Question 1

Which molecular marker was used in the 1970s to split prokaryotes into Bacteria and Archaea, and why is it significant for phylogenetic studies?

Accepted Answer

Small-subunit ribosomal RNA, because it is highly conserved and allows for comparison across all domains of life.

Question 2

Based on phylogenetic analysis, which domain is genetically more closely related to Eukarya?

Accepted Answer

Archaea

Question 3

Which of the following is a unique characteristic of Archaea compared to Bacteria and Eukarya, according to the comparison chart?

Accepted Answer

Membrane lipids composed of branched hydrocarbons

Question 4

Extreme halophiles and extreme thermophiles are examples of which group of prokaryotes, and what environments do they inhabit?

Accepted Answer

Archaea; halophiles live in highly saline environments, thermophiles in very hot environments

Question 5

Methanogens are strict anaerobes. What is the chemical reaction they use to produce methane, and where are they commonly found?

Accepted Answer

They use $$\mathrm{CO_2$ + 4H_2 \rightarrow CH_4$ + 2H_2O}$$ and are found in swamps, marshes, and the guts of cattle and termites.

Question 6

Which subgroup of Proteobacteria is most closely associated with the origin of mitochondria in eukaryotes, and what process led to this association?

Accepted Answer

Alpha Proteobacteria; endosymbiosis of a heterotrophic aerobic alpha proteobacterium with an archaeon

Question 7

Nitrosomonas, a Beta Proteobacterium, plays a crucial role in the nitrogen cycle. What is the specific chemical transformation it performs?

Accepted Answer

It converts $$\mathrm{NH_4$^+} to$$ $$\mathrm{NO_2$^-}$$, increasing nitrogen bioavailability for plants.

Question 8

Which Gamma Proteobacterium is commonly found in the intestines of mammals and is usually not pathogenic?

Accepted Answer

Escherichia coli

Question 9

Delta Proteobacteria are known for their large genomes and industrial usefulness. What is one key ecological behavior that increases their feeding efficiency?

Accepted Answer

Traveling in swarms to increase extracellular enzyme concentration

Question 10

Which Epsilon Proteobacterium is responsible for causing stomach ulcers in humans?

Accepted Answer

Helicobacter pylori

Question 11

Chlamydias are obligate intracellular parasites. Which disease is caused by Chlamydia trachomatis?

Accepted Answer

Blindness and nongonococcal urethritis

Question 12

Spirochetes are helical heterotrophic bacteria. Which of the following is a disease caused by a spirochete?

Accepted Answer

Syphilis, caused by Treponema pallidum

Question 13

Cyanobacteria are important for Earth's atmosphere. What is their primary ecological function?

Accepted Answer

Photoautotrophy that generates $$\mathrm{O_2$}$$

Question 14

Gram-positive bacteria include many important soil decomposers and pathogens. Which genus is a major source of antibiotics?

Accepted Answer

Streptomyces

Question 15

Which of the following statements best explains why most bacterial species remain undiscovered?

Accepted Answer

Many bacteria cannot be cultured in laboratory conditions and may require specific environments to grow.

Question 16

Which process is responsible for the evolution of plant chloroplasts from cyanobacteria?

Accepted Answer

Endosymbiosis

Question 17

A patient presents with blood poisoning after eating undercooked poultry. Which Proteobacterium is most likely responsible?

Accepted Answer

Campylobacter (Epsilon Proteobacteria)

Question 18

Which of the following best describes the evolutionary relationship among Bacteria, Archaea, and Eukarya?

Accepted Answer

Archaea and Eukarya share a more recent common ancestor with each other than with Bacteria.

Question 19

Which of the following is NOT a major group of bacteria according to the phylogenetic tree?

Accepted Answer

Methanogens

Prokaryotic Diversity and Phylogeny: Bacteria and Archaea

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