Question 1

Which of the following statements best describes the difference between Archaea and Eubacteria?

Accepted Answer

Archaea have unique ribosomal RNA sequences and lack peptidoglycan in their cell walls, while Eubacteria have peptidoglycan in their cell walls.

Question 2

A microbiologist is trying to identify an unknown bacterium. Which of the following would be LEAST useful for identifying a mycoplasma?

Accepted Answer

Gram staining

Question 3

Which of the following best explains why viruses are not classified within the five-kingdom system?

Accepted Answer

Viruses are not composed of cells and require host machinery to replicate.

Question 4

A scientist is using a slide agglutination test to identify a bacterial sample. What result would indicate a positive identification?

Accepted Answer

The sample clumps together after mixing with the antiserum.

Question 5

Which of the following is the correct order of taxonomic hierarchy from most specific to most general?

Accepted Answer

Species, genus, family, order, class, phylum, kingdom, domain

Question 6

A bacterial strain is defined as:

Accepted Answer

A collection of cells derived from a single cell that are not identical in all ways to other members of the same species.

Question 7

Which of the following best describes the purpose of Bergey’s Manual of Determinative Bacteriology?

Accepted Answer

It is used for the identification of bacteria based on characteristics such as cell wall composition, morphology, and biochemical tests.

Question 8

A patient’s serum is tested using Western blotting to detect a microbial infection. Which of the following steps is essential for confirming the presence of a specific microbial antigen?

Accepted Answer

Incubating the filter with antibodies tagged with a dye and observing for a colored band.

Question 9

Which of the following molecular methods would be most useful for classifying an unculturable microbe?

Accepted Answer

Polymerase chain reaction (PCR) followed by electrophoresis

Question 10

A researcher is comparing the DNA base composition of two bacterial species. If species A has 40% guanine + cytosine and species B has 60% guanine + cytosine, what can be concluded?

Accepted Answer

Species A and B differ significantly in their DNA base composition, suggesting they are not closely related.

Question 11

Which of the following is a limitation of biochemical testing for bacterial identification?

Accepted Answer

Mutations and plasmid acquisition can result in strains with different biochemical characteristics.

Question 12

A foodborne outbreak is being investigated. Which method would be most appropriate to determine the specific strain of bacteria responsible?

Accepted Answer

Phage typing

Question 13

Which of the following best describes nucleic acid hybridization in microbial classification?

Accepted Answer

It involves mixing DNA from two organisms, denaturing the strands, and measuring the degree of re-annealing to assess similarity.

Question 14

Which of the following is a correct example of binomial nomenclature?

Accepted Answer

Escherichia coli

Question 15

A dichotomous key is used in microbial identification because:

Accepted Answer

It provides a stepwise approach with two choices at each step, leading to identification.

Question 16

Which of the following is NOT a characteristic used to differentiate the five kingdoms?

Accepted Answer

Ability to form endospores

Question 17

A laboratory is using DNA fingerprinting to compare two bacterial isolates. Which step is essential in this process?

Accepted Answer

Cutting DNA with restriction enzymes and separating fragments by electrophoresis.

Question 18

Which of the following best explains why morphological characteristics are of limited usefulness in identifying bacteria?

Accepted Answer

Many different bacterial species look similar morphologically.

Question 19

A scientist is using a DNA probe attached to a fluorescent dye to detect Salmonella in a food sample. This technique is an example of:

Accepted Answer

Nucleic acid hybridization

Question 20

Which of the following statements about the classification and identification of microorganisms is correct?

Accepted Answer

Identification uses as few procedures as possible to determine the organism, while classification provides a list of characteristics for comparison.

Classification of Microorganisms: Taxonomy, Domains, and Identification Methods

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