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Microbiology > Ch. 4 - Archaeal Cell Structure > Flashcards

Ch. 4 - Archaeal Cell Structure Flashcards

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Biology 101 flashcards
1
Q

Archaea features in common with eukaryotes

A
  • The processes and molecules used to replicate and express their genomes
  • both cell types have their chromosomes organized by histones
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2
Q

Elements unique to archaea

A
  • unique rRNA gene structure

* capable of methanogenesis

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3
Q

Archaea are best known for growth in

A 
• anaerobic
• hypersaline
• pH extremes
• high temp habitats 
Also found in
• marine Arctic temps and tropical waters
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4
Q

Archaea cell shapes

A
  • cocci
  • rod
  • branched shapes
  • flat shapes
  • curved rods
  • spiral shapes
  • Pleomorphic (many shaped)
  • NO spirochetes
  • NO mycelial
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5
Q

Sizes of archaea

A
  • typically 1-2 x 1-5 micro meters for rods
  • typically 1-5 micro meters for cocci
  • smallest ➡️ 0.2 micro meter
  • largest ➡️ 30 mm in length
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6
Q

Archaeal cell envelopes

A

• differ from bacterial envelopes in molecular makeup and organization

  • S Layer may be only component outside plasma membrane
  • some lack cell walls
  • capsules and slime layers are rare
  • pseudomuerin (peptidoglycan-like polymer)
  • complex polysaccharides, proteins, or glycoproteins found in some other species
  • only Ignicoccus has outer membrane
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7
Q

Archaeal membranes

A

• composed of unique lipids:
- isoprene units (5 carbon, branched)
-ether linkages (rather than ester linkages to glycerol)
• some have a monolayer structure instead of bilayer

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8
Q

archaeal membrane lipids

A
  • branched chain hydrocarbons attached to glycerol by ETHER linkage
  • polar phospholipids, sulfolipids, glycolipids, and unique lipids are also found in archaeal membranes
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9
Q

What is the only archaea to contain an outer membrane?

A

Ignicoccus

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10
Q

Archaea features common with bacteria

A
  • cell structure - look like canonical prokaryotic cell
  • The processes and molecules used to conserve energy
  • genes for metabolism
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11
Q

Archaeal and bacterial cell wall differences

A
  • lack peptidoglycan
  • most common cell wall is S layer
  • May have protein sheath external to S Layer
  • S layer May be outside membrane and separated by pseudomuerin
  • pseudomuerin May be outermost layer - similar to gram-positive micro organisms
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12
Q

Archaeal nutrient uptake

A

• similar to bacteria
-facilitated diffusion
-Active transport
• no group translocation mechanisms have been discovered yet

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13
Q

Archaeal vs bacterial cytoplasm

A
  • very similar- lack of membrane enclosed organelles

* May contain inclusion bodies (ex. gas vesicles for buoyancy control)

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14
Q

Differences of Archaeal flagella

A
  • flagella thinner
  • more than one type of flagellin protein
  • flagellum are not hollow
  • hook and basal body difficult to distinguish
  • more related to type IV secretions systems
  • growth occurs at the base not at the end
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15
Q

Cell envelope of archaea

A

• defined as the plasma membrane and everything external to it

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16
Q

What can you expect to find in cytoplasm of Archaeal cells?

A 
• inclusions:
-polyhydroxyalkonates
-polyphosphate granules
-glycogen granules 
-gas vacuoles
• ribosomes
• a nucleoid
• plasmids (in some cases)
17
Q

Archaeal flagellum function

A
  • their rotation is powered by ATP hydrolysis

* The cell changes direction by changing the direction of flagellar rotation

18
Q

Nucleoid

A

• The irregularly shaped region in the cytoplasm of a prokaryotic cell that contains the genetic material and some proteins

19
Q

The surfaces of an archaeal membrane, both internal and external to the cell are

A

Hydrophilic

20
Q

Hami

A
  • The External cell structures that resemble miniature grappling hooks
  • not well understood
  • involved in cell adhesion mechanism?
21
Q

S layer components

A
  • glycoproteins
  • protein
  • may be as thick as 20 to 40 nm
22
Q

Archaeal ribosomal proteins 3 groups

A

1) those observed in all three domains of life
2) those unique to archaea
3) those observed in both archaea and eukaryotes
• all the ribosomal proteins present in both archaeal and bacterial ribosomes are also seen in eukaryotic ribosomes

23
Q

What is true regarding the RNA component of ribosomal RNA?

A
  • knowing the rRNA sequence of an organism would permit you to identify it as archaeal or bacterial
  • archaea were originally defined as different from bacteria on the basis of their rRNA sequences
24
Q

Cannulae

A
  • hollowed tubelike structures on the surface of thermophilic archaea in the genus Pyrodictium
  • function is unknown
  • May be involved in the formation of networks of multiple daughter cells
  • unique to archaea
25
Q

2 major types of Archaeal lipids

A
  • glycerol diethers

* diglycerol tetraethers

26
Q

Glycerol diether lipids

A
  • formed when two hydrocarbons are attached to glycerol

* usually hydrocarbon chains are 20 carbons in length

27
Q

Diglycerol tetraether lipids

A
  • formed when two glycerol residues are linked by two long hydrocarbons that are 40 carbons in length
  • tetraethers are more rigid lipids then diethers
  • cells can adjust the overall length of the tetraethers and increased their rigidity by cycling the chains to form pentacyclic rings
28
Q

Proteins found in nucleoid

A 
• histones
• condensin
• Alba 
Function:
• Aid in folding
29
Q

Pseudomuerin

A

• A peptidoglycan like molecule
• separate S layer from plasma membrane
• differs from peptidoglycan in that it has
-L amino acids instead of D amino acids and it’s cross links
-N-acetyltalosaminuronic acid instead of N-acetylmuramic acid
-B(1–>3) glycosidic bonds instead of B(1–>4) glycosidic bonds
• these differences mean that lysozyme, penicillin, and other chemicals that affect bacterial cell wall structure and synthesis have no effect on archaeal cell walls

30
Q

Branching of the hydrocarbon chains in archaeal lipids affects what?

A

• membrane fluidity and permeability

31
Q

Pili

A
  • composed of pilin protein and homologous to bacterial type IV Pili proteins
  • pili formed have a central lumen similar to bacterial flagella
  • may be involved in adhesion
  • not well understood
32
Q

Which cell component would be involved in compacting DNA?

A

• protein

33
Q

If an archaeal cell has no cell wall, what do you expect to find?

A

• plasma membrane and a layer of slime

34
Q

The lipids of extreme thermophiles can be expected to exhibit which chemical composition?

A

• tetraether monolayers

35
Q

Phototaxis

A

• Halobacterium species can move toward the light by flagella mediated motility

Microbiology (5 decks)

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