Deck 16: Diversity of Archaea

Question 1

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

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

Answer 1

A

Question 2

Some members of the Thermoplasmatales can grow at pH levels below

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

Answer 2

C

Question 3

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

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

Answer 3

B

Question 4

The taxonomy of the methanogens is based on

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

Question 5

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

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

Question 6

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 7

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 8

Retinal in prokaryotes is part of

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

Question 9

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

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

Question 10

The cytoplasmic proteins of Halobacterium are

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

Question 11

Which of the following metabolisms is NOT found in Archaea?

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

Question 12

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 13

Most known methanogens are nonhalophilic

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

Question 14

The 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)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.

Question 15

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,methylamine,and methylmercaptan

Question 16

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.

Question 17

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 18

Some of the largest naturally occurring plasmids occur in the

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

Question 19

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 20

What do MOST halobacteria use for carbon substrates?

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

Question 21

Which archaeal phylum contains primarily extreme halophiles and methanogens?

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

Question 22

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 23

Which of the following bioenergetic processes CANNOT occur in hyperthermophiles?

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

Question 24

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

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

Question 25

The most common electron donor among hyperthermophilic Archaea is

A)Fe⁺³.
B)H₂.
C)SO₄.
D)Sᵒ.

Question 26

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 donors in its energy metabolism and is thermophilic,thus representing the earliest hypothesized forms of life.
C)Ferroglobus lacks cells wall and becomes encrusted in oxidized iron.
D)Ferroglobus is both an iron- and nitrate-reducer and is probably the last common ancestor of all iron- and nitrate-reducing organisms.

Question 27

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

Question 28

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

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

Question 29

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

A)behaves like peptidoglycan and creates a strong cell wall.
B)forms a monolayer that stabilizes the cytoplasmic membrane.
C)contains ether linkages.
D)contains ether linkages and forms a monolayer that stabilizes the cytoplasmic membrane.

Question 30

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 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

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 33

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 34

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 35

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

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

Question 36

Laboratory isolation of Nanoarchaeum equitans requires the presence of

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

Question 37

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

Question 38

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 39

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

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

Question 40

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 41

Many hyperthermophiles are chemolithoautotrophs.

Question 42

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

Question 43

Archaea is divided into three phyla.

Question 44

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 / NH₃
C)CO₂ / NH₃
D)organic acids / NO

Question 45

There are many genes in archaeal genomes that have no known function.

Question 46

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

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

Question 47

In chemolithotrophic Archaea,H₂ is a common electron donor.

Question 48

Nitrifying Thaumarchaeota outcompete nitrifying bacteria in many aquatic and terrestrial 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 nutrient and electron donor concentrations.
D)have very resistant specialized cells that survive long periods of dehydration and nutrient starvation.

Question 49

The rRNA gene sequences of hyperthermophilic Archaea and Bacteria have diverged ________ over time,likely due to ________.

A)relatively little / strong constraints on sequence changes at higher temperatures
B)substantially / higher mutation rates at higher temperatures
C)relatively little / low mutation rates in these ancient organisms
D)substantially / DNA damage at higher temperatures

Question 50

Most halobacteria are motile by means of lophotrichous flagella.

Question 51

The topoisomerase ________ 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 52

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

Question 53

Proteins known as ________ function to refold partially denatured proteins.

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

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

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

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

Question 56

Most of the Archaea are phenotypically quite similar.

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

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

Question 59

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

A)several abiotic reactions could have formed Fe³⁺.
B)there are multiple forms of anoxygenic photosynthesis.
C)there are multiple groups of oxygenic photosynthetic bacteria.
D)several ancient anaerobic metabolisms form Fe³⁺.

Question 60

Cyclic 2,3-diphosphoglycerate (cDPG)is present in molar quantities 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)counteract the effects of high osmotic environments.
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

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 63

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

Question 64

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

Question 65

Many halophiles require a high ionic environment for survival.

Question 66

Though the known diversity of acetotrophic methanogens is low,they are ecologically significant in nature.

Question 67

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 68

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 69

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

Question 70

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

Question 71

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

Question 72

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

Question 73

Thermoplasma metabolizes organic compounds leached from hot coal refuse.

Question 74

Thermoplasma grows either aerobically or anaerobically by sulfur respiration.

Question 75

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

Question 76

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 77

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

Question 78

With few exceptions,hyperthermophilic crenarchaeotes are obligate aerobes.

Question 79

Halophilic Archaea are the only inhabitants of highly saline environments.

Question 80

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