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Questions and Answers
The phylogenetic tree of Archaea is constructed based on comparative sequences of ______ proteins.
The phylogenetic tree of Archaea is constructed based on comparative sequences of ______ proteins.
ribosomal
The exact ancestry of Archaea groups remains a ______ issue.
The exact ancestry of Archaea groups remains a ______ issue.
contentious
All Archaea have ______-linked lipids in their cell membranes.
All Archaea have ______-linked lipids in their cell membranes.
ether
Archaea lack ______ in their cell walls.
Archaea lack ______ in their cell walls.
Chemoorganotrophy is a widespread metabolic process among ______.
Chemoorganotrophy is a widespread metabolic process among ______.
Hydrogen (H2) is a common ______ donor in chemolithotrophic metabolisms.
Hydrogen (H2) is a common ______ donor in chemolithotrophic metabolisms.
ELEMENTAL ______ (S0) is a common electron acceptor in anaerobic respiration.
ELEMENTAL ______ (S0) is a common electron acceptor in anaerobic respiration.
Methanogenesis is a globally important process that is only present in ______.
Methanogenesis is a globally important process that is only present in ______.
Archaea are also well known for containing many species of ______, including species that are hyperthermophiles
Archaea are also well known for containing many species of ______, including species that are hyperthermophiles
A great many species in the ______ and most Thaumarchaeota are not extremophiles and are found in soils, sediments, oceans, lakes, in association with animals, and even in the human gut.
A great many species in the ______ and most Thaumarchaeota are not extremophiles and are found in soils, sediments, oceans, lakes, in association with animals, and even in the human gut.
The phylum ______ comprise a large and physiologically diverse group of Archaea.
The phylum ______ comprise a large and physiologically diverse group of Archaea.
Methanogens are the strictest of ______ while extreme halophiles are primarily obligate aerobes.
Methanogens are the strictest of ______ while extreme halophiles are primarily obligate aerobes.
The hyperthermophilic methanogen ______ is an example of a euryarchaeote.
The hyperthermophilic methanogen ______ is an example of a euryarchaeote.
The cell wall–less ______ is an organism phenotypically similar to the mycoplasmas.
The cell wall–less ______ is an organism phenotypically similar to the mycoplasmas.
Extremely halophilic Archaea, often called the “______”, are a diverse group that inhabits environments high in salt.
Extremely halophilic Archaea, often called the “______”, are a diverse group that inhabits environments high in salt.
The key genera of extremely halophilic Archaea include ______, Haloferax, and Natronobacterium.
The key genera of extremely halophilic Archaea include ______, Haloferax, and Natronobacterium.
Methanogens show a diversity of ______ wall chemistries.
Methanogens show a diversity of ______ wall chemistries.
Physiologically, methanogens are obligate ______, and strict anoxic techniques are necessary to culture them.
Physiologically, methanogens are obligate ______, and strict anoxic techniques are necessary to culture them.
Most methanogens are ______ and nonhalophilic, although species that grow optimally at very high or very low temperatures, at very high salt concentrations, or at extremes of pH, have also been described.
Most methanogens are ______ and nonhalophilic, although species that grow optimally at very high or very low temperatures, at very high salt concentrations, or at extremes of pH, have also been described.
Several substrates can be converted to ______ by methanogens.
Several substrates can be converted to ______ by methanogens.
Compounds such as ______ can be converted to CH4, but only in reactions in which methanogens and other anaerobes cooperate.
Compounds such as ______ can be converted to CH4, but only in reactions in which methanogens and other anaerobes cooperate.
Three classes of compounds make up the list of ______ substrates shown in Table 2.
Three classes of compounds make up the list of ______ substrates shown in Table 2.
CO2-type substrates include CO2 itself, which is reduced to ______ using H2 as the electron donor.
CO2-type substrates include CO2 itself, which is reduced to ______ using H2 as the electron donor.
The reactions of ______ production are summarized in the following equations:
The reactions of ______ production are summarized in the following equations:
The term ______ is used to indicate that these organisms are not only halophilic, but that their requirement for salt is very high.
The term ______ is used to indicate that these organisms are not only halophilic, but that their requirement for salt is very high.
Many Euryarchaeota are ______, microorganisms that produce methane as an integral part of their energy metabolism.
Many Euryarchaeota are ______, microorganisms that produce methane as an integral part of their energy metabolism.
Such salty habitats are called ______.
Such salty habitats are called ______.
An organism is considered an ______ if it requires 1.5 M (about 9%) or more sodium chloride for growth.
An organism is considered an ______ if it requires 1.5 M (about 9%) or more sodium chloride for growth.
The reaction CH4 + 3HC03- --> 4HC02- + H20 + H is a process of ______ respiration.
The reaction CH4 + 3HC03- --> 4HC02- + H20 + H is a process of ______ respiration.
Thermoplasma, Ferroplasma, and Picrophilus are highly ______ and thermophilic microorganisms.
Thermoplasma, Ferroplasma, and Picrophilus are highly ______ and thermophilic microorganisms.
______ is the terminal step in the biodegradation of organic matter in many anoxic habitats in nature.
______ is the terminal step in the biodegradation of organic matter in many anoxic habitats in nature.
Thermoplasma has a unique cytoplasmic membrane structure that contains a ______ material called lipoglycan.
Thermoplasma has a unique cytoplasmic membrane structure that contains a ______ material called lipoglycan.
Some phylogenetic relatives of extremely halophilic Archaea, for example species of ______ and Natronobacterium, are able to grow at much lower salinities.
Some phylogenetic relatives of extremely halophilic Archaea, for example species of ______ and Natronobacterium, are able to grow at much lower salinities.
The lipoglycan in Thermoplasma's membrane consists of a ______ lipid monolayer with mannose and glucose.
The lipoglycan in Thermoplasma's membrane consists of a ______ lipid monolayer with mannose and glucose.
The taxonomy of methanogens is based on both ______ and phylogenetic analyses.
The taxonomy of methanogens is based on both ______ and phylogenetic analyses.
Thermoplasma is a facultative ______, growing either aerobically or anaerobically by sulfur respiration.
Thermoplasma is a facultative ______, growing either aerobically or anaerobically by sulfur respiration.
Methanogens show a variety of ______.
Methanogens show a variety of ______.
Archaeoglobus was isolated from hot ______ sediments near hydrothermal vents.
Archaeoglobus was isolated from hot ______ sediments near hydrothermal vents.
Archaeoglobus couples the oxidation of H2, lactate, pyruvate, glucose, or complex organic compounds to the reduction of ______ to H2S.
Archaeoglobus couples the oxidation of H2, lactate, pyruvate, glucose, or complex organic compounds to the reduction of ______ to H2S.
Ferroglobus is related to Archaeoglobus but is not a ______ reducer.
Ferroglobus is related to Archaeoglobus but is not a ______ reducer.
Study Notes
Diversity of Archaea
- Archaea domain consists of several phyla, including Euryarchaeota, Crenarchaeota, Thaumarchaeota, Korarchaeota, and Nanoarchaeota.
- The exact ancestry of these groups remains a contentious issue, and phylogenetic trees constructed from 16S ribosomal RNA gene sequences often conflict with those made using other genomic locations.
- Archaea share common features such as ether-linked lipids, lack of peptidoglycan in cell walls, and structurally complex RNA polymerases, which resemble those of Eukarya.
- Archaea show enormous phenotypic diversity, with species carrying out chemoorganotrophic or chemolithotrophic metabolisms, and both aerobic and anaerobic species are common.
Metabolic Features of Archaea
- Chemoorganotrophy is widespread among Archaea, with fermentations and anaerobic respirations being common.
- Chemolithotrophy is also well established in the Archaea, with H2 being a common electron donor.
- Anaerobic respiration, especially forms employing elemental sulfur (S0) as an electron acceptor, is prevalent among the Archaea, especially Crenarchaeota.
- Aerobic respiration occurs widely in Thaumarchaeota and is common among a few groups of Euryarchaeota but is characteristic of only a few species of Crenarchaeota.
Euryarchaeota
- Euryarchaeota comprise a large and physiologically diverse group of Archaea.
- This phylum includes methanogens as well as many genera of extremely halophilic (salt-loving) Archaea.
- Methanogens are the strictest of anaerobes while extreme halophiles are primarily obligate aerobes.
Extremely Halophilic Archaea (Haloarchaea)
- Extremely halophilic Archaea inhabit environments high in salt, such as solar salt evaporation ponds and salt lakes, and artificial saline habitats.
- These organisms require very high salt concentrations, often near saturation, for growth.
- Key genera include Halobacterium, Haloferax, and Natronobacterium.
Methanogenic Archaea
- Methanogens are microorganisms that produce methane (CH4) as an integral part of their energy metabolism (methanogenesis).
- Methanogenesis is the terminal step in the biodegradation of organic matter in many anoxic habitats in nature.
- Key genera include Methanobacterium, Methanocaldococcus, and Methanosarcina.
- Methanogens show a diversity of morphologies and cell wall chemistries.
- Physiologically, methanogens are obligate anaerobes, and strict anoxic techniques are necessary to culture them.
- Substrates converted to CH4 by methanogens include CO2-type substrates, methylated substrates, and acetate.
Thermoplasmatales
- Thermoplasmatales are a phylogenetically distinct line of Archaea that contain thermophilic and extremely acidophilic genera.
- Key genera include Thermoplasma, Picrophilus, and Ferroplasma.
- These prokaryotes are among the most acidophilic of all known microorganisms, with Picrophilus being capable of growth even below pH 0.
- Most are thermophilic as well.
- Species of Thermoplasma are facultative aerobes, growing either aerobically or anaerobically by sulfur respiration.
Archaeoglobales
- Archaeoglobales are a group of Archaea that includes Archaeoglobus and Ferroglobus.
- Archaeoglobus was isolated from hot marine sediments near hydrothermal vents and couples the oxidation of H2, lactate, pyruvate, glucose, or complex organic compounds to the reduction of SO42− to H2S.
- Ferroglobus is related to Archaeoglobus but is not a sulfate reducer.
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Description
This quiz covers the diversity of Archaea, a domain of microorganisms, and their phylogenetic relationships, including phyla such as Euryarchaeota and Crenarchaeota.
