Question 1

Which of the following best describes the main structural difference between Gram-positive and Gram-negative bacteria?

Accepted Answer

Gram-positive bacteria have a thick peptidoglycan layer and lack an outer membrane, while Gram-negative bacteria have a thin peptidoglycan layer and possess an outer membrane.

Question 2

A patient presents with pneumonia. Laboratory analysis reveals a Gram-negative, rod-shaped bacterium that grows in aquatic environments and is associated with outbreaks in air conditioning systems. Which genus is most likely responsible?

Accepted Answer

Legionella

Question 3

Which of the following statements about the G+C ratio in bacterial DNA is correct?

Accepted Answer

A higher G+C ratio increases DNA thermal stability because G-C pairs form three hydrogen bonds, compared to two in A-T pairs.

Question 4

Which of the following genera is known for producing endospores and includes species that cause anthrax and food poisoning?

Accepted Answer

Bacillus

Question 5

A dichotomous key is used in microbiology to:

Accepted Answer

Systematically identify organisms by making a series of choices based on observable traits.

Question 6

Which of the following best differentiates yeast from molds?

Accepted Answer

Yeasts are unicellular fungi that reproduce by budding, while molds are multicellular and form hyphae.

Question 7

Which of the following is a medically important fungus that can cause oral thrush in immunocompromised patients?

Accepted Answer

Candida albicans

Question 8

Which of the following best describes the mutualistic relationship in lichens?

Accepted Answer

A fungus provides protection and anchorage, while an alga or cyanobacterium provides carbohydrates via photosynthesis.

Question 9

Which of the following protozoa is transmitted by mosquitoes and causes malaria?

Accepted Answer

Plasmodium spp.

Question 10

A patient presents with severe diarrhea after recent antibiotic therapy. Laboratory tests reveal a Gram-positive, spore-forming anaerobe. Which organism is most likely responsible?

Accepted Answer

Clostridioides difficile

Question 11

Which of the following is a defining characteristic of all fungi?

Accepted Answer

They are eukaryotic heterotrophs that absorb nutrients from organic material.

Question 12

Which of the following best describes the life cycle of Plasmodium species (malaria parasite) in humans?

Accepted Answer

Sporozoites enter the liver, develop into merozoites, which then infect red blood cells.

Question 13

Which of the following is a distinguishing feature of Mycoplasma pneumoniae compared to other bacteria?

Accepted Answer

It lacks a cell wall, making it resistant to antibiotics that target cell wall synthesis.

Question 14

Which of the following best describes the role of arthropods as vectors in disease transmission?

Accepted Answer

They transmit pathogens between hosts, sometimes allowing the pathogen to multiply or undergo part of its life cycle within the vector.

Question 15

Which of the following is a correct statement about nematode (roundworm) infections?

Accepted Answer

Some nematodes infect humans via ingestion of eggs, while others infect via skin penetration by larvae.

Question 16

Which of the following best explains why fungi can survive in environments with high sugar or salt concentrations?

Accepted Answer

Fungi are osmotolerant and can grow in hypertonic environments that inhibit most bacteria.

Question 17

Which of the following is a correct pairing of a medically important protozoan and the disease it causes?

Accepted Answer

Entamoeba histolytica – amoebic dysentery

Question 18

Which of the following best describes the function of a dichotomous key in identifying bacteria?

Accepted Answer

It uses a series of paired statements to guide the user to the correct identification based on observable characteristics.

Question 19

Which of the following is a correct statement about the reproduction of fungi?

Accepted Answer

Fungi can reproduce both sexually and asexually, often through the production of spores.

Microbiology for Nurses: Classification of Prokaryotes and Key Microbial Groups

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