Question 1

Which experiment by Louis Pasteur most conclusively disproved the theory of spontaneous generation by demonstrating that microbial growth only occurred when the flask was tilted, allowing the liquid to contact trapped microbes in the neck?

Accepted Answer

Swan-neck flask experiment, where microbial growth occurred only after tilting the flask

Question 2

Which of the following statements about bacterial cell membranes is TRUE?

Accepted Answer

Bacterial membranes use hopanoids instead of cholesterol to stabilize the membrane

Question 3

A bacterial cell is placed in a hypertonic environment. What is the most likely outcome?

Accepted Answer

Water will leave the cell, causing plasmolysis and shrinkage of the cytoplasm

Question 4

Which molecule can pass most easily through the bacterial plasma membrane by simple diffusion?

Accepted Answer

CO$$_2$$

Question 5

Which of the following is a unique feature of bacterial energy production compared to eukaryotes?

Accepted Answer

Plasma membrane is the site of electron transport chain and energy generation

Question 6

Gram-negative bacteria are characterized by which of the following cell wall features?

Accepted Answer

Thin peptidoglycan layer, outer membrane containing lipopolysaccharides, and periplasmic space

Question 7

Which antibiotic is most effective against actively growing Gram-positive bacteria, and what is its mechanism?

Accepted Answer

Penicillin; prevents cross-bridge formation in peptidoglycan during cell wall synthesis

Question 8

Mycobacterial cell envelopes are highly pathogenic and resistant to desiccation due to which structural features?

Accepted Answer

Multiple layers including mycolic acid and arabinogalactan, forming a sticky, slow-growing envelope

Question 9

Which structure allows bacteria to move in aqueous environments, and what is the energy source for its rotation?

Accepted Answer

Flagella; proton gradient across the membrane

Question 10

A bacterium with peritrichous flagella is exposed to a nutrient attractant. What is the expected behavior?

Accepted Answer

More running (counterclockwise rotation) than tumbling

Question 11

Which bacterial cytoskeletal protein is essential for maintaining rod shape, and what happens if it is disrupted?

Accepted Answer

MreB; rod-shaped cells become spherical

Question 12

What is the function of carboxysomes in photosynthetic bacteria?

Accepted Answer

Concentration of CO$$_2$$ around Rubisco to enhance carbon fixation and reduce photorespiration

Question 13

Which of the following statements about bacterial endospores is TRUE?

Accepted Answer

Endospores are dormant, highly resistant cells formed for survival under harsh conditions

Question 14

A batch culture of bacteria is grown in a closed system. Which phase is characterized by equal rates of cell division and cell death?

Accepted Answer

Stationary phase

Question 15

Given the formula $$N_t = N_0$ 	imes 2^n$$, where $$N_t is $$the final cell number, $$N_0 is $$the initial cell number, and $$n is $$the number of generations, how many generations have occurred if a culture grows from 1,000 cells to 32,000 cells?

Accepted Answer

$$n = 5$$

Question 16

Which adaptation allows psychrophilic bacteria to maintain membrane fluidity at low temperatures?

Accepted Answer

Increased unsaturated fatty acids and shorter carbon chains

Question 17

Which enzyme is responsible for detoxifying hydrogen peroxide in aerobic bacteria?

Accepted Answer

Catalase

Question 18

Obligate anaerobes are unable to survive in the presence of oxygen because:

Accepted Answer

They lack enzymes to detoxify oxygen radicals

Question 19

Which of the following best describes the role of biofilms in bacterial survival?

Accepted Answer

Biofilms provide protection from environmental stress, antibiotics, and immune cells

Question 20

In a biofilm, which type of bacteria would most likely be found near the core where oxygen concentration is lowest?

Accepted Answer

Facultative anaerobes and obligate anaerobes

Foundations of Microbiology: Cell Structure, Growth, and Environmental Adaptations

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