Question 1

Which molecule is most commonly used for constructing the universal phylogenetic tree of life, and why is it particularly suitable for this purpose?

Accepted Answer

Small subunit rRNA (16S in prokaryotes, 18S in eukaryotes), because it is universally present, functionally constant, sufficiently conserved, and of sufficient length

Question 2

According to the binomial system of nomenclature, which of the following is the correct way to write the scientific name of a prokaryote?

Accepted Answer

Genus species (italicized), e.g., Escherichia coli

Question 3

Which of the following statements best describes the endosymbiotic theory for the origin of mitochondria and chloroplasts?

Accepted Answer

Mitochondria and chloroplasts arose from symbiotic associations of prokaryotes within another cell

Question 4

A newly discovered bacterium has a 16S rRNA gene sequence that differs by 4% from any named strain. According to the species concept in microbiology, how should this organism be classified?

Accepted Answer

It should be considered a new species

Question 5

Which of the following is NOT a characteristic used to distinguish between Archaea, Bacteria, and Eukarya?

Accepted Answer

Ability to form endospores

Question 6

Which of the following best explains why 16S rRNA gene sequences are considered the 'gold standard' for bacterial taxonomy?

Accepted Answer

They are universally present, highly conserved, and allow for comparison across all bacteria

Question 7

Which of the following features supports the hypothesis that eukaryotic cells are chimeric in origin?

Accepted Answer

Eukaryotes have lipids and energy metabolisms similar to Bacteria, but transcription and translation machinery similar to Archaea

Question 8

Which of the following is a key difference between prokaryotic and eukaryotic cells as shown in Table 10.2?

Accepted Answer

Prokaryotic cells divide by binary fission, while eukaryotic cells divide by mitosis

Question 9

Which of the following statements about methanogens is correct?

Accepted Answer

Methanogens are present in wetlands and the guts of animals

Question 10

A microbiologist isolates a population of cells from a single colony and finds that some cells differ genetically from others. What is the correct term for these genetically different cells within the same clone?

Accepted Answer

Strain

Question 11

Which of the following is NOT a criterion used by Bergey’s Manual of Determinative Bacteriology for identifying bacteria?

Accepted Answer

16S rRNA gene sequencing

Question 12

Which of the following best describes the difference between a clone and a strain in microbiology?

Accepted Answer

A clone is a group of genetically identical cells, while a strain consists of genetically different cells within a clone

Question 13

Which of the following is true regarding the cell wall composition of Archaea, Bacteria, and Eukarya?

Accepted Answer

Bacteria have cell walls containing peptidoglycan, Archaea have variable cell wall composition, and Eukarya may or may not have cell walls

Question 14

Which of the following is a defining feature of the domain Bacteria according to the universal phylogenetic tree?

Accepted Answer

It contains at least 80 major evolutionary groups, many defined only by environmental sequences

Question 15

Which of the following statements about viruses is correct?

Accepted Answer

Viruses lack ribosomal RNA and are not considered living organisms

Question 16

A researcher is comparing the ribosomes of a prokaryotic cell, a eukaryotic cell, and a mitochondrion. Which of the following statements is correct?

Accepted Answer

Prokaryotic cells and mitochondria have 70S ribosomes, while eukaryotic cells have 80S ribosomes

Question 17

Which of the following best describes the process of generating a phylogenetic tree using rRNA gene sequences?

Accepted Answer

Isolate DNA, amplify rRNA gene by PCR, sequence DNA, align sequences, and construct the tree

Question 18

Which of the following is a correct statement about the membrane lipids of Archaea compared to Bacteria and Eukarya?

Accepted Answer

Archaea have membrane lipids composed of branched carbon chains attached to glycerol by ether linkage

Microbial Classification, Phylogeny, and the Three-Domain System

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