2.8 -Unique Aspects of Archaeal cells

Question 1

what is the difference between bacteria and archaea?

Answer 1

• similar in superficial ways- prokaryotes, usually single cell, overall similar sizes/morphologies
• Evolutionarily, Archaea domain shares a more recent
  common ancestor with Eukarya than with Bacteria

-Archaea DNA-related biology/processes more similar to eukaryotes
than to bacteria

Question 2

what are the unique cell membranes of archaea?

Answer 2

• Bacteria/Eukarya – ester-linked lipids. Archaea – ether-linked
• Bacteria/Eukarya – Lipids are fatty acids. Archaea – isoprenoid

-Archaea lipids contain side branches and rings

-Some archaea produce transmembrane phospholipids - a lipid
monolayer – similar to bilayer, but lipid tails are joined

• Archaea’s unique membrane structure is thought to be important
  for its ability to survive harsh environments. More robust
  structure.

Question 3

Do archaeal cells use peptidoglycan?

Answer 3

No, they do not!!

Question 4

what acts as a cell wall in acrchaea?

Answer 4

• proteinaceous S-layers act as cell walls.
  -They are actually supplementary structures and are not thought of as part of the cell wall.
• it is outside of the cell in addition to the cell wall, it is a rigid protein layer, protecting the cell from osmotic pressures.

Question 5

Do archaea have second membranes?

Answer 5

• ONLY rare archaeas have second membranes.
• however, it is nothing similar to an LPS that is contained in the membrane of an OM of gram-negative bacteria.

Question 6

Do all archaea have cell walls?

Answer 6

No, not all archaea have cell walls.

-For many archaea cell envelopes are not yet characterized.

Question 7

what is the archaeal cell made up of?

Answer 7

• it is made up of a similar polymer called pseudomurein.
• the pseudomurein lacks D amino acids, and has different sugar linakge, but the NAM sugar is replaced with a N-acetyltalosainuronic acid.
• thought to have evolved independently from peptidoglycan synthesis.
  a. peptidoglycan has L and D isomers,
  but pseudomurein has only L
  isomers of a.a

Question 8

what are the unique appendages found in archaea?

Answer 8

• Hamus (hami -plural), it fixes cells to a surface or to other cells to mediate biofilm formation
• Proteinaceous grappling hook.
  a. Many bacteria, including important pathogens, move by projecting grappling-hook-like extensions called type IV pili from their cell bodies. After these pili attach to other cells or objects in their environment, the bacteria retract the pili to pull themselves forward.

Question 9

What does Archaea use to move or to be motile?

Answer 9

• archaea swims motile via an analogous flagellum like apparatus which is called an archeallum.

-it is similar to a propeller appendage that sticks out, roattaion by a motor drives movement (can be chemotactic -orientation or movement of an organism or cell in relation to chemical agents.)

• the archaeallum has simpler structure meaning it has fewer proteins.
• the archaeallum is driven by ATP hydrolysis. (The flagellum is driven by PMF)
• similar to flagella, the archaellum is built inside out.

Question 10

Do bacteria swim more slowly than bacteria?

Answer 10

True, generally they do.

Question 11

what is Haloquadratum walsbyi?

Answer 11

• it is an extreme halophile.
• it is found in hyper-saline lakes with saturating salt.
• identified in 1980
• it produced PHA granules and gas vesicles.
• it is a very morphology - very thin squares.
  -has a high surface-to-volume ratio. (adaption to high salt concentration)

Question 12

Evolution of Euakraya -The Endosymbiotic theory

Answer 12

• The endosymbiotic theory states that some of the organelles in eukaryotic cells were once prokaryotic microbes. Mitochondria (alpha-proteobacterium) and chloroplasts are the same size as prokaryotic cells and divide by binary fission. Mitochondria and chloroplasts have their own DNA which is circular, not linear.

Question 13

what is Lokiarchaeota?

Answer 13

• it is a superphylum of archaea - multiple distinct sub-phyla have been identified.
• it was found first in marine sediments.
• it contains many eukaryote specific proteins which allows to build cytoplasm. it shows signs of euakryote like cell biology features of vesicle trafficking.

Question 14

what is vesicle trafficking?

Answer 14

-help move materials, such as proteins and other molecules, from one part of a cell to another.

Question 15

Do some phylogenetic trees place Eukarya within the Archaea linage?

Answer 15

• yes
  -eukaryotes branches off as a subsection of archaea. (branch of archaea)