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Microbiology > Dr Clokie - Archaea > Flashcards

Dr Clokie - Archaea Flashcards

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Biology 101 flashcards
1
Q

Describe archaea cell wall

A
  • Pseudopeptidoglycan

- Basic components are N-acetylglucosamine and N-acetyltalosaminuronic acid, which are linked by β-1,3-glycosidic bonds

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2
Q

Differences in archaea cell wall and bacterial cell wall

A
  • Bacterial peptidoglycan has N-acetylmuramic acid instead of N-acetyltalosaminuronic acid
  • β-1,4-glycosidic bonds (not 1,3)
  • Lysozyme cannot break the archaea’s 1,4 bond to degrade it, making it useless
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3
Q

Why is a lipid membrane important to cells?

A
  • Prokaryotes expend energy to maintain a chemiosmotic potential - drives basic cellular processes
  • Membrane is a barrier for this potential - futile ion cycling, ions moving across membranes is a source of energy loss
  • Organisms require membrane fidelity to avoid futile ion cycling
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4
Q

In what 4 ways are archaeal lipids unique?

A
  • Ether-linked lipids (not ester-linked)
  • Side-chains are not fatty acids, but branched isoprenes
  • Different chiral form of glycerol
  • Some archaea possess lipid monolayers
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5
Q

What type of bacteria do archaea most resemble?

A

Gram-positive bacteria

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6
Q

Compare the structure of archaea lipids?

A

Archea:

1) Branched isoprene chains
2) Ether-linked lipids
3) L-glycerol
4) Phosphate

Bacteria & Eukaryotes:

1) Unbranched fatty acids
2) Ester-linked lipids
3) D-glycerol
4) Phosphate

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7
Q

What is the significance of the ether rather than ester bonds?

A
  • Ether bonds are chemically more resistant than ester bonds.
  • This stability might help archaea to survive extreme temperatures and very acidic or alkaline environments
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8
Q

What is a unique ability of the phospholipid bilayer in some archaea? Give an example

A
  • The lipid bilayer is replaced by a monolayer.
  • Essentially the tails of two independent phospholipid molecules fuse into a single molecule with two polar heads
  • Fusion may make their membranes more rigid and better able to resist harsh environments
  • Eg. Ferroplasma - highly acid conditions
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9
Q

Compare archaeal and bacterial flagella

A
  • Bacterial flagella are helical filaments that rotate providing motility
  • Archaeal flagella are superficially similar to bacterial flagella, but are different in many ways and considered non-homologous (convergent evolution)
  • Bacterial flagella are produced by the addition of flagellin subunits at the tip; archaeal flagella grow by the addition to the base
  • Bacterial flagella are thicker and hollow allowing flagellin subunits to pass through
  • No sequence similarity being detected between the genes of the two systems
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10
Q

What features does archaea have in common with bacteria?

A
  • No membrane defined nucleus
  • Can have plasmids
  • Not multicellular
  • Genes organised as operons
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11
Q

What features does archaea have in common with eukarya?

A 
- No sensitivity to streptomycin, chloramphenicol,
rifampicin
- Sensitivity to diphtheria toxin
- Presence of histones
- Complex DNA & RNA polymerase
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12
Q

What features are unique to archaea?

A
  • No ester-linked lipids
  • No peptidoglycan cell wall
  • No pathogens
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13
Q

Name 5 viruses unique to the crenarchaeal group

A
  • Fuselloviridae
  • Rudiviridae
  • Lipothrixviridae
  • Ampullaviridae
  • Salterprovirus
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14
Q

Describe Fuselloviridae

A
  • ‘Lemon’ shaped
  • Typically infect Sulfolobus sp. that inhabit volcanic springs (70-80°C, pH 2-3)
  • SSV1, SSV2, SSV RH and SSV K1
  • SSV1: Integrates into host genome via integrase protein (site specific)
  • D-63: Dimeric homologues in SSV2 & SSVK1
  • F-93: Dimeric homologues in SSV2 & SSVK1
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15
Q

Describe Rudviridae

A
  • Double stranded linear DNA
  • SIRV1 and SIRV2
  • Typically infect Sulfolobus sp. that inhabit volcanic springs (70-80°C, pH 2-3)
  • Very host specific
  • SIRV1: no integration into host genome
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16
Q

Describe Lipothrixviridae

A
  • Double stranded DNA
  • SIFV, AFV, DAFS, TTV1, TTV2 and TTV3
  • Typically infect Sulfolobus, Acidianus and Thermoproteus spp. that inhabit volcanic springs (70-80°C, pH 2-3)
  • SIFV: Thick lipid envelope, virus core surrounded by lipid bilayer, no integration into host genome
17
Q

Describe Ampullaviridae

A
  • Double stranded DNA
  • 5 different morphotypes ABVS
  • Only known to infect Acidianus convivator that inhabit Pozzuai Italy hot springs (87-93°C, pH 1.5)
  • Host specific
  • ABVS: shape of virus thought to aid transfer of DNA - bottle neck/stopped host cell
    receptors
18
Q

Describe Salterprovirus

A
  • Double stranded linear DNA
  • HIS1 and HIS2
  • Only known to infect Haloaracula hispanica which inhabit Pink Lakes Victoria Australia (20-50°C, pH 2-9)
  • Host specific
  • HIS1: heavily elongated versions observed
  • HIS2: No short tail or elongated forms as seen in HIS1
19
Q

Generally speaking, what group are usually:

1) Hyperthermophiles
2) Acidophiles
3) Methanogens
4) Halophiles
5) Ammonia oxidisers

A

1) Crenarchaea
2) Both Crenarchaea and Euryarchaeota
3) Euryarchaeota
4) Euryarchaeota
5) Thaumarchaeota

20
Q

Name 3 hyperthermophiles

A

Thermococcus, Thermoproteus and Pryrodictium

21
Q

Describe Thermoproteus and Pryrodictium

A
  • Sulphur-dependent
  • They are H2S autotrophs
  • > 95°C
22
Q

Describe Thermococcus

A
  • Gram -ve coccoids with flagella
  • They are organotrophic anaerobes
  • > 70°C.
  • Need S as an e- acceptor and make H2S + CO2
  • Thermococcus coalescens can fuse
23
Q

Name 5 electron acceptors and their products when H2 is the electron donor

A
  • CO2 - Methane
  • Fe(OH)3 - Magnetite
  • Pyrite; SO4(2-) - Hydrogen sulphide
  • NO3(-) - Nitrogen (NH3)
  • O2 (traces) - Water
24
Q

What is the electron acceptor and product when pyrite is the electron donor?

A
  • O2

- H2SO4 (+FeSO4)

25
Q

What additional growth requirements can be needed?

A
  • Heat
  • Trace minerals
  • Liquid water
26
Q

Describe Sulfolobus

A
  • Grow at 80 C and pH 2
  • Oxidise organic compounds with oxygen, or oxidise Sulphur to sulphuric acid
  • Internal pH is 6.5
  • Easy to grow so studied extensively
  • Many viruses infect this species
27
Q

Name the three methanogen metabolisms

A
  • Hydrogenotrophic
  • Methylotrophic
  • Acetotrophic
28
Q

Describe hydrogenotrophic methanogen metabolism

A
  • Use CO2-type substrates (electrons derived from H2)
  • Carbon dioxide (CO2)
  • Formate (HCOO-)
  • Carbon monoxide (CO)
29
Q

Describe methylotrophic methanogen metabolism

A
  • Methyl substrates
  • Methanol (CH3OH)
  • Methylamine (CH3NH3+)
  • Dimethylamine (CH3)2 NH2+
  • Trimethylamine (CH3)3 NH+
30
Q

Describe acetotrophic methanogen metabolism

A
  • Acetotrophic substrates
  • Acetate (CH3COO-)
  • Pyruvate (CH3COCOO-)
31
Q

Describe 4 main features of methanogens

A
  • Most diverse physiology
  • Diverse habitats
    (rubbish dumps, sewage, deep sea vents, deep subsurface groundwater, guts (cows, sheep, goats, and deer), human digestive tract)
  • Grows in colonies and shows primitive cellular differentiation
  • Large genomes (eg 5,751,492 bp)
32
Q

Describe Halobacteriales

A
  • Found in water saturated with salt
  • Common where salt, moisture, + organic material are available
  • Large blooms appear reddish, from the pigment bacteriorhodopsin.
  • This pigment is used to absorb light, which provides energy to create ATP
  • Also uses halorhodopsin
  • Unique ‘photosynthesis’
33
Q

Describe nanoarchaeota

A
  • Smallest genome ever sequenced
  • High gene density
  • Cannot make lipids, vitamins, amino acids, etc.
  • Not primitive - complete set of information pathway and cell cycle genes
  • Hyperthermophile
  • Obligate symbiont with Ignicoccus
  • Diverged early in evolution from other Archaea
34
Q

Describe the process of nitrification

A
  • Increases availability of N for uptake by plants
  • NO3- leached from soil results in groundwater pollution
  • NO3- available for denitrification processes
  • Generates N2O (greenhouse gas & depletes ozone)
35
Q

What do some archaea possess that takes part in nitrogen cycle?

A

Ammonia-Oxidising Bacteria’s
key functional enzyme - ammonia monooxygenase (AMO)
- More archaeal ammonia oxidisers than
bacterial ammonia oxidisers

Microbiology (4 decks)

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