Question 1

Which of the following best explains why cyanobacteria were crucial to the evolution of aerobic life on Earth?

Accepted Answer

They produced oxygen as a byproduct of photosynthesis, leading to the oxygenation of Earth's atmosphere.

Question 2

A patient is diagnosed with a bacterial infection. The causative agent is isolated from the patient, grown in pure culture, and shown to cause the same disease in a healthy animal. Which of Koch's postulates is being fulfilled when the organism is re-isolated from the experimentally infected animal?

Accepted Answer

The pathogenic organism must be re-isolated from the diseased animal.

Question 3

During the Gram stain procedure, which chemical acts as the secondary stain and what is its function?

Accepted Answer

Safranin; stains Gram-negative cells pink/red after decolorization.

Question 4

Which of the following statements about the bacterial cell wall is INCORRECT?

Accepted Answer

It regulates the transport of ions and molecules across the membrane.

Question 5

A bacterium that grows optimally at 37°C, is rod-shaped, and stains pink in a Gram stain is best described as:

Accepted Answer

A Gram negative, rod-shaped, mesophile.

Question 6

Which of the following is NOT a characteristic of chemolithotrophs?

Accepted Answer

They can utilize complex carbon compounds such as fatty acids.

Question 7

A bacterium that is killed by exposure to oxygen is classified as:

Accepted Answer

An obligate anaerobe.

Question 8

Which of the following environments is most likely to contain hyperthermophilic microorganisms?

Accepted Answer

Hydrothermal vent at the bottom of the ocean.

Question 9

Which of the following compounds is NOT used as a terminal electron acceptor in bacterial respiration under anoxic conditions?

Accepted Answer

$$\mathrm{O_2$}$$

Question 10

A mutation that changes a codon for an amino acid into a stop codon is called:

Accepted Answer

A nonsense mutation.

Question 11

In the lac operon, allolactose acts as an inducer by binding to the repressor, resulting in which outcome?

Accepted Answer

Transcription proceeds.

Question 12

Which of the following statements about DNA replication in bacteria is FALSE?

Accepted Answer

The suspected organism must be identified by microscopy.

Question 13

Which phase of bacterial growth is penicillin, an antibiotic that inhibits cell wall synthesis, most effective against?

Accepted Answer

Log phase.

Question 14

Which of the following best describes the genome of a Class III virus in the Baltimore classification system?

Accepted Answer

Double stranded RNA genome.

Question 15

A water sample from a mining site has a pH of 1.5. Which type of microorganism is most likely to thrive in this environment?

Accepted Answer

Acidophile.

Question 16

Which of the following best describes protists?

Accepted Answer

Phylogenetically diverse, unicellular eukaryotes, with ingestive nutrition.

Question 17

Which of the following is NOT associated with contaminated drinking water?

Accepted Answer

Meningitis.

Question 18

Which of the following best describes the function of the septum in fungi?

Accepted Answer

It is a membrane-based structure which divides the hyphae into compartments.

Question 19

Which of the following statements about transduction is FALSE?

Accepted Answer

Lytic phage are involved in specialized transduction.

Question 20

Photoautotrophs use which of the following as an energy source and which as a carbon source?

Accepted Answer

Light as an energy source and $$\mathrm{CO_2$} as a $$carbon source.

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