Earth's carbon cycle.

Question 2

Which of the following bacteria is responsible for converting ammonium ions ($$NH_4$$^+$$) to nitrite (NO_2$^-) in $$the nitrogen cycle?

Accepted Answer

Nitrosomonas

Question 3

A patient presents with a high fever, muscle aches, and a dry cough after working with livestock. Which bacterium is most likely responsible for these symptoms?

Accepted Answer

Coxiella burnetii

Question 4

Which of the following is a distinguishing feature of Chlamydiae compared to other Gram-negative bacteria?

Accepted Answer

They form elementary bodies that are infective and lack peptidoglycan in their cell wall.

Question 5

Which of the following bacteria is most likely to cause a red pigment in hospital-acquired infections?

Accepted Answer

Serratia marcescens

Question 6

A rose plant develops a tumor-like growth at its stem base. Which bacterium is most likely responsible, and what is the mechanism?

Accepted Answer

Agrobacterium; insertion of a plasmid into plant cells

Question 7

Which of the following best describes the motility mechanism of spirochetes such as Treponema pallidum?

Accepted Answer

Corkscrew motion generated by axial filaments located between the cell wall and sheath

Question 8

Which of the following is a correct pairing of a bacterium and the disease it causes?

Accepted Answer

Bordetella pertussis – whooping cough

Question 9

Which of the following bacteria is an obligate intracellular parasite transmitted by ticks and causes ehrlichiosis?

Accepted Answer

Ehrlichia

Question 10

Which of the following is a characteristic of the genus Bacillus?

Accepted Answer

Forms endospores and is commonly found in soil

Question 11

Which of the following best explains why Cyanobacteria are considered oxygenic photosynthetic bacteria?

Accepted Answer

They use $$H_2O as an $$electron donor and release $$O_2 as a $$byproduct.

Question 12

Which of the following is true about methanogenic archaea?

Accepted Answer

They are anaerobic and produce methane as a metabolic byproduct.

Question 13

A patient is diagnosed with peptic ulcers and stomach cancer. Which bacterium is most likely involved?

Accepted Answer

Helicobacter pylori

Question 14

Which of the following bacteria is commonly used as an indicator of fecal contamination in water testing?

Accepted Answer

Escherichia coli

Question 15

Which of the following best describes the difference between oxygenic and anoxygenic photosynthetic bacteria?

Accepted Answer

Oxygenic bacteria use $$H_2O as an $$electron donor and produce $$O_2$$, while anoxygenic bacteria use compounds like $$H_2S$$ and do not produce $$O_2.$$

Question 16

Which of the following is a plausible reason why some bacteria cannot be detected by traditional culturing methods?

Accepted Answer

They require specific nutrients or conditions not provided in standard laboratory media.

Question 17

Which of the following bacteria is associated with swarming motility and the formation of concentric rings on agar plates?

Accepted Answer

Proteus mirabilis

Question 18

Which of the following is a correct description of the genus Streptococcus?

Accepted Answer

Forms chains of cocci and has a low G+C content in its DNA

Question 19

Which of the following bacteria is responsible for causing Lyme disease?

Accepted Answer

Borrelia burgdorferi

Question 20

Which of the following best explains why Bacteroides are important in the human large intestine?

Accepted Answer

They are anaerobic bacteria that help break down complex carbohydrates.

The Prokaryotes: Domains Bacteria and Archaea – Classification, Structure, and Diversity

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