Deck 19: Archaea

Question 1

Cellular integrity and cell wall stabilization of the Halobacterium are aided by

A) magnesium ions.
B) chloride ions.
C) sodium ions.
D) potassium ions.

Answer 1

C

Question 2

What do most halobacteria use for carbon substrates?

A) carbohydrates
B) lipids
C) nucleic acids
D) amino and organic acids

Answer 2

D

Question 3

Thermoplasma survive in coal refuse piles, because these piles

A) tend to self- heat by spontaneous combustion.
B) contain coal fragments and pyrite.
C) contain organic materials extracted from coal.
D) all of the above.

Answer 3

D

Question 4

Which genus within Archaea is capable of growth at the hottest temperature recorded of 122°C?

A) Thermosphaera
B) Methanopyrus
C) Pyrococcus
D) Thermoproteus

Question 5

The factor that MOST affects the thermostability of a protein is its

A) folding pattern.
B) highly hydrophobic core regions.
C) number of hydrogen bonds.
D) ionic surface interactions.

Question 6

Which of the following bioenergetic processes CANNOT occur in hyperthermophiles?

A) photosynthesis
B) chemolithotrophy
C) chemoorganotrophy
D) all of the above

Question 7

What is the minimum concentration of sodium chloride that an extreme halophile requires for growth?

A) 2 M
B) 6 M
C) 4 M
D) 10 M

Question 8

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

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

Question 9

Within the archaeal order Thermoplasmatales, which genus is the most acidotolerant and can grow in an environment with a pH of less than 0?

A) Ferroplasma
B) Aciduliprofundum
C) Picrophilus
D) Thermoplasma

Question 10

What characteristic do mycoplasmas (Bacteria) and Thermoplasma and Ferroplasma (Archaea) have in common?

A) relatively large genomes from duplicated genes
B) contain plasmids
C) hyperthermophilic
D) lack cell walls

Question 11

Which statement is NOT correct regarding Ferroglobus?

A) Ferroglobus is a sulfate- reducing bacterium.
B) Ferroglobus was isolated from a shallow marine hydrothermal vent.
C) Ferroglobus can use H2 or H2S as electron donors in its energy metabolism.
D) Ferroglobus is an iron- oxidizing chemolithotrophic autotroph.

Question 12

Some Archaea oxidize acetate to CO2 using

A) the citric acid cycle.
B) the acetyl- CoA pathway.
C) variations on the citric acid cycle.
D) all of the above.

Question 13

The taxonomy of the methanogens is based on

A) phylogenetic (comparative nucleic acid sequencing) analysis.
B) neither phenotypic nor phylogenetic analysis.
C) phenotypic analysis.
D) phenotypic and phylogenetic analyses.

Question 14

The cytoplasmic proteins of Halobacterium are

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

Question 15

Which statement is TRUE of methanogenic and extremely halophilic Archaea?

A) The methanogens are obligate aerobes; the extreme halophiles are obligate anaerobes.
B) The methanogens are obligate anaerobes; the extreme halophiles are mostly obligate aerobes.
C) Both the methanogens and the extreme halophiles are obligate aerobes.
D) Both the methanogens and the extreme halophiles are obligate anaerobes.

Question 16

The presence of genes encoding RubisCO enzymes in Methanocaldococcus jannaschii and a species of Pyrococcus indicates that the organisms

A) incorporate carbon dioxide via the reverse citric acid cycle.
B) incorporate carbon dioxide via the acetyl- CoA pathway.
C) utilize molecular hydrogen as an electron donor in chemolithotrophic metabolism.
D) incorporate carbon dioxide via the Calvin cycle.

Question 17

Which archaeal phylum contains primarily extreme halophiles and methanogens?

A) Euryarchaeota
B) Nanoarchaeota
C) Crenarchaeota
D) Thaumarchaeota

Question 18

Some strains of Halobacterium exhibit

A) reduction of nitrate or fumarate.
B) anaerobic respiration.
C) anoxic growth at the expense of sugar fermentation.
D) all of the above.

Question 19

What is thought to be the maximum temperature for life to exist?

A) 125°C
B) 500°C
C) 150°C
D) 250°C

Question 20

The predominant cation in the Great Salt Lake is _ _; the predominant cation in the Dead Sea is .

A) magnesium / sodium
B) magnesium / magnesium
C) sodium / magnesium
D) sodium / sodium

Question 21

Retinal is found in

A) bacteriorhodopsin.
B) halorhodopsin.
C) both bacteriorhodopsin and halorhodopsin.
D) neither bacteriorhodopsin nor halorhodopsin.

Question 22

The rRNA gene sequences of hyperthermophilic Archaea and Bacteria over time have diverged relatively , and this is likely due to unusually _ regarding sequence changes.

Question 23

is a strict anaerobe with an optimum growth temperature of 105°C that grows chemolithotrophically on H2 with S0 as an electron receptor or chemoorganotrophically on complex mixtures of organic compounds.

A) Desulfurococcus
B) Pyrodictium
C) Pyrobaculum
D) Pyrolobus

Question 24

Some of the largest naturally occurring plasmids occur in the

A) extreme halophiles.
B) genus Picrophilus.
C) genus Thermoplasma.
D) methanogens.

Question 25

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

Question 26

Methanogens

A) utilize methane as an energy source.
B) process and store methane as a part of their repair mechanism.
C) produce methane as a part of their energy metabolism.
D) do all of the above.

Question 27

Nitrifying Archaea such as Nitrosopumilus maritimus use as a sole carbon source and are capable of obtaining sufficient energy by aerobically oxidizing , despite its relatively low concentration in the open ocean.

Question 28

Compounds that counteract the tendency of the cell to become dehydrated under conditions of high osmotic strength are known as .

Question 29

A chemoorganotroph growing optimally at 55°C and pH 2 in complex media would most likely be a member of the genus

A) Methanococcus.
B) Aciduliprofundum.
C) Thermoplasma.
D) Halobacterium.

Question 30

Most known methanogens are nonhalophilic

A) thermophiles.
B) psychrophiles.
C) mesophiles.
D) extremophiles (at either the psychrophilic or thermophilic end).

Question 31

Approximately of the Methanocaldococcus jannaschii genes have no counterparts in known genes from any group of organisms.

A) 25%
B) 70%
C) 10%
D) 40%

Question 32

Which of the following are NOT substrates for methanogens?

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

Question 33

Thermostable proteins tend to have additional features that improve thermostability. Which of the following is NOT one of these features?

A) highly hydrophilic cores
B) decreased tendency of the protein to unfold
C) highly hydrophobic cores
D) increased ionic interactions on the protein surfaces

Question 34

Which of the following is TRUE about Sulfolobus?

A) Sulfolobus is an anaerobic chemolithotroph.
B) Sulfolobus can grow chemoorganotrophically.
C) Sulfolobus is a gram- positive rod.
D) Sulfolobus grows in sulfur- rich hot alkaline springs.

Question 35

Laboratory isolation of Nanoarchaeum equitans requires the presence of

A) fatty acids.
B) sunlight.
C) oxygen.
D) Ignicoccus.

Question 36

Many hyperthermophiles of Archaea are chemolithotrophs, however Staphylothermus is a

A) mixotroph.
B) chemoorganotroph.
C) photoheterotroph.
D) parasite.

Question 37

The cytoplasmic membrane of Thermoplasma contains a lipopolysaccharide- like material called , which consists of a(n) lipid monolayer membrane containing
and sugars.

Question 38

Halobacterium salinarum and certain other extreme halophiles carry out light- driven synthesis of ATP under what condition?

A) high carbon dioxide concentrations
B) low light
C) low oxygen concentrations
D) high oxygen concentrations

Question 39

Compared with other Archaea, hyperthermophilic crenarchaeotes are thought to be

A) evolving faster.
B) undergoing erratic evolutionary progression.
C) evolving at about the same pace.
D) evolving slower.

Question 40

Which microbial grouping is the major oxygenic phototroph in most salt lakes?

A) Dunaliella, a eukaryotic alga
B) halophilic Archaea
C) cyanobacteria
D) purple nonsulfur bacteria

Question 41

A compound that is present in molar quantities in the cytoplasm of many hyperthermophilic methanogens and that prevents chemical damage to DNA, such as depurination and depyrimidization, from high temperatures is called _.

Question 42

Although lacking in known diversity, acetotrophic methanogens are ecologically significant in nature.

Question 43

Thus far, only Archaea have been found in the salt lakes, while Bacteria and Eukarya are noticeably absent.

Question 44

is a light- driven protein present in Halobacteria that pumps Cl- into the cell as an anion for K+.

Question 45

Proteins known as function to refold partially denatured proteins.

Question 46

Archaeal histones assist in maintaining the DNA in a double- stranded form at very high temperatures in species of Euryarchaeota.

Question 47

Crenarchaeotes whose optimal growth temperature is over 80°C are called .

Question 48

Extremely halophilic Archaea stain gram- , reproduce by , and do not form resting stages or spores.

Question 49

It is difficult to estimate when cyanobacteria appeared on Earth, because .

Question 50

Little is known about the biosynthesis of amino acids and other macromolecule precursors in
Archaea.

Question 51

Many hyperthermophiles are chemolithoautotrophs.

Question 52

Hyperthermophilic Archaea, which oxidize , often couple it to the reduction of an anion such as nitrate or a cation such as ferric iron.

Question 53

Although Archaea contains many acidophilic organisms, there are still many others within the domain that grow well in environments with a neutral pH.

Question 54

Hot sulfur- rich environments are called .

Question 55

With few exceptions, hyperthermophilic crenarchaeotes are obligate aerobes.

Question 56

In general, the cold- dwelling crenarchaeotes are evolving more slowly than the hyperthermophilic crenarchaeotes.

Question 57

An organism that is suspended freely or is attached to suspended particles in the water column is known as .

Question 58

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

Question 59

The light- stimulated proton pump of Halobacterium salinarum functions to pump sodium out of the cell by the activity of a Na+/H+ antiport system.

Question 60

Much like in Bacteria, the bioenergetics of anaerobic respiring Archaea such as those of the
Crenarchaeota involve from which energy is synthesized via .

Question 61

A small, heat- stable DNA- binding protein present in the cells of some Archaea, called Sac7d, binds to the minor groove of DNA in a very specific manner and increases its melting temperature by 40°C.

Question 62

The cytoplasmic membrane of Picrophilus is extremely acid impermeable at very low pH.

Question 63

Thermoplasma grows either aerobically or anaerobically by sulfur respiration.

Question 64

While many Archaea are bacillus or coccus in shape, unusual morphologies such as square, flattened and irregular discs have also been identified in certain species.

Question 65

In general, the halophiles are well adapted, both internally and externally, to life in a highly ionic environment.

Question 66

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

Question 67

Pseudopeptidoglycan (pseudomurein) is part of the cell wall of some methanogens.

Question 68

Most halobacteria are motile by means of lophotrichous flagella.

Question 69

Thermoplasma metabolizes organic compounds leached from hot coal refuse.

Question 70

Halophilic Archaea have been found in marine salterns, which are enclosed basins filled with seawater that are left to evaporate.

Question 71

Most of the Archaea are phenotypically quite similar.

Question 72

Despite GC pairs having an additional hydrogen bond than AT pairs, hyperthermophilic Archaea generally have a lower GC ratio in their genomes when compared to other heat- sensitive prokaryotes.

Question 73

When retinal in bacteriorhodopsin becomes excited, it switches from the trans to cis configuration, which facilitates the translocation of photons across the cytoplasmic membrane.

Question 74

Replacing sodium with potassium can satisfy the requirement for sodium in the halobacteria.

Question 75

Archaea is divided into three phyla.

Question 76

Methanogenesis is coupled with proton motive force formation and ATP synthesis through the activity of ATPases.

Question 77

Some Archaea are chemoorganotrophs and use organic compounds as electron donors for energy metabolism.

Question 78

In chemolithotrophic Archaea, H2 is a common electron donor.

Question 79

Some crenarchaeotes have growth optima above the boiling point of water (at atmospheric pressure).

Question 80

Thermoplasma contains an extremely small genome complexed with a highly basic DNA- binding protein.