Q: A bacterial culture is in the exponential (log) phase of growth. If the initial number of cells is $$N_0$$ and the population doubles every $$t_d$$ minutes, what is the population size $$N$$ after time $$t$$? (Assume $$t is a $$multiple of $$t_d.)$$

$$N = N_0$ \times 2$$^{t/t_d}$$

Question 1

Which of the following best describes a facultative anaerobe?

Accepted Answer

A microbe that can utilize oxygen but can also grow in its absence.

Question 2

A bacterium isolated from a salt lake requires at least 9% NaCl for growth and grows optimally at 25% NaCl. Which term best describes this organism?

Accepted Answer

Obligate halophile

Question 3

Which of the following environmental factors does NOT directly affect the function of microbial metabolic enzymes?

Accepted Answer

Light intensity

Question 4

A patient is infected with a virus that has a helical capsid and an envelope. Which of the following statements about this virus is most likely TRUE?

Accepted Answer

It acquires its envelope from the host cell membrane during budding.

Question 5

Which of the following best explains why prions are difficult to destroy using standard sterilization techniques?

Accepted Answer

They are composed of misfolded proteins with no nucleic acid.

Question 6

A microbiologist is studying a bacterial population using turbidometry. What is being measured in this method?

Accepted Answer

The degree of cloudiness in the culture medium.

Question 7

Which of the following is a correct sequence of events in the multiplication cycle of an enveloped animal virus?

Accepted Answer

Adsorption → Penetration → Uncoating → Synthesis → Assembly → Release

Question 8

A virus with a segmented, single-stranded RNA genome that is ready for immediate translation is classified as:

Accepted Answer

$$+ssRNA$$ virus

Question 9

Which of the following is an example of lysogenic conversion, where a bacteriophage imparts new pathogenic properties to its bacterial host?

Accepted Answer

Corynebacterium diphtheriae producing diphtheria toxin

Question 10

Which of the following best describes the relationship between Cassiopeia jellyfish and dinoflagellates?

Accepted Answer

Obligate mutualism

Question 11

A laboratory is attempting to culture a virus that infects only animal cells. Which of the following methods would be LEAST appropriate for this purpose?

Accepted Answer

Nutrient agar plate

Question 12

Which of the following statements about HIV is CORRECT?

Accepted Answer

HIV can only infect cells with a CD4 marker and a co-receptor.

Question 13

A bacterial culture is in the exponential (log) phase of growth. If the initial number of cells is $$N_0$$ and the population doubles every $$t_d$$ minutes, what is the population size $$N$$ after time $$t$$? (Assume $$t is a $$multiple of $$t_d.)$$

Accepted Answer

$$N = N_0$ 	imes 2$$^{t/t_d}$$

Question 14

Which of the following is a characteristic of an aerotolerant anaerobe?

Accepted Answer

Does not utilize oxygen but can survive and grow in its presence.

Question 15

Which of the following best describes the process of binary fission in bacteria?

Accepted Answer

The parent cell enlarges, duplicates its chromosome, and forms a transverse septum dividing the cell into two daughter cells.

Question 16

A virus is found to lack an envelope and has a symmetrical polygonal capsid with 20 sides and 12 corners. Which term best describes its capsid structure?

Accepted Answer

Icosahedral

Question 17

Which of the following is TRUE regarding persistent viral infections?

Accepted Answer

The infection can last for weeks or the host's lifetime, with possible periodic reactivation.

Question 18

Which of the following statements about viroids is CORRECT?

Accepted Answer

Viroids are short pieces of RNA with no protein coat, and are only found in plants.

Question 19

A microbiologist is analyzing a sample using direct cell count. Which of the following is TRUE about this method?

Accepted Answer

It can be performed manually or with automated instruments.

Question 20

Which of the following is a real-world example of an acidophile?

Accepted Answer

A bacterium growing in a hot spring with pH 2.

Environmental Factors Influencing Microbial Growth and Population Analysis

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