7 - Characteristics and diversity of Archaea

Question 1

Who discovered Archaea and when

Answer 1

Carl Woese 1970s

Question 2

Are archaea prokaryotes or eukaryotes

Answer 2

Prokaryotes, but evolved separately from bacteria

Question 3

What is the grouping of Archaea based on

Answer 3

16s rRNA sequence analysos

Question 4

where are archea found

Answer 4

used to be considered extermophiles

Now found in a wide range of environments like oceans, lakes, soils, digestive tracts as well as high and low areas of ph, temperature, salt conc., high pressure

Question 5

Archaeal cell walls

Answer 5

Do not contain peptidoglycan.

Composed of pseudomurein (peptidoglycan-like) or polysaccharide or protein (S-layer)

Some have no CW

Question 6

How do archaeal membrane lipids differ from bacterial and eukaryotic lipids

Answer 6

Branch hydrocarbons with ether linkages to gycerol

Bacteria and Eurkaya are ester linked straight hydrocarbon chains

Question 7

What are the external structures of archaea

Answer 7

Pili (type 4), Cannulae and Hami, flagella

Question 8

Cannulae

Answer 8

Unique to archaea (Pyrodictium), hollow, tube-like surface structures, connect cells to form a network, function unknown

Question 9

Hami

Answer 9

Unique to archaea (Euryarchaeon), tiny grappling hooks, each barbed fibre ends in a 3-pronged tip, function adhesion in biofilms?

Question 10

Crenarchaeota/Thermoproteota

Answer 10

• All are thermophiles or hyperthermophiles (55 degree)
• Dependent on sulphur for energy metabolism
• Strict anaerobes
• contains >25 genera

Question 11

Genus of Crenarchaeota/Thermoproteota

Answer 11

• Pyrodictium (has cannulae)
• Pyrolobus: hyperthermophile isolated from hydrothermal vent (105c-113c), irreguar cocci with S-layer CW
• Geogemma: A new hyperthermophile record holder which can reproduce at 121C, shown by its reduction of Fe(III) to magnetite, oval shaped, S-layer CW
• Sulfolobus: one of the best-studied, a thermoacidophile (heat and acid-loving)

Question 12

what are the genus of Euryarchaeota

Answer 12

• Methanogens and Methanotrophs
• Haloarchaea
• Thermoplasms
• Extremely thermophilic S0 reducers
• Sulfate reducing Euryarchaeota

Question 13

Methanogens and Methanotrophs

Answer 13

• Methanogens produce methane and Methanotrophs oxidise methane
• Largest group >25 genera
• Use H2 and CO2 or short-chain organic compounds as substrates to generate energy and methane.
• Obligate anaerobes.
• The levels of methane generated by archaea would be toxic to most life, if not for the anaerobic oxidation of methane by methanotrophic microbes

Question 14

Haloarchaea

Answer 14

Only grow in high salinity (17-23%)
Often have red yellow pigmentation
variety of shapes (cubes, pyramids, rods, cocci)
Best studied genus is Halobacterium

Question 15

2 ways that haloarchaea cope with osmotic stress

Answer 15

• Increase cytoplasmic osmolarity by accumulating small organic molecules like glycine
• Concentrate salt inside cell to levels equivalent to external environment

Question 16

Thermoplasms

Answer 16

• Thermoacidophiles that lack cell walls
• Grow in refuse streams/piles of coal mines
• Bacteria oxidise pyrite to sulphuric acid thus piles are hot and acidic
• Genus thermoplasma optimal temp 55-59ºC

Question 17

Extremely thermophilic S0 reducers

Answer 17

PYROCOCCUS
- Reduce sulphur to sulfide
- Pyrococcus optimal temp 100ºC
- Rapid mobility due to multiple polar flagella
- Has industrial uses (PCR, introducing gene to plants to increase heat tolerance)
- Species: P.Furiosus

Question 18

Self reducing Euryarchaeota

Answer 18

• Genus archaeoglobus
• Thermophilic (optimal temp 83ºC)
• Found in deep sea vents, oil deposits, hot springs
• Reduce sulphate to sulphide by extracting electrons from H2, lactate and glucose

Question 19

Thaumarchaeota/Nitrosphaeria

Answer 19

• Mesophilic aerobic
• Abundant in all oceans, soils, sediments
• Oxidise ammonia to nitrite, important in global nitrogen cycle
• Some live in symbioses with bacteria