Exam 2 Archaea 10/10

Question 1

Distinctive properties of Archaea:

Answer 1

Archaeons “look” like bacteria.

However, genetic analyses show them to be different.

They live in some of the most inhospitable places (for humans) on Earth.

Question 2

Distinctive properties of Archaea:

Answer 2

Phylogeny

Comparisons of rRNA gene sequences can establish phylogenetic “trees.”

The first portion termed “archaeons” were the methanogens.

Question 3

Archaea Structure-Bacterial

Answer 3

Size is usually 0.5–5 μm in diameter

Similar shapes

Singular, circular chromosome

Lack a membrane-bound nucleus

Question 4

Archaea Structure-Eukaryal

Answer 4

Archaeal DNA is complexed with histones

Homologues of DNA replication enzymes/transcription and translation machinary

Question 5

Distinct Archaeal Feature

Answer 5

Plasma Membrane – Organization and Composition

Question 6

Archaeal cell structure:

Answer 6

Generally 0.5–5 μm in diameter

Can vary greatly (N. equitans = 0.4 μm in diameter, Thermoproteus spp. can be 100 μm long!)

Question 7

Archaeal cell structure: Shapes can vary

Answer 7

Rods, spheres, spirals
Irregular shapes (Sulfolobus spp.)
Rectangular shapes (Thermoproteus spp.)

Question 8

Archaeal cell structure:

Answer 8

The cell envelope
- All archaeons possess a plasma membrane.
- Most archaeons have a cell wall.

Question 9

Plasma Membrane

Answer 9

Can be bilayer OR monolayer
- Contain hydrocarbons derived from isoprene units
- Hydrocarbons attached to glycerol by ether rather than ester linkages

Question 10

Archaeal cell walls:

Answer 10

The cell wall provides physical and osmotic protection

Pseudomurein (N-acetyltalosaminuronic acid)

Some Archaea lack a cell wall

Question 11

Will lysozyme work against Archaea? Why/why not?

Question 12

Cytoplasm

Answer 12

Histones form structures that DNA wraps around.
Histone structure/wrapping is different in Archaea from Eukarya.

Question 13

Cytoskeleton

Answer 13

Cytoskeletal homologues

Ta0583 is an actin homolog in Thermoplasma acidophilum that resembles eukaryal actin.

Cytoskeletal proteins from M. thermoautotrophicum and M. kandleri more closely resemble bacterial cytoskeletal proteins.

Question 14

Cell Surface

Answer 14

S-layer (single layer of many identical armorlike subunits)

Cannulae, hollow glycoprotein tubes that link cells together to form a complex network.

Question 15

Hami

Answer 15

Surface structures

Attachment

Question 16

Flagella

Answer 16

Similar to bacteria in that they rotate to move the cell

Different from bacteria because they are
- thinner (10‒14 nm vs. 20‒24 nm)
- usually composed of two or more different versions of flagellin protein
- likely growing from BASE rather than from TIP

Question 17

Archaeal cell structure:

Answer 17

The cell surface
- Some archaeons possess flagella.
-Different from bacteria because they are
likely growing from BASE rather than
from TIP