Archaea Flashcards Preview

Microbiology & Infectious Disease > Archaea > Flashcards

Flashcards in Archaea Deck (19):

Do archaea always live in extreme environments?

- no
- but they are the main or only organisms that do live in the extreme environments when they do


Describe the archaeal cytoplasmic membrane

- a stable membrane is needed to compensate for living in extreme environments or lacking pep in membrane
- Lipid bilayer: glycerol diethers made from C20 phytantyl liquids
- Lipid monolayer: diglycerol tetraethers made from C40 Biphytanyl lipids. **most stable

**both are extremely resistant to heat denaturation. Widespread among thermophiles.


Domain: Archaea
- what are the two main groups?

- Crenarchaeota : many hyperthermophylic species, often chemolithotrophic (energy from oxidation of inorganic compounds), autotrophic (CO2 as sole carbon source)
- Euryarchaeota : physiologically diverse, many extremophiles


Archaea: Crenarchaeota:
- Hyperthermophiles
L> describe these hooligans.
- where are they isolated from. How do they live? Temps? Populations>

-isolated from geothermal springs and soils (temp of 100C or more)
- sulphur rich springs (Solfatarans)
L> pH ranges from mildly alkaline to pH 1. Low pH (H2SO4)
-Hydrothermal vents: under sea hot spring , water is under pressure, temperatures above 100C (up to 500)
**They live in biofilms in mixtures of species


Give an example of a sulfolobales. Describe it as well.

- Sulfolobus acidocaldarius
L> grows in sulphur rich acidic hot springs
L> aerobic chemolithotrophs that oxidize reduced sulphur or iron
L> 90C, pH 1-5
L> Spherical/lobed
L> Adheres to sulphur crystals


Compare the S layer of Bacteria and Archaea

- Bacteria: Gram +, attachment via LPS associated
L> Gram -, attachment via PG and Teichoic Acids
- Archaea: Gram -, attachment via hydrophobic anchor
L> Gram +, attachment via pseudomurein


Describe sulfolobales S-layer.

- S layer, crystalline array of proteins, anchored in the cytoplasmic membrane
**lobes bc of irregular pattern


Give an example of Desulfurococcales. Describe it.

- Pyrolobus fumarii.
- optimum growth temp 106C
- lives in the walls of black smokers
- S layer composed of protein
- Membranes composed of glycerol tetraethers ( lipid monolayer)
- Autotrophic
**it can withstand the temp we sterilize at (121)
- Facultative aerobe
- obligate H2 chemolithotroph
- NO3- is used as a terminal acceptor in strict anaerobic conditions
(NO3- and H2---> NH4)


What problems are encountered by organisms living in high temperatures?

- instability of biomolecules at high temperatures


Adaptations to life at high temperatures:
- Proteins?

- molecular chaperones (heat shock proteins)
- proteins which refold partially denatured proteins
- thermosome
-produced in very high amounts at growth limiting temperatures


Adaptations to life at high temperatures:
- Lipids?

- glycerol tetraethers in membranes


Adaptations to life at high temperatures:
- DNA?

- reverse DNA Gyrase
L> introduces positive supercoils, coiling the DNA tightly to protect it
- DNA binding proteins
L> Sac7d in Sulfolobus, binds the minor groove increases Tm by 40C(increases melting temp)
L> Archeael histones, DNA wound and compacted


Explain nonthermophilic crenarchaeota

- found in nutrient poor marine environments
- can survive in very cold seawater and ice
- planktonic (floating)
- identified by SSU rRNA sampling
- Can fix inorganic carbon
L> probably play a key role in the carbon cycle


- Halophilic archaea
L> example? Explain it

- Halobacterium salinarum
L> extreme halophile
L> have requirement for high salt concentrations, typically at least 1.5 M ~9% NaCl for growth
L> found in sea salt evaporation pounds, salt lakes and artificial habitats (ie salted foods)


- Halophilic archaea
L> explain the problems of living in high salt and adaptations to high salt concentrations

- problems: osmotic forces, high solute levels inside cells
-maintain positive water balance by pumping K+ in to cells (Higher K+ inside the cell vs Na+ outside cell)
- Glycoprotein cell wall: cell wall stabilized by NA+
- cellular proteins composed of more acidic amino acids making more soluble at high solute concentration


- Methanogens
L> explain them

- produce methane (CH4)
- ATP is produced
- Unique to Archaea..important in degradation of organic matter
- Found in: sediments low in O2 (marsh, swamp etc), animal digestive tracts, hydrothermal vents
- obligate anaerobes
- Methanobacterium: Pseudomurin in cell wall


Explain the outer cell wall components of an organism in Archaea.

- composed of: Pseudomurein which is very similar to peptidoglycan ( N-acetylglucosamine, N-acetyltalosaminurnic acid
- B(1-3) glycosidic linkages
- all amino acids are of the L-stereoisomer
- lysozyme insensitive


What characteristics do archaea share with eukaryotes?

- absence of peptidoglycan cell wall
- presence of Histones
- one complex RNA polymerase similar to RNA poly 1 (archaea) and complex RNA polymerases, types 1,11 and 222.
- both have a promoter structure known as TATA box (TTTATATA)


What are some adaptations they have for extreme conditions? (Just list don't explain for now)

- Membrane lipids
- Cell walls
- proteins
- chromosomal structure