ch 4 archaeal cell structure

Question 1

gram-positive cell walls

Answer 1

• composed primarily of peptidoglycan
• may also contain teichoic acids

Question 2

teichoic acids

Answer 2

• polymers of glycerol
• help maintain cell envelope
• protect from environmental substances
• may bind to host cells to initiate infection

Question 3

gram-negative cell wall

Answer 3

• thin layer of peptidoglycan surrounded by an outer membrane
• outer membrane composed of lipids, lipoproteins, and lipopolysaccharides

Question 4

cell envelope

Answer 4

the plasma membrane and any layers external to it

Question 5

archaeal cell envelope

Answer 5

usually cell wall, S-layers, capsules, and slime layer

Question 6

archaeal membrane

Answer 6

monolayer structure
- composed of unique lipid
change the fluidity and permeability of membranes
- branched chain hydrocarbons attached to glycerol by ether linkages

Question 7

S-layer

Answer 7

can be up to 70nm thick
tether to the plasma membrane
resembles a protein canopy from the side or a geometric pattern on the top
can have carbohydrates for stabilization

Question 8

nanotubes/nanopods

Answer 8

arrays of plasma membrane vesicles enclosed in the S-layer
- cargo packed within includes cytoplasmic contents, proteins, and nucleic acids
- thought to be important for intracellular gene transfer in thermophiles to protect DNA from denaturing in high temps

Question 9

nutrient uptake in archaea

Answer 9

• passive and facilitated diffusion
• active transport (primary and secondary)
• phosphoenolpyruvate: sugar phosphotransferase system (PTS) group translocation mechanism

Question 10

ribosomes in archaea

Answer 10

same size as bacterial ribosomes
70S constructed of a 50S and 30S subunit
rRNA molecules similar in size to bacteria but nucleotide sequence differs
protein composition differs
- archaeal ribosomes have more r-proteins
- archaeal ribosomes more similar to eukarya
intrinsic resistance to tetracyclines and macrolides

Question 11

nucleoid in archaea

Answer 11

• usually not membrane bound
• some evidence for polyploidy (bacteria are monoploid)
• circular DS DNA that is supercoiled to fit
• have histones - organize chromosomes into nucleosomes similar to eukaryotes

Question 12

pili

Answer 12

composed of pilin proteins made in cytoplasm then anchor to a protein complex in the plasma membrane

Question 13

cannulae

Answer 13

specialized archaeal pili
hollow, tubelike structures observed on the surface of thermophilic archaea
- function unknown, but daughter cells arising from a round of cell division remain connected to each other by cannulae

Question 14

hami

Answer 14

specialized archaeal pili
resemble tiny grappling hooks
may function to attach cells to surfaces
seen in biofilm communities

Question 15

archaella

Answer 15

archaeal flagella
thinner than bacterial flagella
have multiple proteins
filament is solid
rotation powered by ATP hydrolysis instead of proton motive force
direction moves cell forward or backwards
no runs and tumbles

Question 16

methanogens

Answer 16

archaea that produce methane

Question 17

S-layer functions

Answer 17

in gram-negatives, adheres to outer membrane
in gram-positive, associated with peptidoglycan
protect from ion and pH fluctuations, osmotic stress, enzymes and predation
maintains shape and rigidity
promotes adhesion to surfaces
protects from host defenses
potential use in nanotechnology