Question 1

Which of the following is the correct way to write the scientific name for a bacterium according to bacterial nomenclature rules?

Accepted Answer

Escherichia coli

Question 2

A microbiologist is trying to identify an unknown bacterium. She observes that the bacterium is able to use lactose as a carbon source and forms yellow colonies. Which classification method is she primarily using?

Accepted Answer

Phenetic classification

Question 3

Which of the following statements about Gram staining is TRUE?

Accepted Answer

Gram-positive bacteria appear purple after staining.

Question 4

A clinical sample is tested for catalase activity. Bubbles form when hydrogen peroxide is added. What does this indicate about the bacterium?

Accepted Answer

The bacterium is catalase-positive.

Question 5

Which of the following is a limitation of phylogenetic classification in bacteria?

Accepted Answer

There is a lack of extensive fossil records for bacteria.

Question 6

A bacterium is tested in an oxidation/fermentation (O/F) test. The medium turns yellow in both the sealed and unsealed tubes. What does this result indicate?

Accepted Answer

The bacterium is fermentative.

Question 7

Why is it important to establish a pure culture before performing phenetic identification tests?

Accepted Answer

To ensure that observed traits belong to a single bacterial species.

Question 8

Which of the following best describes the principle behind genotypic classification?

Accepted Answer

Grouping organisms based on genetic similarity, often using a threshold such as 70% DNA identity.

Question 9

A laboratory is using rRNA sequencing to classify a newly discovered bacterium. What is the main advantage of this method?

Accepted Answer

It uses conserved genetic sequences to determine evolutionary relationships.

Question 10

During a motility test using semi-solid media, a student observes that the growth radiates outward from the stab line. What does this indicate?

Accepted Answer

The bacterium is motile.

Question 11

Which of the following is NOT a first stage test in phenetic identification of bacteria?

Accepted Answer

Haemolysis on blood agar

Question 12

A bacterium is found to be catalase-negative and strictly anaerobic. Which genus is it most likely to belong to?

Accepted Answer

Clostridium

Question 13

Which of the following best describes the process of fermentation in bacteria?

Accepted Answer

A catabolic process where organic molecules serve as both electron donors and acceptors, resulting in acid production.

Question 14

In the context of bacterial taxonomy, what is the correct order of taxonomic ranks from broadest to most specific?

Accepted Answer

Domain, Phylum, Class, Order, Family, Genus, Species

Question 15

A sample is tested using the oxidation/fermentation (O/F) test. The unsealed tube turns yellow, but the sealed tube remains green. What does this result indicate?

Accepted Answer

The bacterium is oxidative.

Question 16

Which of the following is a key feature of the ELISA (Enzyme Linked Immunosorbent Assay) used in bacterial identification?

Accepted Answer

It uses specific antibodies to detect bacterial antigens.

Question 17

A hospital is investigating an outbreak of foodborne illness. They use Multilocus Sequence Typing (MLST) to compare isolates. What is the main advantage of MLST in this context?

Accepted Answer

It provides high-resolution genetic typing to distinguish between closely related strains.

Question 18

Restriction Fragment Length Polymorphism (RFLP) is used in bacterial identification. What is the principle behind this method?

Accepted Answer

It detects differences in DNA fragment lengths after restriction enzyme digestion.

Question 19

A bacterium is tested for its ability to grow in the presence and absence of oxygen. It grows equally well in both conditions. Which term best describes its oxygen requirement?

Accepted Answer

Facultative anaerobe

Question 20

Which of the following best explains why 16S rRNA gene sequencing is widely used in bacterial phylogenetic studies?

Accepted Answer

The 16S rRNA gene contains both conserved and variable regions, allowing for comparison across different taxa.

Bacterial Taxonomy and Identification Methods

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