Question 1

Which of the following best describes an endospore?

Accepted Answer

A dormant, highly resistant structure formed by certain bacteria to survive extreme conditions.

Question 2

Which two genera are well-known for forming endospores?

Accepted Answer

Bacillus and Clostridium

Question 3

The metabolically active, growing form of a bacterium that forms an endospore is called:

Accepted Answer

Vegetative cell

Question 4

During endospore staining, why is steaming the slide with malachite green necessary?

Accepted Answer

It helps the primary stain penetrate the tough endospore coat.

Question 5

Which of the following is the correct sequence of steps in the Schaeffer-Fulton endospore staining method?

Accepted Answer

Primary stain with malachite green, steam, rinse, counterstain with safranin

Question 6

After endospore staining, what color do the vegetative cells and endospores appear, respectively?

Accepted Answer

Red (vegetative cells), green (endospores)

Question 7

What is the primary stain used in the Schaeffer-Fulton endospore staining method?

Accepted Answer

Malachite green

Question 8

Which of the following best describes the function of a decolorizing agent in endospore staining?

Accepted Answer

It removes excess primary stain from vegetative cells but not from endospores.

Question 9

Which structure is responsible for bacterial motility?

Accepted Answer

Flagellum

Question 10

A bacterium exhibits a 'biased random walk' when moving toward a chemical attractant. What does this mean?

Accepted Answer

The bacterium increases the length of runs toward the attractant and decreases tumbles.

Question 11

What happens when the flagella of a bacterium switch from counterclockwise to clockwise rotation?

Accepted Answer

The bacterium tumbles and changes direction.

Question 12

Which of the following best describes chemotaxis?

Accepted Answer

Movement of bacteria toward or away from a chemical stimulus.

Question 13

Axial filaments are found in which type of bacteria, and where are they located?

Accepted Answer

Spirochetes; located between the cell wall and outer sheath, wrapped around the cell

Question 14

Which of the following methods is NOT suitable for detecting bacterial motility?

Accepted Answer

Gram staining

Question 15

Why is 0.3% agar used in motility test medium instead of 3% agar?

Accepted Answer

0.3% agar allows motile bacteria to move through the medium, while 3% agar is too solid for movement.

Question 16

A student inoculates a motility test medium with a bacterial sample using a straight stab. After incubation, growth radiates outward from the stab line. What does this indicate?

Accepted Answer

The organism is motile.

Question 17

Which of the following is a correct statement about the structure of a bacterial flagellum?

Accepted Answer

It consists of a filament, a hook, and a basal body anchored in the cell membrane.

Question 18

Which of the following equations best represents the relationship between the number of endospores ($$N_e) $$and vegetative cells ($$N_v) $$after a heat shock treatment, assuming all vegetative cells are killed and only endospores survive?

Accepted Answer

$$N_e = N_{total} - N_v$$

Question 19

A clinical sample is stained using the Schaeffer-Fulton method. Under the microscope, you observe green oval structures inside red cells. What is the most accurate interpretation?

Accepted Answer

The green ovals are endospores within vegetative cells.

Question 20

Which of the following best explains why thin flagella are not visible under a standard light microscope without special staining?

Accepted Answer

Flagella are below the resolution limit of light microscopes and require staining to increase their diameter.

Microbiology Study Guide: Endospores and Bacterial Motility

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