Question 1

Which of the following is a characteristic feature of a gene that has been horizontally transferred into a bacterial genome?

Accepted Answer

It is often flanked by mobile genetic elements and has a codon usage different from the host.

Question 2

Why is annotating bacterial genomes generally easier than annotating eukaryotic genomes?

Accepted Answer

Bacterial genomes have fewer introns and are typically smaller in size.

Question 3

What is the main metabolic difference between aerotolerant anaerobes and facultative anaerobes?

Accepted Answer

Aerotolerant anaerobes only ferment, while facultative anaerobes can switch between fermentation and aerobic respiration.

Question 4

Which adaptation is unique to select Archaea that allows survival at extremely high temperatures?

Accepted Answer

Membrane lipids composed of ether bonds and monolayer structure.

Question 5

In Archaea, the phosphoglycerol is bound to the lipid chain by a $$	ext{ether}$$ linkage, while in Bacteria it is bound by a $$	ext{ester}$$ linkage. What is the significance of this difference?

Accepted Answer

Ether linkages confer increased stability to membranes under extreme conditions.

Question 6

A cell produces a gas vesicle. What is the most likely reason for this adaptation?

Accepted Answer

To regulate buoyancy and position in the water column.

Question 7

Which protein is required for a bacterial cell to elongate as a rod, and which protein is required for a cell to develop the vibrio (curved) shape?

Accepted Answer

MreB for rod shape, CreS for vibrio shape.

Question 8

What is the purpose of pasteurization in food safety?

Accepted Answer

To reduce the microbial load and kill pathogenic bacteria without affecting food quality.

Question 9

Why is peptidoglycan synthesis sensitive to penicillin, but pseudomurein is not?

Accepted Answer

Penicillin inhibits the transpeptidase enzyme specific to peptidoglycan, which is absent in pseudomurein.

Question 10

Which step in cell wall synthesis is blocked by penicillin?

Accepted Answer

Transpeptidation of peptide cross-links.

Question 11

You conduct a serial dilution and plate 0.1 mL of a $$10^{-4}$$ dilution, counting 579 colonies. What is the CFU/mL for the original sample?

Accepted Answer

$$5.79 	imes 10$$^{6}$$

Question 12

Which of the following best describes competitive exclusion in microbial ecology?

Accepted Answer

One species outcompetes another for the same resources, leading to the exclusion of the less competitive species.

Question 13

How do some bacteria maintain a positive water balance in a hypertonic environment?

Accepted Answer

By accumulating compatible solutes such as proline and glycine betaine.

Question 14

Which experiment by Louis Pasteur disproved the theory of spontaneous generation?

Accepted Answer

He used swan-necked flasks to show that broth remained sterile unless exposed to airborne microbes.

Question 15

Which method would you use to identify the DNA sequence bound by a regulatory protein in bacteria?

Accepted Answer

Chromatin immunoprecipitation followed by sequencing (ChIP-seq).

Question 16

What is a pseudogene?

Accepted Answer

A gene that has lost its function due to mutations.

Question 17

Which of the following is a function of superoxide dismutase in the cell?

Accepted Answer

It converts superoxide radicals to hydrogen peroxide, protecting the cell from oxidative damage.

Question 18

Which of the following is a hallmark of the Domain Archaea compared to Bacteria?

Accepted Answer

Membrane lipids with ether bonds and isoprenoid chains.

Question 19

Which process is used by bacteria to limit or increase the diversity of DNA molecules they can take in via transformation and conjugation?

Accepted Answer

Restriction-modification systems.

Question 20

Which step in the bacterial growth curve is characterized by a balance between cell division and cell death, with no net increase in cell number?

Accepted Answer

Stationary phase.

Comprehensive Study Guide: Core Concepts in Microbiology

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