26. Prokaryotes

Prokaryote Lineages

Taxonomy of Bacteria: Identification and Classification

Plantlike photosynthesis that releases O2 occurs in
a. cyanobacteria.
b. archaea.
c. gram-positive bacteria.
d. chemoautotrophic bacteria.

No. This group is not known for lacking peptidoglycan.

No. Although gram-negative bacteria contain less peptidoglycan than gram-positive bacteria, they usually do include some.

Review the major groups of bacteria.

Which group of bacteria is unusual in that they lack peptidoglycan in their cell walls?

Microbial evolution and phylogenetic trees

Which of the following prokaryotes is not pathogenic?
a. Chlamydia
b. Rhizobium
c. Streptococcus
d. Salmonella

No. Bacteria are placed in the domain Bacteria.

No. Spirochetes are spiral-shaped bacteria.

No. Cyanobacteria, as their name implies, are in the domain Bacteria.

No. Clostridium botulinum is in the domain Bacteria.

Consider which of these is not a type of bacteria.

Which of the following groups of prokaryotes is classified as a member of the domain Archaea?

Bacteria

Evaluate these statements about Koch’s postulates, which are used to establish a causative link between a specific microbe and a specific disease. Select True or False for each statement.
T/F The microbe must be present in individuals suffering from the disease and absent from healthy individuals.
T/F The microbe must be isolated and grown in pure culture.
T/F If organisms from the pure culture are injected into a healthy experimental animal, the disease symptoms should appear.
T/F The microbe does not have to be isolated from the experimental animal as long as the disease is present.

On examining cells under a microscope, you notice that they occur singly and have no evidence of a nucleus. These cells must belong to a a.domain Eukarya;
b. domain Bacteria;
c. domain Archaea;
d. the Protista;
e. more than one of the above could be correct

Prokaryote Lineages 1

The traditional tree of life (shown above) presents the three domains as distinct, monophyletic lineages. However, other hypotheses propose different views on the relationships among the Archaea, Bacteria, and Eukarya. In particular, the two-domain hypothesis—or eocyte hypothesis—is emerging as a well-supported alternative to the three-domain hypothesis. The eocyte hypothesis, illustrated below, suggests that eukaryotes evolved from eocytes (also known as the Crenarchaeota—a major lineage of the Archaea). Resolving the relationships among these ancient lineages is difficult, but it has profound implications on our understanding of the origin of eukaryotic cells. 

What other types of evidence or features might be used to ascertain whether the tree of life is best represented according to the three-domain or the eocyte hypothesis?<img class="fr-dib" src="https://lightcat-files.s3.amazonaws.com/problem_images/19d91b6c3d2a2583-1677306580219.jpg" style="width: 300px;">

The traditional tree of life (shown above) presents the three domains as distinct, monophyletic lineages. However, other hypotheses propose different views on the relationships among the Archaea, Bacteria, and Eukarya. In particular, the two-domain hypothesis—or eocyte hypothesis—is emerging as a well-supported alternative to the three-domain hypothesis. The eocyte hypothesis, illustrated below, suggests that eukaryotes evolved from eocytes (also known as the Crenarchaeota—a major lineage of the Archaea). Resolving the relationships among these ancient lineages is difficult, but it has profound implications on our understanding of the origin of eukaryotic cells. 

Early ideas on the classification of life recognized all organisms as belonging to one of two fundamental lineages—prokaryotes or eukaryotes. Is this view compatible with either of the hypotheses illustrated here? Explain.<img class="fr-dib" src="https://lightcat-files.s3.amazonaws.com/problem_images/fdd84ff649bc5258-1677306411656.jpg" style="width: 300px;">

The traditional tree of life (shown above) presents the three domains as distinct, monophyletic lineages. However, other hypotheses propose different views on the relationships among the Archaea, Bacteria, and Eukarya. In particular, the two-domain hypothesis—or eocyte hypothesis—is emerging as a well-supported alternative to the three-domain hypothesis. The eocyte hypothesis, illustrated below, suggests that eukaryotes evolved from eocytes (also known as the Crenarchaeota—a major lineage of the Archaea). Resolving the relationships among these ancient lineages is difficult, but it has profound implications on our understanding of the origin of eukaryotic cells. <IMAGE>

Evaluate this statement: According to the two-domain hypothesis, all members of the domain Archaea are prokaryotes and therefore lack membrane-bound nuclei.

Phylogenetic diversity of microbes - Dianne Newman (Cal Tech/HHMI)

No. This is not the most likely answer. Convergent evolution usually endows distantly related organisms with similar morphological or nutritional traits, without causing them to be genetically similar.

identical mutations occurring independently in these distantly related lineages

genetic variation arising from binary fission

No. Binary fission generally produces genetically identical daughter cells.

No. Meiosis is a kind of nuclear division, and because prokaryotes lack nuclei, meiosis is not a possibility.

Without sexual reproduction, how could genomes have recombined?

Portions of the genomes of certain prokaryotic species are very similar to portions of the genomes of distantly related prokaryotes. The process that most likely accounts for this genetic similarity is __________.

The traditional tree of life (shown above) presents the three domains as distinct, monophyletic lineages. However, other hypotheses propose different views on the relationships among the Archaea, Bacteria, and Eukarya. In particular, the two-domain hypothesis—or eocyte hypothesis—is emerging as a well-supported alternative to the three-domain hypothesis. The eocyte hypothesis, illustrated below, suggests that eukaryotes evolved from eocytes (also known as the Crenarchaeota—a major lineage of the Archaea). Resolving the relationships among these ancient lineages is difficult, but it has profound implications on our understanding of the origin of eukaryotic cells. <IMAGE>

Early ideas on the classification of life recognized all organisms as belonging to one of two fundamental lineages—prokaryotes or eukaryotes. Is this view compatible with either of the hypotheses illustrated here? Explain.

No. Cyanobacteria would not survive under these conditions.

No. Chlamydias are obligate endoparasites that survive within animal cells.

No. Methanogens produce methane as a waste product.

No. Extreme thermophiles thrive in extremely hot temperatures.

They would have to love salt.

Prokaryotes found inhabiting the Great Salt Lake would be __________.

Old & Odd: Archaea, Bacteria & Protists - CrashCourse Biology #35

Overview of Archaea, Protista, and Bacteria | Cells | MCAT | Khan Academy

The traditional tree of life (shown above) presents the three domains as distinct, monophyletic lineages. However, other hypotheses propose different views on the relationships among the Archaea, Bacteria, and Eukarya. In particular, the two-domain hypothesis—or eocyte hypothesis—is emerging as a well-supported alternative to the three-domain hypothesis. The eocyte hypothesis, illustrated below, suggests that eukaryotes evolved from eocytes (also known as the Crenarchaeota—a major lineage of the Archaea). Resolving the relationships among these ancient lineages is difficult, but it has profound implications on our understanding of the origin of eukaryotic cells. 

Evaluate this statement: According to the two-domain hypothesis, all members of the domain Archaea are prokaryotes and therefore lack membrane-bound nuclei.<img class="fr-dib" src="https://lightcat-files.s3.amazonaws.com/problem_images/ab4e2b558067e616-1677306542464.jpg" style="width: 300px;">

No. These proteobacteria are not known for symbiotic relationships.

No. This group includes several well-known pathogens that cause human disease.

No. This group includes species that congregate into relatively large slimy colonies and species that are predators of other bacteria.

No. Most species in this subgroup are pathogenic to humans or other animals.

Which subgroup of proteobacteria contains many species that are closely associated with eukaryotic hosts in mutualistic or parasitic relationships?

Prokaryote Lineages 2

No. This clade does contain some of the extreme thermophiles, but not most of them.

No. Although these archaea were first discovered in a hot spring in Yellowstone National Park, most of the extreme thermophiles are included in another archaean clade.

No. This group is a close relative to the correct group.

No. This is a term used to describe archaea that thrive in harsh environments, but this is not a clade.

Review the major groups of archaea.

Which clade of archaea includes most of the extreme thermophiles?

Which of the following statements is not true?
a. Archaea and bacteria have different membrane lipids.
b. The cell walls of archaea lack peptidoglycan.
c. Only bacteria have histones associated with DNA.
d. Only some archaea use CO2 to oxidize H2, releasing methane.

the high number of mutations that occur in this type of bacteria

No. Approximately 25% of the genes in O157:H7 have no counterpart on K-12. This cannot be explained by mutations.

the immense number of plasmids associated with this group of bacteria

No. Scientists compared the chromosomal genome of the two strains, not plasmids.

the frequent abuse of antibiotics used to treat this bacteria

No. The emergence of the pathogenic strains is a natural phenomenon brought on by evolution of the prokaryote.

the higher-than-average rate of binary fission that occurs in this type of bacteria

No. One bacterial cell splitting does not explain how new genes emerge in a bacterium.

horizontal gene transfer over many years, most likely through transduction

How do bacteria obtain new and different genes?

Scientists hypothesize that the O157:H7 strain of E. coli is so different from the K-12 strain because of __________.

The traditional tree of life (shown above) presents the three domains as distinct, monophyletic lineages. However, other hypotheses propose different views on the relationships among the Archaea, Bacteria, and Eukarya. In particular, the two-domain hypothesis—or eocyte hypothesis—is emerging as a well-supported alternative to the three-domain hypothesis. The eocyte hypothesis, illustrated below, suggests that eukaryotes evolved from eocytes (also known as the Crenarchaeota—a major lineage of the Archaea). Resolving the relationships among these ancient lineages is difficult, but it has profound implications on our understanding of the origin of eukaryotic cells. 

Other hypotheses for the tree of life present the Archaea as the ancestors to all other organisms. Sketch a phylogenetic tree that presents Bacteria and Eukarya as more closely related to each other than to Archaea, and that has Archaea as a sister group to Bacteria and Eukarya.<img class="fr-dib" src="https://lightcat-files.s3.amazonaws.com/problem_images/b72feed4d16fbe25-1677306497709.jpg" style="width: 300px;">

Archaea are unicellular, and bacteria are colonial.

No. Both are unicellular; some species sometimes form colonies.

Many archaea are extremophiles, but no bacteria are.

No. There are bacteria that live in extreme environments.

Bacteria are autotrophic, and archaea are heterotrophic.

No. Only some species of bacteria are autotrophic. Some species of archaea are also autotrophic.

No. Both bacteria and archaea have circular chromosomes.

They have different chemicals in their cell membranes and cell walls.

Review the characteristics of the two groups.

Which of the following is a difference between bacteria and archaea?

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