Question 1

Why does Halobacterium pump large quantities of K⁺ cations into its cytoplasm from the environment? What would happen if Halobacterium did not do this?

Accepted Answer

Halobacterium maintains a high intracell

Question 2

Sulfolobus can only grow chemoorganotrophically.

Accepted Answer

A) True 
 B)False

Question 3

Ignicoccus has several unique structural features that have lead scientists to propose that it may be the modern descendent of the ancestral cell type that gave rise to the origin of eukaryotic cells. What are the unique features of Ignicoccus and why do they support this hypothesis?

Accepted Answer

Ignicoccus lacks a cell wall, but has bo

Question 4

The microorganisms that are thought to resemble the first cellular forms of life on Earth are

Accepted Answer

A)  H₂-oxidizing hyperthermophiles. 
B)  acidophilic Archaea. 
C)  the Nanoarchaeota. 
D)  fermentative thermophiles. 
A)  H₂-oxidizing hyperthermophiles. 
B)  acidophilic Archaea. 
C)  the Nanoarchaeota. 
D)  fermentative thermophiles.

Question 5

The cytoplasmic proteins of Halobacterium are

Accepted Answer

A)  highly acidic. 
B)  highly basic. 
C)  generally neutral. 
D)  variable, depending on the species. 
A)  highly acidic. 
B)  highly basic. 
C)  generally neutral. 
D)  variable, depending on the species.

Question 6

The acetoclastic methanogens are mainly classified within one order.

Accepted Answer

A) True 
 B)False

Question 7

There are many unique archaeal genes, as exhibited by Methanocaldococcus jannaschii.

Accepted Answer

A) True 
 B)False

Question 8

What best describes the methanogens?

Accepted Answer

A)  They are a monophyletic group. 
B)  They are phylogenetically similar. 
C)  They are a diverse group that is spread across at least 7 orders. 
D)  They are functionally but not phylogenetically diverse group. 
A)  They are a monophyletic group. 
B)  They are phylogenetically similar. 
C)  They are a diverse group that is spread across at least 7 orders. 
D)  They are functionally but not phylogenetically diverse group.

Question 9

What makes the metabolism of Ferroglobus interesting in the context of evolution?

Accepted Answer

A)  Ferroglobus is an anaerobic iron-oxidizing chemolithotrophic autotroph that may represent a key metabolism that allowed for the oxidation of ferrous iron without molecular oxygen. 
B)  Ferroglobus can use H₂ or H₂S as electron acceptors in its energy metabolism and is thermophilic, thus representing the earliest hypothesized forms of life. 
C)  Ferroglobus lacks cell walls and becomes encrusted in oxidized iron, suggesting that it may be an ancestor of other archaeans that lack cell walls. 
D)  Ferroglobus is both an iron- and nitrate-reducer and is probably the last common ancestor of all iron- and nitrate-reducing organisms. 
A)  Ferroglobus is an anaerobic iron-oxidizing chemolithotrophic autotroph that may represent a key metabolism that allowed for the oxidation of ferrous iron without molecular oxygen. 
B)  Ferroglobus can use H₂ or H₂S as electron acceptors in its energy metabolism and is thermophilic, thus representing the earliest hypothesized forms of life. 
C)  Ferroglobus lacks cell walls and becomes encrusted in oxidized iron, suggesting that it may be an ancestor of other archaeans that lack cell walls. 
D)  Ferroglobus is both an iron- and nitrate-reducer and is probably the last common ancestor of all iron- and nitrate-reducing organisms.

Question 10

Archaeoglobus is a true sulfate reducer that forms a phylogenetically distinct lineage within the Euryarchaeota.

Accepted Answer

A) True 
 B)False

Question 11

With few exceptions, hyperthermophilic crenarchaeotes are obligate aerobes.

Accepted Answer

A) True 
 B)False

Question 12

The topoisomerase called ________ introduces positive supercoils in DNA, which stabilizes DNA and prevents the DNA helix from denaturing at high temperatures.

Accepted Answer

A)  reverse ligase 
B)  ligase 
C)  DNA gyrase 
D)  reverse DNA gyrase 
A)  reverse ligase 
B)  ligase 
C)  DNA gyrase 
D)  reverse DNA gyrase

Question 13

The amino acid composition of thermostable proteins is not particularly unusual, except for a bias for increased levels of amino acids that form α-helices.

Accepted Answer

A) True 
 B)False

Question 14

Retinal in prokaryotes is part of

Accepted Answer

A)  photosynthesis. 
B)  phototaxis. 
C)  light-driven ATP synthesis. 
D)  light-driven ATP synthesis and phototaxis. 
A)  photosynthesis. 
B)  phototaxis. 
C)  light-driven ATP synthesis. 
D)  light-driven ATP synthesis and phototaxis.

Question 15

The cytoplasmic membrane of Thermoplasma contains a lipopolysaccharide-like material called lipoglycan that

Accepted Answer

A)  never contains sugars such as glucose. 
B)  forms an unusual and flexible cell wall. 
C)  contributes to membrane stability. 
D)  may be present or absent dependent upon the temperature. 
A)  never contains sugars such as glucose. 
B)  forms an unusual and flexible cell wall. 
C)  contributes to membrane stability. 
D)  may be present or absent dependent upon the temperature.

Question 16

Many halophiles require a high ionic environment for survival.

Accepted Answer

A) True 
 B)False

Question 17

Detail the mechanism by which halophilic Archaea obtain energy from light.

Accepted Answer

Halobacteria have the ability to increas

Question 18

One factor that seems to aid in maintaining lipid stability in hyperthermophilic Archaea is that dibiphytanyl tetraether lipids form a(n)

Accepted Answer

A)  covalently bonded monolayer cytoplasmic membrane. 
B)  interlocking bilayer cytoplasmic membrane. 
C)  interlocking lattice with the cell wall. 
D)  pseudomembrane immediately inside the cytoplasmic membrane. 
A)  covalently bonded monolayer cytoplasmic membrane. 
B)  interlocking bilayer cytoplasmic membrane. 
C)  interlocking lattice with the cell wall. 
D)  pseudomembrane immediately inside the cytoplasmic membrane.

Question 19

Which of the following are NOT substrates for methanogens?

Accepted Answer

A)  acetate and pyruvate 
B)  carbon dioxide, carbon monoxide, and formate 
C)  glucose and sucrose 
D)  methanol and methylamine 
A)  acetate and pyruvate 
B)  carbon dioxide, carbon monoxide, and formate 
C)  glucose and sucrose 
D)  methanol and methylamine

Question 20

Speculate on the possibility of life on other planets. Use representatives of the hyperthermophilic Archaea and hydrogen chemolithotrophs as a guide to this discussion.

Accepted Answer

Answers will vary, but the environment d

Exam 17: Diversity of Archaea

Why does Halobacterium pump large quantities of K⁺ cations into its cytoplasm from the environment? What would happen if Halobacterium did not do this?

Sulfolobus can only grow chemoorganotrophically.

Ignicoccus has several unique structural features that have lead scientists to propose that it may be the modern descendent of the ancestral cell type that gave rise to the origin of eukaryotic cells. What are the unique features of Ignicoccus and why do they support this hypothesis?

The microorganisms that are thought to resemble the first cellular forms of life on Earth are

The cytoplasmic proteins of Halobacterium are

The acetoclastic methanogens are mainly classified within one order.

There are many unique archaeal genes, as exhibited by Methanocaldococcus jannaschii.

What best describes the methanogens?

What makes the metabolism of Ferroglobus interesting in the context of evolution?

Archaeoglobus is a true sulfate reducer that forms a phylogenetically distinct lineage within the Euryarchaeota.

With few exceptions, hyperthermophilic crenarchaeotes are obligate aerobes.

The topoisomerase called ________ introduces positive supercoils in DNA, which stabilizes DNA and prevents the DNA helix from denaturing at high temperatures.

The amino acid composition of thermostable proteins is not particularly unusual, except for a bias for increased levels of amino acids that form α-helices.

Retinal in prokaryotes is part of

The cytoplasmic membrane of Thermoplasma contains a lipopolysaccharide-like material called lipoglycan that

Many halophiles require a high ionic environment for survival.

Detail the mechanism by which halophilic Archaea obtain energy from light.

One factor that seems to aid in maintaining lipid stability in hyperthermophilic Archaea is that dibiphytanyl tetraether lipids form a(n)

Which of the following are NOT substrates for methanogens?

Speculate on the possibility of life on other planets. Use representatives of the hyperthermophilic Archaea and hydrogen chemolithotrophs as a guide to this discussion.

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