Question 1

Which of the following best explains why capsules appear as clear halos around bacterial cells after performing the capsule stain described in the experiment?

Accepted Answer

Capsules are non-ionic and do not bind with the cationic Carbol Fuchsin stain, resulting in a clear halo.

Question 2

A student prepares a capsule stain using Klebsiella pneumoniae. After viewing the slide under oil immersion, they observe pinkish-red cells surrounded by clear zones. What do these clear zones represent?

Accepted Answer

The capsule surrounding the bacteria

Question 3

Which of the following steps is critical to avoid destroying the capsule during the capsule staining procedure?

Accepted Answer

Gently heat fixing the smear for only 5 seconds

Question 4

Why is albumin (egg white) used in the capsule staining procedure?

Accepted Answer

It serves as both a fixative and a background medium for the smear.

Question 5

Which of the following genera is correctly matched with its capsule composition?

Accepted Answer

Bacillus anthracis – polypeptide capsule

Question 6

A patient presents with pneumonia. A capsule stain of their sputum reveals pink rods with clear halos. Which organism is most likely present?

Accepted Answer

Klebsiella pneumoniae

Question 7

Which of the following best describes the metabolism of Enterobacter aerogenes?

Accepted Answer

Facultative anaerobe with both respiratory and fermentative metabolism

Question 8

What is the primary advantage conferred by the bacterial capsule in pathogenic species?

Accepted Answer

Resistance to phagocytosis and enhanced virulence

Question 9

Which of the following statements about Streptococcus mutans is correct?

Accepted Answer

It is a Gram-positive coccus that produces dextran, contributing to tooth decay.

Question 10

During the capsule staining procedure, why is it important NOT to blot the slide after washing?

Accepted Answer

Blotting could disrupt or remove the delicate capsule structure.

Question 11

Which of the following best describes the appearance of Klebsiella pneumoniae after capsule staining, as shown in the provided images?

Accepted Answer

Pink rods with a clear halo around each cell

Question 12

A microbiologist is comparing capsule stains of Klebsiella pneumoniae and Enterobacter aerogenes. Which feature would help distinguish these two organisms under the microscope?

Accepted Answer

Klebsiella pneumoniae forms larger capsules than Enterobacter aerogenes.

Question 13

Which of the following is a correct step in preparing a capsule stain, as illustrated in the first image?

Accepted Answer

Spreading the mixture across the slide at a 45° angle to create a thin smear

Question 14

Which of the following best explains why capsules are important for bacterial survival in the environment?

Accepted Answer

Capsules help bacteria adhere to surfaces and protect against desiccation.

Question 15

Which of the following equations best represents the relationship between the observed field diameter ($$D_{obs}$$), the actual field diameter ($$D_{actual}$$), and the magnification ($$M) $$when using oil immersion microscopy?

Accepted Answer

$$D_{actual} = \frac{D_{obs}}{M}$$

Question 16

A clinical sample is stained using the capsule stain technique. The cells appear as pink cocci in chains with clear halos. Which organism is most likely present?

Accepted Answer

Streptococcus mutans

Question 17

Which of the following is a common misconception about the capsule staining procedure?

Accepted Answer

Capsules are stained directly by Carbol Fuchsin.

Question 18

Which of the following best describes the ecological distribution of Enterobacter aerogenes?

Accepted Answer

Widely distributed in fresh water, soil, sewage, plants, vegetables, and animal and human feces

Question 19

Which of the following is a key difference between the capsules of Streptococcus pneumoniae and Bacillus anthracis?

Accepted Answer

Bacillus anthracis produces a polypeptide capsule, while Streptococcus pneumoniae produces a polysaccharide capsule.

Capsule Staining and Capsule-Forming Bacteria

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