Microbio: Module 3: Archael Cell Structure

4.1 Archaea Are Diverse but Share Some Common Features

1. In the past, archaea and bacteria were jointly referred to as _____.

2. Archaea highly diverse with respect to what? (4 things)

3. what they best known for growth in? (4 things)

1. prokaryotes

2. morphology, physiology, reproduction, and ecology

3. best known for growth in anaerobic, hypersaline(super salty), pH extremes, and high-temp habitats

4.1 Archaea Are Diverse but Share Some Common Features

Comparison of Bacterial and Archaeal Cells

1. describe Archaea’s plasma membrane lipids

2. describe archaea’s cell wall constitutents. Most have what? are their peptidoglycans?

3. Are their capsule or slime layers?

know red

4.1 Archaea Are Diverse but Share Some Common Features

Archaeal Shape, Arrangement, and Size

1. wht shapes are common?

2. what forms haven’t been discovered yet?

3. Unique ___ and ___ shape have been observed.

Cocci and rods are common shapes.

Other shapes can also exist.

• No spirochete-like or mycelial forms discovered yet.

• Unique branched and flat shapes have been observed.

Sizes vary

• Rods = 1 to 2 μm wide × 1 to 5 μm long

• Cocci = 1 to 3 μm in diameter

Smallest observed is 0.2 μm in diameter.

Largest (so far) is a multicellular form that can reach 30 mm

in length!

4.1 Archaea Are Diverse but Share Some Common Features

Other Shapes and Aggregations (Bacteria)

name 6 same as bacteria

Bacilli (s., bacillus)—rods

• The length-to-width ratio differ.

• Coccobacilli—short and wide.

Vibrios—comma shaped

Spirilla—rigid spiral-shaped

Spirochetes—flexible spiral-shaped

Mycelium—network of long filaments (hyphae).

Pleomorphic—organisms that are variable in shape.

4.2 Archaeal Cell Envelopes Are Structurally Diverse

Archaeal Cell Envelopes

how do they differ fr bacterial cell envelopes?

describe cell wall?

describe their components outside plasma membrane.

Differ from bacterial cell envelopes in the molecular makeup and organization.

• S-layer may be only component outside plasma membrane.

• Some lack cell wall.

• Slime layers are observed to mediate cell-cell interactions

but little is known about composition and regulation

4.2 Archaeal Cell Envelopes Are Structurally Diverse

Plasma Membrane Structure is Dynamic (Bacteria)

Plasma membrane is a thin structure (7 to 8 nm) composed of 2 lipid sheets.

Amphipathic lipids

• Hydrophilic—Polar ends that interact with water.

• Hydrophobic—Non-polar tails that are insoluble in water and interact with each other.

Bilayer forms spontaneously

in aqueous environment.

• Hydrophilic on surface.

• Hydrophobic ends buried

4.2 Archaeal Cell Envelopes Are Structurally Diverse

Archaeal Membranes

how are the hydrocarbons attached to glycerol compared to bacteria?

is membrane bilayer?

Composed of unique lipids.

• Hydrocarbons derived from isoprene units (5-carbon, branched molecules).

• Hydrocarbons attached to glycerol by ether linkages rather than ester linkages.

Some have a monolayer structure instead of a bilayer structure.

4.2 Archaeal Cell Envelopes Are Structurally Diverse

Archaeal Membrane Lipids

1. what are the two major types? What are they attached to?

2. which is more rigid, diethers or traethers?

3. which makes a bilayer and monolayer?

Two major types:

• Glycerol diether lipids—hydrocarbons (20 carbons) attached to glycerol.

  • C20 diethers make a bilayer.

• Diglycerol tetraether lipids—2 hydrocarbons (40 carbons) attached to 2 glycerol.

• Tetraethers are more rigid than diethers.

• C40 diethers make a monolayer.

Polar phospholipids, sulfolipids, glycolipids, and unique lipids are also found in archaeal membranes

4.2 Archaeal Cell Envelopes Are Structurally Diverse

Archaeal Lipids and Membranes

what does it look like hydrocarbon wise and what is it attached to with what?

Bacteria/Eukaryotes

Fatty acids attached to glycerol by ester linkages.

Archaea

Branched chain hydrocarbons attached to glycerol by ether linkages

4.2 Archaeal Cell Envelopes Are Structurally Diverse

Archaeal Cell Envelope Compositions know diff between archaea and bacteria; branching;linkage? bilayerC20 and C40

whats the most common cell-envelope for archael cells? what is it composed of?

• Most common cell envelope is an S-layer composed of many copies of a single protein.

• Some could have an extra protein or carbohydrate layer above, below or in place of the S-layer.

• A few have a double membrane.

4.2 Archaeal Cell Envelopes Are Structurally Diverse

Archael S-Layer Structure

S-layer can be up to 70 nm thick.

Tethered to the plasma membrane.

• Resembles a protein canopy from the side or a geometric pattern on the top.

S-layer proteins decorated with carbohydrates for stabilization.

4.2 Archaeal Cell Envelopes Are Structurally Diverse

Archaeal Extracellular Vesicles and Nanotubes

• Vesicles composed of the plasma membrane and the surrounding cell wall material, or simply 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 temperatures.

4.2 Archaeal Cell Envelopes Are Structurally Diverse

Archaeal Cells and Nutrient Uptake

1. what mechanisms do archael cells use to get nutrients?

2. whats phosphoenolpyruvate?

Archaeal cells use many of the same mechanisms for nutrient uptake exhibited in bacteria.

• Passive and facilitated diffusion

• Active transport (primary and secondary)

The phosphoenolpyruvate: sugar phosphotransferase system (PTS) group translocation mechanism has been found in some archaea.

4.2 Archaeal Cell Envelopes Are Structurally Diverse

Methods for Uptake of Nutrients Bacteria

what transport mechanisms can bacteria microorganisms use?

Microbes can only take in dissolved particles across a selectively permeable membrane.

Microorganisms use transport mechanisms.

• Passive diffusion

• Facilitated diffusion

• Primary and secondary active transport

• Group translocation

4.2 Archaeal Cell Envelopes Are Structurally Diverse

Facilitated versus Passive Diffusion Bacteria

both dont use energy

• plateau of red line at top means the carrier proteins are completely saturated (busy) think of a store with only two cashiers and 100 customers. once carrier protein is wrking fully the rate of transport cant get faster

4.2 Archaeal Cell Envelopes Are Structurally Diverse

Primary/Secondary Active Transport Bacteria

1. use energy? where they get E? with concentr gradient or against?

2. uniporters?

3. ABC transporters? what are they made of?

Use energy from ATP hydrolysis to move substances against concentration gradient without

modifying them.

Uniporters—single molecule

transported across membrane.

ATP-binding cassette (ABC) transporters

Consist of:

• 2 hydrophobic membrane spanning domains.

• 2 cytoplasmic associated ATP-binding domains.

4.2 Archaeal Cell Envelopes Are Structurally Diverse

Group Translocation Bacteria

1. r they energy dependent?

2. what does it do to mlcl?

3. name example of one group translocation bacteria

Energy dependent transport that chemically modifies the molecule as it is brought into cell.

Best known translocation system is phosphoenolpyruvate: sugar phosphotransferase system (PTS).

• Imports sugars while phosphorylating them.

4.3 Archaeal Cytoplasm is Similar to Bacterial Cytoplasm

Archaeal versus Bacterial Cytoplasm

Very similar—lack of membrane-enclosed organelles.

May contain inclusion bodies (that is, gas vacuoles).

All the usual components:

• Ribosomes

• Nucleoid region

• Plasmids

Some structures, however, may be different.

Ribosomes

Archaeal ribosomes are the same size as bacterial ribosomes.

• 70s constructed of a 50S and 30S subunit.

Composition of archaeal ribosomes differs from bacterial ribosomes.

• rRNA molecule is similar size to bacteria; however, the nucleotide sequence is different.

• Protein composition differs.

  • Archaeal ribosomes have more r-proteins.

  • The different composition makes archaeal ribosomes unaffected by antibiotics that target the ribosome.

  • Archaea more similar to eukarya than to bacteria

Nucleoid

Nucleoid–region in the cytoplasm that contains the circular chromosome and nucleoid-associated proteins (NAPs).

Irregularly shaped region in bacteria and archaea.

Usually not membrane bound (few exceptions).

Some evidence for polyploidy in archaea.

Supercoiling and nucleoid-associated proteins

• Aid in folding and chromosome condensation.

• Histones organize the chromosome into nucleosomes that are related to those in eukaryotes.

4.4 Many Archaea Have External Structures Used for Attachment and Motility

Archaeal External Structures

Pili

Composed of pilin proteins that are made in the cytoplasm

and then anchor to a protein complex in the plasma

membrane.

• Two archaeal pili:

  • Cannulae—hollow, tube-like structures on surface of thermophilic archaea.

    • Shown that daughter cells that arise from cell division remain connected to each other by cannulae.

  • Hami—resemble grappling hooks.

    • May function to attach cells to surfaces.

    • Seen in biofilm communities

4.4 Many Archaea Have External Structures Used for Attachment and Motility

Archaella and Motility

know red part dont focus on extra stuff like ArcB,ArcF, etc

Flagella are thinner than bacteria.

Some made of more than one type of protein.

Filament is not hollow.

Rotation:

• Powered by ATP hydrolysis instead of proton motive force.

• Direction moves cell forward or backwards rather than runs and tumbles.

• Swimming motility has extremely fast speeds.