Question 1

Which of the following best describes the difference between classification and identification in microbiology?

Accepted Answer

Classification is the process of grouping organisms based on shared characteristics, while identification is determining the identity of an unknown organism.

Question 2

Bergey’s Manual is a critical resource in microbiology. What is the main difference between the Systematic and Determinative versions of Bergey’s Manual?

Accepted Answer

The Systematic Manual focuses on evolutionary relationships and taxonomy, while the Determinative Manual is used for identifying unknown bacteria.

Question 3

A hospital lab receives a sample suspected of containing Enterobacteriaceae. Which multitest system would be most appropriate for rapid identification of the bacteria?

Accepted Answer

EnteroPluri or API 20E, as both allow simultaneous testing of multiple biochemical reactions.

Question 4

Which of the following best describes the principle behind automated rapid tests using mass spectrophotometry for microbial identification?

Accepted Answer

They identify microorganisms by analyzing the unique protein mass spectra produced by each species.

Question 5

A patient’s serum is tested for the presence of antibodies against a viral antigen using ELISA. What is the main principle of this test?

Accepted Answer

Antigen-antibody binding is detected by an enzyme-linked indicator that produces a color change.

Question 6

Which of the following statements correctly differentiates a Western blot from a Southern blot?

Accepted Answer

A Western blot detects specific proteins, while a Southern blot detects specific DNA sequences.

Question 7

Phage typing is a method used to identify bacterial strains. What is the underlying principle of this technique?

Accepted Answer

Bacteriophages infect only specific bacterial strains, so lysis patterns can be used for identification.

Question 8

A DNA fingerprinting experiment uses restriction enzymes, RFLPs, and gel electrophoresis. What is the main purpose of the DNA ladder in this process?

Accepted Answer

To provide reference fragment sizes for comparison with sample bands.

Question 9

In a gel electrophoresis experiment, DNA samples are loaded into wells at one end of the gel. Which direction will the DNA fragments move, and why?

Accepted Answer

Toward the positive electrode, because DNA is negatively charged.

Question 10

A researcher uses nucleic acid hybridization to identify a bacterial species. Which of the following best describes this process?

Accepted Answer

Single-stranded DNA or RNA probes bind to complementary sequences in the target organism.

Question 11

Which of the following is a key advantage of using nucleic acid amplification tests (NAATs) in microbial identification?

Accepted Answer

They can detect very small amounts of microbial DNA or RNA by amplifying target sequences.

Question 12

A dichotomous key is used in microbiology for which primary purpose?

Accepted Answer

To systematically identify unknown organisms by following a series of paired choices.

Question 13

When comparing banding patterns from gel electrophoresis of two bacterial isolates, what conclusion can be drawn if the patterns are identical?

Accepted Answer

The isolates are likely to be the same strain or closely related.

Question 14

Which of the following best describes a cladogram?

Accepted Answer

A diagram that shows evolutionary relationships among organisms based on shared characteristics.

Question 15

Which serological test is most appropriate for detecting the presence of a specific protein in a sample, and what is the key step in this method?

Accepted Answer

Western blot; transferring proteins to a membrane and detecting them with labeled antibodies.

Question 16

Which of the following is NOT a component required for DNA fingerprinting using gel electrophoresis?

Accepted Answer

Antibodies specific to the DNA sequence.

Question 17

A rapid test for strep throat uses antibodies to detect the presence of Streptococcus pyogenes antigens in a throat swab. Which type of test is this?

Accepted Answer

A serological rapid test based on antigen-antibody reactions.

Question 18

Which of the following best explains why ribotyping is useful for bacterial identification?

Accepted Answer

It analyzes variations in ribosomal RNA gene sequences, which are highly conserved yet species-specific.

Question 19

A DNA chip (microarray) is used in microbial identification. What is the main principle behind this technology?

Accepted Answer

It uses thousands of DNA probes fixed on a chip to detect complementary sequences in a sample.

Question 20

Which of the following best describes the role of loading dye in gel electrophoresis?

Accepted Answer

It helps visualize the progress of DNA migration and increases sample density for loading.

Microbial Classification and Identification: Key Terms and Concepts

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