7 - Characteristics and diversity of Archaea Flashcards
Who discovered Archaea and when
Carl Woese 1970s
Are archaea prokaryotes or eukaryotes
Prokaryotes, but evolved separately from bacteria
What is the grouping of Archaea based on
16s rRNA sequence analysos
where are archea found
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
Archaeal cell walls
Do not contain peptidoglycan.
Composed of pseudomurein (peptidoglycan-like) or polysaccharide or protein (S-layer)
Some have no CW
How do archaeal membrane lipids differ from bacterial and eukaryotic lipids
Branch hydrocarbons with ether linkages to gycerol
Bacteria and Eurkaya are ester linked straight hydrocarbon chains
What are the external structures of archaea
Pili (type 4), Cannulae and Hami, flagella
Cannulae
Unique to archaea (Pyrodictium), hollow, tube-like surface structures, connect cells to form a network, function unknown
Hami
Unique to archaea (Euryarchaeon), tiny grappling hooks, each barbed fibre ends in a 3-pronged tip, function adhesion in biofilms?
Crenarchaeota/Thermoproteota
- All are thermophiles or hyperthermophiles (55 degree)
- Dependent on sulphur for energy metabolism
- Strict anaerobes
- contains >25 genera
Genus of Crenarchaeota/Thermoproteota
- 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)
what are the genus of Euryarchaeota
- Methanogens and Methanotrophs
- Haloarchaea
- Thermoplasms
- Extremely thermophilic S0 reducers
- Sulfate reducing Euryarchaeota
Methanogens and Methanotrophs
- 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
Haloarchaea
Only grow in high salinity (17-23%)
Often have red yellow pigmentation
variety of shapes (cubes, pyramids, rods, cocci)
Best studied genus is Halobacterium
2 ways that haloarchaea cope with osmotic stress
- Increase cytoplasmic osmolarity by accumulating small organic molecules like glycine
- Concentrate salt inside cell to levels equivalent to external environment
Thermoplasms
- 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
Extremely thermophilic S0 reducers
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
Self reducing Euryarchaeota
- 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
Thaumarchaeota/Nitrosphaeria
- Mesophilic aerobic
- Abundant in all oceans, soils, sediments
- Oxidise ammonia to nitrite, important in global nitrogen cycle
- Some live in symbioses with bacteria
