Deck 17: Diversity of Archaea

Question 1

A chemoorganotroph growing optimally at 55°C and pH₂ in complex media would most likely be a member of the genus

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

Answer 1

D

Question 2

Methanogens

A) produce methane as a part of their energy metabolism.
B) utilize methane as an energy source.
C) process and store methane to detoxify it.
D) produce, utilize, and detoxify methane.

Answer 2

A

Question 3

Archaea are

A) primarily ancient organisms that have not evolved very much in the last billion years.
B) phylogenetically diverse, but functionally restricted to extremophiles and chemolithotrophs.
C) a group of diverse microorganisms that inhabit almost every environment on Earth, including the colon of humans and other mammals.
D) functionally diverse, but restricted to thermophilic or hyperthermophilic environments.

Answer 3

C

Question 4

What special adaptation(s) has/have Thermoplasma evolved to survive in hot acidic environments?

A) Thermoplasma stabilize their cytoplasmic membrane by incorporation of tetraether lipoglycans in the cytoplasmic membrane.
B) Thermoplasma have a reinforced cell wall containing basic amino linkers in the peptidoglycan.
C) Thermoplasma excrete hydrogen ions and import hydroxyl ions.
D) Thermoplasma are highly motile to avoid destruction.

Question 5

Most known methanogens are nonhalophilic

A) psychrophiles.
B) mesophiles.
C) thermophiles.
D) extremophiles.

Question 6

What best describes the methanogens?

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 7

Some members of the Thermoplasmatales can grow at pH levels below

A) 4.
B) 7.
C) 0.
D) 10.

Question 8

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 9

Approximately ________ of the Methanocaldococcus jannaschii genes have no counterparts in known genes from other sequenced organisms.

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

Question 10

Which of the following types of metabolisms is NOT found in Archaea?

A) photosynthesis
B) chemolithotrophy
C) chemoorganotrophy
D) aerobic respiration

Question 11

What characteristic do bacterial mycoplasmas and the archaeal Thermoplasma and Ferroplasma have in common?

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

Question 12

The cytoplasmic proteins of Halobacterium are

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

Question 13

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

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

Question 14

Which of the following are NOT substrates for methanogens?

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

Question 15

In most salt lakes, which microbial group is the major oxygenic phototroph?

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

Question 16

Some strains of haloarchaea exhibit

A) anoxic growth at the expense of sugar fermentation.
B) anaerobic respiration.
C) anoxygenic photosynthesis.
D) light-driven ATP synthesis under oxygen-limiting conditions.

Question 17

Most haloarchaea use which of the following for electron donors?

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

Question 18

Some of the largest naturally occurring plasmids occur in the

A) methanogens.
B) Archaea lacking cell walls.
C) extreme halophiles.
D) genus Thermococcus.

Question 19

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

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

Question 20

Retinal in prokaryotes is part of

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

Question 21

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

A) 125°C
B) 150°C
C) 250°C
D) 500°C

Question 22

Which of the following bioenergetic processes CANNOT occur in hyperthermophiles?

A) chemoorganotrophy
B) chemolithotrophy
C) photosynthesis
D) chemoorganotrophy and chemolithotrophy

Question 23

Extremely halophilic Archaea often form ________, probably in order to access ________.

A) stalks / nutrients
B) intracellular inclusions / elemental sulfur
C) gas vesicles / oxygen
D) intracellular membranes / sunlight

Question 24

Laboratory isolation of Nanoarchaeum equitans requires the presence of

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

Question 25

Compatible solutes counteract the tendency of a cell to become

A) buoyant in high ionic strength environments.
B) hyperosmotic in low ionic strength environments.
C) dehydrated in high ionic strength environments.
D) viscous in low ionic strength environments.

Question 26

Many archaeal hyperthermophiles are ________; however, Staphylothermus is a chemoorganotroph.

A) chemolithotrophs
B) mixotrophs
C) parasites
D) photoheterotrophs

Question 27

________ is a strict anaerobe with irregularly disc-shaped cells and an optimum growth temperature of 105°C. It grows chemolithotrophically on H₂ with S⁰ as an electron acceptor or chemoorganotrophically on complex mixtures of organic compounds.

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

Question 28

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

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

Question 29

One unusual feature of Pyrococcus is that

A) it incorporates carbon dioxide via the acetyl-CoA pathway.
B) it is very motile due to a tuft of polar archaealla.
C) it incorporates carbon dioxide via the reverse citric acid cycle.
D) it is a thermophilic aerobic chemoorganotroph that uses elemental sulfur.

Question 30

Which archaeal phylum contains many extreme halophiles, methanogens, some marine hyperthermophiles, and Thermoplasma?

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

Question 31

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

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 32

The most common electron donor used among hyperthermophilic Archaea is

A) Fe⁺³
B) H₂.
C) SO₄.
D) Sᵒ.

Question 33

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

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 34

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

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 35

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

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

Question 36

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

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

Question 37

Which of the following is TRUE about the crenarchael genera Sulfolobus?

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

Question 38

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

A) 1.5 M
B) 4 M
C) 6 M
D) 10 M

Question 39

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

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

Question 40

The ribosomes of Halobacterium require high ________ levels for stability and activity.

A) KCl
B) NaCl
C) NaSO₄
D) acidic amino acid

Question 41

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

A) hyperthermophiles.
B) thermophiles.
C) extreme halophiles.
D) halophiles.

Question 42

The bioenergetics of anaerobic respiring Archaea such as those of the Crenarchaeota involve ________ from which ________ is synthesized.

A) proton-translocating ATPases / ATP
B) substrate level phosphorylation / ATP
C) sodium translocation / ATP
D) substrate level phosphorylation / GTP

Question 43

Sulfolobus can only grow chemoorganotrophically.

Question 44

Nitrifying Thaumarchaeota can outcompete nitrifying bacteria in acidic environments because Thaumarchaeota

A) are well-adapted to high salinity and extreme UV irradiation.
B) are well-adapted to temperature extremes.
C) are well-adapted to very low NH₃ concentrations.
D) have very resistant specialized cells that survive long periods of dehydration and nutrient starvation.

Question 45

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

Question 46

Most halobacteria are motile by means of lophotrichous archaella.

Question 47

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

Question 48

Most of the Archaea are phenotypically quite similar.

Question 49

In chemolithotrophic Archaea, H₂ is a common electron donor.

Question 50

Proteins known as ________ function to refold partially denatured proteins.

A) histones
B) chaperonins
C) HU proteins
D) histones and chaperonins

Question 51

The small ribosomal rRNA gene sequences of hyperthermophilic Archaea and Bacteria have relatively high GC content, which

A) increased stability at high temperatures because GC pairs are joined by 3 hydrogen bonds.
B) decreased stability at high temperatures because GC pairs are joined by 2 hydrogen bonds.
C) increased mutation rates at high temperatures compared with other rRNA.
D) considerable variation in their GC content, making this unhelpful as a distinguishing feature between them and non-hyperthermophilic Archaea and Bacteria.

Question 52

It is difficult to estimate when cyanobacteria appeared on Earth using the evidence from the oxidation state of the Earthʹs crust because

A) several ancient anaerobic metabolisms require O₂.
B) there are multiple forms of anoxygenic photosynthesis.
C) there are multiple groups of oxygenic photosynthetic bacteria.
D) several ancient anaerobic metabolisms form Fe³⁺ without requiring O₂.

Question 53

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

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

Question 54

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

Question 55

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

Question 56

The domain Archaea is divided into three phyla.

Question 57

Hot sulfur-rich environments associated with terrestrial sulfur-rich springs are called

A) acid-mine drainage.
B) hydrothermal vents.
C) solfataras.
D) terrestrial volcanoes.

Question 58

Many hyperthermophiles are chemolithoautotrophs.

Question 59

Nitrifying Archaea such as Nitrosopumilus maritimus use ________ as a sole carbon source and are capable of obtaining sufficient energy by aerobically oxidizing ________.

A) CO₂ / NO
B) sugars / ammonia
C) CO₂ / ammonia
D) organic acids / NO

Question 60

Potassium cyclic 2,3-diphosphoglycerate (cDPG) is present at concentrations of 1M or more in the cytoplasm of many hyperthermophilic methanogens. The function of this compound is to

A) prevent rRNA misfolding.
B) prevent chemical damage to DNA at high temperatures.
C) introduce supercoils into DNA.
D) activate hydrogen gas.

Question 61

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

Question 62

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

Question 63

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

Question 64

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

Question 65

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

Question 66

The acetoclastic methanogens are mainly classified within one order.

Question 67

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.

Question 68

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

Question 69

Pseudomurein (pseudopeptidoglycan) is part of the cell wall of some methanogens.

Question 70

Many halophiles require a high ionic environment for survival.

Question 71

Thermoplasma are facultative aerobes, growing either aerobically or anaerobically by sulfur respiration.

Question 72

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

Question 73

Halophilic Archaea are the only inhabitants of highly saline environments.

Question 74

With few exceptions, hyperthermophilic crenarchaeotes are obligate aerobes.

Question 75

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

Question 76

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

Question 77

When retinal in bacteriorhodopsin becomes excited, it directly catalyzes the formation of ATP.

Question 78

Hyperthermophilic Archaea generally have a lower GC ratio in their genomic DNA than in their ribosomal RNA.

Question 79

Some species, mostly classified as Euryarchaeota, have archaeal histones that may contribute to DNA stability as well as having other functions.

Question 80

Thermoplasma metabolizes organic compounds leached from hot coal refuse.